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+ <title>ECMAScript Language Specification ECMA-262 6th Edition – DRAFT</title>
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+<div id="unofficial">
+ <p><strong>This is <em>not</em> the official ECMAScript Language Specification.</strong></p>
+
+ <p>This is a draft of the next edition of the standard. See also:</p>
+
+ <ul>
+ <li><a href="http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-262.pdf">ECMAScript Language Specification,
+ Edition 5.1 (PDF)</a>, the most recent official, final standard.</li>
+ <li><a href="http://wiki.ecmascript.org/doku.php?id=harmony:specification_drafts">The ES specification drafts archive</a> for
+ PDF and Word versions of this document, and older drafts.</li>
+ <li><a href="https://github.com/jorendorff/es-spec-html">The script that produced this web page</a>, and especially the <a
+ href="https://github.com/jorendorff/es-spec-html/issues?state=open">issue tracker — please file bugs when you find
+ them</a>. Patches are welcome too.</li>
+ </ul>
+
+ <p>For copyright information, see Ecma International’s legal disclaimer in the document itself.</p>
+</div>
+
+<hgroup>
+ <h1>Draft</h1>
+ <h1>ECMA-262</h1>
+ <h1>6<sup>th</sup> Edition / Draft February 20, 2015</h1>
+ <h1>Ecma/TC39/2015/016</h1>
+</hgroup>
+<hgroup>
+ <h1>ECMAScript 2015</h1>
+ <h1>Language Specification</h1>
+
+ <p>Draft<br>Release Candidate #1</p>
+
+ <p>Report Errors and Issues at: https://bugs.ecmascript.org</p>
+
+ <p>Product: Draft for 6th Edition</p>
+
+ <p>Component: choose an appropriate one</p>
+
+ <p>Version: Rev 34, February 20, 2015 Draft</p>
+</hgroup>
+
+<section id="contents">
+ <h1>Contents</h1>
+ <ol class="toc">
+ <li>Introduction</li>
+ <li><span class="secnum"><a href="#sec-scope">1</a></span> Scope</li>
+ <li><span class="secnum"><a href="#sec-conformance">2</a></span> Conformance</li>
+ <li><span class="secnum"><a href="#sec-normative-references">3</a></span> Normative references</li>
+ <li><span class="secnum"><a href="#sec-overview">4</a></span> Overview
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-web-scripting">4.1</a></span> Web Scripting</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-overview">4.2</a></span> ECMAScript Overview
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-objects">4.2.1</a></span> Objects</li>
+ <li><span class="secnum"><a href="#sec-strict-variant-of-ecmascript">4.2.2</a></span> The Strict Variant of
+ ECMAScript</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions">4.3</a></span> Terms and definitions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-type">4.3.1</a></span> type</li>
+ <li><span class="secnum"><a href="#sec-primitive-value">4.3.2</a></span> primitive value</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-object">4.3.3</a></span> object</li>
+ <li><span class="secnum"><a href="#sec-constructor">4.3.4</a></span> constructor</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-prototype">4.3.5</a></span> prototype</li>
+ <li><span class="secnum"><a href="#sec-ordinary-object">4.3.6</a></span> ordinary object</li>
+ <li><span class="secnum"><a href="#sec-exotic-object">4.3.7</a></span> exotic object</li>
+ <li><span class="secnum"><a href="#sec-standard-object">4.3.8</a></span> standard object</li>
+ <li><span class="secnum"><a href="#sec-built-in-object">4.3.9</a></span> built-in object</li>
+ <li><span class="secnum"><a href="#sec-undefined-value">4.3.10</a></span> undefined value</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-undefined-type">4.3.11</a></span> Undefined type</li>
+ <li><span class="secnum"><a href="#sec-null-value">4.3.12</a></span> null value</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-null-type">4.3.13</a></span> Null type</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-boolean-value">4.3.14</a></span> Boolean value</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-boolean-type">4.3.15</a></span> Boolean type</li>
+ <li><span class="secnum"><a href="#sec-boolean-object">4.3.16</a></span> Boolean object</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-string-value">4.3.17</a></span> String value</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-string-type">4.3.18</a></span> String type</li>
+ <li><span class="secnum"><a href="#sec-string-object">4.3.19</a></span> String object</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-number-value">4.3.20</a></span> Number value</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-number-type">4.3.21</a></span> Number type</li>
+ <li><span class="secnum"><a href="#sec-number-object">4.3.22</a></span> Number object</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-infinity">4.3.23</a></span> Infinity</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-nan">4.3.24</a></span> NaN</li>
+ <li><span class="secnum"><a href="#sec-symbol-value">4.3.25</a></span> Symbol value</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-symbol-type">4.3.26</a></span> Symbol type</li>
+ <li><span class="secnum"><a href="#sec-symbol-object">4.3.27</a></span> Symbol object</li>
+ <li><span class="secnum"><a href="#sec-terms-and-definitions-function">4.3.28</a></span> function</li>
+ <li><span class="secnum"><a href="#sec-built-in-function">4.3.29</a></span> built-in function</li>
+ <li><span class="secnum"><a href="#sec-property">4.3.30</a></span> property</li>
+ <li><span class="secnum"><a href="#sec-method">4.3.31</a></span> method</li>
+ <li><span class="secnum"><a href="#sec-built-in-method">4.3.32</a></span> built-in method</li>
+ <li><span class="secnum"><a href="#sec-attribute">4.3.33</a></span> attribute</li>
+ <li><span class="secnum"><a href="#sec-own-property">4.3.34</a></span> own property</li>
+ <li><span class="secnum"><a href="#sec-inherited-property">4.3.35</a></span> inherited property</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-organization-of-this-specification">4.4</a></span> Organization of This
+ Specification</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-notational-conventions">5</a></span> Notational Conventions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-syntactic-and-lexical-grammars">5.1</a></span> Syntactic and Lexical Grammars
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-context-free-grammars">5.1.1</a></span> Context-Free Grammars</li>
+ <li><span class="secnum"><a href="#sec-lexical-and-regexp-grammars">5.1.2</a></span> The Lexical and RegExp
+ Grammars</li>
+ <li><span class="secnum"><a href="#sec-numeric-string-grammar">5.1.3</a></span> The Numeric String Grammar</li>
+ <li><span class="secnum"><a href="#sec-syntactic-grammar">5.1.4</a></span> The Syntactic Grammar</li>
+ <li><span class="secnum"><a href="#sec-grammar-notation">5.1.5</a></span> Grammar Notation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-algorithm-conventions">5.2</a></span> Algorithm Conventions</li>
+ <li><span class="secnum"><a href="#sec-static-semantic-rules">5.3</a></span> Static Semantic Rules</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-data-types-and-values">6</a></span> ECMAScript Data Types and Values
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-ecmascript-language-types">6.1</a></span> ECMAScript Language Types
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-ecmascript-language-types-undefined-type">6.1.1</a></span> The Undefined
+ Type</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-types-null-type">6.1.2</a></span> The Null Type</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-types-boolean-type">6.1.3</a></span> The Boolean Type</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-types-string-type">6.1.4</a></span> The String Type</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-types-symbol-type">6.1.5</a></span> The Symbol Type</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-types-number-type">6.1.6</a></span> The Number Type</li>
+ <li><span class="secnum"><a href="#sec-object-type">6.1.7</a></span> The Object Type</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-specification-types">6.2</a></span> ECMAScript Specification Types
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-list-and-record-specification-type">6.2.1</a></span> The List and Record
+ Specification Type</li>
+ <li><span class="secnum"><a href="#sec-completion-record-specification-type">6.2.2</a></span> The Completion Record
+ Specification Type</li>
+ <li><span class="secnum"><a href="#sec-reference-specification-type">6.2.3</a></span> The Reference Specification
+ Type</li>
+ <li><span class="secnum"><a href="#sec-property-descriptor-specification-type">6.2.4</a></span> The Property
+ Descriptor Specification Type</li>
+ <li><span class="secnum"><a
+ href="#sec-lexical-environment-and-environment-record-specification-types">6.2.5</a></span> The Lexical
+ Environment and Environment Record Specification Types</li>
+ <li><span class="secnum"><a href="#sec-data-blocks">6.2.6</a></span> Data Blocks</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-abstract-operations">7</a></span> Abstract Operations
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-type-conversion">7.1</a></span> Type Conversion
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-toprimitive">7.1.1</a></span> ToPrimitive ( input [, PreferredType] )</li>
+ <li><span class="secnum"><a href="#sec-toboolean">7.1.2</a></span> ToBoolean ( argument )</li>
+ <li><span class="secnum"><a href="#sec-tonumber">7.1.3</a></span> ToNumber ( argument )</li>
+ <li><span class="secnum"><a href="#sec-tointeger">7.1.4</a></span> ToInteger ( argument )</li>
+ <li><span class="secnum"><a href="#sec-toint32">7.1.5</a></span> ToInt32 ( argument )</li>
+ <li><span class="secnum"><a href="#sec-touint32">7.1.6</a></span> ToUint32 ( argument )</li>
+ <li><span class="secnum"><a href="#sec-toint16">7.1.7</a></span> ToInt16 ( argument )</li>
+ <li><span class="secnum"><a href="#sec-touint16">7.1.8</a></span> ToUint16 ( argument )</li>
+ <li><span class="secnum"><a href="#sec-toint8">7.1.9</a></span> ToInt8 ( argument )</li>
+ <li><span class="secnum"><a href="#sec-touint8">7.1.10</a></span> ToUint8 ( argument )</li>
+ <li><span class="secnum"><a href="#sec-touint8clamp">7.1.11</a></span> ToUint8Clamp ( argument )</li>
+ <li><span class="secnum"><a href="#sec-tostring">7.1.12</a></span> ToString ( argument )</li>
+ <li><span class="secnum"><a href="#sec-toobject">7.1.13</a></span> ToObject ( argument )</li>
+ <li><span class="secnum"><a href="#sec-topropertykey">7.1.14</a></span> ToPropertyKey ( argument )</li>
+ <li><span class="secnum"><a href="#sec-tolength">7.1.15</a></span> ToLength ( argument )</li>
+ <li><span class="secnum"><a href="#sec-canonicalnumericindexstring">7.1.16</a></span> CanonicalNumericIndexString (
+ argument )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-testing-and-comparison-operations">7.2</a></span> Testing and Comparison Operations
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-requireobjectcoercible">7.2.1</a></span> RequireObjectCoercible ( argument
+ )</li>
+ <li><span class="secnum"><a href="#sec-isarray">7.2.2</a></span> IsArray ( argument )</li>
+ <li><span class="secnum"><a href="#sec-iscallable">7.2.3</a></span> IsCallable ( argument )</li>
+ <li><span class="secnum"><a href="#sec-isconstructor">7.2.4</a></span> IsConstructor ( argument )</li>
+ <li><span class="secnum"><a href="#sec-isextensible-o">7.2.5</a></span> IsExtensible (O)</li>
+ <li><span class="secnum"><a href="#sec-isinteger">7.2.6</a></span> IsInteger ( argument )</li>
+ <li><span class="secnum"><a href="#sec-ispropertykey">7.2.7</a></span> IsPropertyKey ( argument )</li>
+ <li><span class="secnum"><a href="#sec-isregexp">7.2.8</a></span> IsRegExp ( argument )</li>
+ <li><span class="secnum"><a href="#sec-samevalue">7.2.9</a></span> SameValue(x, y)</li>
+ <li><span class="secnum"><a href="#sec-samevaluezero">7.2.10</a></span> SameValueZero(x, y)</li>
+ <li><span class="secnum"><a href="#sec-abstract-relational-comparison">7.2.11</a></span> Abstract Relational
+ Comparison</li>
+ <li><span class="secnum"><a href="#sec-abstract-equality-comparison">7.2.12</a></span> Abstract Equality
+ Comparison</li>
+ <li><span class="secnum"><a href="#sec-strict-equality-comparison">7.2.13</a></span> Strict Equality Comparison</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-operations-on-objects">7.3</a></span> Operations on Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-get-o-p">7.3.1</a></span> Get (O, P)</li>
+ <li><span class="secnum"><a href="#sec-getv">7.3.2</a></span> GetV (V, P)</li>
+ <li><span class="secnum"><a href="#sec-set-o-p-v-throw">7.3.3</a></span> Set (O, P, V, Throw)</li>
+ <li><span class="secnum"><a href="#sec-createdataproperty">7.3.4</a></span> CreateDataProperty (O, P, V)</li>
+ <li><span class="secnum"><a href="#sec-createmethodproperty">7.3.5</a></span> CreateMethodProperty (O, P, V)</li>
+ <li><span class="secnum"><a href="#sec-createdatapropertyorthrow">7.3.6</a></span> CreateDataPropertyOrThrow (O, P,
+ V)</li>
+ <li><span class="secnum"><a href="#sec-definepropertyorthrow">7.3.7</a></span> DefinePropertyOrThrow (O, P, desc)</li>
+ <li><span class="secnum"><a href="#sec-deletepropertyorthrow">7.3.8</a></span> DeletePropertyOrThrow (O, P)</li>
+ <li><span class="secnum"><a href="#sec-getmethod">7.3.9</a></span> GetMethod (O, P)</li>
+ <li><span class="secnum"><a href="#sec-hasproperty">7.3.10</a></span> HasProperty (O, P)</li>
+ <li><span class="secnum"><a href="#sec-hasownproperty">7.3.11</a></span> HasOwnProperty (O, P)</li>
+ <li><span class="secnum"><a href="#sec-call">7.3.12</a></span> Call(F, V, [argumentsList])</li>
+ <li><span class="secnum"><a href="#sec-invoke">7.3.13</a></span> Invoke(O,P, [argumentsList])</li>
+ <li><span class="secnum"><a href="#sec-construct">7.3.14</a></span> Construct (F, [argumentsList], [newTarget])</li>
+ <li><span class="secnum"><a href="#sec-setintegritylevel">7.3.15</a></span> SetIntegrityLevel (O, level)</li>
+ <li><span class="secnum"><a href="#sec-testintegritylevel">7.3.16</a></span> TestIntegrityLevel (O, level)</li>
+ <li><span class="secnum"><a href="#sec-createarrayfromlist">7.3.17</a></span> CreateArrayFromList (elements)</li>
+ <li><span class="secnum"><a href="#sec-createlistfromarraylike">7.3.18</a></span> CreateListFromArrayLike (obj [,
+ elementTypes] )</li>
+ <li><span class="secnum"><a href="#sec-ordinaryhasinstance">7.3.19</a></span> OrdinaryHasInstance (C, O)</li>
+ <li><span class="secnum"><a href="#sec-speciesconstructor">7.3.20</a></span> SpeciesConstructor ( O,
+ defaultConstructor )</li>
+ <li><span class="secnum"><a href="#sec-enumerableownnames">7.3.21</a></span> EnumerableOwnNames (O)</li>
+ <li><span class="secnum"><a href="#sec-getfunctionrealm">7.3.22</a></span> GetFunctionRealm ( obj )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-operations-on-iterator-objects">7.4</a></span> Operations on Iterator Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-getiterator">7.4.1</a></span> GetIterator ( obj, method )</li>
+ <li><span class="secnum"><a href="#sec-iteratornext">7.4.2</a></span> IteratorNext ( iterator, value )</li>
+ <li><span class="secnum"><a href="#sec-iteratorcomplete">7.4.3</a></span> IteratorComplete ( iterResult )</li>
+ <li><span class="secnum"><a href="#sec-iteratorvalue">7.4.4</a></span> IteratorValue ( iterResult )</li>
+ <li><span class="secnum"><a href="#sec-iteratorstep">7.4.5</a></span> IteratorStep ( iterator )</li>
+ <li><span class="secnum"><a href="#sec-iteratorclose">7.4.6</a></span> IteratorClose( iterator, completion )</li>
+ <li><span class="secnum"><a href="#sec-createiterresultobject">7.4.7</a></span> CreateIterResultObject ( value, done
+ )</li>
+ <li><span class="secnum"><a href="#sec-createlistiterator">7.4.8</a></span> CreateListIterator ( list )</li>
+ <li><span class="secnum"><a href="#sec-createcompounditerator">7.4.9</a></span> CreateCompoundIterator ( iterator1,
+ iterator2 )</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-executable-code-and-execution-contexts">8</a></span> Executable Code and Execution
+ Contexts
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-lexical-environments">8.1</a></span> Lexical Environments
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-environment-records">8.1.1</a></span> Environment Records</li>
+ <li><span class="secnum"><a href="#sec-lexical-environment-operations">8.1.2</a></span> Lexical Environment
+ Operations</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-code-realms">8.2</a></span> Code Realms
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-createrealm">8.2.1</a></span> CreateRealm ( )</li>
+ <li><span class="secnum"><a href="#sec-createintrinsics">8.2.2</a></span> CreateIntrinsics ( realmRec )</li>
+ <li><span class="secnum"><a href="#sec-setrealmglobalobject">8.2.3</a></span> SetRealmGlobalObject ( realmRec,
+ globalObj )</li>
+ <li><span class="secnum"><a href="#sec-setdefaultglobalbindings">8.2.4</a></span> SetDefaultGlobalBindings ( realmRec
+ )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-execution-contexts">8.3</a></span> Execution Contexts
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-resolvebinding">8.3.1</a></span> ResolveBinding ( name )</li>
+ <li><span class="secnum"><a href="#sec-getthisenvironment">8.3.2</a></span> GetThisEnvironment ( )</li>
+ <li><span class="secnum"><a href="#sec-resolvethisbinding">8.3.3</a></span> ResolveThisBinding ( )</li>
+ <li><span class="secnum"><a href="#sec-getnewtarget">8.3.4</a></span> GetNewTarget ( )</li>
+ <li><span class="secnum"><a href="#sec-getglobalobject">8.3.5</a></span> GetGlobalObject ( )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-jobs-and-job-queues">8.4</a></span> Jobs and Job Queues
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-enqueuejob">8.4.1</a></span> EnqueueJob ( queueName, job, arguments)</li>
+ <li><span class="secnum"><a href="#sec-nextjob-result">8.4.2</a></span> NextJob result</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-initialization">8.5</a></span> Initialization()
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-initializehostdefinedrealm">8.5.1</a></span> InitializeHostDefinedRealm ( realm
+ )</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ordinary-and-exotic-objects-behaviours">9</a></span> Ordinary and Exotic Objects
+ Behaviours
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a></span> Ordinary Object
+ Internal Methods and Internal Slots
+ <ol class="toc">
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-getprototypeof">9.1.1</a></span> [[GetPrototypeOf]]
+ ( )</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-setprototypeof-v">9.1.2</a></span>
+ [[SetPrototypeOf]] (V)</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-isextensible">9.1.3</a></span> [[IsExtensible]] (
+ )</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-preventextensions">9.1.4</a></span>
+ [[PreventExtensions]] ( )</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-getownproperty-p">9.1.5</a></span>
+ [[GetOwnProperty]] (P)</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-defineownproperty-p-desc">9.1.6</a></span>
+ [[DefineOwnProperty]] (P, Desc)</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-hasproperty-p">9.1.7</a></span>
+ [[HasProperty]](P)</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver">9.1.8</a></span> [[Get]] (P,
+ Receiver)</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-set-p-v-receiver">9.1.9</a></span> [[Set]] ( P, V,
+ Receiver)</li>
+ <li><span class="secnum"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-delete-p">9.1.10</a></span>
+ [[Delete]] (P)</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-enumerate">9.1.11</a></span> [[Enumerate]] ()</li>
+ <li><span class="secnum"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-ownpropertykeys">9.1.12</a></span>
+ [[OwnPropertyKeys]] ( )</li>
+ <li><span class="secnum"><a href="#sec-objectcreate">9.1.13</a></span> ObjectCreate(proto, internalSlotsList)</li>
+ <li><span class="secnum"><a href="#sec-ordinarycreatefromconstructor">9.1.14</a></span> OrdinaryCreateFromConstructor
+ ( constructor, intrinsicDefaultProto, internalSlotsList )</li>
+ <li><span class="secnum"><a href="#sec-getprototypefromconstructor">9.1.15</a></span> GetPrototypeFromConstructor (
+ constructor, intrinsicDefaultProto )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-function-objects">9.2</a></span> ECMAScript Function Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-ecmascript-function-objects-getownproperty-p">9.2.1</a></span>
+ [[GetOwnProperty]] (P)</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-function-objects-call-thisargument-argumentslist">9.2.2</a></span>
+ [[Call]] ( thisArgument, argumentsList)</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-function-objects-construct-argumentslist-newtarget">9.2.3</a></span>
+ [[Construct]] ( argumentsList, newTarget)</li>
+ <li><span class="secnum"><a href="#sec-functionallocate">9.2.4</a></span> FunctionAllocate (functionPrototype, strict
+ [,functionKind] )</li>
+ <li><span class="secnum"><a href="#sec-functioninitialize">9.2.5</a></span> FunctionInitialize (F, kind,
+ ParameterList, Body, Scope)</li>
+ <li><span class="secnum"><a href="#sec-functioncreate">9.2.6</a></span> FunctionCreate (kind, ParameterList, Body,
+ Scope, Strict, prototype)</li>
+ <li><span class="secnum"><a href="#sec-generatorfunctioncreate">9.2.7</a></span> GeneratorFunctionCreate (kind,
+ ParameterList, Body, Scope, Strict)</li>
+ <li><span class="secnum"><a href="#sec-addrestrictedfunctionproperties">9.2.8</a></span>
+ AddRestrictedFunctionProperties ( F, realm )</li>
+ <li><span class="secnum"><a href="#sec-makeconstructor">9.2.9</a></span> MakeConstructor (F, writablePrototype,
+ prototype)</li>
+ <li><span class="secnum"><a href="#sec-makeclassconstructor">9.2.10</a></span> MakeClassConstructor ( F)</li>
+ <li><span class="secnum"><a href="#sec-makemethod">9.2.11</a></span> MakeMethod ( F, homeObject)</li>
+ <li><span class="secnum"><a href="#sec-setfunctionname">9.2.12</a></span> SetFunctionName (F, name, prefix)</li>
+ <li><span class="secnum"><a href="#sec-functiondeclarationinstantiation">9.2.13</a></span>
+ FunctionDeclarationInstantiation(func, argumentsList)</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-built-in-function-objects">9.3</a></span> Built-in Function Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-built-in-function-objects-call-thisargument-argumentslist">9.3.1</a></span>
+ [[Call]] ( thisArgument, argumentsList)</li>
+ <li><span class="secnum"><a href="#sec-built-in-function-objects-construct-argumentslist-newtarget">9.3.2</a></span>
+ [[Construct]] (argumentsList, newTarget)</li>
+ <li><span class="secnum"><a href="#sec-createbuiltinfunction">9.3.3</a></span> CreateBuiltinFunction(realm, steps,
+ prototype, internalSlotsList)</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-built-in-exotic-object-internal-methods-and-slots">9.4</a></span> Built-in Exotic
+ Object Internal Methods and Slots
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-bound-function-exotic-objects">9.4.1</a></span> Bound Function Exotic
+ Objects</li>
+ <li><span class="secnum"><a href="#sec-array-exotic-objects">9.4.2</a></span> Array Exotic Objects</li>
+ <li><span class="secnum"><a href="#sec-string-exotic-objects">9.4.3</a></span> String Exotic Objects</li>
+ <li><span class="secnum"><a href="#sec-arguments-exotic-objects">9.4.4</a></span> Arguments Exotic Objects</li>
+ <li><span class="secnum"><a href="#sec-integer-indexed-exotic-objects">9.4.5</a></span> Integer Indexed Exotic
+ Objects</li>
+ <li><span class="secnum"><a href="#sec-module-namespace-exotic-objects">9.4.6</a></span> Module Namespace Exotic
+ Objects</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-proxy-object-internal-methods-and-internal-slots">9.5</a></span> Proxy Object
+ Internal Methods and Internal Slots
+ <ol class="toc">
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-getprototypeof">9.5.1</a></span> [[GetPrototypeOf]] (
+ )</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-setprototypeof-v">9.5.2</a></span> [[SetPrototypeOf]]
+ (V)</li>
+ <li><span class="secnum"><a href="#sec-proxy-object-internal-methods-and-internal-slots-isextensible">9.5.3</a></span>
+ [[IsExtensible]] ( )</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-preventextensions">9.5.4</a></span>
+ [[PreventExtensions]] ( )</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-getownproperty-p">9.5.5</a></span> [[GetOwnProperty]]
+ (P)</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-defineownproperty-p-desc">9.5.6</a></span>
+ [[DefineOwnProperty]] (P, Desc)</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-hasproperty-p">9.5.7</a></span> [[HasProperty]]
+ (P)</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver">9.5.8</a></span> [[Get]] (P,
+ Receiver)</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-set-p-v-receiver">9.5.9</a></span> [[Set]] ( P, V,
+ Receiver)</li>
+ <li><span class="secnum"><a href="#sec-proxy-object-internal-methods-and-internal-slots-delete-p">9.5.10</a></span>
+ [[Delete]] (P)</li>
+ <li><span class="secnum"><a href="#sec-proxy-object-internal-methods-and-internal-slots-enumerate">9.5.11</a></span>
+ [[Enumerate]] ()</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-ownpropertykeys">9.5.12</a></span> [[OwnPropertyKeys]]
+ ( )</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-call-thisargument-argumentslist">9.5.13</a></span>
+ [[Call]] (thisArgument, argumentsList)</li>
+ <li><span class="secnum"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-construct-argumentslist-newtarget">9.5.14</a></span>
+ [[Construct]] ( argumentsList, newTarget)</li>
+ <li><span class="secnum"><a href="#sec-proxycreate">9.5.15</a></span> ProxyCreate(target, handler)</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-source-code">10</a></span> ECMAScript Language: Source Code
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-source-text">10.1</a></span> Source Text
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-utf16encoding">10.1.1</a></span> Static Semantics: <i>UTF16Encoding ( cp
+ )</i></li>
+ <li><span class="secnum"><a href="#sec-utf16decode">10.1.2</a></span> Static Semantics: UTF16Decode( lead, trail
+ )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-types-of-source-code">10.2</a></span> Types of Source Code
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-strict-mode-code">10.2.1</a></span> Strict Mode Code</li>
+ <li><span class="secnum"><a href="#sec-non-ecmascript-functions">10.2.2</a></span> Non-ECMAScript Functions</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-lexical-grammar">11</a></span> ECMAScript Language: Lexical Grammar
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-unicode-format-control-characters">11.1</a></span> Unicode Format-Control
+ Characters</li>
+ <li><span class="secnum"><a href="#sec-white-space">11.2</a></span> White Space</li>
+ <li><span class="secnum"><a href="#sec-line-terminators">11.3</a></span> Line Terminators</li>
+ <li><span class="secnum"><a href="#sec-comments">11.4</a></span> Comments</li>
+ <li><span class="secnum"><a href="#sec-tokens">11.5</a></span> Tokens</li>
+ <li><span class="secnum"><a href="#sec-names-and-keywords">11.6</a></span> Names and Keywords
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-identifier-names">11.6.1</a></span> Identifier Names</li>
+ <li><span class="secnum"><a href="#sec-reserved-words">11.6.2</a></span> Reserved Words</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-punctuators">11.7</a></span> Punctuators</li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-lexical-grammar-literals">11.8</a></span> Literals
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-null-literals">11.8.1</a></span> Null Literals</li>
+ <li><span class="secnum"><a href="#sec-boolean-literals">11.8.2</a></span> Boolean Literals</li>
+ <li><span class="secnum"><a href="#sec-literals-numeric-literals">11.8.3</a></span> Numeric Literals</li>
+ <li><span class="secnum"><a href="#sec-literals-string-literals">11.8.4</a></span> String Literals</li>
+ <li><span class="secnum"><a href="#sec-literals-regular-expression-literals">11.8.5</a></span> Regular Expression
+ Literals</li>
+ <li><span class="secnum"><a href="#sec-template-literal-lexical-components">11.8.6</a></span> Template Literal Lexical
+ Components</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-automatic-semicolon-insertion">11.9</a></span> Automatic Semicolon Insertion
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-rules-of-automatic-semicolon-insertion">11.9.1</a></span> Rules of Automatic
+ Semicolon Insertion</li>
+ <li><span class="secnum"><a href="#sec-examples-of-automatic-semicolon-insertion">11.9.2</a></span> Examples of
+ Automatic Semicolon Insertion</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-expressions">12</a></span> ECMAScript Language: Expressions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-identifiers">12.1</a></span> Identifiers
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-identifiers-static-semantics-early-errors">12.1.1</a></span> Static Semantics:
+ Early Errors</li>
+ <li><span class="secnum"><a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a></span> Static Semantics:
+ BoundNames</li>
+ <li><span class="secnum"><a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a></span>
+ Static Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-identifiers-static-semantics-stringvalue">12.1.4</a></span> Static
+ Semantics<span style="font-family: sans-serif">:</span> <i>StringValue</i></li>
+ <li><span class="secnum"><a href="#sec-identifiers-runtime-semantics-bindinginitialization">12.1.5</a></span> Runtime
+ Semantics: BindingInitialization</li>
+ <li><span class="secnum"><a href="#sec-identifiers-runtime-semantics-evaluation">12.1.6</a></span> Runtime Semantics:
+ Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-primary-expression">12.2</a></span> Primary Expression
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-primary-expression-semantics">12.2.0</a></span> Semantics</li>
+ <li><span class="secnum"><a href="#sec-this-keyword">12.2.1</a></span> The <code>this</code> Keyword</li>
+ <li><span class="secnum"><a href="#sec-identifier-reference">12.2.2</a></span> Identifier Reference</li>
+ <li><span class="secnum"><a href="#sec-primary-expression-literals">12.2.3</a></span> Literals</li>
+ <li><span class="secnum"><a href="#sec-array-initializer">12.2.4</a></span> Array Initializer</li>
+ <li><span class="secnum"><a href="#sec-object-initializer">12.2.5</a></span> Object Initializer</li>
+ <li><span class="secnum"><a href="#sec-function-defining-expressions">12.2.6</a></span> Function Defining
+ Expressions</li>
+ <li><span class="secnum"><a href="#sec-primary-expression-regular-expression-literals">12.2.7</a></span> Regular
+ Expression Literals</li>
+ <li><span class="secnum"><a href="#sec-template-literals">12.2.8</a></span> Template Literals</li>
+ <li><span class="secnum"><a href="#sec-grouping-operator">12.2.9</a></span> The Grouping Operator</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-left-hand-side-expressions">12.3</a></span> Left-Hand-Side Expressions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-static-semantics">12.3.1</a></span> Static Semantics</li>
+ <li><span class="secnum"><a href="#sec-property-accessors">12.3.2</a></span> Property Accessors</li>
+ <li><span class="secnum"><a href="#sec-new-operator">12.3.3</a></span> The <code>new</code> Operator</li>
+ <li><span class="secnum"><a href="#sec-function-calls">12.3.4</a></span> Function Calls</li>
+ <li><span class="secnum"><a href="#sec-super-keyword">12.3.5</a></span> The <code>super</code> Keyword</li>
+ <li><span class="secnum"><a href="#sec-argument-lists">12.3.6</a></span> Argument Lists</li>
+ <li><span class="secnum"><a href="#sec-tagged-templates">12.3.7</a></span> Tagged Templates</li>
+ <li><span class="secnum"><a href="#sec-meta-properties">12.3.8</a></span> Meta Properties</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-postfix-expressions">12.4</a></span> Postfix Expressions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-postfix-expressions-static-semantics-early-errors">12.4.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a></span> Static Semantics:
+ IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-postfix-increment-operator">12.4.4</a></span> Postfix Increment Operator</li>
+ <li><span class="secnum"><a href="#sec-postfix-decrement-operator">12.4.5</a></span> Postfix Decrement Operator</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-unary-operators">12.5</a></span> Unary Operators
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-unary-operators-static-semantics-early-errors">12.5.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a></span> Static
+ Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a></span> Static Semantics:
+ IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-delete-operator">12.5.4</a></span> The <code>delete</code> Operator</li>
+ <li><span class="secnum"><a href="#sec-void-operator">12.5.5</a></span> The <code>void</code> Operator</li>
+ <li><span class="secnum"><a href="#sec-typeof-operator">12.5.6</a></span> The <code>typeof</code> Operator</li>
+ <li><span class="secnum"><a href="#sec-prefix-increment-operator">12.5.7</a></span> Prefix Increment Operator</li>
+ <li><span class="secnum"><a href="#sec-prefix-decrement-operator">12.5.8</a></span> Prefix Decrement Operator</li>
+ <li><span class="secnum"><a href="#sec-unary-plus-operator">12.5.9</a></span> Unary <code>+</code> Operator</li>
+ <li><span class="secnum"><a href="#sec-unary-minus-operator">12.5.10</a></span> Unary <code>-</code> Operator</li>
+ <li><span class="secnum"><a href="#sec-bitwise-not-operator">12.5.11</a></span> Bitwise NOT Operator ( <code>~</code>
+ )</li>
+ <li><span class="secnum"><a href="#sec-logical-not-operator">12.5.12</a></span> Logical NOT Operator ( <code>!</code>
+ )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-multiplicative-operators">12.6</a></span> Multiplicative Operators
+ <ol class="toc">
+ <li><span class="secnum"><a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a></span> Static Semantics:
+ IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a></span> Static
+ Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-multiplicative-operators-runtime-semantics-evaluation">12.6.3</a></span>
+ Runtime Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-additive-operators">12.7</a></span> Additive Operators
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a></span> Static Semantics:
+ IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-addition-operator-plus">12.7.3</a></span> The Addition operator (
+ <code>+</code> )</li>
+ <li><span class="secnum"><a href="#sec-subtraction-operator-minus">12.7.4</a></span> The Subtraction Operator (
+ <code>-</code> )</li>
+ <li><span class="secnum"><a href="#sec-applying-the-additive-operators-to-numbers">12.7.5</a></span> Applying the
+ Additive Operators to Numbers</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-bitwise-shift-operators">12.8</a></span> Bitwise Shift Operators
+ <ol class="toc">
+ <li><span class="secnum"><a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a></span> Static Semantics:
+ IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a></span> Static
+ Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-left-shift-operator">12.8.3</a></span> The Left Shift Operator (
+ <code><<</code> )</li>
+ <li><span class="secnum"><a href="#sec-signed-right-shift-operator">12.8.4</a></span> The Signed Right Shift Operator
+ ( <code>>></code> )</li>
+ <li><span class="secnum"><a href="#sec-unsigned-right-shift-operator">12.8.5</a></span> The Unsigned Right Shift
+ Operator ( <code>>>></code> )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-relational-operators">12.9</a></span> Relational Operators
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a></span> Static
+ Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-relational-operators-runtime-semantics-evaluation">12.9.3</a></span> Runtime
+ Semantics: Evaluation</li>
+ <li><span class="secnum"><a href="#sec-instanceofoperator">12.9.4</a></span> Runtime Semantics: InstanceofOperator(O,
+ C)</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-equality-operators">12.10</a></span> Equality Operators
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a></span> Static Semantics:
+ IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-equality-operators-runtime-semantics-evaluation">12.10.3</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-binary-bitwise-operators">12.11</a></span> Binary Bitwise Operators
+ <ol class="toc">
+ <li><span class="secnum"><a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a></span> Static Semantics:
+ IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a></span> Static
+ Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-binary-bitwise-operators-runtime-semantics-evaluation">12.11.3</a></span>
+ Runtime Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-binary-logical-operators">12.12</a></span> Binary Logical Operators
+ <ol class="toc">
+ <li><span class="secnum"><a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a></span> Static Semantics:
+ IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a></span> Static
+ Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-binary-logical-operators-runtime-semantics-evaluation">12.12.3</a></span>
+ Runtime Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-conditional-operator">12.13</a></span> Conditional Operator ( <code>? : )</code>
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a></span> Static
+ Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-conditional-operator-runtime-semantics-evaluation">12.13.3</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-assignment-operators">12.14</a></span> Assignment Operators
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-assignment-operators-static-semantics-early-errors">12.14.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a></span> Static
+ Semantics: IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-assignment-operators-runtime-semantics-evaluation">12.14.4</a></span> Runtime
+ Semantics: Evaluation</li>
+ <li><span class="secnum"><a href="#sec-destructuring-assignment">12.14.5</a></span> Destructuring Assignment</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-comma-operator">12.15</a></span> Comma Operator ( <code>, )</code>
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a></span> Static
+ Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a></span> Static Semantics:
+ IsValidSimpleAssignmentTarget</li>
+ <li><span class="secnum"><a href="#sec-comma-operator-runtime-semantics-evaluation">12.15.3</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-statements-and-declarations">13</a></span> ECMAScript Language:
+ Statements and Declarations
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-statement-semantics">13.0</a></span> Statement Semantics
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a></span>
+ Static Semantics: ContainsDuplicateLabels</li>
+ <li><span class="secnum"><a
+ href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a></span> Static Semantics:
+ ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a
+ href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a></span> Static
+ Semantics: ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-declarationpart">13.0.4</a></span> Static Semantics:
+ DeclarationPart</li>
+ <li><span class="secnum"><a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a></span> Static
+ Semantics: VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a></span>
+ Static Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-statement-semantics-runtime-semantics-labelledevaluation">13.0.7</a></span>
+ Runtime Semantics: LabelledEvaluation</li>
+ <li><span class="secnum"><a href="#sec-statement-semantics-runtime-semantics-evaluation">13.0.8</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-block">13.1</a></span> Block
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-block-static-semantics-early-errors">13.1.1</a></span> Static Semantics: Early
+ Errors</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a></span> Static
+ Semantics: ContainsDuplicateLabels</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a></span> Static
+ Semantics: ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a></span>
+ Static Semantics: ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-lexicallydeclarednames">13.1.5</a></span> Static
+ Semantics: LexicallyDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a></span> Static
+ Semantics: LexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-toplevellexicallydeclarednames">13.1.7</a></span> Static
+ Semantics: TopLevelLexicallyDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-toplevellexicallyscopeddeclarations">13.1.8</a></span>
+ Static Semantics: TopLevelLexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-toplevelvardeclarednames">13.1.9</a></span> Static
+ Semantics: TopLevelVarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-toplevelvarscopeddeclarations">13.1.10</a></span> Static
+ Semantics: TopLevelVarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-vardeclarednames">13.1.11</a></span> Static Semantics:
+ VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a></span> Static
+ Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-block-runtime-semantics-evaluation">13.1.13</a></span> Runtime Semantics:
+ Evaluation</li>
+ <li><span class="secnum"><a href="#sec-blockdeclarationinstantiation">13.1.14</a></span> Runtime Semantics:
+ BlockDeclarationInstantiation( code, env )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-declarations-and-the-variable-statement">13.2</a></span> Declarations and the
+ Variable Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-let-and-const-declarations">13.2.1</a></span> Let and Const Declarations</li>
+ <li><span class="secnum"><a href="#sec-variable-statement">13.2.2</a></span> Variable Statement</li>
+ <li><span class="secnum"><a href="#sec-destructuring-binding-patterns">13.2.3</a></span> Destructuring Binding
+ Patterns</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-empty-statement">13.3</a></span> Empty Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-empty-statement-runtime-semantics-evaluation">13.3.1</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-expression-statement">13.4</a></span> Expression Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-expression-statement-runtime-semantics-evaluation">13.4.1</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-if-statement">13.5</a></span> The <code>if</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-if-statement-static-semantics-early-errors">13.5.1</a></span> Static Semantics:
+ Early Errors</li>
+ <li><span class="secnum"><a href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a></span> Static
+ Semantics: ContainsDuplicateLabels</li>
+ <li><span class="secnum"><a href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a></span>
+ Static Semantics: ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a></span> Static Semantics:
+ ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a></span> Static
+ Semantics: VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a></span> Static
+ Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-if-statement-runtime-semantics-evaluation">13.5.7</a></span> Runtime Semantics:
+ Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-iteration-statements">13.6</a></span> Iteration Statements
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-iteration-statements-semantics">13.6.0</a></span> Semantics</li>
+ <li><span class="secnum"><a href="#sec-do-while-statement">13.6.1</a></span> The <code>do</code>-<code>while</code>
+ Statement</li>
+ <li><span class="secnum"><a href="#sec-while-statement">13.6.2</a></span> The <code>while</code> Statement</li>
+ <li><span class="secnum"><a href="#sec-for-statement">13.6.3</a></span> The <code>for</code> Statement</li>
+ <li><span class="secnum"><a href="#sec-for-in-and-for-of-statements">13.6.4</a></span> The
+ <code>for</code>-<code>in</code> and <code>for</code>-<code>of</code> Statements</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-continue-statement">13.7</a></span> The <code>continue</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-continue-statement-static-semantics-early-errors">13.7.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a></span> Static
+ Semantics: ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-continue-statement-runtime-semantics-evaluation">13.7.3</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-break-statement">13.8</a></span> The <code>break</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-break-statement-static-semantics-early-errors">13.8.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a></span> Static Semantics:
+ ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a href="#sec-break-statement-runtime-semantics-evaluation">13.8.3</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-return-statement">13.9</a></span> The <code>return</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-return-statement-runtime-semantics-evaluation">13.9.1</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-with-statement">13.10</a></span> The <code>with</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-with-statement-static-semantics-early-errors">13.10.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a></span>
+ Static Semantics: ContainsDuplicateLabels</li>
+ <li><span class="secnum"><a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a></span> Static Semantics:
+ ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a></span> Static Semantics:
+ ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a></span> Static
+ Semantics: VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a></span>
+ Static Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-with-statement-runtime-semantics-evaluation">13.10.7</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-switch-statement">13.11</a></span> The <code>switch</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-switch-statement-static-semantics-early-errors">13.11.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a></span>
+ Static Semantics: ContainsDuplicateLabels</li>
+ <li><span class="secnum"><a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a></span> Static Semantics:
+ ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a></span> Static Semantics:
+ ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-switch-statement-static-semantics-lexicallydeclarednames">13.11.5</a></span>
+ Static Semantics: LexicallyDeclaredNames</li>
+ <li><span class="secnum"><a
+ href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a></span> Static Semantics:
+ LexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a></span> Static
+ Semantics: VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a></span>
+ Static Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-runtime-semantics-caseblockevaluation">13.11.9</a></span> Runtime Semantics:
+ CaseBlockEvaluation</li>
+ <li><span class="secnum"><a href="#sec-runtime-semantics-caseselectorevaluation">13.11.10</a></span> Runtime
+ Semantics: CaseSelectorEvaluation</li>
+ <li><span class="secnum"><a href="#sec-switch-statement-runtime-semantics-evaluation">13.11.11</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-labelled-statements">13.12</a></span> Labelled Statements
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-labelled-statements-static-semantics-early-errors">13.12.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a></span> Static Semantics:
+ ContainsDuplicateLabels</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a></span> Static Semantics:
+ ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a></span> Static
+ Semantics: ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-islabelledfunction">13.12.5</a></span> Static Semantics: IsLabelledFunction (
+ stmt )</li>
+ <li><span class="secnum"><a href="#sec-labelled-statements-static-semantics-lexicallydeclarednames">13.12.6</a></span>
+ Static Semantics: LexicallyDeclaredNames</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a></span> Static Semantics:
+ LexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-toplevellexicallydeclarednames">13.12.8</a></span> Static
+ Semantics: TopLevelLexicallyDeclaredNames</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-toplevellexicallyscopeddeclarations">13.12.9</a></span> Static
+ Semantics: TopLevelLexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-toplevelvardeclarednames">13.12.10</a></span> Static Semantics:
+ TopLevelVarDeclaredNames</li>
+ <li><span class="secnum"><a
+ href="#sec-labelled-statements-static-semantics-toplevelvarscopeddeclarations">13.12.11</a></span> Static
+ Semantics: TopLevelVarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a></span>
+ Static Semantics: VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a></span>
+ Static Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-labelled-statements-runtime-semantics-labelledevaluation">13.12.14</a></span>
+ Runtime Semantics: LabelledEvaluation</li>
+ <li><span class="secnum"><a href="#sec-labelled-statements-runtime-semantics-evaluation">13.12.15</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-throw-statement">13.13</a></span> The <code>throw</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-throw-statement-runtime-semantics-evaluation">13.13.1</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-try-statement">13.14</a></span> The <code>try</code> Statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-try-statement-static-semantics-early-errors">13.14.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a></span>
+ Static Semantics: ContainsDuplicateLabels</li>
+ <li><span class="secnum"><a href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a></span>
+ Static Semantics: ContainsUndefinedBreakTarget</li>
+ <li><span class="secnum"><a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a></span> Static Semantics:
+ ContainsUndefinedContinueTarget</li>
+ <li><span class="secnum"><a href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a></span> Static
+ Semantics: VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a></span> Static
+ Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-runtime-semantics-catchclauseevaluation">13.14.7</a></span> Runtime Semantics:
+ CatchClauseEvaluation</li>
+ <li><span class="secnum"><a href="#sec-try-statement-runtime-semantics-evaluation">13.14.8</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-debugger-statement">13.15</a></span> The <code>debugger</code> statement
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-debugger-statement-runtime-semantics-evaluation">13.15.1</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-functions-and-classes">14</a></span> ECMAScript Language: Functions
+ and Classes
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-function-definitions">14.1</a></span> Function Definitions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-directive-prologues-and-the-use-strict-directive">14.1.1</a></span> Directive
+ Prologues and the Use Strict Directive</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-early-errors">14.1.2</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a></span> Static
+ Semantics: BoundNames</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-contains">14.1.4</a></span> Static
+ Semantics: Contains</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-containsexpression">14.1.5</a></span>
+ Static Semantics: ContainsExpression</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-expectedargumentcount">14.1.6</a></span>
+ Static Semantics: ExpectedArgumentCount</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-hasinitializer">14.1.7</a></span> Static
+ Semantics: HasInitializer</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-hasname">14.1.8</a></span> Static
+ Semantics: HasName</li>
+ <li><span class="secnum"><a href="#sec-isanonymousfunctiondefinition">14.1.9</a></span> Static Semantics:
+ IsAnonymousFunctionDefinition ( production )</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-isconstantdeclaration">14.1.10</a></span>
+ Static Semantics: IsConstantDeclaration</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-issimpleparameterlist">14.1.12</a></span>
+ Static Semantics: IsSimpleParameterList</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-isstrict">14.1.13</a></span> Static
+ Semantics: IsStrict</li>
+ <li><span class="secnum"><a
+ href="#sec-function-definitions-static-semantics-lexicallydeclarednames">14.1.14</a></span> Static Semantics:
+ LexicallyDeclaredNames</li>
+ <li><span class="secnum"><a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a></span> Static Semantics:
+ LexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a></span>
+ Static Semantics: VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a></span>
+ Static Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-runtime-semantics-evaluatebody">14.1.18</a></span> Runtime
+ Semantics: EvaluateBody</li>
+ <li><span class="secnum"><a
+ href="#sec-function-definitions-runtime-semantics-iteratorbindinginitialization">14.1.19</a></span> Runtime
+ Semantics: IteratorBindingInitialization</li>
+ <li><span class="secnum"><a
+ href="#sec-function-definitions-runtime-semantics-instantiatefunctionobject">14.1.20</a></span> Runtime Semantics:
+ InstantiateFunctionObject</li>
+ <li><span class="secnum"><a href="#sec-function-definitions-runtime-semantics-evaluation">14.1.21</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions">14.2</a></span> Arrow Function Definitions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions-static-semantics-early-errors">14.2.1</a></span>
+ Static Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a></span>
+ Static Semantics: BoundNames</li>
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions-static-semantics-contains">14.2.3</a></span> Static
+ Semantics: Contains</li>
+ <li><span class="secnum"><a
+ href="#sec-arrow-function-definitions-static-semantics-containsexpression">14.2.4</a></span> Static Semantics:
+ ContainsExpression</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-coveredformalslist">14.2.5</a></span> Static Semantics:
+ CoveredFormalsList</li>
+ <li><span class="secnum"><a
+ href="#sec-arrow-function-definitions-static-semantics-expectedargumentcount">14.2.6</a></span> Static Semantics:
+ ExpectedArgumentCount</li>
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions-static-semantics-hasinitializer">14.2.7</a></span>
+ Static Semantics: HasInitializer</li>
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions-static-semantics-hasname">14.2.8</a></span> Static
+ Semantics: HasName</li>
+ <li><span class="secnum"><a
+ href="#sec-arrow-function-definitions-static-semantics-issimpleparameterlist">14.2.9</a></span> Static Semantics:
+ IsSimpleParameterList</li>
+ <li><span class="secnum"><a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">14.2.10</a></span> Static
+ Semantics: LexicallyDeclaredNames</li>
+ <li><span class="secnum"><a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a></span> Static
+ Semantics: LexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a></span> Static Semantics:
+ VarScopedDeclarations</li>
+ <li><span class="secnum"><a
+ href="#sec-arrow-function-definitions-runtime-semantics-iteratorbindinginitialization">14.2.13</a></span> Runtime
+ Semantics: IteratorBindingInitialization</li>
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions-runtime-semantics-evaluatebody">14.2.14</a></span>
+ Runtime Semantics: EvaluateBody</li>
+ <li><span class="secnum"><a href="#sec-arrow-function-definitions-runtime-semantics-evaluation">14.2.15</a></span>
+ Runtime Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-method-definitions">14.3</a></span> Method Definitions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-method-definitions-static-semantics-early-errors">14.3.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-method-definitions-static-semantics-computedpropertycontains">14.3.2</a></span>
+ Static Semantics: ComputedPropertyContains</li>
+ <li><span class="secnum"><a href="#sec-method-definitions-static-semantics-expectedargumentcount">14.3.3</a></span>
+ Static Semantics: ExpectedArgumentCount</li>
+ <li><span class="secnum"><a href="#sec-method-definitions-static-semantics-hascomputedpropertykey">14.3.4</a></span>
+ Static Semantics: HasComputedPropertyKey</li>
+ <li><span class="secnum"><a href="#sec-method-definitions-static-semantics-hasdirectsuper">14.3.5</a></span> Static
+ Semantics: HasDirectSuper</li>
+ <li><span class="secnum"><a href="#sec-method-definitions-static-semantics-propname">14.3.6</a></span> Static
+ Semantics: PropName</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-needssuperbinding">14.3.7</a></span> Static Semantics:
+ NeedsSuperBinding</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-specialmethod">14.3.8</a></span> Static Semantics:
+ SpecialMethod</li>
+ <li><span class="secnum"><a href="#sec-runtime-semantics-definemethod">14.3.9</a></span> Runtime Semantics:
+ DefineMethod</li>
+ <li><span class="secnum"><a
+ href="#sec-method-definitions-runtime-semantics-propertydefinitionevaluation">14.3.10</a></span> Runtime
+ Semantics: PropertyDefinitionEvaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-generator-function-definitions">14.4</a></span> Generator Function Definitions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-generator-function-definitions-static-semantics-early-errors">14.4.1</a></span>
+ Static Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a></span>
+ Static Semantics: BoundNames</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-static-semantics-computedpropertycontains">14.4.3</a></span> Static
+ Semantics: ComputedPropertyContains</li>
+ <li><span class="secnum"><a href="#sec-generator-function-definitions-static-semantics-contains">14.4.4</a></span>
+ Static Semantics: Contains</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-static-semantics-hascomputedpropertykey">14.4.5</a></span> Static
+ Semantics: HasComputedPropertyKey</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-static-semantics-hasdirectsuper">14.4.6</a></span> Static Semantics:
+ HasDirectSuper</li>
+ <li><span class="secnum"><a href="#sec-generator-function-definitions-static-semantics-hasname">14.4.7</a></span>
+ Static Semantics: HasName</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-static-semantics-isconstantdeclaration">14.4.8</a></span> Static
+ Semantics: IsConstantDeclaration</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a></span> Static
+ Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a href="#sec-generator-function-definitions-static-semantics-propname">14.4.10</a></span>
+ Static Semantics: PropName</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-runtime-semantics-evaluatebody">14.4.11</a></span> Runtime Semantics:
+ EvaluateBody</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-runtime-semantics-instantiatefunctionobject">14.4.12</a></span> Runtime
+ Semantics: InstantiateFunctionObject</li>
+ <li><span class="secnum"><a
+ href="#sec-generator-function-definitions-runtime-semantics-propertydefinitionevaluation">14.4.13</a></span>
+ Runtime Semantics: PropertyDefinitionEvaluation</li>
+ <li><span class="secnum"><a href="#sec-generator-function-definitions-runtime-semantics-evaluation">14.4.14</a></span>
+ Runtime Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-class-definitions">14.5</a></span> Class Definitions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-early-errors">14.5.1</a></span> Static
+ Semantics: Early Errors</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a></span> Static
+ Semantics: BoundNames</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-constructormethod">14.5.3</a></span> Static Semantics:
+ ConstructorMethod</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-contains">14.5.4</a></span> Static
+ Semantics: Contains</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-computedpropertycontains">14.5.5</a></span>
+ Static Semantics: ComputedPropertyContains</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-hasname">14.5.6</a></span> Static Semantics:
+ HasName</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-isconstantdeclaration">14.5.7</a></span>
+ Static Semantics: IsConstantDeclaration</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a></span>
+ Static Semantics: IsFunctionDefinition</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-isstatic">14.5.9</a></span> Static Semantics: IsStatic</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-nonconstructormethoddefinitions">14.5.10</a></span> Static
+ Semantics: NonConstructorMethodDefinitions</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-prototypepropertynamelist">14.5.11</a></span> Static
+ Semantics: PrototypePropertyNameList</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-static-semantics-propname">14.5.12</a></span> Static
+ Semantics: PropName</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-staticpropertynamelist">14.5.13</a></span> Static Semantics:
+ StaticPropertyNameList</li>
+ <li><span class="secnum"><a href="#sec-runtime-semantics-classdefinitionevaluation">14.5.14</a></span> Runtime
+ Semantics: ClassDefinitionEvaluation</li>
+ <li><span class="secnum"><a href="#sec-runtime-semantics-bindingclassdeclarationevaluation">14.5.15</a></span> Runtime
+ Semantics: BindingClassDeclarationEvaluation</li>
+ <li><span class="secnum"><a href="#sec-class-definitions-runtime-semantics-evaluation">14.5.16</a></span> Runtime
+ Semantics: Evaluation</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-tail-position-calls">14.6</a></span> Tail Position Calls
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-isintailposition">14.6.1</a></span> Static Semantics:
+ IsInTailPosition(nonterminal)</li>
+ <li><span class="secnum"><a href="#sec-static-semantics-hasproductionintailposition">14.6.2</a></span> Static
+ Semantics: HasProductionInTailPosition</li>
+ <li><span class="secnum"><a href="#sec-preparefortailcall">14.6.3</a></span> Runtime Semantics: PrepareForTailCall (
+ )</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-language-scripts-and-modules">15</a></span> ECMAScript Language: Scripts and
+ Modules
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-scripts">15.1</a></span> Scripts
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-scripts-static-semantics-early-errors">15.1.1</a></span> Static Semantics:
+ Early Errors</li>
+ <li><span class="secnum"><a href="#sec-scripts-static-semantics-isstrict">15.1.2</a></span> Static Semantics:
+ IsStrict</li>
+ <li><span class="secnum"><a href="#sec-scripts-static-semantics-lexicallydeclarednames">15.1.3</a></span> Static
+ Semantics: LexicallyDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a></span> Static
+ Semantics: LexicallyScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a></span> Static Semantics:
+ VarDeclaredNames</li>
+ <li><span class="secnum"><a href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a></span> Static
+ Semantics: VarScopedDeclarations</li>
+ <li><span class="secnum"><a href="#sec-runtime-semantics-scriptevaluation">15.1.7</a></span> Runtime Semantics:
+ ScriptEvaluation</li>
+ <li><span class="secnum"><a href="#sec-globaldeclarationinstantiation">15.1.8</a></span> Runtime Semantics:
+ GlobalDeclarationInstantiation (script, env)</li>
+ <li><span class="secnum"><a href="#sec-scriptevaluationjob">15.1.9</a></span> Runtime Semantics: ScriptEvaluationJob (
+ <span style="font-family: sans-serif">sourceText</span> )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-modules">15.2</a></span> Modules
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-module-semantics">15.2.1</a></span> Module Semantics</li>
+ <li><span class="secnum"><a href="#sec-imports">15.2.2</a></span> Imports</li>
+ <li><span class="secnum"><a href="#sec-exports">15.2.3</a></span> Exports</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-error-handling-and-language-extensions">16</a></span> Error Handling and Language
+ Extensions
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-forbidden-extensions">16.1</a></span> Forbidden Extensions</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-ecmascript-standard-built-in-objects">17</a></span> ECMAScript Standard Built-in
+ Objects</li>
+ <li><span class="secnum"><a href="#sec-global-object">18</a></span> The Global Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-value-properties-of-the-global-object">18.1</a></span> Value Properties of the
+ Global Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-value-properties-of-the-global-object-infinity">18.1.1</a></span> Infinity</li>
+ <li><span class="secnum"><a href="#sec-value-properties-of-the-global-object-nan">18.1.2</a></span> NaN</li>
+ <li><span class="secnum"><a href="#sec-undefined">18.1.3</a></span> undefined</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-function-properties-of-the-global-object">18.2</a></span> Function Properties of
+ the Global Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-eval-x">18.2.1</a></span> eval (x)</li>
+ <li><span class="secnum"><a href="#sec-isfinite-number">18.2.2</a></span> isFinite (number)</li>
+ <li><span class="secnum"><a href="#sec-isnan-number">18.2.3</a></span> isNaN (number)</li>
+ <li><span class="secnum"><a href="#sec-parsefloat-string">18.2.4</a></span> parseFloat (string)</li>
+ <li><span class="secnum"><a href="#sec-parseint-string-radix">18.2.5</a></span> parseInt (string , radix)</li>
+ <li><span class="secnum"><a href="#sec-uri-handling-functions">18.2.6</a></span> URI Handling Functions</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object">18.3</a></span> Constructor Properties
+ of the Global Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-array">18.3.1</a></span> Array ( .
+ . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-arraybuffer">18.3.2</a></span>
+ ArrayBuffer ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-boolean">18.3.3</a></span> Boolean
+ ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-dataview">18.3.4</a></span>
+ DataView ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-date">18.3.5</a></span> Date ( . .
+ . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-error">18.3.6</a></span> Error ( .
+ . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-evalerror">18.3.7</a></span>
+ EvalError ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-float32array">18.3.8</a></span> Float32Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-float64array">18.3.9</a></span> Float64Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-function">18.3.10</a></span>
+ Function ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-int8array">18.3.11</a></span> Int8Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-int16array">18.3.12</a></span> Int16Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-int32array">18.3.13</a></span> Int32Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-map">18.3.14</a></span> Map ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-number">18.3.15</a></span> Number (
+ . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-object">18.3.16</a></span> Object (
+ . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-proxy">18.3.17</a></span> Proxy ( .
+ . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-promise">18.3.18</a></span> Promise
+ ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-rangeerror">18.3.19</a></span>
+ RangeError ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-referenceerror">18.3.20</a></span>
+ ReferenceError ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-regexp">18.3.21</a></span> RegExp (
+ . . . )</li>
+ <li><span class="secnum"><a href="#sec-set">18.3.22</a></span> Set ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-string">18.3.23</a></span> String (
+ . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-symbol">18.3.24</a></span> Symbol (
+ . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-syntaxerror">18.3.25</a></span>
+ SyntaxError ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-typeerror">18.3.26</a></span>
+ TypeError ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-uint8array">18.3.27</a></span> Uint8Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-uint8clampedarray">18.3.28</a></span> Uint8ClampedArray ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-uint16array">18.3.29</a></span> Uint16Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-uint32array">18.3.30</a></span> Uint32Array ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-urierror">18.3.31</a></span>
+ URIError ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-weakmap">18.3.32</a></span> WeakMap
+ ( . . . )</li>
+ <li><span class="secnum"><a href="#sec-constructor-properties-of-the-global-object-weakset">18.3.33</a></span> WeakSet
+ ( . . . )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-other-properties-of-the-global-object">18.4</a></span> Other Properties of the
+ Global Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-json">18.4.1</a></span> JSON</li>
+ <li><span class="secnum"><a href="#sec-math">18.4.2</a></span> Math</li>
+ <li><span class="secnum"><a href="#sec-reflect">18.4.3</a></span> Reflect</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-fundamental-objects">19</a></span> Fundamental Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-object-objects">19.1</a></span> Object Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-object-constructor">19.1.1</a></span> The Object Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-object-constructor">19.1.2</a></span> Properties of the
+ Object Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-object-prototype-object">19.1.3</a></span> Properties of the
+ Object Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-object-instances">19.1.4</a></span> Properties of Object
+ Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-function-objects">19.2</a></span> Function Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-function-constructor">19.2.1</a></span> The Function Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-function-constructor">19.2.2</a></span> Properties of the
+ Function Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-function-prototype-object">19.2.3</a></span> Properties of
+ the Function Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-function-instances">19.2.4</a></span> Function Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-boolean-objects">19.3</a></span> Boolean Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-boolean-constructor">19.3.1</a></span> The Boolean Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-boolean-constructor">19.3.2</a></span> Properties of the
+ Boolean Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-boolean-prototype-object">19.3.3</a></span> Properties of the
+ Boolean Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-boolean-instances">19.3.4</a></span> Properties of Boolean
+ Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-symbol-objects">19.4</a></span> Symbol Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-symbol-constructor">19.4.1</a></span> The Symbol Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-symbol-constructor">19.4.2</a></span> Properties of the
+ Symbol Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-symbol-prototype-object">19.4.3</a></span> Properties of the
+ Symbol Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-symbol-instances">19.4.4</a></span> Properties of Symbol
+ Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-error-objects">19.5</a></span> Error Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-error-constructor">19.5.1</a></span> The Error Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-error-constructor">19.5.2</a></span> Properties of the Error
+ Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-error-prototype-object">19.5.3</a></span> Properties of the
+ Error Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-error-instances">19.5.4</a></span> Properties of Error
+ Instances</li>
+ <li><span class="secnum"><a href="#sec-native-error-types-used-in-this-standard">19.5.5</a></span> Native Error Types
+ Used in This Standard</li>
+ <li><span class="secnum"><a href="#sec-nativeerror-object-structure">19.5.6</a></span> <i>NativeError</i> Object
+ Structure</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-numbers-and-dates">20</a></span> Numbers and Dates
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-number-objects">20.1</a></span> Number Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-number-constructor">20.1.1</a></span> The Number Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-number-constructor">20.1.2</a></span> Properties of the
+ Number Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-number-prototype-object">20.1.3</a></span> Properties of the
+ Number Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-number-instances">20.1.4</a></span> Properties of Number
+ Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-math-object">20.2</a></span> The Math Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-value-properties-of-the-math-object">20.2.1</a></span> Value Properties of the
+ Math Object</li>
+ <li><span class="secnum"><a href="#sec-function-properties-of-the-math-object">20.2.2</a></span> Function Properties
+ of the Math Object</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-date-objects">20.3</a></span> Date Objects
+ <ol class="toc">
+ <li><span class="secnum"><a
+ href="#sec-overview-of-date-objects-and-definitions-of-abstract-operations">20.3.1</a></span> Overview of Date
+ Objects and Definitions of Abstract Operations</li>
+ <li><span class="secnum"><a href="#sec-date-constructor">20.3.2</a></span> The Date Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-date-constructor">20.3.3</a></span> Properties of the Date
+ Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-date-prototype-object">20.3.4</a></span> Properties of the
+ Date Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-date-instances">20.3.5</a></span> Properties of Date
+ Instances</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-text-processing">21</a></span> Text Processing
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-string-objects">21.1</a></span> String Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-string-constructor">21.1.1</a></span> The String Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-string-constructor">21.1.2</a></span> Properties of the
+ String Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-string-prototype-object">21.1.3</a></span> Properties of the
+ String Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-string-instances">21.1.4</a></span> Properties of String
+ Instances</li>
+ <li><span class="secnum"><a href="#sec-string-iterator-objects">21.1.5</a></span> String Iterator Objects</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-regexp-regular-expression-objects">21.2</a></span> RegExp (Regular Expression)
+ Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-patterns">21.2.1</a></span> Patterns</li>
+ <li><span class="secnum"><a href="#sec-pattern-semantics">21.2.2</a></span> Pattern Semantics</li>
+ <li><span class="secnum"><a href="#sec-regexp-constructor">21.2.3</a></span> The RegExp Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-regexp-constructor">21.2.4</a></span> Properties of the
+ RegExp Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-regexp-prototype-object">21.2.5</a></span> Properties of the
+ RegExp Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-regexp-instances">21.2.6</a></span> Properties of RegExp
+ Instances</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-indexed-collections">22</a></span> Indexed Collections
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-array-objects">22.1</a></span> Array Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-array-constructor">22.1.1</a></span> The Array Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-array-constructor">22.1.2</a></span> Properties of the Array
+ Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-array-prototype-object">22.1.3</a></span> Properties of the
+ Array Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-array-instances">22.1.4</a></span> Properties of Array
+ Instances</li>
+ <li><span class="secnum"><a href="#sec-array-iterator-objects">22.1.5</a></span> Array Iterator Objects</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-typedarray-objects">22.2</a></span> <i>TypedArray</i> Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-%typedarray%-intrinsic-object">22.2.1</a></span> The %TypedArray% Intrinsic
+ Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-%typedarray%-intrinsic-object">22.2.2</a></span> Properties
+ of the %TypedArray% Intrinsic Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-%typedarrayprototype%-object">22.2.3</a></span> Properties of
+ the %TypedArrayPrototype% Object</li>
+ <li><span class="secnum"><a href="#sec-typedarray-constructors">22.2.4</a></span> The <i>TypedArray</i>
+ Constructors</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-typedarray-constructors">22.2.5</a></span> Properties of the
+ <i>TypedArray</i> Constructors</li>
+ <li><span class="secnum"><a href="#sec-properties-of-typedarray-prototype-objects">22.2.6</a></span> Properties of
+ <i>TypedArray</i> Prototype Objects</li>
+ <li><span class="secnum"><a href="#sec-properties-of-typedarray-instances">22.2.7</a></span> Properties of
+ <i>TypedArray</i> Instances</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-keyed-collection">23</a></span> Keyed Collection
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-map-objects">23.1</a></span> Map Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-map-constructor">23.1.1</a></span> The Map Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-map-constructor">23.1.2</a></span> Properties of the Map
+ Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-map-prototype-object">23.1.3</a></span> Properties of the Map
+ Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-map-instances">23.1.4</a></span> Properties of Map Instances</li>
+ <li><span class="secnum"><a href="#sec-map-iterator-objects">23.1.5</a></span> Map Iterator Objects</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-set-objects">23.2</a></span> Set Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-set-constructor">23.2.1</a></span> The Set Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-set-constructor">23.2.2</a></span> Properties of the Set
+ Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-set-prototype-object">23.2.3</a></span> Properties of the Set
+ Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-set-instances">23.2.4</a></span> Properties of Set Instances</li>
+ <li><span class="secnum"><a href="#sec-set-iterator-objects">23.2.5</a></span> Set Iterator Objects</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-weakmap-objects">23.3</a></span> WeakMap Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-weakmap-constructor">23.3.1</a></span> The WeakMap Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-weakmap-constructor">23.3.2</a></span> Properties of the
+ WeakMap Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-weakmap-prototype-object">23.3.3</a></span> Properties of the
+ WeakMap Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-weakmap-instances">23.3.4</a></span> Properties of WeakMap
+ Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-weakset-objects">23.4</a></span> WeakSet Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-weakset-constructor">23.4.1</a></span> The WeakSet Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-weakset-constructor">23.4.2</a></span> Properties of the
+ WeakSet Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-weakset-prototype-object">23.4.3</a></span> Properties of the
+ WeakSet Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-weakset-instances">23.4.4</a></span> Properties of WeakSet
+ Instances</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-structured-data">24</a></span> Structured Data
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-arraybuffer-objects">24.1</a></span> ArrayBuffer Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-abstract-operations-for-arraybuffer-objects">24.1.1</a></span> Abstract
+ Operations For ArrayBuffer Objects</li>
+ <li><span class="secnum"><a href="#sec-arraybuffer-constructor">24.1.2</a></span> The ArrayBuffer Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-arraybuffer-constructor">24.1.3</a></span> Properties of the
+ ArrayBuffer Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-arraybuffer-prototype-object">24.1.4</a></span> Properties of
+ the ArrayBuffer Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-arraybuffer-instances">24.1.5</a></span> Properties of the
+ ArrayBuffer Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-dataview-objects">24.2</a></span> DataView Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-abstract-operations-for-dataview-objects">24.2.1</a></span> Abstract Operations
+ For DataView Objects</li>
+ <li><span class="secnum"><a href="#sec-dataview-constructor">24.2.2</a></span> The DataView Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-dataview-constructor">24.2.3</a></span> Properties of the
+ DataView Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-dataview-prototype-object">24.2.4</a></span> Properties of
+ the DataView Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-dataview-instances">24.2.5</a></span> Properties of DataView
+ Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-json-object">24.3</a></span> The JSON Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-json.parse">24.3.1</a></span> JSON.parse ( text [ , reviver ] )</li>
+ <li><span class="secnum"><a href="#sec-json.stringify">24.3.2</a></span> JSON.stringify ( value [ , replacer [ , space
+ ] ] )</li>
+ <li><span class="secnum"><a href="#sec-json-@@tostringtag">24.3.3</a></span> JSON [ @@toStringTag ]</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-control-abstraction-objects">25</a></span> Control Abstraction Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-iteration">25.1</a></span> Iteration
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-common-iteration-interfaces">25.1.1</a></span> Common Iteration Interfaces</li>
+ <li><span class="secnum"><a href="#sec-%iteratorprototype%-object">25.1.2</a></span> The %IteratorPrototype%
+ Object</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-generatorfunction-objects">25.2</a></span> GeneratorFunction Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-generatorfunction-constructor">25.2.1</a></span> The GeneratorFunction
+ Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-generatorfunction-constructor">25.2.2</a></span> Properties
+ of the GeneratorFunction Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-generatorfunction-prototype-object">25.2.3</a></span>
+ Properties of the GeneratorFunction Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-generatorfunction-instances">25.2.4</a></span> GeneratorFunction Instances</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-generator-objects">25.3</a></span> Generator Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-properties-of-generator-prototype">25.3.1</a></span> Properties of Generator
+ Prototype</li>
+ <li><span class="secnum"><a href="#sec-properties-of-generator-instances">25.3.2</a></span> Properties of Generator
+ Instances</li>
+ <li><span class="secnum"><a href="#sec-generator-abstract-operations">25.3.3</a></span> Generator Abstract
+ Operations</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-promise-objects">25.4</a></span> Promise Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-promise-abstract-operations">25.4.1</a></span> Promise Abstract Operations</li>
+ <li><span class="secnum"><a href="#sec-promise-jobs">25.4.2</a></span> Promise Jobs</li>
+ <li><span class="secnum"><a href="#sec-promise-constructor">25.4.3</a></span> The Promise Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-promise-constructor">25.4.4</a></span> Properties of the
+ Promise Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-promise-prototype-object">25.4.5</a></span> Properties of the
+ Promise Prototype Object</li>
+ <li><span class="secnum"><a href="#sec-properties-of-promise-instances">25.4.6</a></span> Properties of Promise
+ Instances</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-reflection">26</a></span> Reflection
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-reflect-object">26.1</a></span> The Reflect Object
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-reflect.apply">26.1.1</a></span> Reflect.apply ( target, thisArgument,
+ argumentsList )</li>
+ <li><span class="secnum"><a href="#sec-reflect.construct">26.1.2</a></span> Reflect.construct ( target, argumentsList
+ [, newTarget] )</li>
+ <li><span class="secnum"><a href="#sec-reflect.defineproperty">26.1.3</a></span> Reflect.defineProperty ( target,
+ propertyKey, attributes )</li>
+ <li><span class="secnum"><a href="#sec-reflect.deleteproperty">26.1.4</a></span> Reflect.deleteProperty ( target,
+ propertyKey )</li>
+ <li><span class="secnum"><a href="#sec-reflect.enumerate">26.1.5</a></span> Reflect.enumerate ( target )</li>
+ <li><span class="secnum"><a href="#sec-reflect.get">26.1.6</a></span> Reflect.get ( target, propertyKey [ , receiver
+ ])</li>
+ <li><span class="secnum"><a href="#sec-reflect.getownpropertydescriptor">26.1.7</a></span>
+ Reflect.getOwnPropertyDescriptor ( target, propertyKey )</li>
+ <li><span class="secnum"><a href="#sec-reflect.getprototypeof">26.1.8</a></span> Reflect.getPrototypeOf ( target
+ )</li>
+ <li><span class="secnum"><a href="#sec-reflect.has">26.1.9</a></span> Reflect.has ( target, propertyKey )</li>
+ <li><span class="secnum"><a href="#sec-reflect.isextensible">26.1.10</a></span> Reflect.isExtensible (target)</li>
+ <li><span class="secnum"><a href="#sec-reflect.ownkeys">26.1.11</a></span> Reflect.ownKeys ( target )</li>
+ <li><span class="secnum"><a href="#sec-reflect.preventextensions">26.1.12</a></span> Reflect.preventExtensions (
+ target )</li>
+ <li><span class="secnum"><a href="#sec-reflect.set">26.1.13</a></span> Reflect.set ( target, propertyKey, V [ ,
+ receiver ] )</li>
+ <li><span class="secnum"><a href="#sec-reflect.setprototypeof">26.1.14</a></span> Reflect.setPrototypeOf ( target,
+ proto )</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-proxy-objects">26.2</a></span> Proxy Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-proxy-constructor">26.2.1</a></span> The Proxy Constructor</li>
+ <li><span class="secnum"><a href="#sec-properties-of-the-proxy-constructor">26.2.2</a></span> Properties of the Proxy
+ Constructor</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-module-namespace-objects">26.3</a></span> Module Namespace Objects
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-@@tostringtag">26.3.1</a></span> @@toStringTag</li>
+ <li><span class="secnum"><a href="#sec-@@iterator">26.3.2</a></span> [ @@iterator ] ( )</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-grammar-summary">Annex A</a></span> <span
+ class="section-status">(informative)</span> Grammar Summary
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-lexical-grammar">A.1</a></span> Lexical Grammar</li>
+ <li><span class="secnum"><a href="#sec-expressions">A.2</a></span> Expressions</li>
+ <li><span class="secnum"><a href="#sec-statements">A.3</a></span> Statements</li>
+ <li><span class="secnum"><a href="#sec-functions-and-classes">A.4</a></span> Functions and Classes</li>
+ <li><span class="secnum"><a href="#sec-scripts-and-modules">A.5</a></span> Scripts and Modules</li>
+ <li><span class="secnum"><a href="#sec-number-conversions">A.6</a></span> Number Conversions</li>
+ <li><span class="secnum"><a href="#sec-universal-resource-identifier-character-classes">A.7</a></span> Universal Resource
+ Identifier Character Classes</li>
+ <li><span class="secnum"><a href="#sec-regular-expressions">A.8</a></span> Regular Expressions</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-additional-ecmascript-features-for-web-browsers">Annex B</a></span> <span
+ class="section-status">(normative)</span> Additional ECMAScript Features for Web Browsers
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-additional-syntax">B.1</a></span> Additional Syntax
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-additional-syntax-numeric-literals">B.1.1</a></span> Numeric Literals</li>
+ <li><span class="secnum"><a href="#sec-additional-syntax-string-literals">B.1.2</a></span> String Literals</li>
+ <li><span class="secnum"><a href="#sec-html-like-comments">B.1.3</a></span> HTML-like Comments</li>
+ <li><span class="secnum"><a href="#sec-regular-expressions-patterns">B.1.4</a></span> Regular Expressions
+ Patterns</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-additional-built-in-properties">B.2</a></span> Additional Built-in Properties
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-additional-properties-of-the-global-object">B.2.1</a></span> Additional
+ Properties of the Global Object</li>
+ <li><span class="secnum"><a href="#sec-additional-properties-of-the-object.prototype-object">B.2.2</a></span>
+ Additional Properties of the Object.prototype Object</li>
+ <li><span class="secnum"><a href="#sec-additional-properties-of-the-string.prototype-object">B.2.3</a></span>
+ Additional Properties of the String.prototype Object</li>
+ <li><span class="secnum"><a href="#sec-additional-properties-of-the-date.prototype-object">B.2.4</a></span> Additional
+ Properties of the Date.prototype Object</li>
+ <li><span class="secnum"><a href="#sec-additional-properties-of-the-regexp.prototype-object">B.2.5</a></span>
+ Additional Properties of the RegExp.prototype Object</li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-other-additional-features">B.3</a></span> Other Additional Features
+ <ol class="toc">
+ <li><span class="secnum"><a href="#sec-__proto__-property-names-in-object-initializers">B.3.1</a></span> __proto__
+ Property Names in Object Initializers</li>
+ <li><span class="secnum"><a href="#sec-labelled-function-declarations">B.3.2</a></span> Labelled Function
+ Declarations</li>
+ <li><span class="secnum"><a
+ href="#sec-block-level-function-declarations-web-legacy-compatibility-semantics">B.3.3</a></span> Block-Level
+ Function Declarations Web Legacy Compatibility Semantics</li>
+ <li><span class="secnum"><a href="#sec-functiondeclarations-in-ifstatement-statement-clauses">B.3.4</a></span>
+ FunctionDeclarations in IfStatement Statement Clauses</li>
+ <li><span class="secnum"><a href="#sec-variablestatements-in-catch-blocks">B.3.5</a></span> VariableStatements in
+ Catch blocks</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><span class="secnum"><a href="#sec-strict-mode-of-ecmascript">Annex C</a></span> <span
+ class="section-status">(informative)</span> The Strict Mode of ECMAScript</li>
+ <li><span class="secnum"><a
+ href="#sec-corrections-and-clarifications-in-edition-6-with-possible-compatibility-impact">Annex D</a></span> <span
+ class="section-status">(informative)</span> Corrections and Clarifications in Edition 6 with Possible Compatibility
+ Impact</li>
+ <li><span class="secnum"><a
+ href="#sec-additions-and-changes-that-introduce-incompatibilities-with-prior-editions">Annex E</a></span> <span
+ class="section-status">(informative)</span> Additions and Changes That Introduce Incompatibilities with Prior
+ Editions</li>
+ <li>Bibliography</li>
+ </ol>
+</section>
+
+<section>
+ <h1>Introduction</h1>
+
+ <p>This is the sixth edition of ECMAScript Language Specification. Since publication of the first edition in 1997, ECMAScript
+ has grown to be one of the world’s most widely used general purpose programming languages. It is best known as the
+ language embedded in web browsers but has also been widely adopted for server and embedded applications. The sixth edition is
+ the most extensive update to ECMAScript since the publication of the first edition in 1997.</p>
+
+ <p>Goals for the sixth edition include providing better support for large applications, library creation, and for use of
+ ECMAScript as a compilation target for other languages. Some of its major enhancements include modules, class declarations,
+ lexical block scoping, iterators and generators, promises for asynchronous programming, destructuring patterns, and proper tail
+ calls. The ECMAScript library of built-ins has been expanded to support additional data abstractions including maps, sets, and
+ arrays of binary numeric values as well as additional support for Unicode supplemental characters in strings and regular
+ expressions. The built-ins are now extensible via subclassing.</p>
+
+ <p>Focused development of the sixth edition started in 2009, as the fifth edition was being prepared for publication. However,
+ this was preceded by significant experimentation and language enhancement design efforts dating to the publication of the third
+ edition in 1999. In a very real sense, the completion of the sixth edition is the culmination of a fifteen year effort. Dozens
+ of individuals representing many organizations have made very significant contributions within TC39 to the development of this
+ edition and the prior editions. In additional, a vibrant informal community has emerged supporting TC39’s ECMAScript
+ efforts. This community has reviewed numerous drafts, filed thousands of bug reports, performed implementation experiments,
+ contributed test suites, and educate the world-wide developer community about ECMAScript. Unfortunately, it is impossible to
+ identify and acknowledge every person and organization who has contributed to this effort.</p>
+
+ <p>New uses and requirements for ECMAScript continue to emerge. The sixth edition provides the foundation for regular,
+ incremental language and library enhancements.</p>
+
+ <p>Allen Wirfs-Brock<br>ECMA-262, 6<sup>th</sup> Edition Project Editor</p>
+
+ <p>This Ecma Standard has been adopted by the General Assembly of <month> <year>.</p>
+
+ <p><b>ECMA-262 Edition History</b></p>
+
+ <p>This Ecma Standard is based on several originating technologies, the most well-known being JavaScript (Netscape) and JScript
+ (Microsoft). The language was invented by Brendan Eich at Netscape and first appeared in that company’s Navigator 2.0
+ browser. It has appeared in all subsequent browsers from Netscape and in all browsers from Microsoft starting with Internet
+ Explorer 3.0.</p>
+
+ <p>The development of this Standard started in November 1996. The first edition of this Ecma Standard was adopted by the Ecma
+ General Assembly of June 1997.</p>
+
+ <p>That Ecma Standard was submitted to ISO/IEC JTC 1 for adoption under the fast-track procedure, and approved as international
+ standard ISO/IEC 16262, in April 1998. The Ecma General Assembly of June 1998 approved the second edition of ECMA-262 to keep it
+ fully aligned with ISO/IEC 16262. Changes between the first and the second edition are editorial in nature.</p>
+
+ <p>The third edition of the Standard introduced powerful regular expressions, better string handling, new control statements,
+ try/catch exception handling, tighter definition of errors, formatting for numeric output and minor changes in anticipation
+ future language growth. The third edition of the ECMAScript standard was adopted by the Ecma General Assembly of December 1999
+ and published as ISO/IEC 16262:2002 in June 2002.</p>
+
+ <p>After publication of the third edition, ECMAScript achieved massive adoption in conjunction with the World Wide Web where it
+ has become the programming language that is supported by essentially all web browsers. Significant work was done to develop a
+ fourth edition of ECMAScript. However, that work was not completed and not published as the fourth edition of ECMAScript but
+ some of it was incorporated into the development of the sixth edition.</p>
+
+ <p>The fifth edition of ECMAScript (published as ECMA-262 5<sup>th</sup> edition) codified de facto interpretations of the
+ language specification that have become common among browser implementations and added support for new features that had emerged
+ since the publication of the third edition. Such features include accessor properties, reflective creation and inspection of
+ objects, program control of property attributes, additional array manipulation functions, support for the JSON object encoding
+ format, and a strict mode that provides enhanced error checking and program security. The Fifth Edition was adopted by the Ecma
+ General Assembly of December 1999.</p>
+
+ <p>The Fifth Edition was submitted to ISO/IEC JTC 1 for adoption under the fast-track procedure, and approved as international
+ standard ISO/IEC 16262:2011. Edition 5.1 of the ECMAScript Standard incorporated minor corrections and is the same text as
+ ISO/IEC 16262:2011. The 5.1 Edition was adopted by the Ecma General Assembly of June 2011.</p>
+
+ <p><i>"DISCLAIMER</i></p>
+
+ <p><i>This draft document may be copied and furnished to others, and derivative works that comment on or otherwise explain it or
+ assist in its implementation may be prepared, copied, published, and distributed, in whole or in part, without restriction of
+ any kind, provided that the above copyright notice and this section are included on all such copies and derivative works.
+ However, this document itself may not be modified in any way, including by removing the copyright notice or references to Ecma
+ International, except as needed for the purpose of developing any document or deliverable produced by Ecma
+ International.</i></p>
+
+ <p><i>This disclaimer is valid only prior to final version of this document. After approval all rights on the standard are
+ reserved by Ecma International.</i></p>
+
+ <p><i>The limited permissions are granted through the standardization phase and will not be revoked by Ecma International or its
+ successors or assigns during this time.</i></p>
+
+ <p><i>This document and the information contained herein is provided on an "AS IS" basis and ECMA INTERNATIONAL DISCLAIMS ALL
+ WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
+ INFRINGE ANY OWNERSHIP RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."</i></p>
+</section>
+
+<div class="inner-title">ECMAScript 2015 Language Specification</div>
+
+<section id="sec-scope">
+ <h1><span class="secnum" id="sec-1"><a href="#sec-scope" title="link to this section">1</a></span> Scope</h1>
+
+ <p>This Standard defines the ECMAScript 2015 general purpose programming language.</p>
+</section>
+
+<section id="sec-conformance">
+ <h1><span class="secnum" id="sec-2"><a href="#sec-conformance" title="link to this section">2</a></span> Conformance</h1>
+
+ <p>A conforming implementation of ECMAScript must provide and support all the types, values, objects, properties, functions, and
+ program syntax and semantics described in this specification.</p>
+
+ <p>A conforming implementation of ECMAScript must interpret source text input in conformance with the Unicode Standard, Version
+ 5.1.0 or later and ISO/IEC 10646. If the adopted ISO/IEC 10646-1 subset is not otherwise specified, it is presumed to be the
+ Unicode set, collection 10646.</p>
+
+ <p>A conforming implementation of ECMAScript that provides an application programming interface that supports programs that need
+ to adapt to the linguistic and cultural conventions used by different human languages and countries must implement the interface
+ defined by the most recent edition of ECMA-402 that is compatible with this specification.</p>
+
+ <p>A conforming implementation of ECMAScript may provide additional types, values, objects, properties, and functions beyond
+ those described in this specification. In particular, a conforming implementation of ECMAScript may provide properties not
+ described in this specification, and values for those properties, for objects that are described in this specification.</p>
+
+ <p>A conforming implementation of ECMAScript may support program and regular expression syntax not described in this
+ specification. In particular, a conforming implementation of ECMAScript may support program syntax that makes use of the
+ “future reserved words” listed in <a href="#sec-future-reserved-words">subclause 11.6.2.2</a> of this
+ specification.</p>
+
+ <p>A conforming implementation of ECMAScript must not implement any extension that is listed as a Forbidden Extension in <a
+ href="#sec-forbidden-extensions">subclause 16.1</a>.</p>
+</section>
+
+<section id="sec-normative-references">
+ <h1><span class="secnum" id="sec-3"><a href="#sec-normative-references" title="link to this section">3</a></span> Normative
+ references</h1>
+
+ <p>The following referenced documents are indispensable for the application of this document. For dated references, only the
+ edition cited applies. For undated references, the latest edition of the referenced document (including any amendments)
+ applies.</p>
+
+ <p class="formal-reference">IEEE Std 754-2008: <i>IEEE Standard for Floating-Point Arithmetic</i>. Institute of Electrical and
+ Electronic Engineers, New York (2008)</p>
+
+ <p class="formal-reference">ISO/IEC 10646:2003: <i>Information Technology – Universal Multiple-Octet Coded Character Set
+ (UCS) plus Amendment 1:2005, Amendment 2:2006, Amendment 3:2008, and Amendment 4:2008</i>, plus additional amendments and
+ corrigenda, or successor</p>
+
+ <p class="formal-reference"><i>The Unicode Standard, Version 5.0</i>, as amended by Unicode 5.1.0, or successor.<br><a
+ href="http://www.unicode.org/versions/latest">http://www.unicode.org/versions/latest</a></p>
+
+ <p class="formal-reference"><i>Unicode Standard Annex #15, Unicode Normalization Forms, version Unicode 5.1.0</i>, or
+ successor.<br><a href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a></p>
+
+ <p class="formal-reference"><i>Unicode Standard Annex #31, Unicode Identifiers and Pattern Syntax, version Unicode 5.1.0</i>, or
+ successor. <a href="http://www.unicode.org/reports/tr31/">http://www.unicode.org/reports/tr31/</a></p>
+
+ <p>ECMA-402, <i>ECMAScript 2015 Internationalization API Specification</i>.<br><a
+ href="http://www.ecma-international.org/publications/standards/Ecma-402.htm">http://www.ecma-international.org/publications/standards/Ecma-402.htm</a></p>
+
+ <p>ECMA-404, <i>The JSON Data Interchange Format</i>.<br><a
+ href="http://www.ecma-international.org/publications/standards/Ecma-404.htm">http://www.ecma-international.org/publications/standards/Ecma-404.htm</a></p>
+</section>
+
+<section id="sec-overview">
+ <div class="front">
+ <h1><span class="secnum" id="sec-4"><a href="#sec-overview" title="link to this section">4</a></span> Overview</h1>
+
+ <p>This section contains a non-normative overview of the ECMAScript language.</p>
+
+ <p>ECMAScript is an object-oriented programming language for performing computations and manipulating computational objects
+ within a host environment. ECMAScript as defined here is not intended to be computationally self-sufficient; indeed, there are
+ no provisions in this specification for input of external data or output of computed results. Instead, it is expected that the
+ computational environment of an ECMAScript program will provide not only the objects and other facilities described in this
+ specification but also certain environment-specific objects, whose description and behaviour are beyond the scope of this
+ specification except to indicate that they may provide certain properties that can be accessed and certain functions that can
+ be called from an ECMAScript program.</p>
+
+ <p>ECMAScript was originally designed to be used as a scripting language, but has become widely used as a general purpose
+ programming language. A <b><i>scripting language</i></b> is a programming language that is used to manipulate, customize, and
+ automate the facilities of an existing system. In such systems, useful functionality is already available through a user
+ interface, and the scripting language is a mechanism for exposing that functionality to program control. In this way, the
+ existing system is said to provide a host environment of objects and facilities, which completes the capabilities of the
+ scripting language. A scripting language is intended for use by both professional and non-professional programmers.</p>
+
+ <p>ECMAScript was originally designed to be a <b><i>Web scripting language</i></b>, providing a mechanism to enliven Web pages
+ in browsers and to perform server computation as part of a Web-based client-server architecture. ECMAScript is now used to
+ provide core scripting capabilities for a variety of host environments. Therefore the core language is specified in this
+ document apart from any particular host environment.</p>
+
+ <p>ECMAScript usage has moved beyond simple scripting and it is now used for the full spectrum of programming tasks in many
+ different environments and scales. As the usage of ECMAScript has expanded, so has the features and facilities it provides.
+ ECMAScript is now a fully featured general propose programming language.</p>
+
+ <p>Some of the facilities of ECMAScript are similar to those used in other programming languages; in particular C,
+ Java™, Self, and Scheme as described in:</p>
+
+ <p>ISO/IEC 9899:1996, Programming Languages – C.</p>
+
+ <p class="formal-reference">Gosling, James, Bill Joy and Guy Steele. <span class="book-title">The Java™ Language
+ Specification</span>. Addison Wesley Publishing Co., 1996.</p>
+
+ <p class="formal-reference">Ungar, David, and Smith, Randall B. <span class="book-title">Self: The Power of Simplicity</span>.
+ OOPSLA '87 Conference Proceedings, pp. 227–241, Orlando, FL, October 1987.</p>
+
+ <p class="formal-reference"><span class="book-title">IEEE Standard for the Scheme Programming Language</span>. IEEE Std
+ 1178-1990.</p>
+ </div>
+
+ <section id="sec-web-scripting">
+ <h1><span class="secnum" id="sec-4.1"><a href="#sec-web-scripting" title="link to this section">4.1</a></span> Web
+ Scripting</h1>
+
+ <p>A web browser provides an ECMAScript host environment for client-side computation including, for instance, objects that
+ represent windows, menus, pop-ups, dialog boxes, text areas, anchors, frames, history, cookies, and input/output. Further, the
+ host environment provides a means to attach scripting code to events such as change of focus, page and image loading,
+ unloading, error and abort, selection, form submission, and mouse actions. Scripting code appears within the HTML and the
+ displayed page is a combination of user interface elements and fixed and computed text and images. The scripting code is
+ reactive to user interaction and there is no need for a main program.</p>
+
+ <p>A web server provides a different host environment for server-side computation including objects representing requests,
+ clients, and files; and mechanisms to lock and share data. By using browser-side and server-side scripting together, it is
+ possible to distribute computation between the client and server while providing a customized user interface for a Web-based
+ application.</p>
+
+ <p>Each Web browser and server that supports ECMAScript supplies its own host environment, completing the ECMAScript execution
+ environment.</p>
+ </section>
+
+ <section id="sec-ecmascript-overview">
+ <div class="front">
+ <h1><span class="secnum" id="sec-4.2"><a href="#sec-ecmascript-overview" title="link to this section">4.2</a></span>
+ ECMAScript Overview</h1>
+
+ <p>The following is an informal overview of ECMAScript—not all parts of the language are described. This overview is
+ not part of the standard proper.</p>
+
+ <p>ECMAScript is object-based: basic language and host facilities are provided by objects, and an ECMAScript program is a
+ cluster of communicating objects. In ECMAScript, an <b><i>object</i></b> is a collection of zero or more
+ <b><i>properties</i></b> each with <b><i>attributes</i></b> that determine how each property can be used—for example,
+ when the Writable attribute for a property is set to <b>false</b>, any attempt by executed ECMAScript code to assign a
+ different value to the property fails. Properties are containers that hold other objects, <b><i>primitive values</i></b>, or
+ <b><i>functions</i></b>. A primitive value is a member of one of the following built-in types: <b>Undefined</b>,
+ <b>Null</b>, <b>Boolean</b>, <b>Number</b>, <b>String,</b> and <b>Symbol;</b> an object is a member of the built-in type
+ <b>Object</b>; and a function is a callable object. A function that is associated with an object via a property is called a
+ <b><i>method</i></b>.</p>
+
+ <p>ECMAScript defines a collection of <b><i>built-in objects</i></b> that round out the definition of ECMAScript entities.
+ These built-in objects include the global object; objects that are fundamental to the runtime semantics of the language
+ including <b>Object</b>, <b>Function</b>, <b>Boolean</b>, <b>Symbol</b>, and various <b>Error</b> objects; objects that
+ represent and manipulate numeric values including <b>Math</b>, <b>Number</b>, and <b>Date</b>; the text processing objects
+ <b>String</b> and <b>RegExp</b>; objects that are indexed collections of values including <b>Array</b> and nine different
+ kinds of Typed Arrays whose elements all have a specific numeric data representation; keyed collections including <b>Map</b>
+ and <b>Set</b> objects; objects supporting structured data including the <b>JSON</b> object, <b>ArrayBuffer</b>, and
+ <b>DataView</b>; objects supporting control abstractions including generator functions and <b>Promise</b> objects;
+ and<b>,</b> reflection objects including <b>Proxy</b> and <b>Reflect</b>.</p>
+
+ <p>ECMAScript also defines a set of built-in <b><i>operators</i></b>. ECMAScript operators include various unary operations,
+ multiplicative operators, additive operators, bitwise shift operators, relational operators, equality operators, binary
+ bitwise operators, binary logical operators, assignment operators, and the comma operator.</p>
+
+ <p>Large ECMAScript programs are supported by <b><i>modules</i></b> which allow a program to be divided into multiple
+ sequences of statements and declarations. Each module explicitly identifies declarations it uses that need to be provided by
+ other modules and which of its declarations are available for use by other modules.</p>
+
+ <p>ECMAScript syntax intentionally resembles Java syntax. ECMAScript syntax is relaxed to enable it to serve as an
+ easy-to-use scripting language. For example, a variable is not required to have its type declared nor are types associated
+ with properties, and defined functions are not required to have their declarations appear textually before calls to
+ them.</p>
+ </div>
+
+ <section id="sec-objects">
+ <h1><span class="secnum" id="sec-4.2.1"><a href="#sec-objects" title="link to this section">4.2.1</a></span> Objects</h1>
+
+ <p>Even though ECMAScript includes syntax for class definitions, ECMAScript objects are not fundamentally class-based such
+ as those in C++, Smalltalk, or Java. Instead objects may be created in various ways including via a literal notation or via
+ <b><i>constructors</i></b> which create objects and then execute code that initializes all or part of them by assigning
+ initial values to their properties. Each constructor is a function that has a property named
+ “<code>prototype</code>” that is used to implement <b><i>prototype-based inheritance</i></b> and <b><i>shared
+ properties</i></b>. Objects are created by using constructors in <b>new</b> expressions; for example, <code>new
+ Date(2009,11)</code> creates a new Date object. Invoking a constructor without using <b>new</b> has consequences that depend
+ on the constructor. For example, <code>Date()</code> produces a string representation of the current date and time rather
+ than an object.</p>
+
+ <p>Every object created by a constructor has an implicit reference (called the object’s <i>prototype</i>) to the value
+ of its constructor’s “<code>prototype</code>” property. Furthermore, a prototype may have a non-null
+ implicit reference to its prototype, and so on; this is called the <i>prototype chain</i>. When a reference is made to a
+ property in an object, that reference is to the property of that name in the first object in the prototype chain that
+ contains a property of that name. In other words, first the object mentioned directly is examined for such a property; if
+ that object contains the named property, that is the property to which the reference refers; if that object does not contain
+ the named property, the prototype for that object is examined next; and so on.</p>
+
+ <figure>
+ <object data="figure-1.svg" height="354" type="image/svg+xml" width="719">
+ <img alt="An image of lots of boxes and arrows." height="354" src="figure-1.png" width="719">
+ </object>
+ <figcaption>Figure 1 — Object/Prototype Relationships</figcaption>
+ </figure>
+
+ <p>In a class-based object-oriented language, in general, state is carried by instances, methods are carried by classes, and
+ inheritance is only of structure and behaviour. In ECMAScript, the state and methods are carried by objects, while
+ structure, behaviour, and state are all inherited.</p>
+
+ <p>All objects that do not directly contain a particular property that their prototype contains share that property and its
+ value. Figure 1 illustrates this:</p>
+
+ <p><b>CF</b> is a constructor (and also an object). Five objects have been created by using <code>new</code> expressions:
+ <b>cf<sub>1</sub></b>, <b>cf<sub>2</sub></b>, <b>cf<sub>3</sub></b>, <b>cf<sub>4</sub></b>, and <b>cf<sub>5</sub></b>. Each
+ of these objects contains properties named <code>q1</code> and <code>q2</code>. The dashed lines represent the implicit
+ prototype relationship; so, for example, <b>cf<sub>3</sub></b>’s prototype is <b>CF<sub>p</sub></b>. The constructor,
+ <b>CF</b>, has two properties itself, named <code>P1</code> and <code>P2</code>, which are not visible to
+ <b>CF<sub>p</sub></b>, <b>cf<sub>1</sub></b>, <b>cf<sub>2</sub></b>, <b>cf<sub>3</sub></b>, <b>cf<sub>4</sub></b>, or
+ <b>cf<sub>5</sub></b>. The property named <code>CFP1</code> in <b>CF<sub>p</sub></b> is shared by <b>cf<sub>1</sub></b>,
+ <b>cf<sub>2</sub></b>, <b>cf<sub>3</sub></b>, <b>cf<sub>4</sub></b>, and <b>cf<sub>5</sub></b> (but not by <b>CF</b>), as
+ are any properties found in <b>CF<sub>p</sub></b>’s implicit prototype chain that are not named <code>q1</code>,
+ <code>q2</code>, or <code>CFP1</code>. Notice that there is no implicit prototype link between <b>CF</b> and
+ <b>CF<sub>p</sub></b>.</p>
+
+ <p>Unlike most class-based object languages, properties can be added to objects dynamically by assigning values to them.
+ That is, constructors are not required to name or assign values to all or any of the constructed object’s properties.
+ In the above diagram, one could add a new shared property for <b>cf<sub>1</sub></b>, <b>cf<sub>2</sub></b>,
+ <b>cf<sub>3</sub></b>, <b>cf<sub>4</sub></b>, and <b>cf<sub>5</sub></b> by assigning a new value to the property in
+ <b>CF<sub>p</sub></b>.</p>
+
+ <p>Although ECMAScript objects are not inherently class-based, it is often convenient to define class-like abstractions
+ based upon a common pattern of constructor functions, prototype objects, and methods. The ECMAScript built-in objects
+ themselves follow such a class-like pattern. Beginning with the sixth edition, the ECMAScript language includes syntactic
+ class definitions that permit programmers to concisely define objects that conform to the same class-like abstraction
+ pattern used by the built-in objects.</p>
+ </section>
+
+ <section id="sec-strict-variant-of-ecmascript">
+ <h1><span class="secnum" id="sec-4.2.2"><a href="#sec-strict-variant-of-ecmascript"
+ title="link to this section">4.2.2</a></span> The Strict Variant of ECMAScript</h1>
+
+ <p>The ECMAScript Language recognizes the possibility that some users of the language may wish to restrict their usage of
+ some features available in the language. They might do so in the interests of security, to avoid what they consider to be
+ error-prone features, to get enhanced error checking, or for other reasons of their choosing. In support of this
+ possibility, ECMAScript defines a strict variant of the language. The strict variant of the language excludes some specific
+ syntactic and semantic features of the regular ECMAScript language and modifies the detailed semantics of some features. The
+ strict variant also specifies additional error conditions that must be reported by throwing error exceptions in situations
+ that are not specified as errors by the non-strict form of the language.</p>
+
+ <p>The strict variant of ECMAScript is commonly referred to as the <i>strict mode</i> of the language. Strict mode selection
+ and use of the strict mode syntax and semantics of ECMAScript is explicitly made at the level of individual ECMAScript code
+ units. Because strict mode is selected at the level of a syntactic code unit, strict mode only imposes restrictions that
+ have local effect within such a code unit. Strict mode does not restrict or modify any aspect of the ECMAScript semantics
+ that must operate consistently across multiple code units. A complete ECMAScript program may be composed for both strict
+ mode and non-strict mode ECMAScript code units. In this case, strict mode only applies when actually executing code that is
+ defined within a <a href="#sec-strict-mode-code">strict mode code</a> unit.</p>
+
+ <p>In order to conform to this specification, an ECMAScript implementation must implement both the full unrestricted
+ ECMAScript language and the strict mode variant of the ECMAScript language as defined by this specification. In addition, an
+ implementation must support the combination of unrestricted and <a href="#sec-strict-mode-code">strict mode code</a> units
+ into a single composite program.</p>
+ </section>
+ </section>
+
+ <section id="sec-terms-and-definitions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-4.3"><a href="#sec-terms-and-definitions" title="link to this section">4.3</a></span> Terms
+ and definitions</h1>
+
+ <p>For the purposes of this document, the following terms and definitions apply.</p>
+ </div>
+
+ <section id="sec-type">
+ <h1><span class="secnum" id="sec-4.3.1"><a href="#sec-type" title="link to this section">4.3.1</a></span> type</h1>
+
+ <p>set of data values as defined in <a href="#sec-ecmascript-data-types-and-values">clause 6</a> of this specification</p>
+ </section>
+
+ <section id="sec-primitive-value">
+ <h1><span class="secnum" id="sec-4.3.2"><a href="#sec-primitive-value" title="link to this section">4.3.2</a></span>
+ primitive value</h1>
+
+ <p>member of one of the types Undefined, Null, Boolean, Number, Symbol, or String as defined in <a
+ href="#sec-ecmascript-data-types-and-values">clause 6</a></p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A primitive value is a datum that is represented directly at the lowest level of the
+ language implementation.</p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-object">
+ <h1><span class="secnum" id="sec-4.3.3"><a href="#sec-terms-and-definitions-object"
+ title="link to this section">4.3.3</a></span> object</h1>
+
+ <p>member of the type Object</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An object is a collection of properties and has a single prototype object. The prototype
+ may be the null value.</p>
+ </div>
+ </section>
+
+ <section id="sec-constructor">
+ <h1><span class="secnum" id="sec-4.3.4"><a href="#sec-constructor" title="link to this section">4.3.4</a></span>
+ constructor</h1>
+
+ <p>function object that creates and initializes objects</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of a constructor’s “<code>prototype</code>” property is a
+ prototype object that is used to implement inheritance and shared properties.</p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-prototype">
+ <h1><span class="secnum" id="sec-4.3.5"><a href="#sec-terms-and-definitions-prototype"
+ title="link to this section">4.3.5</a></span> prototype</h1>
+
+ <p>object that provides shared properties for other objects</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When a constructor creates an object, that object implicitly references the
+ constructor’s “<code>prototype</code>” property for the purpose of resolving property references. The
+ constructor’s “<code>prototype</code>” property can be referenced by the program expression
+ <code><i>constructor</i><b>.prototype</b></code>, and properties added to an object’s prototype are shared, through
+ inheritance, by all objects sharing the prototype. Alternatively, a new object may be created with an explicitly specified
+ prototype by using the <code><a href="#sec-object.create">Object.create</a></code> built-in function.</p>
+ </div>
+ </section>
+
+ <section id="sec-ordinary-object">
+ <h1><span class="secnum" id="sec-4.3.6"><a href="#sec-ordinary-object" title="link to this section">4.3.6</a></span>
+ ordinary object</h1>
+
+ <p>object that has the default behaviour for the essential internal methods that must be supported by all objects.</p>
+ </section>
+
+ <section id="sec-exotic-object">
+ <h1><span class="secnum" id="sec-4.3.7"><a href="#sec-exotic-object" title="link to this section">4.3.7</a></span> exotic
+ object</h1>
+
+ <p>object that does not have the default behaviour for one or more of the essential internal methods that must be supported
+ by all objects.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Any object that is not an ordinary object is an exotic object.</p>
+ </div>
+ </section>
+
+ <section id="sec-standard-object">
+ <h1><span class="secnum" id="sec-4.3.8"><a href="#sec-standard-object" title="link to this section">4.3.8</a></span>
+ standard object</h1>
+
+ <p>object whose semantics are defined by this specification</p>
+ </section>
+
+ <section id="sec-built-in-object">
+ <h1><span class="secnum" id="sec-4.3.9"><a href="#sec-built-in-object" title="link to this section">4.3.9</a></span>
+ built-in object</h1>
+
+ <p>object specified and supplied by an ECMAScript implementation</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Standard built-in objects are defined in this specification. An ECMAScript implementation
+ may specify and supply additional kinds of built-in objects. A <i>built-in constructor</i> is a built-in object that is
+ also a constructor.</p>
+ </div>
+ </section>
+
+ <section id="sec-undefined-value">
+ <h1><span class="secnum" id="sec-4.3.10"><a href="#sec-undefined-value" title="link to this section">4.3.10</a></span>
+ undefined value</h1>
+
+ <p>primitive value used when a variable has not been assigned a value</p>
+ </section>
+
+ <section id="sec-terms-and-definitions-undefined-type">
+ <h1><span class="secnum" id="sec-4.3.11"><a href="#sec-terms-and-definitions-undefined-type"
+ title="link to this section">4.3.11</a></span> Undefined type</h1>
+
+ <p>type whose sole value is the <b>undefined</b> value</p>
+ </section>
+
+ <section id="sec-null-value">
+ <h1><span class="secnum" id="sec-4.3.12"><a href="#sec-null-value" title="link to this section">4.3.12</a></span> null
+ value</h1>
+
+ <p>primitive value that represents the intentional absence of any object value</p>
+ </section>
+
+ <section id="sec-terms-and-definitions-null-type">
+ <h1><span class="secnum" id="sec-4.3.13"><a href="#sec-terms-and-definitions-null-type"
+ title="link to this section">4.3.13</a></span> Null type</h1>
+
+ <p>type whose sole value is the null value</p>
+ </section>
+
+ <section id="sec-terms-and-definitions-boolean-value">
+ <h1><span class="secnum" id="sec-4.3.14"><a href="#sec-terms-and-definitions-boolean-value"
+ title="link to this section">4.3.14</a></span> Boolean value</h1>
+
+ <p>member of the Boolean type</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> There are only two Boolean values, <b>true</b> and <b>false</b></p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-boolean-type">
+ <h1><span class="secnum" id="sec-4.3.15"><a href="#sec-terms-and-definitions-boolean-type"
+ title="link to this section">4.3.15</a></span> Boolean type</h1>
+
+ <p>type consisting of the primitive values <b>true</b> and <b>false</b></p>
+ </section>
+
+ <section id="sec-boolean-object">
+ <h1><span class="secnum" id="sec-4.3.16"><a href="#sec-boolean-object" title="link to this section">4.3.16</a></span>
+ Boolean object</h1>
+
+ <p>member of the Object type that is an instance of the standard built-in <code>Boolean</code> constructor</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A Boolean object is created by using the <code>Boolean</code> constructor in a
+ <code>new</code> expression, supplying a Boolean value as an argument. The resulting object has an <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value is the Boolean value. A Boolean
+ object can be coerced to a Boolean value.</p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-string-value">
+ <h1><span class="secnum" id="sec-4.3.17"><a href="#sec-terms-and-definitions-string-value"
+ title="link to this section">4.3.17</a></span> String value</h1>
+
+ <p>primitive value that is a finite ordered sequence of zero or more 16-bit unsigned integer</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A String value is a member of the String type. Each integer value in the sequence usually
+ represents a single 16-bit unit of UTF-16 text. However, ECMAScript does not place any restrictions or requirements on the
+ values except that they must be 16-bit unsigned integers.</p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-string-type">
+ <h1><span class="secnum" id="sec-4.3.18"><a href="#sec-terms-and-definitions-string-type"
+ title="link to this section">4.3.18</a></span> String type</h1>
+
+ <p>set of all possible String values</p>
+ </section>
+
+ <section id="sec-string-object">
+ <h1><span class="secnum" id="sec-4.3.19"><a href="#sec-string-object" title="link to this section">4.3.19</a></span> String
+ object</h1>
+
+ <p>member of the Object type that is an instance of the standard built-in <code>String</code> constructor</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A String object is created by using the <code>String</code> constructor in a
+ <code>new</code> expression, supplying a String value as an argument. The resulting object has an <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value is the String value. A String object
+ can be coerced to a String value by calling the <code>String</code> constructor as a function (<a
+ href="#sec-string-constructor-string-value">21.1.1.1</a>).</p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-number-value">
+ <h1><span class="secnum" id="sec-4.3.20"><a href="#sec-terms-and-definitions-number-value"
+ title="link to this section">4.3.20</a></span> Number value</h1>
+
+ <p>primitive value corresponding to a double-precision 64-bit binary format IEEE 754 value</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A Number value is a member of the Number type and is a direct representation of a
+ number.</p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-number-type">
+ <h1><span class="secnum" id="sec-4.3.21"><a href="#sec-terms-and-definitions-number-type"
+ title="link to this section">4.3.21</a></span> Number type</h1>
+
+ <p>set of all possible Number values including the special “Not-a-Number” (NaN) value, positive infinity, and
+ negative infinity</p>
+ </section>
+
+ <section id="sec-number-object">
+ <h1><span class="secnum" id="sec-4.3.22"><a href="#sec-number-object" title="link to this section">4.3.22</a></span> Number
+ object</h1>
+
+ <p>member of the Object type that is an instance of the standard built-in <code>Number</code> constructor</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A Number object is created by using the <code>Number</code> constructor in a
+ <code>new</code> expression, supplying a Number value as an argument. The resulting object has an <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value is the Number value. A Number object
+ can be coerced to a Number value by calling the <code>Number</code> constructor as a function (<a
+ href="#sec-number-constructor-number-value">20.1.1.1</a>).</p>
+ </div>
+ </section>
+
+ <section id="sec-terms-and-definitions-infinity">
+ <h1><span class="secnum" id="sec-4.3.23"><a href="#sec-terms-and-definitions-infinity"
+ title="link to this section">4.3.23</a></span> Infinity</h1>
+
+ <p>number value that is the positive infinite Number value</p>
+ </section>
+
+ <section id="sec-terms-and-definitions-nan">
+ <h1><span class="secnum" id="sec-4.3.24"><a href="#sec-terms-and-definitions-nan"
+ title="link to this section">4.3.24</a></span> NaN</h1>
+
+ <p>number value that is an IEEE 754 “Not-a-Number” value</p>
+ </section>
+
+ <section id="sec-symbol-value">
+ <h1><span class="secnum" id="sec-4.3.25"><a href="#sec-symbol-value" title="link to this section">4.3.25</a></span> Symbol
+ value</h1>
+
+ <p>primitive value that represents a unique, non-String Object <a href="#sec-object-type">property key</a></p>
+ </section>
+
+ <section id="sec-terms-and-definitions-symbol-type">
+ <h1><span class="secnum" id="sec-4.3.26"><a href="#sec-terms-and-definitions-symbol-type"
+ title="link to this section">4.3.26</a></span> Symbol type</h1>
+
+ <p>set of all possible Symbol values</p>
+ </section>
+
+ <section id="sec-symbol-object">
+ <h1><span class="secnum" id="sec-4.3.27"><a href="#sec-symbol-object" title="link to this section">4.3.27</a></span> Symbol
+ object</h1>
+
+ <p>member of the Object type that is an instance of the standard built-in <code>Symbol</code> constructor</p>
+ </section>
+
+ <section id="sec-terms-and-definitions-function">
+ <h1><span class="secnum" id="sec-4.3.28"><a href="#sec-terms-and-definitions-function"
+ title="link to this section">4.3.28</a></span> function</h1>
+
+ <p>member of the Object type that may be invoked as a subroutine</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In addition to its properties, a function contains executable code and state that
+ determine how it behaves when invoked. A function’s code may or may not be written in ECMAScript.</p>
+ </div>
+ </section>
+
+ <section id="sec-built-in-function">
+ <h1><span class="secnum" id="sec-4.3.29"><a href="#sec-built-in-function" title="link to this section">4.3.29</a></span>
+ built-in function</h1>
+
+ <p>built-in object that is a function</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Examples of built-in functions include <code>parseInt</code> and <code><a
+ href="#sec-math.exp">Math.exp</a></code>. An implementation may provide implementation-dependent built-in functions that
+ are not described in this specification.</p>
+ </div>
+ </section>
+
+ <section id="sec-property">
+ <h1><span class="secnum" id="sec-4.3.30"><a href="#sec-property" title="link to this section">4.3.30</a></span>
+ property</h1>
+
+ <p>association between a key and a value that is a part of an object. The key be either a String value or a Symbol value</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Depending upon the form of the property the value may be represented either directly as a
+ data value (a primitive value, an object, or a function object) or indirectly by a pair of accessor functions.</p>
+ </div>
+ </section>
+
+ <section id="sec-method">
+ <h1><span class="secnum" id="sec-4.3.31"><a href="#sec-method" title="link to this section">4.3.31</a></span> method</h1>
+
+ <p>function that is the value of a property</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When a function is called as a method of an object, the object is passed to the function
+ as its <b>this</b> value.</p>
+ </div>
+ </section>
+
+ <section id="sec-built-in-method">
+ <h1><span class="secnum" id="sec-4.3.32"><a href="#sec-built-in-method" title="link to this section">4.3.32</a></span>
+ built-in method</h1>
+
+ <p>method that is a built-in function</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Standard built-in methods are defined in this specification, and an ECMAScript
+ implementation may specify and provide other additional built-in methods.</p>
+ </div>
+ </section>
+
+ <section id="sec-attribute">
+ <h1><span class="secnum" id="sec-4.3.33"><a href="#sec-attribute" title="link to this section">4.3.33</a></span>
+ attribute</h1>
+
+ <p>internal value that defines some characteristic of a property</p>
+ </section>
+
+ <section id="sec-own-property">
+ <h1><span class="secnum" id="sec-4.3.34"><a href="#sec-own-property" title="link to this section">4.3.34</a></span> own
+ property</h1>
+
+ <p>property that is directly contained by its object</p>
+ </section>
+
+ <section id="sec-inherited-property">
+ <h1><span class="secnum" id="sec-4.3.35"><a href="#sec-inherited-property" title="link to this section">4.3.35</a></span>
+ inherited property</h1>
+
+ <p>property of an object that is not an own property but is a property (either own or inherited) of the object’s
+ prototype</p>
+ </section>
+ </section>
+
+ <section id="sec-organization-of-this-specification">
+ <h1><span class="secnum" id="sec-4.4"><a href="#sec-organization-of-this-specification"
+ title="link to this section">4.4</a></span> Organization of This Specification</h1>
+
+ <p>The remainder of this specification is organized as follows:</p>
+
+ <p>Clause 5 defines the notational conventions used throughout the specification.</p>
+
+ <p>Clauses 6−9 define the execution environment within which ECMAScript programs operate.</p>
+
+ <p>Clauses 10−16 define the actual ECMAScript programming language including its syntactic encoding and the execution
+ semantics of all language features.</p>
+
+ <p>Clauses 17−26 define the ECMAScript standard library. It includes the definitions of all of the standard objects that
+ are available for use by ECMAScript programs as they execute.</p>
+ </section>
+</section>
+
+<section id="sec-notational-conventions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-5"><a href="#sec-notational-conventions" title="link to this section">5</a></span> Notational
+ Conventions</h1>
+ </div>
+
+ <section id="sec-syntactic-and-lexical-grammars">
+ <div class="front">
+ <h1><span class="secnum" id="sec-5.1"><a href="#sec-syntactic-and-lexical-grammars"
+ title="link to this section">5.1</a></span> Syntactic and Lexical Grammars</h1>
+ </div>
+
+ <section id="sec-context-free-grammars">
+ <h1><span class="secnum" id="sec-5.1.1"><a href="#sec-context-free-grammars" title="link to this section">5.1.1</a></span>
+ Context-Free Grammars</h1>
+
+ <p>A <i>context-free grammar</i> consists of a number of <i>productions</i>. Each production has an abstract symbol called a
+ <i>nonterminal</i> as its <i>left-hand side</i>, and a sequence of zero or more nonterminal and <i>terminal</i> symbols as
+ its <i>right-hand side</i>. For each grammar, the terminal symbols are drawn from a specified alphabet.</p>
+
+ <p>A <i>chain production</i> is a production that has exactly one nonterminal symbol on its right-hand side along with zero
+ or more terminal symbols.</p>
+
+ <p>Starting from a sentence consisting of a single distinguished nonterminal, called the <i>goal symbol</i>, a given
+ context-free grammar specifies a <i>language</i>, namely, the (perhaps infinite) set of possible sequences of terminal
+ symbols that can result from repeatedly replacing any nonterminal in the sequence with a right-hand side of a production for
+ which the nonterminal is the left-hand side.</p>
+ </section>
+
+ <section id="sec-lexical-and-regexp-grammars">
+ <h1><span class="secnum" id="sec-5.1.2"><a href="#sec-lexical-and-regexp-grammars"
+ title="link to this section">5.1.2</a></span> The Lexical and RegExp Grammars</h1>
+
+ <p>A <i>lexical grammar</i> for ECMAScript is given in <a href="#sec-ecmascript-language-lexical-grammar">clause 11</a>.
+ This grammar has as its terminal symbols Unicode code points that conform to the rules for <span
+ class="nt">SourceCharacter</span> defined in <a href="#sec-source-text">10.1</a>. It defines a set of productions, starting
+ from the goal symbol <var>InputElementDiv,</var> <var>InputElementTemplateTail,</var> or <span
+ class="nt">InputElementRegExp</span>, that describe how sequences of such code points are translated into a sequence of
+ input elements.</p>
+
+ <p>Input elements other than white space and comments form the terminal symbols for the syntactic grammar for ECMAScript and
+ are called ECMAScript <i>tokens</i>. These tokens are the reserved words, identifiers, literals, and punctuators of the
+ ECMAScript language. Moreover, line terminators, although not considered to be tokens, also become part of the stream of
+ input elements and guide the process of <a href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a> (<a
+ href="#sec-automatic-semicolon-insertion">11.9</a>). Simple white space and single-line comments are discarded and do not
+ appear in the stream of input elements for the syntactic grammar. A <span class="nt">MultiLineComment</span> (that is, a
+ comment of the form “<code>/*</code>…<code>*/</code>” regardless of whether it spans more than one line)
+ is likewise simply discarded if it contains no line terminator; but if a <span class="nt">MultiLineComment</span> contains
+ one or more line terminators, then it is replaced by a single line terminator, which becomes part of the stream of input
+ elements for the syntactic grammar.</p>
+
+ <p>A <i>RegExp grammar</i> for ECMAScript is given in <a href="#sec-patterns">21.2.1</a>. This grammar also has as its
+ terminal symbols the code points as defined by <span class="nt">SourceCharacter</span>. It defines a set of productions,
+ starting from the goal symbol <span class="nt">Pattern</span>, that describe how sequences of code points are translated
+ into regular expression patterns.</p>
+
+ <p>Productions of the lexical and RegExp grammars are distinguished by having two colons “<b>::</b>” as
+ separating punctuation. The lexical and RegExp grammars share some productions.</p>
+ </section>
+
+ <section id="sec-numeric-string-grammar">
+ <h1><span class="secnum" id="sec-5.1.3"><a href="#sec-numeric-string-grammar" title="link to this section">5.1.3</a></span>
+ The Numeric String Grammar</h1>
+
+ <p>Another grammar is used for translating Strings into numeric values. This grammar is similar to the part of the lexical
+ grammar having to do with numeric literals and has as its terminal symbols <span class="nt">SourceCharacter</span>. This
+ grammar appears in <a href="#sec-tonumber-applied-to-the-string-type">7.1.3.1</a>.</p>
+
+ <p>Productions of the numeric string grammar are distinguished by having three colons “<b>:::</b>” as
+ punctuation.</p>
+ </section>
+
+ <section id="sec-syntactic-grammar">
+ <h1><span class="secnum" id="sec-5.1.4"><a href="#sec-syntactic-grammar" title="link to this section">5.1.4</a></span> The
+ Syntactic Grammar</h1>
+
+ <p>The <i>syntactic grammar</i> for ECMAScript is given in clauses 11, 12, 13, 14, and 15. This grammar has ECMAScript
+ tokens defined by the lexical grammar as its terminal symbols (<a href="#sec-lexical-and-regexp-grammars">5.1.2</a>). It
+ defines a set of productions, starting from two alternative goal symbols <span class="nt">Script</span> and <span
+ class="nt">Module</span>, that describe how sequences of tokens form syntactically correct independent components of
+ ECMAScript programs.</p>
+
+ <p>When a stream of code points is to be parsed as an ECMAScript <span class="nt">Script</span> or <span
+ class="nt">Module</span>, it is first converted to a stream of input elements by repeated application of the lexical
+ grammar; this stream of input elements is then parsed by a single application of the syntactic grammar. The input stream is
+ syntactically in error if the tokens in the stream of input elements cannot be parsed as a single instance of the goal
+ nonterminal (<span class="nt">Script</span> or <span class="nt">Module</span>), with no tokens left over.</p>
+
+ <p>Productions of the syntactic grammar are distinguished by having just one colon “<b>:</b>” as
+ punctuation.</p>
+
+ <p>The syntactic grammar as presented in clauses 12, 13, 14 and 15 is not a complete account of which token sequences are
+ accepted as a correct ECMAScript <span class="nt">Script</span> or <span class="nt">Module</span>. Certain additional token
+ sequences are also accepted, namely, those that would be described by the grammar if only semicolons were added to the
+ sequence in certain places (such as before line terminator characters). Furthermore, certain token sequences that are
+ described by the grammar are not considered acceptable if a line terminator character appears in certain
+ “awkward” places.</p>
+
+ <p>In certain cases in order to avoid ambiguities the syntactic grammar uses generalized productions that permit token
+ sequences that do not form a valid ECMAScript <span class="nt">Script</span> or <span class="nt">Module</span>. For example,
+ this technique is used for object literals and object destructuring patterns. In such cases a more restrictive
+ <i>supplemental grammar</i> is provided that further restricts the acceptable token sequences. In certain contexts, when
+ explicitly specific, the input elements corresponding to such a production are parsed again using a goal symbol of a
+ supplemental grammar. The input stream is syntactically in error if the tokens in the stream of input elements parsed by a
+ cover grammar cannot be parsed as a single instance of the corresponding supplemental goal symbol, with no tokens left
+ over.</p>
+ </section>
+
+ <section id="sec-grammar-notation">
+ <h1><span class="secnum" id="sec-5.1.5"><a href="#sec-grammar-notation" title="link to this section">5.1.5</a></span>
+ Grammar Notation</h1>
+
+ <p>Terminal symbols of the lexical, RegExp, and numeric string grammars are shown in <code>fixed width</code> font, both in
+ the productions of the grammars and throughout this specification whenever the text directly refers to such a terminal
+ symbol. These are to appear in a script exactly as written. All terminal symbol code points specified in this way are to be
+ understood as the appropriate Unicode code points from the Basic Latin range, as opposed to any similar-looking code points
+ from other Unicode ranges.</p>
+
+ <p>Nonterminal symbols are shown in <var>italic</var> type. The definition of a nonterminal (also called a
+ “production”) is introduced by the name of the nonterminal being defined followed by one or more colons. (The
+ number of colons indicates to which grammar the production belongs.) One or more alternative right-hand sides for the
+ nonterminal then follow on succeeding lines. For example, the syntactic definition:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">WhileStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <p>states that the nonterminal <span class="nt">WhileStatement</span> represents the token <code>while</code>, followed by a
+ left parenthesis token, followed by an <span class="nt">Expression</span>, followed by a right parenthesis token, followed
+ by a <span class="nt">Statement</span>. The occurrences of <span class="nt">Expression</span> and <span
+ class="nt">Statement</span> are themselves nonterminals. As another example, the syntactic definition:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArgumentList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AssignmentExpression</span></div>
+ <div class="rhs"><span class="nt">ArgumentList</span> <code class="t">,</code> <span class="nt">AssignmentExpression</span></div>
+ </div>
+
+ <p>states that an <span class="nt">ArgumentList</span> may represent either a single <span
+ class="nt">AssignmentExpression</span> or an <span class="nt">ArgumentList</span>, followed by a comma, followed by an <span
+ class="nt">AssignmentExpression</span>. This definition of <span class="nt">ArgumentList</span> is recursive, that is, it is
+ defined in terms of itself. The result is that an <span class="nt">ArgumentList</span> may contain any positive number of
+ arguments, separated by commas, where each argument expression is an <span class="nt">AssignmentExpression</span>. Such
+ recursive definitions of nonterminals are common.</p>
+
+ <p>The subscripted suffix “<sub>opt</sub>”, which may appear after a terminal or nonterminal, indicates an
+ optional symbol. The alternative containing the optional symbol actually specifies two right-hand sides, one that omits the
+ optional element and one that includes it. This means that:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ </div>
+
+ <p>is a convenient abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span></div>
+ </div>
+
+ <p>and that:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <p>is a convenient abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <p>which in turn is an abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <code class="t">;</code> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <code class="t">;</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span> <code class="t">;</code> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span> <code class="t">;</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <p>so, in this example, the nonterminal <span class="nt">IterationStatement</span> actually has four alternative right-hand
+ sides.</p>
+
+ <p>A production may be parameterized by a subscripted annotation of the form “<sub>[parameters]</sub>”, which
+ may appear as a suffix to the nonterminal symbol defined by the production. “<sub>parameters</sub>” may be
+ either a single name or a comma separated list of names. A parameterized production is shorthand for a set of productions
+ defining all combinations of the parameter names, preceded by an underscore, appended to the parameterized nonterminal
+ symbol. This means that:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span><sub>[Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>is a convenient abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList_Return</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>and that:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span><sub>[Return, In]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>is an abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList_Return</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList_In</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList_Return_In</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>Multiple parameters produce a combinatory number of productions, not all of which are necessarily referenced in a
+ complete grammar.</p>
+
+ <p>References to nonterminals on the right-hand side of a production can also be parameterized. For example:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span><sub>[In]</sub></div>
+ </div>
+
+ <p>is equivalent to saying:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement_In</span></div>
+ </div>
+
+ <p>A nonterminal reference may have both a parameter list and an “<sub>opt</sub>” suffix. For example:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>[In]</sub><sub>opt</sub></div>
+ </div>
+
+ <p>is an abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span> <span class="nt">Initializer_In</span></div>
+ </div>
+
+ <p>Prefixing a parameter name with “<sub>?</sub>” on a right-hand side nonterminal reference makes that
+ parameter value dependent upon the occurrence of the parameter name on the reference to the current production’s
+ left-hand side symbol. For example:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration</span><sub>[In]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>[?In]</sub></div>
+ </div>
+
+ <p>is an abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration_In</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span> <span class="nt">Initializer_In</span></div>
+ </div>
+
+ <p>If a right-hand side alternative is prefixed with “[+parameter]” that alternative is only available if the
+ named parameter was used in referencing the production’s nonterminal symbol. If a right-hand side alternative is
+ prefixed with “[~parameter]” that alternative is only available if the named parameter was <i>not</i> used in
+ referencing the production’s nonterminal symbol. This means that:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span><sub>[Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[+Return]</span> <span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>is an abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList_Return</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>and that</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span><sub>[Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[~Return]</span> <span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>is an abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList_Return</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ </div>
+
+ <p>When the words “<b>one of</b>” follow the colon(s) in a grammar definition, they signify that each of the
+ terminal symbols on the following line or lines is an alternative definition. For example, the lexical grammar for
+ ECMAScript contains the production:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonZeroDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <p>which is merely a convenient abbreviation for:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonZeroDigit</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">1</code></div>
+ <div class="rhs"><code class="t">2</code></div>
+ <div class="rhs"><code class="t">3</code></div>
+ <div class="rhs"><code class="t">4</code></div>
+ <div class="rhs"><code class="t">5</code></div>
+ <div class="rhs"><code class="t">6</code></div>
+ <div class="rhs"><code class="t">7</code></div>
+ <div class="rhs"><code class="t">8</code></div>
+ <div class="rhs"><code class="t">9</code></div>
+ </div>
+
+ <p>If the phrase “[empty]” appears as the right-hand side of a production, it indicates that the production's
+ right-hand side contains no terminals or nonterminals.</p>
+
+ <p>If the phrase “[lookahead ∉ <var>set</var>]” appears in the right-hand side of a production, it
+ indicates that the production may not be used if the immediately following input token is a member of the given
+ <var>set</var>. The <var>set</var> can be written as a list of terminals enclosed in curly brackets. For convenience, the
+ set can also be written as a nonterminal, in which case it represents the set of all terminals to which that nonterminal
+ could expand. If the <var>set</var> consists of a single terminal the phrase “[lookahead ≠
+ <var>terminal</var>]” may be used.</p>
+
+ <p>For example, given the definitions</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalDigits</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <span class="nt">DecimalDigit</span></div>
+ </div>
+
+ <p>the definition</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LookaheadExample</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">n</code> <span class="grhsannot">[lookahead ∉ {<code class="t">1</code>, <code class="t">3</code>, <code class="t">5</code>, <code class="t">7</code>, <code class="t">9</code>}]</span> <span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span> <span class="grhsannot">[lookahead ∉ <span class="nt">DecimalDigit</span>]</span></div>
+ </div>
+
+ <p>matches either the letter <code>n</code> followed by one or more decimal digits the first of which is even, or a decimal
+ digit not followed by another decimal digit.</p>
+
+ <p>If the phrase “[no <span class="nt">LineTerminator</span> here]” appears in the right-hand side of a
+ production of the syntactic grammar, it indicates that the production is <i>a restricted production</i>: it may not be used
+ if a <span class="nt">LineTerminator</span> occurs in the input stream at the indicated position. For example, the
+ production:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ThrowStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">throw</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span> <code class="t">;</code></div>
+ </div>
+
+ <p>indicates that the production may not be used if a <span class="nt">LineTerminator</span> occurs in the script between
+ the <code>throw</code> token and the <span class="nt">Expression</span>.</p>
+
+ <p>Unless the presence of a <span class="nt">LineTerminator</span> is forbidden by a restricted production, any number of
+ occurrences of <span class="nt">LineTerminator</span> may appear between any two consecutive tokens in the stream of input
+ elements without affecting the syntactic acceptability of the script.</p>
+
+ <p>When an alternative in a production of the lexical grammar or the numeric string grammar appears to be a multi-code point
+ token, it represents the sequence of code points that would make up such a token.</p>
+
+ <p>The right-hand side of a production may specify that certain expansions are not permitted by using the phrase
+ “<b>but not</b>” and then indicating the expansions to be excluded. For example, the production:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Identifier</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <span class="grhsmod">but not</span> <span class="nt">ReservedWord</span></div>
+ </div>
+
+ <p>means that the nonterminal <span class="nt">Identifier</span> may be replaced by any sequence of code points that could
+ replace <span class="nt">IdentifierName</span> provided that the same sequence of code points could not replace <span
+ class="nt">ReservedWord</span>.</p>
+
+ <p>Finally, a few nonterminal symbols are described by a descriptive phrase in sans-serif type in cases where it would be
+ impractical to list all the alternatives:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SourceCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="gprose">any Unicode code point</span></div>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-algorithm-conventions">
+ <h1><span class="secnum" id="sec-5.2"><a href="#sec-algorithm-conventions" title="link to this section">5.2</a></span>
+ Algorithm Conventions</h1>
+
+ <p>The specification often uses a numbered list to specify steps in an algorithm. These algorithms are used to precisely
+ specify the required semantics of ECMAScript language constructs. The algorithms are not intended to imply the use of any
+ specific implementation technique. In practice, there may be more efficient algorithms available to implement a given
+ feature.</p>
+
+ <p>Algorithms may be explicitly parameterized, in which case the names and usage of the parameters must be provided as part of
+ the algorithm’s definition. In order to facilitate their use in multiple parts of this specification, some algorithms,
+ called <i>abstract</i> <i>operations</i>, are named and written in parameterized functional form so that they may be
+ referenced by name from within other algorithms. Abstract operations are typically referenced using a functional application
+ style such as <span style="font-family: Times New Roman">operationName(<i>arg1</i>, <i>arg2</i>)</span>. Some abstract
+ operations are treated as polymorphically dispatched methods of class-like specification abstractions. Such method-like
+ abstract operations are typically referenced using a method application style such as <span style="font-family: Times New
+ Roman"><i>someValue</i>.operationName(<i>arg1</i>, <i>arg2</i>)</span>.</p>
+
+ <p>Algorithms may be associated with productions of one of the ECMAScript grammars. A production that has multiple alternative
+ definitions will typically have a distinct algorithm for each alternative. When an algorithm is associated with a grammar
+ production, it may reference the terminal and nonterminal symbols of the production alternative as if they were parameters of
+ the algorithm. When used in this manner, nonterminal symbols refer to the actual alternative definition that is matched when
+ parsing the source text.</p>
+
+ <p>When an algorithm is associated with a production alternative, the alternative is typically shown without any “[
+ ]” grammar annotations. Such annotations should only affect the syntactic recognition of the alternative and have no
+ effect on the associated semantics for the alternative.</p>
+
+ <p>Unless explicitly specified otherwise, all <a href="#sec-context-free-grammars">chain productions</a> have an implicit
+ definition for every algorithm that might be applied to that production’s left-hand side nonterminal. The implicit
+ definition simply reapplies the same algorithm name with the same parameters, if any, to the <a
+ href="#sec-context-free-grammars">chain production</a>’s sole right-hand side nonterminal and then returns the result.
+ For example, assume there is a production:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Block</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">StatementList</span> <code class="t">}</code></div>
+ </div>
+
+ <p>but there is no corresponding Evaluation algorithm that is explicitly specified for that production. If in some algorithm
+ there is a statement of the form: “<span style="font-family: Times New Roman">Return the result of evaluating
+ <i>Block</i></span>” it is implicit that an Evaluation algorithm exists of the form:</p>
+
+ <p><b>Runtime Semantics: Evaluation</b></p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">StatementList</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>StatementList</i>.</li>
+ </ol>
+
+ <p>For clarity of expression, algorithm steps may be subdivided into sequential substeps. Substeps are indented and may
+ themselves be further divided into indented substeps. Outline numbering conventions are used to identify substeps with the
+ first level of substeps labelled with lower case alphabetic characters and the second level of substeps labelled with lower
+ case roman numerals. If more than three levels are required these rules repeat with the fourth level using numeric labels. For
+ example:</p>
+
+ <ol class="proc">
+ <li>Top-level step
+ <ol class="block">
+ <li>Substep.</li>
+ <li>Substep.
+ <ol class="block">
+ <li>Subsubstep.
+ <ol class="block">
+ <li>Subsubsubstep
+ <ol class="block">
+ <li>Subsubsubsubstep
+ <ol class="block">
+ <li>Subsubsubsubsubstep</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>A step or substep may be written as an “if” predicate that conditions its substeps. In this case, the substeps
+ are only applied if the predicate is true. If a step or substep begins with the word “else”, it is a predicate
+ that is the negation of the preceding “if” predicate step at the same level.</p>
+
+ <p>A step may specify the iterative application of its substeps.</p>
+
+ <p>A step that begins with “Assert:” asserts an invariant condition of its algorithm. Such assertions are used to
+ make explicit algorithmic invariants that would otherwise be implicit. Such assertions add no additional semantic requirements
+ and hence need not be checked by an implementation. They are used simply to clarify algorithms.</p>
+
+ <p>Mathematical operations such as addition, subtraction, negation, multiplication, division, and the mathematical functions
+ defined later in this clause should always be understood as computing exact mathematical results on mathematical real numbers,
+ which unless otherwise noted do not include infinities and do not include a negative zero that is distinguished from positive
+ zero. Algorithms in this standard that model floating-point arithmetic include explicit steps, where necessary, to handle
+ infinities and signed zero and to perform rounding. If a mathematical operation or function is applied to a floating-point
+ number, it should be understood as being applied to the exact mathematical value represented by that floating-point number;
+ such a floating-point number must be finite, and if it is <span class="value">+0</span> or <span class="value">−0</span>
+ then the corresponding mathematical value is simply <span class="value">0</span>.</p>
+
+ <p>The mathematical function <span style="font-family: Times New Roman">abs(<i>x</i>)</span> produces the absolute value of
+ <var>x</var>, which is <span style="font-family: Times New Roman">−<i>x</i></span> if <var>x</var> is negative (less
+ than zero) and otherwise is <var>x</var> itself.</p>
+
+ <p>The mathematical function <span style="font-family: Times New Roman">sign(<i>x</i>)</span> produces <span
+ style="font-family: Times New Roman">1</span> if <var>x</var> is positive and <span style="font-family: Times New
+ Roman">−1</span> if <var>x</var> is negative. The sign function is not used in this standard for cases when <var>x</var>
+ is zero.</p>
+
+ <p>The mathematical function <span style="font-family: Times New Roman">min(<i>x</i><sub>1</sub>,</span> <span
+ style="font-family: Times New Roman"><i>x</i><sub>2</sub>, ..., <i>x</i><sub>n</sub>)</span> produces the mathematically
+ smallest of <span style="font-family: Times New Roman"><i>x</i><sub>1</sub></span> through <span style="font-family: Times New
+ Roman"><i>x</i><sub>n</sub></span>. The mathematical function <span style="font-family: Times New
+ Roman">max(<i>x</i><sub>1</sub>,</span> <span style="font-family: Times New Roman"><i>x</i><sub>2</sub>, ...,
+ <i>x</i><sub>n</sub>)</span> produces the mathematically largest of <span style="font-family: Times New
+ Roman"><i>x</i><sub>1</sub></span> through <span style="font-family: Times New Roman"><i>x</i><sub>n</sub></span>. The domains
+ and range of theses mathematical functions include +<b>∞</b> and <b>−∞</b>.</p>
+
+ <p>The notation “<span style="font-family: Times New Roman"><i>x</i> modulo <i>y</i></span>” (<var>y</var> must be
+ finite and nonzero) computes a value <var>k</var> of the same sign as <var>y</var> (or zero) such that <span
+ style="font-family: Times New Roman">abs(<i>k</i>) < abs(<i>y</i>) and <i>x</i>−<i>k</i> = <i>q</i></span> <span
+ style="font-family: Times New Roman">×</span> <var>y</var> for some integer <var>q</var>.</p>
+
+ <p>The mathematical function <span style="font-family: Times New Roman">floor(<i>x</i>)</span> produces the largest integer
+ (closest to positive infinity) that is not larger than <var>x</var>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> floor(<i>x</i>) = <i>x</i>−(<i>x</i> modulo 1).</p>
+ </div>
+ </section>
+
+ <section id="sec-static-semantic-rules">
+ <h1><span class="secnum" id="sec-5.3"><a href="#sec-static-semantic-rules" title="link to this section">5.3</a></span> Static
+ Semantic Rules</h1>
+
+ <p>Context-free grammars are not sufficiently powerful to express all the rules that define whether a stream of input elements
+ form a valid ECMAScript <span class="nt">Script</span> or <span class="nt">Module</span> that may be evaluated. In some
+ situations additional rules are needed that may be expressed using either ECMAScript algorithm conventions or prose
+ requirements. Such rules are always associated with a production of a grammar and are called the <i>static semantics</i> of
+ the production.</p>
+
+ <p>Static Semantic Rules have names and typically are defined using an algorithm. Named Static Semantic Rules are associated
+ with grammar productions and a production that has multiple alternative definitions will typically have for each alternative a
+ distinct algorithm for each applicable named static semantic rule.</p>
+
+ <p>Unless otherwise specified every grammar production alternative in this specification implicitly has a definition for a
+ static semantic rule named <span style="font-family: Times New Roman">Contains</span> which takes an argument named
+ <var>symbol</var> whose value is a terminal or nonterminal of the grammar that includes the associated production. The default
+ definition of <span style="font-family: Times New Roman">Contains</span> is:</p>
+
+ <ol class="proc">
+ <li>For each terminal and nonterminal grammar symbol, <i>sym</i>, in the definition of this production do
+ <ol class="block">
+ <li>If <i>sym</i> is the same grammar symbol as <i>symbol</i>, return <b>true</b>.</li>
+ <li>If <i>sym</i> is a nonterminal, then
+ <ol class="block">
+ <li>Let <i>contained</i> be the result of <i>sym</i> Contains <i>symbol</i>.</li>
+ <li>If <i>contained</i> is <b>true</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <p>The above definition is explicitly over-ridden for specific productions.</p>
+
+ <p>A special kind of static semantic rule is an Early Error Rule. Early error rules define early error conditions (see <a
+ href="#sec-error-handling-and-language-extensions">clause 16</a>) that are associated with specific grammar productions.
+ Evaluation of most early error rules are not explicitly invoked within the algorithms of this specification. A conforming
+ implementation must, prior to the first evaluation of a <span class="nt">Script</span>, validate all of the early error rules
+ of the productions used to parse that <span class="nt">Script</span>. If any of the early error rules are violated the <span
+ class="nt">Script</span> is invalid and cannot be evaluated.</p>
+ </section>
+</section>
+
+<section id="sec-ecmascript-data-types-and-values">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6"><a href="#sec-ecmascript-data-types-and-values" title="link to this section">6</a></span>
+ ECMAScript Data Types and Values</h1>
+
+ <p>Algorithms within this specification manipulate values each of which has an associated type. The possible value types are
+ exactly those defined in this clause. Types are further subclassified into ECMAScript language types and specification
+ types.</p>
+
+ <p>Within this specification, the notation “<span style="font-family: Times New Roman">Type(<i>x</i>)</span>” is
+ used as shorthand for “<span style="font-family: Times New Roman">the type of <i>x</i></span>” where “<span
+ style="font-family: Times New Roman">type</span>” refers to the ECMAScript language and specification types defined in
+ this clause. When the term “empty” is used as if it was naming a value, it is equivalent to saying “no value
+ of any type”.</p>
+ </div>
+
+ <section id="sec-ecmascript-language-types">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.1"><a href="#sec-ecmascript-language-types" title="link to this section">6.1</a></span>
+ ECMAScript Language Types</h1>
+
+ <p>An ECMAScript language type corresponds to values that are directly manipulated by an ECMAScript programmer using the
+ ECMAScript language. The ECMAScript language types are Undefined, Null, Boolean, String, Symbol, Number, and Object. An
+ ECMAScript language value is a value that is characterized by an ECMAScript language type.</p>
+ </div>
+
+ <section id="sec-ecmascript-language-types-undefined-type">
+ <h1><span class="secnum" id="sec-6.1.1"><a href="#sec-ecmascript-language-types-undefined-type"
+ title="link to this section">6.1.1</a></span> The Undefined Type</h1>
+
+ <p>The Undefined type has exactly one value, called <b>undefined</b>. Any variable that has not been assigned a value has
+ the value <b>undefined</b>.</p>
+ </section>
+
+ <section id="sec-ecmascript-language-types-null-type">
+ <h1><span class="secnum" id="sec-6.1.2"><a href="#sec-ecmascript-language-types-null-type"
+ title="link to this section">6.1.2</a></span> The Null Type</h1>
+
+ <p>The Null type has exactly one value, called <b>null</b>.</p>
+ </section>
+
+ <section id="sec-ecmascript-language-types-boolean-type">
+ <h1><span class="secnum" id="sec-6.1.3"><a href="#sec-ecmascript-language-types-boolean-type"
+ title="link to this section">6.1.3</a></span> The Boolean Type</h1>
+
+ <p>The Boolean type represents a logical entity having two values, called <b>true</b> and <b>false</b>.</p>
+ </section>
+
+ <section id="sec-ecmascript-language-types-string-type">
+ <h1><span class="secnum" id="sec-6.1.4"><a href="#sec-ecmascript-language-types-string-type"
+ title="link to this section">6.1.4</a></span> The String Type</h1>
+
+ <p>The String type is the set of all finite ordered sequences of zero or more 16-bit unsigned integer values
+ (“elements”). The String type is generally used to represent textual data in a running ECMAScript program, in
+ which case each element in the String is treated as a UTF-16 code unit value. Each element is regarded as occupying a
+ position within the sequence. These positions are indexed with nonnegative integers. The first element (if any) is at index
+ 0, the next element (if any) at index 1, and so on. The length of a String is the number of elements (i.e., 16-bit values)
+ within it. The empty String has length zero and therefore contains no elements.</p>
+
+ <p>Where ECMAScript operations interpret String values, each element is interpreted as a single UTF-16 code unit. However,
+ ECMAScript does not place any restrictions or requirements on the sequence of code units in a String value, so they may be
+ ill-formed when interpreted as UTF-16 code unit sequences. Operations that do not interpret String contents treat them as
+ sequences of undifferentiated 16-bit unsigned integers. The function <code><a
+ href="#sec-string.prototype.normalize">String.prototype.normalize</a></code> (<a href="#sec-string.prototype.normalize">see
+ 21.1.3.12</a>) can be used to normalize a string value, but no other operations normalized the strings upon which they
+ operate. Only operations that are explicitly specified to be language or locale sensitive produce language-sensitive
+ results.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The rationale behind this design was to keep the implementation of Strings as simple and
+ high-performing as possible. If ECMAScript source text is in Normalized Form C, string literals are guaranteed to also be
+ normalized, as long as they do not contain any Unicode escape sequences.</p>
+ </div>
+
+ <p>Some operations interpret String contents as UTF-16 encoded Unicode code points. In that case the interpretation is:</p>
+
+ <ul>
+ <li>
+ <p>A code unit in the range <span style="font-family: Times New Roman">0</span> to <span style="font-family: Times New
+ Roman">0xD7FF</span> or in the range <span style="font-family: Times New Roman">0xE000</span> to <span
+ style="font-family: Times New Roman">0xFFFF</span> is interpreted as a code point with the same value.</p>
+ </li>
+
+ <li>
+ <p>A sequence of two code units, where the first code unit <var>c1</var> is in the range <span style="font-family: Times
+ New Roman">0xD800</span> to <span style="font-family: Times New Roman">0xDBFF</span> and the second code unit
+ <var>c2</var> is in the range <span style="font-family: Times New Roman">0xDC00</span> to <span style="font-family:
+ Times New Roman">0xDFFF</span>, is a surrogate pair and is interpreted as a code point with the value (<var>c1</var> -
+ <span style="font-family: Times New Roman">0xD800</span>) × <span style="font-family: Times New
+ Roman">0x400</span> + (<var>c2</var> – <span style="font-family: Times New Roman">0xDC00</span>) + <span
+ style="font-family: Times New Roman">0x10000</span>.</p>
+ </li>
+
+ <li>
+ <p>A code unit that is in the range <span style="font-family: Times New Roman">0xD800</span> to <span
+ style="font-family: Times New Roman">0xDFFF</span>, but is not part of a surrogate pair, is interpreted as a code point
+ with the same value.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-ecmascript-language-types-symbol-type">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.1.5"><a href="#sec-ecmascript-language-types-symbol-type"
+ title="link to this section">6.1.5</a></span> The Symbol Type</h1>
+
+ <p>The Symbol type is the set of all non-String values that may be used as the key of an Object property (<a
+ href="#sec-object-type">6.1.7</a>).</p>
+
+ <p>Each possible Symbol value is unique and immutable.</p>
+
+ <p>Each Symbol value immutably holds an associated value called [[Description]] that is either <span
+ class="value">undefined</span> or a String value.</p>
+ </div>
+
+ <section id="sec-well-known-symbols">
+ <h1><span class="secnum" id="sec-6.1.5.1"><a href="#sec-well-known-symbols"
+ title="link to this section">6.1.5.1</a></span> Well-Known Symbols</h1>
+
+ <p>Well-known symbols are built-in Symbol values that are explicitly referenced by algorithms of this specification. They
+ are typically used as the keys of properties whose values serve as extension points of a specification algorithm. Unless
+ otherwise specified, well-known symbols values are shared by all Code Realms (<a href="#sec-code-realms">8.2</a>).</p>
+
+ <p>Within this specification a well-known symbol is referred to by using a notation of the form @@name, where
+ “name” is one of the values listed in <a href="#table-1">Table 1</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-1">Table 1</span>— Well-known Symbols</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Specification Name</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">[[Description]]</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value and Purpose</th>
+ </tr>
+ <tr>
+ <td>@@hasInstance</td>
+ <td><code>"Symbol.hasInstance"</code></td>
+ <td>A method that determines if a constructor object recognizes an object as one of the constructor’s instances. Called by the semantics of the <code>instanceof</code> operator.</td>
+ </tr>
+ <tr>
+ <td>@@isConcatSpreadable</td>
+ <td><code>"Symbol.isConcatSpreadable"</code></td>
+ <td>A Boolean valued property that if true indicates that an object should be flattened to its array elements by <code><a href="#sec-array.prototype.concat">Array.prototype.concat</a></code>.</td>
+ </tr>
+ <tr>
+ <td>@@iterator</td>
+ <td><code>"Symbol.iterator"</code></td>
+ <td>A method that returns the default Iterator for an object. Called by the semantics of the for-of statement.</td>
+ </tr>
+ <tr>
+ <td>@@match</td>
+ <td><code>"Symbol.match "</code></td>
+ <td>A regular expression method that matches the regular expression against a string. Called by the <code><a href="#sec-string.prototype.match">String.prototype.match</a></code> method.</td>
+ </tr>
+ <tr>
+ <td>@@replace</td>
+ <td><code>"Symbol.replace "</code></td>
+ <td>A regular expression method that replaces matched substrings of a string. Called by the <code><a href="#sec-string.prototype.replace">String.prototype.replace</a></code> method.</td>
+ </tr>
+ <tr>
+ <td>@@search</td>
+ <td><code>"Symbol.search"</code></td>
+ <td>A regular expression method that returns the index within a string that matches the regular expression. Called by the <code><a href="#sec-string.prototype.search">String.prototype.search</a></code> method.</td>
+ </tr>
+ <tr>
+ <td>@@species</td>
+ <td><code>"Symbol.species"</code></td>
+ <td>A function valued property that is the constructor function that is used to create derived objects.</td>
+ </tr>
+ <tr>
+ <td>@@split</td>
+ <td><code>"Symbol.split"</code></td>
+ <td>A regular expression method that splits a string at the indices that match the regular expression. Called by the <code><a href="#sec-string.prototype.split">String.prototype.split</a></code> method.</td>
+ </tr>
+ <tr>
+ <td>@@toPrimitive</td>
+ <td><code>"Symbol.toPrimitive"</code></td>
+ <td>A method that converts an object to a corresponding primitive value. Called by the <a href="#sec-toprimitive">ToPrimitive</a> abstract operation.</td>
+ </tr>
+ <tr>
+ <td>@@toStringTag</td>
+ <td><code>"Symbol.toStringTag"</code></td>
+ <td>A String valued property that is used in the creation of the default string description of an object. Accessed by the built-in method <code><a href="#sec-object.prototype.tostring">Object.prototype.toString</a></code>.</td>
+ </tr>
+ <tr>
+ <td>@@unscopables</td>
+ <td><code>"Symbol.unscopables"</code></td>
+ <td>An object valued property whose own property names are property names that are excluded from the <code>with</code> environment bindings of the associated object.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+
+ <section id="sec-ecmascript-language-types-number-type">
+ <h1><span class="secnum" id="sec-6.1.6"><a href="#sec-ecmascript-language-types-number-type"
+ title="link to this section">6.1.6</a></span> The Number Type</h1>
+
+ <p>The Number type has exactly <span style="font-family: Times New Roman">18437736874454810627</span> (that is, <span
+ style="font-family: Times New Roman">2<sup>64</sup>−2<sup>53</sup>+3</span>) values, representing the double-precision
+ 64-bit format IEEE 754 values as specified in the IEEE Standard for Binary Floating-Point Arithmetic, except that the <span
+ style="font-family: Times New Roman">9007199254740990</span> (that is, <span style="font-family: Times New
+ Roman">2<sup>53</sup>−2</span>) distinct “Not-a-Number” values of the IEEE Standard are represented in
+ ECMAScript as a single special <b>NaN</b> value. (Note that the <b>NaN</b> value is produced by the program expression
+ <code>NaN</code>.) In some implementations, external code might be able to detect a difference between various Not-a-Number
+ values, but such behaviour is implementation-dependent; to ECMAScript code, all NaN values are indistinguishable from each
+ other.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The bit pattern that might be observed in an ArrayBuffer (<a
+ href="#sec-arraybuffer-objects">see 24.1</a>) after a Number value has been stored into it is not necessarily the same as
+ the internal representation of that Number value used by the ECMAScript implementation.</p>
+ </div>
+
+ <p>There are two other special values, called <b>positive Infinity</b> and <b>negative Infinity</b>. For brevity, these
+ values are also referred to for expository purposes by the symbols <span class="value">+∞</span> and <span
+ class="value">−∞</span>, respectively. (Note that these two infinite Number values are produced by the program
+ expressions <code>+Infinity</code> (or simply <code>Infinity</code>) and <code>-Infinity</code>.)</p>
+
+ <p>The other <span style="font-family: Times New Roman">18437736874454810624</span> (that is, <span style="font-family:
+ Times New Roman">2<sup>64</sup>−2<sup>53</sup></span>) values are called the finite numbers. Half of these are
+ positive numbers and half are negative numbers; for every finite positive Number value there is a corresponding negative
+ value having the same magnitude.</p>
+
+ <p>Note that there is both a <b>positive zero</b> and a <b>negative zero</b>. For brevity, these values are also referred to
+ for expository purposes by the symbols <span class="value">+0</span> and <span class="value">−0</span>, respectively.
+ (Note that these two different zero Number values are produced by the program expressions <code>+0</code> (or simply
+ <code>0</code>) and <code>-0</code>.)</p>
+
+ <p>The <span style="font-family: Times New Roman">18437736874454810622</span> (that is, <span style="font-family: Times New
+ Roman">2<sup>64</sup>−2<sup>53</sup>−2</span>) finite nonzero values are of two kinds:</p>
+
+ <p><span style="font-family: Times New Roman">18428729675200069632</span> (that is, <span style="font-family: Times New
+ Roman">2<sup>64</sup>−2<sup>54</sup></span>) of them are normalized, having the form</p>
+
+ <div class="math-display"><i>s</i> × <i>m</i> × 2<sup><i>e</i></sup></div>
+
+ <p>where <var>s</var> is <span style="font-family: Times New Roman">+1</span> or <span style="font-family: Times New
+ Roman">−1</span>, <var>m</var> is a positive integer less than <span style="font-family: Times New
+ Roman">2<sup>53</sup></span> but not less than <span style="font-family: Times New Roman">2<sup>52</sup></span>, and
+ <var>e</var> is an integer ranging from <span style="font-family: Times New Roman">−1074</span> to <span
+ style="font-family: Times New Roman">971</span>, inclusive.</p>
+
+ <p>The remaining <span style="font-family: Times New Roman">9007199254740990</span> (that is, <span style="font-family:
+ Times New Roman">2<sup>53</sup>−2</span>) values are denormalized, having the form</p>
+
+ <div class="math-display"><i>s</i> × <i>m</i> × 2<sup><i>e</i></sup></div>
+
+ <p>where <var>s</var> is <span style="font-family: Times New Roman">+1</span> or <span style="font-family: Times New
+ Roman">−1</span>, <var>m</var> is a positive integer less than <span style="font-family: Times New
+ Roman">2<sup>52</sup></span>, and <var>e</var> is <span style="font-family: Times New Roman">−1074</span>.</p>
+
+ <p>Note that all the positive and negative integers whose magnitude is no greater than <span style="font-family: Times New
+ Roman">2<sup>53</sup></span> are representable in the Number type (indeed, the integer <span style="font-family: Times New
+ Roman">0</span> has two representations, <code>+0</code> and <code>-0</code>).</p>
+
+ <p>A finite number has an <i>odd significand</i> if it is nonzero and the integer <var>m</var> used to express it (in one of
+ the two forms shown above) is odd. Otherwise, it has an <i>even significand</i>.</p>
+
+ <p>In this specification, the phrase “<span style="font-family: Times New Roman">the Number value for
+ <i>x</i></span>” where <var>x</var> represents an exact nonzero real mathematical quantity (which might even be an
+ irrational number such as <span style="font-family: Times New Roman">π</span>) means a Number value chosen in the
+ following manner. Consider the set of all finite values of the Number type, with <span class="value">−0</span> removed
+ and with two additional values added to it that are not representable in the Number type, namely <span style="font-family:
+ Times New Roman">2<sup>1024</sup></span> (which is <span style="font-family: Times New Roman">+1 ×
+ 2<sup>53</sup></span> <span style="font-family: Times New Roman">× 2<sup>971</sup></span>) and <span
+ style="font-family: Times New Roman">−2<sup>1024</sup></span> (which is <span style="font-family: Times New
+ Roman">−1 × 2<sup>53</sup></span> <span style="font-family: Times New Roman">× 2<sup>971</sup></span>).
+ Choose the member of this set that is closest in value to <var>x</var>. If two values of the set are equally close, then the
+ one with an even significand is chosen; for this purpose, the two extra values <span style="font-family: Times New
+ Roman">2<sup>1024</sup></span> and <span style="font-family: Times New Roman">−2<sup>1024</sup></span> are considered
+ to have even significands. Finally, if <span style="font-family: Times New Roman">2<sup>1024</sup></span> was chosen,
+ replace it with <span class="value">+∞</span>; if <span style="font-family: Times New
+ Roman">−2<sup>1024</sup></span> was chosen, replace it with <span class="value">−∞</span>; if <span
+ class="value">+0</span> was chosen, replace it with <span class="value">−0</span> if and only if <var>x</var> is less
+ than zero; any other chosen value is used unchanged. The result is the Number value for <var>x</var>. (This procedure
+ corresponds exactly to the behaviour of the IEEE 754 “round to nearest, ties to even” mode.)</p>
+
+ <p>Some ECMAScript operators deal only with integers in specific ranges such as <span style="font-family: Times New
+ Roman">−2<sup>31</sup></span> through <span style="font-family: Times New Roman">2<sup>31</sup>−1</span>,
+ inclusive, or in the range <span style="font-family: Times New Roman">0</span> through <span style="font-family: Times New
+ Roman">2<sup>16</sup>−1</span>, inclusive. These operators accept any value of the Number type but first convert each
+ such value to an integer value in the expected range. See the descriptions of the numeric conversion operations in <a
+ href="#sec-type-conversion">7.1</a>.</p>
+ </section>
+
+ <section id="sec-object-type">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.1.7"><a href="#sec-object-type" title="link to this section">6.1.7</a></span> The
+ Object Type</h1>
+
+ <p>An Object is logically a collection of properties. Each property is either a data property, or an accessor
+ property:</p>
+
+ <ul>
+ <li>
+ <p>A <i>data property</i> associates a key value with an <a href="#sec-ecmascript-language-types">ECMAScript language
+ value</a> and a set of Boolean attributes.</p>
+ </li>
+
+ <li>
+ <p>An <i>accessor property</i> associates a key value with one or two accessor functions, and a set of Boolean
+ attributes. The accessor functions are used to store or retrieve an <a
+ href="#sec-ecmascript-language-types">ECMAScript language value</a> that is associated with the property.</p>
+ </li>
+ </ul>
+
+ <p>Properties are identified using key values. A property key value is either an ECMAScript String value or a Symbol
+ value. All String and Symbol values, including the empty string, are valid as property keys. A <i>property name</i> is a
+ property key that is a String value.</p>
+
+ <p>An <i>integer index</i> is a String-valued property key that is a canonical numeric String (<a
+ href="#sec-canonicalnumericindexstring">see 7.1.16</a>) and whose numeric value is either <span style="font-family: Times
+ New Roman">+0</span> or a positive integer ≤ 2<sup>53</sup>−1. An <i>array index</i> is an integer index whose
+ numeric value <var>i</var> is in the range <span style="font-family: Times New Roman">+0 ≤ <i>i</i></span> <span
+ style="font-family: Times New Roman">< 2<sup>32</sup>−1.</span></p>
+
+ <p>Property keys are used to access properties and their values. There are two kinds of access for properties: <i>get</i>
+ and <i>set</i>, corresponding to value retrieval and assignment, respectively. The properties accessible via get and set
+ access includes both <i>own properties</i> that are a direct part of an object and <i>inherited properties</i> which are
+ provided by another associated object via a property inheritance relationship. Inherited properties may be either own or
+ inherited properties of the associated object. Each own property of an object must each have a key value that is distinct
+ from the key values of the other own properties of that object.</p>
+
+ <p>All objects are logically collections of properties, but there are multiple forms of objects that differ in their
+ semantics for accessing and manipulating their properties. O<i>rdinary objects</i> are the most common form of objects and
+ have the default object semantics. An <i>exotic object</i> is any form of object whose property semantics differ in any
+ way from the default semantics.</p>
+ </div>
+
+ <section id="sec-property-attributes">
+ <h1><span class="secnum" id="sec-6.1.7.1"><a href="#sec-property-attributes"
+ title="link to this section">6.1.7.1</a></span> Property Attributes</h1>
+
+ <p>Attributes are used in this specification to define and explain the state of Object properties. A data property
+ associates a key value with the attributes listed in <a href="#table-2">Table 2</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-2">Table 2</span> — Attributes of a Data Property</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Attribute Name</th>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Value Domain</th>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Description</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">[[Value]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Any <a href="#sec-ecmascript-language-types">ECMAScript language type</a></td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">The value retrieved by a get access of the property.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">[[Writable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Boolean</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">If <b>false</b>, attempts by ECMAScript code to change the property’s [[Value]] attribute using [[Set]] will not succeed.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">[[Enumerable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Boolean</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">If <b>true</b>, the property will be enumerated by a for-in enumeration (<a href="#sec-for-in-and-for-of-statements">see 13.6.4</a>). Otherwise, the property is said to be non-enumerable.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">[[Configurable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Boolean</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">If <b>false</b>, attempts to delete the property, change the property to be an accessor property, or change its attributes (other than [[Value]], or changing [[Writable]] to <b>false</b>) will fail.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>An accessor property associates a key value with the attributes listed in <a href="#table-3">Table 3</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-3">Table 3</span> — Attributes of an Accessor Property</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Attribute Name</th>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Value Domain</th>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Description</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000">[[Get]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Object <i>or</i> Undefined</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">If the value is an Object it must be a function Object. The function’s [[Call]] internal method (<a href="#table-6">Table 6</a>) is called with an empty arguments list to retrieve the property value each time a get access of the property is performed.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Set]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Object <i>or</i> Undefined</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">If the value is an Object it must be a function Object. The function’s [[Call]] internal method (<a href="#table-6">Table 6</a>) is called with an arguments list containing the assigned value as its sole argument each time a set access of the property is performed. The effect of a property's [[Set]] internal method may, but is not required to, have an effect on the value returned by subsequent calls to the property's [[Get]] internal method.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Enumerable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Boolean</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">If <b>true</b>, the property is to be enumerated by a for-in enumeration (<a href="#sec-for-in-and-for-of-statements">see 13.6.4</a>). Otherwise, the property is said to be non-enumerable.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Configurable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">Boolean</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black">If <b>false</b>, attempts to delete the property, change the property to be a data property, or change its attributes will fail.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>If the initial values of a property’s attributes are not explicitly specified by this specification, the default
+ value defined in <a href="#table-4">Table 4</a> is used.</p>
+
+ <figure>
+ <figcaption><span id="table-4">Table 4</span> — Default Attribute Values</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Attribute Name</th>
+ <th style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">Default Value</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Value]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black"><b>undefined</b></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000">[[Get]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black"><b>undefined</b></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Set]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black"><b>undefined</b></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Writable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black"><b>false</b></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Enumerable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black"><b>false</b></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid #000000; border-top: 1px solid black">[[Configurable]]</td>
+ <td style="border-bottom: 1px solid black; border-right: 1px solid black"><b>false</b></td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-object-internal-methods-and-internal-slots">
+ <h1><span class="secnum" id="sec-6.1.7.2"><a href="#sec-object-internal-methods-and-internal-slots"
+ title="link to this section">6.1.7.2</a></span> Object Internal Methods and Internal Slots</h1>
+
+ <p>The actual semantics of objects, in ECMAScript, are specified via algorithms called <i>internal methods</i>. Each
+ object in an ECMAScript engine is associated with a set of internal methods that defines its runtime behaviour. These
+ internal methods are not part of the ECMAScript language. They are defined by this specification purely for expository
+ purposes. However, each object within an implementation of ECMAScript must behave as specified by the internal methods
+ associated with it. The exact manner in which this is accomplished is determined by the implementation.</p>
+
+ <p>Internal method names are polymorphic. This means that different object values may perform different algorithms when a
+ common internal method name is invoked upon them. That actual object upon which an internal method is invoked is the
+ “target” of the invocaton. If, at runtime, the implementation of an algorithm attempts to use an internal
+ method of an object that the object does not support, a <b>TypeError</b> exception is thrown.</p>
+
+ <p>Internal slots correspond to internal state that is associated with objects and used by various ECMAScript
+ specification algorithms. Internal slots are not object properties and they are not inherited. Depending upon the specific
+ internal slot specification, such state may consist of values of any <a href="#sec-ecmascript-language-types">ECMAScript
+ language type</a> or of specific ECMAScript specification type values. Unless explicitly specified otherwise, internal
+ slots are allocated as part of the process of creating an object and may not be dynamically added to an object. Unless
+ specified otherwise, the initial value of an internal slot is the value <span class="value">undefined</span>. Various
+ algorithms within this specification create objects that have internal slots. However, the ECMAScript language provides no
+ direct way to associate internal slots with an object.</p>
+
+ <p>Internal methods and internal slots are identified within this specification using names enclosed in double square
+ brackets [[ ]].</p>
+
+ <p><a href="#table-5">Table 5</a> summarizes the <i>essential internal methods</i> used by this specification that are
+ applicable to all objects created or manipulated by ECMAScript code. Every object must have algorithms for all of the
+ essential internal methods. However, all objects do not necessarily use the same algorithms for those methods.</p>
+
+ <p>The “Signature” column of <a href="#table-5">Table 5</a> and other similar tables describes the invocation
+ pattern for each internal method. The invocation pattern always includes a parenthesized list of descriptive parameter
+ names. If a parameter name is the same as an ECMAScript type name then the name describes the required type of the
+ parameter value. If an internal method explicitly returns a value, its parameter list is followed by the symbol
+ “→” and the type name of the returned value. The type names used in signatures refer to the types defined
+ in <a href="#sec-ecmascript-data-types-and-values">clause 6</a> augmented by the following additional names.
+ “<i>any</i>” means the value may be any <a href="#sec-ecmascript-language-types">ECMAScript language type</a>.
+ An internal method implicitly returns a <a href="#sec-completion-record-specification-type">Completion Record</a> as
+ described in <a href="#sec-completion-record-specification-type">6.2.2</a>. In addition to its parameters, an internal
+ method always has access to the object that is the target of the method invocation.</p>
+
+ <figure>
+ <figcaption><span id="table-5">Table 5</span> — Essential Internal Methods</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Method</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Signature</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[GetPrototypeOf]]</td>
+ <td>()<b><i>→</i></b>Object or Null</td>
+ <td>Determine the object that provides inherited properties for this object. A <b>null</b> value indicates that there are no inherited properties.</td>
+ </tr>
+ <tr>
+ <td>[[SetPrototypeOf]]</td>
+ <td>(<i>Object</i> or Null)<b><i>→</i></b>Boolean</td>
+ <td>Associate with this object another object that provides inherited properties. Passing <b>null</b> indicates that there are no inherited properties. Returns <b>true</b> indicating that the operation was completed successfully or <b>false</b> indicating that the operation was not successful.</td>
+ </tr>
+ <tr>
+ <td>[[IsExtensible]]</td>
+ <td>( )<b><i>→</i></b>Boolean</td>
+ <td>Determine whether it is permitted to add additional properties to this object.</td>
+ </tr>
+ <tr>
+ <td>[[PreventExtensions]]</td>
+ <td>( )<b><i>→</i></b>Boolean</td>
+ <td>Control whether new properties may be added to this object. Returns <b>true</b> if the operation was successful or <b>false</b> if the operation was unsuccessful.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">[[GetOwnProperty]]</td>
+
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">
+ <p>(<i>propertyKey</i>) →</p>
+
+ <p>Undefined or <a href="#sec-property-descriptor-specification-type">Property Descriptor</a></p>
+ </td>
+
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">Return a <a href="#sec-property-descriptor-specification-type">Property Descriptor</a> for the own property of this object whose key is <i>propertyKey</i>, or <b>undefined</b> if no such property exists.</td>
+ </tr>
+ <tr>
+ <td>[[HasProperty]]</td>
+ <td>(<i>propertyKey</i>) <b><i>→</i></b> Boolean</td>
+ <td>Return a Boolean value indicating whether this object already has either an own or inherited property whose key is <i>propertyKey</i>.</td>
+ </tr>
+ <tr>
+ <td>[[Get]]</td>
+ <td>(<i>propertyKey</i>, <i>Receiver</i>) <i><b>→</b> any</i></td>
+ <td>Return the value of the property whose key is <i>propertyKey</i> from this object. If any ECMAScript code must be executed to retrieve the property value, <i>Receiver</i> is used as the <b>this</b> value when evaluating the code.</td>
+ </tr>
+ <tr>
+ <td>[[Set]]</td>
+ <td>(<i>propertyKey</i>,<i>value</i>, <i>Receiver</i>) <i><b>→</b> Boolean</i></td>
+ <td>Set the value of this object property whose key is <i>propertyKey</i> to <i>value</i>. If any ECMAScript code must be executed to set the property value, <i>Receiver</i> is used as the <b>this</b> value when evaluating the code. Returns <b>true</b> if that the property value was set or <b>false</b> if that it could not be set.</td>
+ </tr>
+ <tr>
+ <td>[[Delete]]</td>
+ <td>(<i>propertyKey</i>) <b><i>→</i></b> Boolean</td>
+ <td>Remove the own property whose key is <i>propertyKey</i> from this object . Return <span class="value">false</span> if the property was not deleted and is still present. Return <span class="value">true</span> if the property was deleted or is not present.</td>
+ </tr>
+ <tr>
+ <td>[[DefineOwnProperty]]</td>
+ <td>(<i>propertyKey, PropertyDescriptor</i>) <b><i>→</i></b> Boolean</td>
+ <td>Create or alter the own property, whose key is <i>propertyKey</i>, to have the state described by <i>PropertyDescriptor</i>. Return <span class="value">true</span> if that the property was successfully created/updated or <span class="value">false</span> if the property could not be created or updated.</td>
+ </tr>
+ <tr>
+ <td>[[Enumerate]]</td>
+ <td>()<b><i>→</i></b>Object</td>
+ <td>Return an iterator object that produces the keys of the string-keyed enumerable properties of the object.</td>
+ </tr>
+ <tr>
+ <td>[[OwnPropertyKeys]]</td>
+ <td>()<b><i>→</i></b><a href="#sec-list-and-record-specification-type">List</a> of propertyKey</td>
+ <td>Return a <a href="#sec-list-and-record-specification-type">List</a> whose elements are all of the own property keys for the object.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p><a href="#table-6">Table 6</a> summarizes additional essential internal methods that are supported by objects that may
+ be called as functions.</p>
+
+ <figure>
+ <figcaption><span id="table-6">Table 6</span> — Additional Essential Internal Methods of Function Objects</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Method</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Signature</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[Call]]</td>
+ <td>(<i>any</i>, a <a href="#sec-list-and-record-specification-type">List</a> of <i>any</i>) <span style="font-family: Times New Roman"><b><i>→</i></b></span> <i>any</i></td>
+ <td>Executes code associated with this object. Invoked via a function call expression. The arguments to the internal method are a <b>this</b> value and a list containing the arguments passed to the function by a call expression. Objects that implement this internal method are <i>callable</i>.</td>
+ </tr>
+ <tr>
+ <td>[[Construct]]</td>
+ <td>(a <a href="#sec-list-and-record-specification-type">List</a> of <i>any</i>, Object) <span style="font-family: Times New Roman"><b><i>→</i></b></span> Object</td>
+ <td>Creates an object. Invoked via the <code>new</code> or <code>super</code> operators. The first arguments to the internal method is a list containing the arguments of the operator. The second argument is the object to which the <code>new</code> operator was initially applied. Objects that implement this internal method are called <i>constructors</i>. A Function object is not necessarily a constructor and such non-constructor Function objects do not have a [[Construct]] internal method.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The semantics of the essential internal methods for ordinary objects and standard exotic objects are specified in <a
+ href="#sec-ordinary-and-exotic-objects-behaviours">clause 9</a>. If any specified use of an internal method of an exotic
+ object is not supported by an implementation, that usage must throw a <b>TypeError</b> exception when attempted.</p>
+ </section>
+
+ <section id="sec-invariants-of-the-essential-internal-methods">
+ <h1><span class="secnum" id="sec-6.1.7.3"><a href="#sec-invariants-of-the-essential-internal-methods"
+ title="link to this section">6.1.7.3</a></span> Invariants of the Essential Internal Methods</h1>
+
+ <p>The Internal Methods of Objects of an ECMAScript engine must conform to the list of invariants specified below.
+ Ordinary ECMAScript Objects as well as all standard exotic objects in this specification maintain these invariants.
+ ECMAScript Proxy objects maintain these invariants by means of runtime checks on the result of traps invoked on the
+ [[ProxyHandler]] object.</p>
+
+ <p>Any implementation provided exotic objects must also maintain these invariants for those objects. Violation of these
+ invariants may cause ECMAScript code to have unpredictable behaviour and create security issues. However, violation of
+ these invariants must never compromise the memory safety of an implementation.</p>
+
+ <p>An implementation must not allow these invariants to be circumvented in any manner such as by providing alternative
+ interfaces that implement the functionality of the essential internal methods without enforcing their invariants.</p>
+
+ <p>Definitions:</p>
+
+ <p>● The <i>target</i> of an internal method is the object upon which the internal method is called.</p>
+
+ <p>● A target is <i>non-extensible</i> if it has been observed to return false from its [[IsExtensible]]
+ internal method, or true from its [[PreventExtensions]] internal method.</p>
+
+ <p>● A <i>non-existent</i> property is a property that does not exist as an own property on a non-extensible
+ target.</p>
+
+ <p>● All references to <i><a href="#sec-samevalue">SameValue</a></i> are according to the definition of <a
+ href="#sec-samevalue">SameValue</a> algorithm specified in <a href="#sec-samevalue">7.2.9</a>.</p>
+
+ <p><b>[[GetPrototypeOf]] ( )</b></p>
+
+ <p>● The Type of the return value must be either Object or Null.</p>
+
+ <p>● If target is non-extensible, and [[GetPrototypeOf]] returns a value v, then any future calls to
+ [[GetPrototypeOf]] should return the <a href="#sec-samevalue">SameValue</a> as v.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An object’s prototype chain should have finite length (that is, starting from any
+ object, recursively applying the [[GetPrototypeOf]] internal method to its result should eventually lead to the value
+ null). However, this requirement is not enforceable as an object level invariant if the prototype chain includes any
+ exotic objects that do not use the ordinary object definition of [[GetPrototypeOf]]. Such a circular prototype chain may
+ result in infinite loops when accessing object properties.</p>
+ </div>
+
+ <p><b>[[SetPrototypeOf]] (V)</b></p>
+
+ <p>● The Type of the return value must be Boolean.</p>
+
+ <p>● If target is non-extensible, [[SetPrototypeOf]] must return false, unless V is the <a
+ href="#sec-samevalue">SameValue</a> as the target’s observed [[GetPrototypeOf]] value.</p>
+
+ <p><b>[[PreventExtensions]] ( )</b></p>
+
+ <p>● The Type of the return value must be Boolean.</p>
+
+ <p>● If [[PreventExtensions]] returns true, all future calls to [[IsExtensible]] on the target must return
+ false and the target is now considered non-extensible.</p>
+
+ <p><b>[[GetOwnProperty]] (P)</b></p>
+
+ <p>● The Type of the return value must be either <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> or Undefined.</p>
+
+ <p>● If the Type of the return value is <a href="#sec-property-descriptor-specification-type">Property
+ Descriptor</a>, the return value must be a complete property descriptor (<a href="#sec-completepropertydescriptor">see
+ 6.2.4.6</a>).</p>
+
+ <p>● If a property P is described as a data property with Desc.[[Value]] equal to v and Desc.[[Writable]] and
+ Desc.[[Configurable]] are both false, then the <a href="#sec-samevalue">SameValue</a> must be returned for the
+ Desc.[[Value]] attribute of the property on all future calls to [[GetOwnProperty]] ( P ).</p>
+
+ <p>● If P’s attributes other than [[Writable]] may change over time or if the property might disappear,
+ then P’s [[Configurable]] attribute must be true.</p>
+
+ <p>● If the [[Writable]] attribute may change from false to true, then the [[Configurable]] attribute must be
+ true.</p>
+
+ <p>● If the target is non-extensible and P is non-existent, then all future calls to [[GetOwnProperty]] (P)
+ on the target must describe P as non-existent (i.e. [[GetOwnProperty]] (P) must return undefined).</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> As a consequence of the third invariant, if a property is described as a data property
+ and it may return different values over time, then either or both of the Desc.[[Writable]] and Desc.[[Configurable]]
+ attributes must be true even if no mechanism to change the value is exposed via the other internal methods.</p>
+ </div>
+
+ <p><b>[[DefineOwnProperty]] (P, Desc)</b></p>
+
+ <p>● The Type of the return value must be Boolean.</p>
+
+ <p>● [[DefineOwnProperty]] must return false if P has previously been observed as a non-configurable own
+ property of the target, unless either:</p>
+
+ <p>1.	P is a non-configurable writable own data property. A non-configurable writable data property can be changed
+ into a non-configurable non-writable data property.</p>
+
+ <p>2.	All attributes in Desc are the <a href="#sec-samevalue">SameValue</a> as P’s attributes.</p>
+
+ <p>● [[DefineOwnProperty]] (P, Desc) must return false if target is non-extensible and P is a non-existent own
+ property. That is, a non-extensible target object cannot be extended with new properties.</p>
+
+ <p><b>[[HasProperty]] ( P )</b></p>
+
+ <p>● The Type of the return value must be Boolean.</p>
+
+ <p>● If P was previously observed as a non-configurable data or accessor own property of the target,
+ [[HasProperty]] must return true.</p>
+
+ <p><b>[[Get]] (P, Receiver)</b></p>
+
+ <p>● If P was previously observed as a non-configurable, non-writable own data property of the target with
+ value v, then [[Get]] must return the <a href="#sec-samevalue">SameValue</a>.</p>
+
+ <p>● If P was previously observed as a non-configurable own accessor property of the target whose [[Get]]
+ attribute is undefined, the [[Get]] operation must return undefined.</p>
+
+ <p><b>[[Set]] ( P, V, Receiver)</b></p>
+
+ <p>● The Type of the return value must be Boolean.</p>
+
+ <p>● If P was previously observed as a non-configurable, non-writable own data property of the target, then
+ [[Set]] must return false unless V is the <a href="#sec-samevalue">SameValue</a> as P’s [[Value]] attribute.</p>
+
+ <p>● If P was previously observed as a non-configurable own accessor property of the target whose [[Set]]
+ attribute is undefined, the [[Set]] operation must return false.</p>
+
+ <p><b>[[Delete]] ( P )</b></p>
+
+ <p>● The Type of the return value must be Boolean.</p>
+
+ <p>● If P was previously observed to be a non-configurable own data or accessor property of the target,
+ [[Delete]] must return false.</p>
+
+ <p><b>[[Enumerate]] ( )</b></p>
+
+ <p>● The Type of the return value must be Object.</p>
+
+ <p><b>[[OwnPropertyKeys]] ( )</b></p>
+
+ <p>● The return value must be a <a href="#sec-list-and-record-specification-type">List</a>.</p>
+
+ <p>●  The Type of each element of the returned <a href="#sec-list-and-record-specification-type">List</a> is
+ either String or Symbol.</p>
+
+ <p>● The returned <a href="#sec-list-and-record-specification-type">List</a> must contain at least the keys of
+ all non-configurable own properties that have previously been observed.</p>
+
+ <p>● If the object is non-extensible, the returned <a href="#sec-list-and-record-specification-type">List</a>
+ must contain only the keys of all own properties of the object that are observable using [[GetOwnProperty]].</p>
+
+ <p><b>[[Construct]] ( )</b></p>
+
+ <p>● The Type of the return value must be Object.</p>
+ </section>
+
+ <section id="sec-well-known-intrinsic-objects">
+ <h1><span class="secnum" id="sec-6.1.7.4"><a href="#sec-well-known-intrinsic-objects"
+ title="link to this section">6.1.7.4</a></span> Well-Known Intrinsic Objects</h1>
+
+ <p>Well-known intrinsics are built-in objects that are explicitly referenced by the algorithms of this specification and
+ which usually have <a href="#sec-code-realms">Realm</a> specific identities. Unless otherwise specified each intrinsic
+ object actually corresponds to a set of similar objects, one per <a href="#sec-code-realms">Realm</a>.</p>
+
+ <p>Within this specification a reference such as %name% means the intrinsic object, associated with <a
+ href="#sec-execution-contexts">the current Realm</a>, corresponding to the name. Determination of <a
+ href="#sec-execution-contexts">the current Realm</a> and its intrinsics is described in <a
+ href="#sec-newglobalenvironment">8.1.2.5</a>. The well-known intrinsics are listed in <a href="#table-7">Table 7</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-7">Table 7</span> — Well-known Intrinsic Objects</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Intrinsic Name</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Global Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">ECMAScript Language Association</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Array</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Array</code> constructor (<a href="#sec-array-constructor">22.1.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ArrayBuffer%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>ArrayBuffer</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>ArrayBuffer</code> constructor (<a href="#sec-arraybuffer-constructor">24.1.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ArrayBufferPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-arraybuffer.prototype">ArrayBuffer.prototype</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %ArrayBuffer%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ArrayIteratorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The prototype of Array iterator objects (<a href="#sec-array-iterator-objects">22.1.5</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Array% (<a href="#sec-properties-of-the-array-prototype-object">22.1.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ArrayProto_values%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-array.prototype.values">Array.prototype.values</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>values</code> data property of %ArrayPrototype% (<a href="#sec-array.prototype.values">22.1.3.29</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Boolean%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Boolean</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Boolean</code> constructor (<a href="#sec-boolean-constructor">19.3.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%BooleanPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Boolean.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Boolean% (<a href="#sec-properties-of-the-boolean-prototype-object">19.3.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%DataView%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>DataView</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>DataView</code> constructor (<a href="#sec-dataview-constructor">24.2.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%DataViewPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-dataview.prototype">DataView.prototype</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %DataView%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Date%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Date</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Date</code> constructor (<a href="#sec-date-constructor">20.3.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%DatePrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Date.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Date%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Error%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Error</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Error</code> constructor (<a href="#sec-error-constructor">19.5.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ErrorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Error.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Error%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%eval%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>eval</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>eval</code> function (<a href="#sec-eval-x">18.2.1</a>).</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%EvalError%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>EvalError</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>EvalError</code> constructor (<a href="#sec-native-error-types-used-in-this-standard-evalerror">19.5.5.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%EvalErrorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>EvalError.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %EvalError%</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Float32Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-float32array">Float32Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-float32array">Float32Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Float32ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Float32Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Float32Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Float64Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-float64array">Float64Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-float64array">Float64Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Float64ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Float64Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Float64Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Function%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Function</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Function</code> constructor (<a href="#sec-function-constructor">19.2.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%FunctionPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Function.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Function%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Generator%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %GeneratorFunction%</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%GeneratorFunction%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The constructor of generator objects(<a href="#sec-generatorfunction-constructor">25.2.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%GeneratorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %Generator%</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Int8Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-int8array">Int8Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-int8array">Int8Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Int8ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Int8Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Int8Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Int16Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-int16array">Int16Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-int16array">Int16Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Int16ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Int16Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Int16Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Int32Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-int32array">Int32Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-int32array">Int32Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Int32ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Int32Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Int32Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%IteratorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">An object that all standard built-in iterator objects indirectly inherit from.</td>
+ </tr>
+ <tr>
+ <td>%JSON%</td>
+ <td><code>JSON</code></td>
+ <td>The <code>JSON</code> object (<a href="#sec-json-object">24.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Map%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Map</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Map</code> constructor (<a href="#sec-map-constructor">23.1.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%MapIteratorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The prototype of Map iterator objects (<a href="#sec-map-iterator-objects">23.1.5</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%MapPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Map.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Map%.</td>
+ </tr>
+ <tr>
+ <td>%Math%</td>
+ <td><code>Math</code></td>
+ <td>The <code>Math</code> object (<a href="#sec-math-object">20.2</a>)</td>
+ </tr>
+ <tr>
+ <td>%Number%</td>
+ <td><code>Number</code></td>
+ <td>The <code>Number</code> constructor (<a href="#sec-number-constructor">20.1.1</a>)</td>
+ </tr>
+ <tr>
+ <td>%NumberPrototype%</td>
+ <td><code>Number.prototype</code></td>
+ <td>The initial value of the <code>prototype</code> property of %Number%</td>
+ </tr>
+ <tr>
+ <td>%Object%</td>
+ <td><code>Object</code></td>
+ <td>The <code>Object</code> constructor (<a href="#sec-object-constructor">19.1.1</a>)</td>
+ </tr>
+ <tr>
+ <td>%ObjectPrototype%</td>
+ <td><code>Object.prototype</code></td>
+ <td>The initial value of the <code>prototype</code> data property of %Object%. (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ObjProto_toString%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Object.prototype.<br>toString</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>toString</code> data property of %ObjectPrototype% (<a href="#sec-object.prototype.tostring">19.1.3.6</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Promise%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Promise</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Promise</code> constructor (<a href="#sec-promise-constructor">25.4.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%PromisePrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Promise.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Promise%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Proxy%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Proxy</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Proxy</code> constructor (<a href="#sec-proxy-constructor">26.2.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%RangeError%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>RangeError</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>RangeError</code> constructor (<a href="#sec-native-error-types-used-in-this-standard-rangeerror">19.5.5.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%RangeErrorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>RangeError.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %RangeError%</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ReferenceError%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>ReferenceError</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>ReferenceError</code> constructor (<a href="#sec-native-error-types-used-in-this-standard-referenceerror">19.5.5.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%ReferenceErrorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>ReferenceError.<br>prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %ReferenceError%</td>
+ </tr>
+ <tr>
+ <td>%Reflect%</td>
+ <td><code>Reflect</code></td>
+ <td>The Reflect object (<a href="#sec-reflect-object">26.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%RegExp%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>RegExp</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>RegExp</code> constructor (<a href="#sec-regexp-constructor">21.2.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%RegExpPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-regexp.prototype">RegExp.prototype</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %RegExp%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Set%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Set</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>Set</code> constructor (<a href="#sec-set-constructor">23.2.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%SetIteratorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The prototype of Set iterator objects (<a href="#sec-set-iterator-objects">23.2.5</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%SetPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Set.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Set%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%String%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>String</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>String</code> constructor (<a href="#sec-string-constructor">21.1.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%StringIteratorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The prototype of String iterator objects (<a href="#sec-string-iterator-objects">21.1.5</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%StringPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>String.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %String%.</td>
+ </tr>
+ <tr>
+ <td>%Symbol%</td>
+ <td><code>Symbol</code></td>
+ <td>The <code>Symbol</code> constructor (<a href="#sec-symbol-constructor">19.4.1</a>)</td>
+ </tr>
+ <tr>
+ <td>%SymbolPrototype%</td>
+ <td><code>Symbol.prototype</code></td>
+ <td>The initial value of the <code>prototype</code> data property of %Symbol%. (<a href="#sec-properties-of-the-symbol-prototype-object">19.4.3</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%SyntaxError%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>SyntaxError</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>SyntaxError</code> constructor (<a href="#sec-native-error-types-used-in-this-standard-syntaxerror">19.5.5.4</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%SyntaxErrorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>SyntaxError.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %SyntaxError%</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-%throwtypeerror%">%ThrowTypeError%</a></td>
+ <td></td>
+ <td>A function object that unconditionally throws a new instance of %TypeError%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%TypedArray%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The super class of all typed Array constructors (<a href="#sec-%typedarray%-intrinsic-object">22.2.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%TypedArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %TypedArray%</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%TypeError%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>TypeError</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>TypeError</code> constructor (<a href="#sec-native-error-types-used-in-this-standard-typeerror">19.5.5.5</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%TypeErrorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>TypeError.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %TypeError%</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint8Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-uint8array">Uint8Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-uint8array">Uint8Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint8ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Uint8Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Uint8Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint8ClampedArray%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-uint8clampedarray">Uint8ClampedArray</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-uint8clampedarray">Uint8ClampedArray</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint8ClampedArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-uint8clampedarray">Uint8ClampedArray</a>.<br>prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Uint8ClampedArray%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint16Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-uint16array">Uint16Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-uint16array">Uint16Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint16ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Uint16Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Uint16Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint32Array%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-uint32array">Uint32Array</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-uint32array">Uint32Array</a></code> constructor (<a href="#sec-typedarray-objects">22.2</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%Uint32ArrayPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>Uint32Array.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %Uint32Array%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%URIError%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code><a href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></code> constructor (<a href="#sec-native-error-types-used-in-this-standard-urierror">19.5.5.6</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%URIErrorPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>URIError.prototype</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> property of %URIError%</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%WeakMap%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>WeakMap</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>WeakMap</code> constructor (<a href="#sec-weakmap-constructor">23.3.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%WeakMapPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-weakmap.prototype">WeakMap.prototype</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %WeakMap%.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%WeakSet%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code>WeakSet</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <code>WeakSet</code> constructor (<a href="#sec-weakset-constructor">23.4.1</a>)</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">%WeakSetPrototype%</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><code><a href="#sec-weakset.prototype">WeakSet.prototype</a></code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The initial value of the <code>prototype</code> data property of %WeakSet%.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-ecmascript-specification-types">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.2"><a href="#sec-ecmascript-specification-types"
+ title="link to this section">6.2</a></span> ECMAScript Specification Types</h1>
+
+ <p>A specification type corresponds to meta-values that are used within algorithms to describe the semantics of ECMAScript
+ language constructs and ECMAScript language types. The specification types are <a
+ href="#sec-reference-specification-type">Reference</a>, <a href="#sec-list-and-record-specification-type">List</a>, <a
+ href="#sec-completion-record-specification-type">Completion</a>, <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a>, <a href="#sec-lexical-environments">Lexical
+ Environment</a>, <a href="#sec-environment-records">Environment Record</a>, and <a href="#sec-data-blocks">Data Block</a>.
+ Specification type values are specification artefacts that do not necessarily correspond to any specific entity within an
+ ECMAScript implementation. Specification type values may be used to describe intermediate results of ECMAScript expression
+ evaluation but such values cannot be stored as properties of objects or values of ECMAScript language variables.</p>
+ </div>
+
+ <section id="sec-list-and-record-specification-type">
+ <h1><span class="secnum" id="sec-6.2.1"><a href="#sec-list-and-record-specification-type"
+ title="link to this section">6.2.1</a></span> The List and Record Specification Type</h1>
+
+ <p>The List type is used to explain the evaluation of argument lists (<a href="#sec-argument-lists">see 12.3.6</a>) in
+ <code>new</code> expressions, in function calls, and in other algorithms where a simple ordered list of values is needed.
+ Values of the List type are simply ordered sequences of list elements containing the individual values. These sequences may
+ be of any length. The elements of a list may be randomly accessed using 0-origin indices. For notational convenience an
+ array-like syntax can be used to access List elements. For example, <i>arguments</i>[2] is shorthand for saying the
+ 3<sup>rd</sup> element of the List <i>arguments</i>.</p>
+
+ <p>For notational convenience within this specification, a literal syntax can be used to express a new List value. For
+ example, «1, 2» defines a List value that has two elements each of which is initialized to a specific value. A
+ new empty List can be expressed as «».</p>
+
+ <p>The Record type is used to describe data aggregations within the algorithms of this specification. A Record type value
+ consists of one or more named fields. The value of each field is either an ECMAScript value or an abstract value represented
+ by a name associated with the Record type. Field names are always enclosed in double brackets, for example [[value]].</p>
+
+ <p>For notational convenience within this specification, an object literal-like syntax can be used to express a Record
+ value. For example, {[[field1]]: 42, [[field2]]: <b>false</b>, [[field3]]: <b>empty</b>} defines a Record value that has
+ three fields, each of which is initialized to a specific value. Field name order is not significant. Any fields that are not
+ explicitly listed are considered to be absent.</p>
+
+ <p>In specification text and algorithms, dot notation may be used to refer to a specific field of a Record value. For
+ example, if R is the record shown in the previous paragraph then R.[[field2]] is shorthand for “the field of R named
+ [[field2]]”.</p>
+
+ <p>Schema for commonly used Record field combinations may be named, and that name may be used as a prefix to a literal
+ Record value to identify the specific kind of aggregations that is being described. For example:
+ PropertyDescriptor{[[Value]]: 42, [[Writable]]: <b>false</b>, [[Configurable]]: <b>true</b>}.</p>
+ </section>
+
+ <section id="sec-completion-record-specification-type">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.2.2"><a href="#sec-completion-record-specification-type"
+ title="link to this section">6.2.2</a></span> The Completion Record Specification Type</h1>
+
+ <p>The Completion type is a Record used to explain the runtime propagation of values and control flow such as the
+ behaviour of statements (<code>break</code>, <code>continue</code>, <code>return</code> and <code>throw</code>) that
+ perform nonlocal transfers of control.</p>
+
+ <p>Values of the Completion type are Record values whose fields are defined as by <a href="#table-8">Table 8</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-8">Table 8</span> — Completion Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[type]]</td>
+ <td>One of <b>normal</b>, <b>break</b>, <b>continue</b>, <b>return</b>, or <b>throw</b></td>
+ <td>The type of completion that occurred.</td>
+ </tr>
+ <tr>
+ <td>[[value]]</td>
+ <td>any <a href="#sec-ecmascript-language-types">ECMAScript language value</a> or <b>empty</b></td>
+ <td>The value that was produced.</td>
+ </tr>
+ <tr>
+ <td>[[target]]</td>
+ <td>any ECMAScript string or <b>empty</b></td>
+ <td>The target label for directed control transfers.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The term “abrupt completion” refers to any completion with a <span style="font-family: Times New
+ Roman">[[type]]</span> value other than <b>normal</b>.</p>
+ </div>
+
+ <section id="sec-normalcompletion">
+ <h1><span class="secnum" id="sec-6.2.2.1"><a href="#sec-normalcompletion" title="link to this section">6.2.2.1</a></span>
+ NormalCompletion</h1>
+
+ <p>The abstract operation NormalCompletion with a single <i>argument</i>, such as:</p>
+
+ <ol class="proc">
+ <li>Return NormalCompletion(<i>argument</i>).</li>
+ </ol>
+
+ <p>Is a shorthand that is defined as follows:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">normal</span>, [[value]]: <i>argument</i>, [[target]]:<span style="font-family:
+ sans-serif">empty</span>}.</li>
+ </ol>
+ </section>
+
+ <section id="sec-implicit-completion-values">
+ <h1><span class="secnum" id="sec-6.2.2.2"><a href="#sec-implicit-completion-values"
+ title="link to this section">6.2.2.2</a></span> Implicit Completion Values</h1>
+
+ <p>The algorithms of this specification often implicitly return <a
+ href="#sec-completion-record-specification-type">Completion</a> Records whose [[type]] is <b>normal</b>. Unless it is
+ otherwise obvious from the context, an algorithm statement that returns a value that is not a <a
+ href="#sec-completion-record-specification-type">Completion Record</a>, such as:</p>
+
+ <ol class="proc">
+ <li>Return "Infinity".</li>
+ </ol>
+
+ <p>Generally means the same thing as:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<code>"Infinity"</code>).</li>
+ </ol>
+
+ <p>A “<span style="font-family: Times New Roman">return</span>” statement without a value in an algorithm step
+ means the same thing as:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+
+ <p>Similarly, any reference to a <a href="#sec-completion-record-specification-type">Completion Record</a> value that is
+ in a context that does not explicitly require a complete <a href="#sec-completion-record-specification-type">Completion
+ Record</a> value is equivalent to an explicit reference to the [[value]] field of the <a
+ href="#sec-completion-record-specification-type">Completion Record</a> value unless the <a
+ href="#sec-completion-record-specification-type">Completion Record</a> is an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</p>
+ </section>
+
+ <section id="sec-throw-an-exception">
+ <h1><span class="secnum" id="sec-6.2.2.3"><a href="#sec-throw-an-exception"
+ title="link to this section">6.2.2.3</a></span> Throw an Exception</h1>
+
+ <p>Algorithms steps that say to throw an exception, such as</p>
+
+ <ol class="proc">
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+
+ <p>mean the same things as:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">throw</span>, [[value]]: a newly created <b>TypeError</b> object, [[target]]:<span style="font-family:
+ sans-serif">empty</span>}.</li>
+ </ol>
+ </section>
+
+ <section id="sec-returnifabrupt">
+ <h1><span class="secnum" id="sec-6.2.2.4"><a href="#sec-returnifabrupt" title="link to this section">6.2.2.4</a></span>
+ ReturnIfAbrupt</h1>
+
+ <p>Algorithms steps that say</p>
+
+ <ol class="proc">
+ <li>ReturnIfAbrupt(<i>argument</i>).</li>
+ </ol>
+
+ <p>mean the same thing as:</p>
+
+ <ol class="proc">
+ <li>If <i>argument</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return
+ <i>argument</i>.</li>
+ <li>Else if <i>argument</i> is a <a href="#sec-completion-record-specification-type">Completion Record</a>, let
+ <i>argument</i> be <i>argument</i>.[[value]].</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-reference-specification-type">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.2.3"><a href="#sec-reference-specification-type"
+ title="link to this section">6.2.3</a></span> The Reference Specification Type</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The Reference type is used to explain the behaviour of such operators as
+ <code>delete</code>, <code>typeof</code>, the assignment operators, the <code>super</code> keyword and other language
+ features. For example, the left-hand operand of an assignment is expected to produce a reference.</p>
+ </div>
+
+ <p>A <b>Reference</b> is a resolved name or property binding. A Reference consists of three components, the
+ <var>base</var> value, the <var>referenced name</var> and the Boolean valued <var>strict reference</var> flag. The
+ <var>base</var> value is either <b>undefined</b>, an Object, a Boolean, a String, a Symbol, a Number, or an environment
+ record (<a href="#sec-environment-records">8.1.1</a>). A <var>base</var> value of <b>undefined</b> indicates that the
+ Reference could not be resolved to a binding. The <var>referenced name</var> is a String or Symbol value.</p>
+
+ <p>A Super Reference is a Reference that is used to represents a name binding that was expressed using the super keyword.
+ A Super Reference has an additional <var>thisValue</var> component and its <var>base</var> value will never be an
+ environment record.</p>
+
+ <p>The following abstract operations are used in this specification to access the components of references:</p>
+
+ <ul>
+ <li>
+ <p>GetBase(V). Returns the <i>base</i> value component of the reference V.</p>
+ </li>
+
+ <li>
+ <p>GetReferencedName(V). Returns the <i>referenced name</i> component of the reference V.</p>
+ </li>
+
+ <li>
+ <p>IsStrictReference(V). Returns the <i>strict reference</i> flag component of the reference V.</p>
+ </li>
+
+ <li>
+ <p>HasPrimitiveBase(V). Returns <b>true</b> if <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>base</i>)
+ is Boolean, String, Symbol, or Number.</p>
+ </li>
+
+ <li>
+ <p>IsPropertyReference(V). Returns <b>true</b> if either the <i>base</i> value is an object or HasPrimitiveBase(V) is
+ <b>true</b>; otherwise returns <b>false</b>.</p>
+ </li>
+
+ <li>
+ <p>IsUnresolvableReference(V). Returns <b>true</b> if the <i>base</i> value is <b>undefined</b> and <b>false</b>
+ otherwise.</p>
+ </li>
+
+ <li>
+ <p>IsSuperReference(V). Returns <b>true</b> if this reference has a <i>thisValue</i> component.</p>
+ </li>
+ </ul>
+
+ <p>The following abstract operations are used in this specification to operate on references:</p>
+ </div>
+
+ <section id="sec-getvalue">
+ <h1><span class="secnum" id="sec-6.2.3.1"><a href="#sec-getvalue" title="link to this section">6.2.3.1</a></span> GetValue
+ (V)</h1>
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>V</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is not <a
+ href="#sec-reference-specification-type">Reference</a>, return <i>V</i>.</li>
+ <li>Let <i>base</i> be <a href="#sec-reference-specification-type">GetBase</a>(<i>V</i>).</li>
+ <li>If <a href="#sec-reference-specification-type">IsUnresolvableReference</a>(<i>V</i>), throw a <b>ReferenceError</b>
+ exception.</li>
+ <li>If <a href="#sec-reference-specification-type">IsPropertyReference</a>(<i>V</i>), then
+ <ol class="block">
+ <li>If <a href="#sec-reference-specification-type">HasPrimitiveBase</a>(<i>V</i>) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: In this case, <i>base</i> will never be <b>null</b> or
+ <b>undefined</b>.</li>
+ <li>Let <i>base</i> be <a href="#sec-toobject">ToObject</a>(<i>base</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>base.</i>[[Get]](<a href="#sec-reference-specification-type">GetReferencedName</a>(<i>V</i>), <a
+ href="#sec-getthisvalue">GetThisValue</a>(<i>V</i>)).</li>
+ </ol>
+ </li>
+ <li>Else <i>base</i> must be an environment record,
+ <ol class="block">
+ <li>Return <i>base.</i>GetBindingValue(<a href="#sec-reference-specification-type">GetReferencedName</a>(<i>V</i>),
+ <a href="#sec-reference-specification-type">IsStrictReference</a>(<i>V</i>)) (<a
+ href="#sec-environment-records">see 8.1.1</a>).</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The object that may be created in step 5.a.ii is not accessible outside of the above
+ abstract operation and the ordinary object [[Get]] internal method. An implementation might choose to avoid the actual
+ creation of the object.</p>
+ </div>
+ </section>
+
+ <section id="sec-putvalue">
+ <h1><span class="secnum" id="sec-6.2.3.2"><a href="#sec-putvalue" title="link to this section">6.2.3.2</a></span> PutValue
+ (V, W)</h1>
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>V</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>W</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is not <a
+ href="#sec-reference-specification-type">Reference</a>, throw a <b>ReferenceError</b> exception.</li>
+ <li>Let <i>base</i> be <a href="#sec-reference-specification-type">GetBase</a>(<i>V</i>).</li>
+ <li>If <a href="#sec-reference-specification-type">IsUnresolvableReference</a>(<i>V</i>), then
+ <ol class="block">
+ <li>If <a href="#sec-reference-specification-type">IsStrictReference</a>(<i>V</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Throw <b>ReferenceError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Let <i>globalObj</i> be <a href="#sec-getglobalobject">GetGlobalObject</a>().</li>
+ <li>Return <a href="#sec-set-o-p-v-throw">Set</a>(<i>globalObj</i>,<a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>V</i>), <i>W</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ <li>Else if <a href="#sec-reference-specification-type">IsPropertyReference</a>(<i>V</i>), then
+ <ol class="block">
+ <li>If <a href="#sec-reference-specification-type">HasPrimitiveBase</a>(<i>V</i>) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: In this case, <i>base</i> will never be <b>null</b> or
+ <b>undefined</b>.</li>
+ <li>Set <i>base</i> to <a href="#sec-toobject">ToObject</a>(<i>base</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>succeeded</i> be <i>base.</i>[[Set]](<a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>V</i>), <i>W</i>, <a
+ href="#sec-getthisvalue">GetThisValue</a>(<i>V</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>succeeded</i>).</li>
+ <li>If <i>succeeded</i> is <b>false</b> and <a
+ href="#sec-reference-specification-type">IsStrictReference</a>(<i>V</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Return.</li>
+ </ol>
+ </li>
+ <li>Else <i>base</i> must be an environment record.
+ <ol class="block">
+ <li>Return <i>base.</i>SetMutableBinding(<a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>V</i>), <i>W</i>, <a
+ href="#sec-reference-specification-type">IsStrictReference</a>(<i>V</i>)) (<a
+ href="#sec-environment-records">see 8.1.1</a>).</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The object that may be created in step 6.a.ii is not accessible outside of the above
+ algorithm and the ordinary object [[Set]] internal method. An implementation might choose to avoid the actual creation
+ of that object.</p>
+ </div>
+ </section>
+
+ <section id="sec-getthisvalue">
+ <h1><span class="secnum" id="sec-6.2.3.3"><a href="#sec-getthisvalue" title="link to this section">6.2.3.3</a></span>
+ GetThisValue (V)</h1>
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-reference-specification-type">IsPropertyReference</a>(<i>V</i>) is <b>true</b>.</li>
+ <li>If <a href="#sec-reference-specification-type">IsSuperReference</a>(<i>V</i>), then
+ <ol class="block">
+ <li>Return the value of the <i>thisValue</i> component of the reference <i>V</i>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-reference-specification-type">GetBase</a>(<i>V</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-initializereferencedbinding">
+ <h1><span class="secnum" id="sec-6.2.3.4"><a href="#sec-initializereferencedbinding"
+ title="link to this section">6.2.3.4</a></span> InitializeReferencedBinding (V, W)</h1>
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>V</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>W</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>)
+ is <a href="#sec-reference-specification-type">Reference</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-reference-specification-type">IsUnresolvableReference</a>(<i>V</i>) is <b>false</b>.</li>
+ <li>Let <i>base</i> be <a href="#sec-reference-specification-type">GetBase</a>(<i>V</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>base</i> is an <a href="#sec-environment-records">Environment
+ Record</a>.</li>
+ <li>Return <i>base.</i>InitializeBinding(<a href="#sec-reference-specification-type">GetReferencedName</a>(<i>V</i>),
+ <i>W</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-property-descriptor-specification-type">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.2.4"><a href="#sec-property-descriptor-specification-type"
+ title="link to this section">6.2.4</a></span> The Property Descriptor Specification Type</h1>
+
+ <p>The Property Descriptor type is used to explain the manipulation and reification of Object property attributes. Values
+ of the Property Descriptor type are Records. Each field’s name is an attribute name and its value is a corresponding
+ attribute value as specified in <a href="#sec-property-attributes">6.1.7.1</a>. In addition, any field may be present or
+ absent. The schema name used within this specification to tag literal descriptions of Property Descriptor records is
+ “PropertyDescriptor”.</p>
+
+ <p>Property Descriptor values may be further classified as data Property Descriptors and accessor Property Descriptors
+ based upon the existence or use of certain fields. A data Property Descriptor is one that includes any fields named either
+ [[Value]] or [[Writable]]. An accessor Property Descriptor is one that includes any fields named either [[Get]] or
+ [[Set]]. Any Property Descriptor may have fields named [[Enumerable]] and [[Configurable]]. A Property Descriptor value
+ may not be both a data Property Descriptor and an accessor Property Descriptor; however, it may be neither. A generic
+ Property Descriptor is a Property Descriptor value that is neither a data Property Descriptor nor an accessor Property
+ Descriptor. A fully populated Property Descriptor is one that is either an accessor Property Descriptor or a data Property
+ Descriptor and that has all of the fields that correspond to the property attributes defined in either <a
+ href="#table-2">Table 2</a> or <a href="#table-3">Table 3</a>.</p>
+
+ <p>The following abstract operations are used in this specification to operate upon Property Descriptor values:</p>
+ </div>
+
+ <section id="sec-isaccessordescriptor">
+ <h1><span class="secnum" id="sec-6.2.4.1"><a href="#sec-isaccessordescriptor"
+ title="link to this section">6.2.4.1</a></span> IsAccessorDescriptor ( Desc )</h1>
+
+ <p>When the abstract operation IsAccessorDescriptor is called with <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span>, the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>Desc</i> is <b>undefined</b>, return <b>false</b>.</li>
+ <li>If both <i>Desc</i>.[[Get]] and <i>Desc</i>.[[Set]] are absent, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isdatadescriptor">
+ <h1><span class="secnum" id="sec-6.2.4.2"><a href="#sec-isdatadescriptor" title="link to this section">6.2.4.2</a></span>
+ IsDataDescriptor ( Desc )</h1>
+
+ <p>When the abstract operation IsDataDescriptor is called with <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span>, the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>Desc</i> is <b>undefined</b>, return <b>false</b>.</li>
+ <li>If both <i>Desc</i>.[[Value]] and <i>Desc</i>.[[Writable]] are absent, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isgenericdescriptor">
+ <h1><span class="secnum" id="sec-6.2.4.3"><a href="#sec-isgenericdescriptor"
+ title="link to this section">6.2.4.3</a></span> IsGenericDescriptor ( Desc )</h1>
+
+ <p>When the abstract operation IsGenericDescriptor is called with <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span>, the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>Desc</i> is <b>undefined</b>, return <b>false</b>.</li>
+ <li>If <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>Desc</i>) and <a
+ href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>Desc</i>) are both <b>false</b>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-frompropertydescriptor">
+ <h1><span class="secnum" id="sec-6.2.4.4"><a href="#sec-frompropertydescriptor"
+ title="link to this section">6.2.4.4</a></span> FromPropertyDescriptor ( Desc )</h1>
+
+ <p>When the abstract operation FromPropertyDescriptor is called with <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span>, the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>Desc</i> is <b>undefined</b>, return <b>undefined</b>.</li>
+ <li>Let <i>obj</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%ObjectPrototype%</span>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>obj</i> is an extensible ordinary object with no own
+ properties.</li>
+ <li>If <i>Desc</i> has a [[Value]] field, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>,
+ "<b><code>value</code>"</b>, <i>Desc</i>.[[Value]]).</li>
+ </ol>
+ </li>
+ <li>If <i>Desc</i> has a [[Writable]] field, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>,
+ "<code>writable</code>", <i>Desc</i>.[[Writable]]).</li>
+ </ol>
+ </li>
+ <li>If <i>Desc</i> has a [[Get]] field, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>,
+ "<code>get",</code> <i>Desc</i>.[[Get]]).</li>
+ </ol>
+ </li>
+ <li>If <i>Desc</i> has a [[Set]] field, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>,
+ "<code>set</code>", <i>Desc</i>.[[Set]])</li>
+ </ol>
+ </li>
+ <li>If <i>Desc</i> has an [[Enumerable]] field, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>,
+ "<code>enumerable</code>", <i>Desc</i>.[[Enumerable]]).</li>
+ </ol>
+ </li>
+ <li>If <i>Desc</i> has a [[Configurable]] field, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i> ,
+ "<code>configurable</code>", <i>Desc</i>.[[Configurable]]).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: all of the above <a
+ href="#sec-createdataproperty">CreateDataProperty</a> operations return <b>true</b>.</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-topropertydescriptor">
+ <h1><span class="secnum" id="sec-6.2.4.5"><a href="#sec-topropertydescriptor"
+ title="link to this section">6.2.4.5</a></span> ToPropertyDescriptor ( Obj )</h1>
+
+ <p>When the abstract operation ToPropertyDescriptor is called with object <span class="nt">Obj</span>, the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>Obj</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>Obj</i>) is not Object throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>desc</i> be a new <a href="#sec-property-descriptor-specification-type">Property Descriptor</a> that
+ initially has no fields.</li>
+ <li>If <a href="#sec-hasproperty">HasProperty</a>(<i>Obj</i>, "<code>enumerable</code>") is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>enum</i> be <a href="#sec-get-o-p">Get</a>(<i>Obj</i>, "<code>enumerable</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>enum</i>).</li>
+ <li>Set the [[Enumerable]] field of <i>desc</i> to <a href="#sec-toboolean">ToBoolean</a>(<i>enum</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-hasproperty">HasProperty</a>(<i>Obj</i>, "<code>configurable</code>") is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>conf</i> be <a href="#sec-get-o-p">Get</a>(<i>Obj</i>, "<code>configurable</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>conf</i>).</li>
+ <li>Set the [[Configurable]] field of <i>desc</i> to <a href="#sec-toboolean">ToBoolean</a>(<i>conf</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-hasproperty">HasProperty</a>(<i>Obj</i>, "<code>value</code>") is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-get-o-p">Get</a>(<i>Obj</i>, "<code>value</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>Set the [[Value]] field of <i>desc</i> to <i>value</i>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-hasproperty">HasProperty</a>(<i>Obj</i>, "<code>writable</code>") is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>writable</i> be <a href="#sec-get-o-p">Get</a>(<i>Obj</i>, "<code>writable</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>writable</i>).</li>
+ <li>Set the [[Writable]] field of <i>desc</i> to <a href="#sec-toboolean">ToBoolean</a>(<i>writable</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-hasproperty">HasProperty</a>(<i>Obj</i>, "<code>get</code>") is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>getter</i> be <a href="#sec-get-o-p">Get</a>(<i>Obj</i>, "<code>get</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>getter</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>getter</i>) is <b>false</b> and <i>getter</i> is not
+ <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Set the [[Get]] field of <i>desc</i> to <i>getter</i>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-hasproperty">HasProperty</a>(<i>Obj</i>, "<code>set</code>") is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>setter</i> be <a href="#sec-get-o-p">Get</a>(<i>Obj</i>, "<code>set</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setter</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>setter</i>) is <b>false</b> and <i>setter</i> is not
+ <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Set the [[Set]] field of <i>desc</i> to <i>setter</i>.</li>
+ </ol>
+ </li>
+ <li>If either <i>desc</i>.[[Get]] or <i>desc</i>.[[Set]] are present, then
+ <ol class="block">
+ <li>If either <i>desc</i>.[[Value]] or <i>desc</i>.[[Writable]] are present, throw a <b>TypeError</b>
+ exception.</li>
+ </ol>
+ </li>
+ <li>Return <i>desc</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-completepropertydescriptor">
+ <h1><span class="secnum" id="sec-6.2.4.6"><a href="#sec-completepropertydescriptor"
+ title="link to this section">6.2.4.6</a></span> CompletePropertyDescriptor ( Desc )</h1>
+
+ <p>When the abstract operation CompletePropertyDescriptor is called with <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span> the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>Desc</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>Desc</i> is a <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a></li>
+ <li>Let <i>like</i> be Record{[[Value]]: <b>undefined</b>, [[Writable]]: <b>false</b>, [[Get]]: <b>undefined</b>,
+ [[Set]]: <b>undefined</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b>}.</li>
+ <li>If either <a href="#sec-isgenericdescriptor">IsGenericDescriptor</a>(<i>Desc</i>) or <a
+ href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>Desc</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>Desc</i> does not have a [[Value]] field, set <i>Desc</i>.[[Value]] to <i>like</i>.[[Value]].</li>
+ <li>If <i>Desc</i> does not have a [[Writable]] field, set <i>Desc</i>.[[Writable]] to
+ <i>like</i>.[[Writable]].</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>If <i>Desc</i> does not have a [[Get]] field, set <i>Desc</i>.[[Get]] to <i>like</i>.[[Get]].</li>
+ <li>If <i>Desc</i> does not have a [[Set]] field, set <i>Desc</i>.[[Set]] to <i>like</i>.[[Set]].</li>
+ </ol>
+ </li>
+ <li>If <i>Desc</i> does not have an [[Enumerable]] field, set <i>Desc</i>.[[Enumerable]] to
+ <i>like</i>.[[Enumerable]].</li>
+ <li>If <i>Desc</i> does not have a [[Configurable]] field, set <i>Desc</i>.[[Configurable]] to
+ <i>like</i>.[[Configurable]].</li>
+ <li>Return <i>Desc</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-lexical-environment-and-environment-record-specification-types">
+ <h1><span class="secnum" id="sec-6.2.5"><a href="#sec-lexical-environment-and-environment-record-specification-types"
+ title="link to this section">6.2.5</a></span> The Lexical Environment and Environment Record Specification Types</h1>
+
+ <p>The <a href="#sec-lexical-environments">Lexical Environment</a> and <a href="#sec-environment-records">Environment
+ Record</a> types are used to explain the behaviour of name resolution in nested functions and blocks. These types and the
+ operations upon them are defined in <a href="#sec-lexical-environments">8.1</a>.</p>
+ </section>
+
+ <section id="sec-data-blocks">
+ <div class="front">
+ <h1><span class="secnum" id="sec-6.2.6"><a href="#sec-data-blocks" title="link to this section">6.2.6</a></span> Data
+ Blocks</h1>
+
+ <p>The Data Block specification type is used to describe a distinct and mutable sequence of byte-sized (8 bit) numeric
+ values. A Data Block value is created with a fixed number of bytes that each have the initial value 0.</p>
+
+ <p>For notational convenience within this specification, an array-like syntax can be used to express to the individual
+ bytes of a Data Block value. This notation presents a Data Block value as a 0-origined integer indexed sequence of bytes.
+ For example, if <var>db</var> is a 5 byte Data Block value then <var>db</var>[2] can be used to express access to its
+ 3<sup>rd</sup> byte.</p>
+
+ <p>The following abstract operations are used in this specification to operate upon Data Block values:</p>
+ </div>
+
+ <section id="sec-createbytedatablock">
+ <h1><span class="secnum" id="sec-6.2.6.1"><a href="#sec-createbytedatablock"
+ title="link to this section">6.2.6.1</a></span> CreateByteDataBlock(size)</h1>
+
+ <p>When the abstract operation CreateByteDataBlock is called with integer argument <var>size</var>, the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>size</i>≥0.</li>
+ <li>Let <i>db</i> be a new <a href="#sec-data-blocks">Data Block</a> value consisting of <i>size</i> bytes. If it is
+ impossible to create such a <a href="#sec-data-blocks">Data Block</a>, throw a <b>RangeError</b> exception.</li>
+ <li>Set all of the bytes of <i>db</i> to 0.</li>
+ <li>Return <i>db</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-copydatablockbytes">
+ <h1><span class="secnum" id="sec-6.2.6.2"><a href="#sec-copydatablockbytes"
+ title="link to this section">6.2.6.2</a></span> CopyDataBlockBytes(toBlock, toIndex, fromBlock, fromIndex, count)</h1>
+
+ <p>When the abstract operation CopyDataBlockBytes is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>fromBlock</i> and <i>toBlock</i> are distinct <a
+ href="#sec-data-blocks">Data Block</a> values.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>fromIndex</i>, <i>toIndex</i>, and <i>count</i> are positive
+ integer values.</li>
+ <li>Let <i>fromSize</i> be the number of bytes in <i>fromBlock</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>fromIndex</i>+<i>count</i> ≤ <i>fromSize</i>.</li>
+ <li>Let <i>toSize</i> be the number of bytes in <i>toBlock</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>toIndex</i>+<i>count</i> ≤ <i>toSize</i>.</li>
+ <li>Repeat, while <i>count</i>>0
+ <ol class="block">
+ <li>Set <i>toBlock</i>[<i>toIndex</i>] to the value of <i>fromBlock</i>[<i>fromIndex</i>].</li>
+ <li>Increment <i>toIndex</i> and <i>fromIndex</i> each by 1.</li>
+ <li>Decrement <i>count</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>)</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+</section>
+
+<section id="sec-abstract-operations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7"><a href="#sec-abstract-operations" title="link to this section">7</a></span> Abstract
+ Operations</h1>
+
+ <p>These operations are not a part of the ECMAScript language; they are defined here to solely to aid the specification of the
+ semantics of the ECMAScript language. Other, more specialized abstract operations are defined throughout this
+ specification.</p>
+ </div>
+
+ <section id="sec-type-conversion">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.1"><a href="#sec-type-conversion" title="link to this section">7.1</a></span> Type
+ Conversion</h1>
+
+ <p>The ECMAScript language implicitly performs automatic type conversion as needed. To clarify the semantics of certain
+ constructs it is useful to define a set of conversion abstract operations. The conversion abstract operations are
+ polymorphic; they can accept a value of any <a href="#sec-ecmascript-language-types">ECMAScript language type</a> or of a <a
+ href="#sec-completion-record-specification-type">Completion Record</a> value. But no other specification types are used with
+ these operations.</p>
+ </div>
+
+ <section id="sec-toprimitive">
+ <h1><span class="secnum" id="sec-7.1.1"><a href="#sec-toprimitive" title="link to this section">7.1.1</a></span> ToPrimitive
+ ( input [, PreferredType] )</h1>
+
+ <p>The abstract operation ToPrimitive takes an <var>input</var> argument and an optional argument <span
+ class="nt">PreferredType</span>. The abstract operation ToPrimitive converts its <var>input</var> argument to a non-Object
+ type. If an object is capable of converting to more than one primitive type, it may use the optional hint <span
+ class="nt">PreferredType</span> to favour that type. Conversion occurs according to <a href="#table-9">Table 9</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-9">Table 9</span> — ToPrimitive Conversions</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Input Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Result</th>
+ </tr>
+ <tr>
+ <td><a href="#sec-completion-record-specification-type">Completion Record</a></td>
+ <td>If <var>input</var> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <var>input</var>. Otherwise return ToPrimitive(<var>input</var>.[[value]]) also passing the optional hint <span class="nt">PreferredType</span>.</td>
+ </tr>
+ <tr>
+ <td>Undefined</td>
+ <td>Return <var>input</var>.</td>
+ </tr>
+ <tr>
+ <td>Null</td>
+ <td>Return <var>input</var>.</td>
+ </tr>
+ <tr>
+ <td>Boolean</td>
+ <td>Return <var>input</var>.</td>
+ </tr>
+ <tr>
+ <td>Number</td>
+ <td>Return <var>input</var>.</td>
+ </tr>
+ <tr>
+ <td>String</td>
+ <td>Return <var>input</var>.</td>
+ </tr>
+ <tr>
+ <td>Symbol</td>
+ <td>Return <var>input</var>.</td>
+ </tr>
+ <tr>
+ <td>Object</td>
+ <td>Perform the steps following this table.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>When <span style="font-family: Times New Roman"><a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>input</i>)</span> is Object, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>PreferredType</i> was not passed, let <i>hint</i> be "<code>default</code>".</li>
+ <li>Else if <i>PreferredType</i> is hint String, let <i>hint</i> be "<code>string</code>".</li>
+ <li>Else <i>PreferredType</i> is hint Number, let <i>hint</i> be "<code>number</code>".</li>
+ <li>Let <i>exoticToPrim</i> be <a href="#sec-getmethod">GetMethod</a>(<i>input</i>, @@toPrimitive).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exoticToPrim</i>).</li>
+ <li>If <i>exoticToPrim</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-call">Call</a>(<i>exoticToPrim</i>, <i>input,</i>
+ «<i>hint</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>result</i>) is not Object, return
+ <i>result</i>.</li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>If <i>hint</i> is "<code>default</code>", let <i>hint</i> be "<code>number</code>".</li>
+ <li>Return OrdinaryToPrimitive(<i>input,hint</i>).</li>
+ </ol>
+
+ <p>When the abstract operation OrdinaryToPrimitive is called with arguments <var>O</var> and <var>hint</var>, the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>hint</i>)
+ is String and its value is either "<code>string</code>" or "<code>number</code>".</li>
+ <li>If <i>hint</i> is "<code>string</code>", then
+ <ol class="block">
+ <li>Let <i>methodNames</i> be «"<code>toString</code>", "<code>valueOf</code>"».</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>methodNames</i> be «"<code>valueOf</code>", "<code>toString</code>"».</li>
+ </ol>
+ </li>
+ <li>For each <i>name</i> in <i>methodNames</i> in <a href="#sec-list-and-record-specification-type">List</a> order, do
+ <ol class="block">
+ <li>Let <i>method</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>name</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>method</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>method</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-call">Call</a>(<i>method</i>, <i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>result</i>) is not Object, return
+ <i>result</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When ToPrimitive is called with no hint, then it generally behaves as if the hint were
+ Number. However, objects may over-ride this behaviour by defining a @@toPrimitive method. Of the objects defined in this
+ specification only Date objects (<a href="#sec-date.prototype-@@toprimitive">see 20.3.4.45</a>) and Symbol objects (<a
+ href="#sec-symbol.prototype-@@toprimitive">see 19.4.3.4</a>) over-ride the default ToPrimitive behaviour. Date objects
+ treat no hint as if the hint were String.</p>
+ </div>
+ </section>
+
+ <section id="sec-toboolean">
+ <h1><span class="secnum" id="sec-7.1.2"><a href="#sec-toboolean" title="link to this section">7.1.2</a></span> ToBoolean (
+ argument )</h1>
+
+ <p>The abstract operation ToBoolean converts <var>argument</var> to a value of type Boolean according to <a
+ href="#table-10">Table 10</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-10">Table 10</span> — ToBoolean Conversions</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Argument Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Result</th>
+ </tr>
+ <tr>
+ <td><a href="#sec-completion-record-specification-type">Completion Record</a></td>
+ <td>If <var>argument</var> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <var>argument</var>. Otherwise return ToBoolean(<var>argument</var>.[[value]]).</td>
+ </tr>
+ <tr>
+ <td>Undefined</td>
+ <td>Return <b>false</b>.</td>
+ </tr>
+ <tr>
+ <td>Null</td>
+ <td>Return <b>false</b>.</td>
+ </tr>
+ <tr>
+ <td>Boolean</td>
+ <td>Return <var>argument</var>.</td>
+ </tr>
+ <tr>
+ <td>Number</td>
+ <td>Return <b>false</b> if <var>argument</var> is <b>+0</b>, <b>−0</b>, or <b>NaN</b>; otherwise return <b>true</b>.</td>
+ </tr>
+ <tr>
+ <td>String</td>
+ <td>Return <b>false</b> if <var>argument</var> is the empty String (its length is zero); otherwise return <b>true</b>.</td>
+ </tr>
+ <tr>
+ <td>Symbol</td>
+ <td>Return <b>true</b>.</td>
+ </tr>
+ <tr>
+ <td>Object</td>
+ <td>Return <b>true</b>.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-tonumber">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.1.3"><a href="#sec-tonumber" title="link to this section">7.1.3</a></span> ToNumber (
+ argument )</h1>
+
+ <p>The abstract operation ToNumber converts <var>argument</var> to a value of type Number according to <a
+ href="#table-11">Table 11</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-11">Table 11</span> — ToNumber Conversions</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Argument Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Result</th>
+ </tr>
+ <tr>
+ <td><a href="#sec-completion-record-specification-type">Completion Record</a></td>
+ <td>If <var>argument</var> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <var>argument</var>. Otherwise return ToNumber(<var>argument</var>.[[value]]).</td>
+ </tr>
+ <tr>
+ <td>Undefined</td>
+ <td>Return <b>NaN</b>.</td>
+ </tr>
+ <tr>
+ <td>Null</td>
+ <td>Return <b>+0</b>.</td>
+ </tr>
+ <tr>
+ <td>Boolean</td>
+ <td>Return <b>1</b> if <var>argument</var> is <b>true</b>. Return <b>+0</b> if <var>argument</var> is <b>false</b>.</td>
+ </tr>
+ <tr>
+ <td>Number</td>
+ <td>Return <var>argument</var> (no conversion).</td>
+ </tr>
+ <tr>
+ <td>String</td>
+ <td>See grammar and conversion algorithm below.</td>
+ </tr>
+ <tr>
+ <td>Symbol</td>
+ <td>Throw a <b>TypeError</b> exception.</td>
+ </tr>
+ <tr>
+ <td>Object</td>
+
+ <td>
+ <p>Apply the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>primValue</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>argument</i>, hint Number).</li>
+ <li>Return ToNumber(<i>primValue</i>).</li>
+ </ol>
+ </td>
+ </tr>
+ </table>
+ </figure>
+ </div>
+
+ <section id="sec-tonumber-applied-to-the-string-type">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.1.3.1"><a href="#sec-tonumber-applied-to-the-string-type"
+ title="link to this section">7.1.3.1</a></span> ToNumber Applied to the String Type</h1>
+
+ <p><a href="#sec-tonumber">ToNumber</a> applied to Strings applies the following grammar to the input String interpreted
+ as a sequence of UTF-16 encoded code points (<a href="#sec-ecmascript-language-types-string-type">6.1.4</a>). If the
+ grammar cannot interpret the String as an expansion of <span class="nt">StringNumericLiteral</span>, then the result of
+ <a href="#sec-tonumber">ToNumber</a> is <b>NaN</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The terminal symbols of this grammar are all composed of Unicode BMP code points so
+ the result will be <b>NaN</b> if the string contains the UTF-16 encoding of any supplementary code points or any
+ unpaired surrogate code points</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StringNumericLiteral</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">StrWhiteSpace</span><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">StrWhiteSpace</span><sub>opt</sub> <span class="nt">StrNumericLiteral</span> <span class="nt">StrWhiteSpace</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StrWhiteSpace</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">StrWhiteSpaceChar</span> <span class="nt">StrWhiteSpace</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StrWhiteSpaceChar</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StrNumericLiteral</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">StrDecimalLiteral</span></div>
+ <div class="rhs"><span class="nt">BinaryIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">OctalIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">HexIntegerLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StrDecimalLiteral</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">StrUnsignedDecimalLiteral</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">StrUnsignedDecimalLiteral</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">StrUnsignedDecimalLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">Infinity</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <code class="t">.</code> <span class="nt">DecimalDigits</span><sub>opt</sub> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">.</code> <span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalDigits</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <span class="nt">DecimalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalDigit</span> <span class="geq">:::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExponentPart</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">ExponentIndicator</span> <span class="nt">SignedInteger</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExponentIndicator</span> <span class="geq">:::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">e</code> <code class="t">E</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SignedInteger</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">DecimalDigits</span></div>
+ </div>
+
+ <p>All grammar symbols not explicitly defined above have the definitions used in the Lexical Grammar for numeric
+ literals (<a href="#sec-literals-numeric-literals">11.8.3</a>)</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Some differences should be noted between the syntax of a <i>StringNumericLiteral</i>
+ and a <i>NumericLiteral</i> (<a href="#sec-literals-numeric-literals">see 11.8.3</a>):</p>
+
+ <ul>
+ <li>
+ <p>A <i>StringNumericLiteral</i> may include leading and/or trailing white space and/or line terminators.</p>
+ </li>
+
+ <li>
+ <p>A <i>StringNumericLiteral</i> that is decimal may have any number of leading <code>0</code> digits.</p>
+ </li>
+
+ <li>
+ <p>A <i>StringNumericLiteral</i> that is decimal may include a <code>+</code> or <code>-</code> to indicate its
+ sign.</p>
+ </li>
+
+ <li>
+ <p>A <i>StringNumericLiteral</i> that is empty or contains only white space is converted to <b>+0</b>.</p>
+ </li>
+
+ <li>
+ <p><code>Infinity</code> <code>and –Infinity</code> are recognized as a <i>StringNumericLiteral</i> but not
+ as a <i>NumericLiteral</i>.</p>
+ </li>
+ </ul>
+ </div>
+ </div>
+
+ <section id="sec-runtime-semantics-mv-s">
+ <h1><span class="secnum" id="sec-7.1.3.1.1"><a href="#sec-runtime-semantics-mv-s"
+ title="link to this section">7.1.3.1.1</a></span> Runtime Semantics: MV’s</h1>
+
+ <p>The conversion of a String to a Number value is similar overall to the determination of the Number value for a
+ numeric literal (<a href="#sec-literals-numeric-literals">see 11.8.3</a>), but some of the details are different, so the
+ process for converting a String numeric literal to a value of Number type is given here. This value is determined in two
+ steps: first, a mathematical value (MV) is derived from the String numeric literal; second, this mathematical value is
+ rounded as described below. The MV on any grammar symbol, not provided below, is the MV for that symbol defined in <a
+ href="#sec-static-semantics-mv-s">11.8.3.1</a>.</p>
+
+ <ul>
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StringNumericLiteral</span> <span class="geq">:::</span> <span
+ class="grhsannot">[empty]</span></span> is 0.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StringNumericLiteral</span> <span class="geq">:::</span> <span
+ class="nt">StrWhiteSpace</span></span> is 0.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StringNumericLiteral</span> <span class="geq">:::</span> <span
+ class="nt">StrWhiteSpace</span><sub>opt</sub> <span class="nt">StrNumericLiteral</span> <span
+ class="nt">StrWhiteSpace</span><sub>opt</sub></span> is the MV of <span class="nt">StrNumericLiteral</span>, no
+ matter whether white space is present or not.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrNumericLiteral</span> <span class="geq">:::</span> <span
+ class="nt">StrDecimalLiteral</span></span> is the MV of <span class="nt">StrDecimalLiteral</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrNumericLiteral</span> <span class="geq">:::</span> <span
+ class="nt">BinaryIntegerLiteral</span></span> is the MV of <span class="nt">BinaryIntegerLiteral</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrNumericLiteral</span> <span class="geq">:::</span> <span
+ class="nt">OctalIntegerLiteral</span></span> is the MV of <span class="nt">OctalIntegerLiteral</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrNumericLiteral</span> <span class="geq">:::</span> <span
+ class="nt">HexIntegerLiteral</span></span> is the MV of <span class="nt">HexIntegerLiteral</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">StrUnsignedDecimalLiteral</span></span> is the MV of <span
+ class="nt">StrUnsignedDecimalLiteral</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrDecimalLiteral</span> <span class="geq">:::</span> <code
+ class="t">+</code> <span class="nt">StrUnsignedDecimalLiteral</span></span> is the MV of <span
+ class="nt">StrUnsignedDecimalLiteral</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrDecimalLiteral</span> <span class="geq">:::</span> <code
+ class="t">-</code> <span class="nt">StrUnsignedDecimalLiteral</span></span> is the negative of the MV of <span
+ class="nt">StrUnsignedDecimalLiteral</span>. (Note that if the MV of <span
+ class="nt">StrUnsignedDecimalLiteral</span> is 0, the negative of this MV is also 0. The rounding rule described
+ below handles the conversion of this signless mathematical zero to a floating-point <b>+0</b> or <b>−0</b> as
+ appropriate.)</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">Infinity</span></span> is <span style="font-family: Times New Roman">10<sup>10000</sup></span> (a value
+ so large that it will round to <b>+∞</b>).</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">DecimalDigits</span> <code class="t">.</code></span> is the MV of <span
+ class="nt">DecimalDigits</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">DecimalDigits</span> <code class="t">.</code> <span class="nt">DecimalDigits</span></span> is the MV of
+ the first <span class="nt">DecimalDigits</span> plus (the MV of the second <span class="nt">DecimalDigits</span>
+ times <span style="font-family: Times New Roman">10<sup>−<i>n</i></sup></span>), where <var>n</var> is the
+ number of code points in the second <span class="nt">DecimalDigits</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">DecimalDigits</span> <code class="t">.</code> <span class="nt">ExponentPart</span></span> is the MV of
+ <i>DecimalDigits</i> times 10<sup><i>e</i></sup>, where <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">DecimalDigits</span> <code class="t">.</code> <span class="nt">DecimalDigits</span> <span
+ class="nt">ExponentPart</span></span> is (the MV of the first <i>DecimalDigits</i> plus (the MV of the second
+ <i>DecimalDigits</i> times 10<sup>−<i>n</i></sup>)) times 10<sup><i>e</i></sup>, where <i>n</i> is the number
+ of code points in the second <i>DecimalDigits</i> and <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <code
+ class="t">.</code> <span class="nt">DecimalDigits</span></span> is the MV of <i>DecimalDigits</i> times
+ 10<sup>−<i>n</i></sup>, where <i>n</i> is the number of code points in <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <code
+ class="t">.</code> <span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span></span> is the MV of
+ <i>DecimalDigits</i> times 10<sup><i>e</i>−<i>n</i></sup>, where <i>n</i> is the number of code points in
+ <i>DecimalDigits</i> and <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">DecimalDigits</span></span> is the MV of <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> <span
+ class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span></span> is the MV of <i>DecimalDigits</i> times
+ 10<sup><i>e</i></sup>, where <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+ </ul>
+
+ <p>Once the exact MV for a String numeric literal has been determined, it is then rounded to a value of the Number type.
+ If the MV is 0, then the rounded value is +0 unless the first non white space code point in the String numeric literal
+ is ‘<code>-</code>’, in which case the rounded value is −0. Otherwise, the rounded value must be the
+ Number value for the MV (in the sense defined in <a href="#sec-ecmascript-language-types-number-type">6.1.6</a>), unless
+ the literal includes a <span class="nt">StrUnsignedDecimalLiteral</span> and the literal has more than 20 significant
+ digits, in which case the Number value may be either the Number value for the MV of a literal produced by replacing each
+ significant digit after the 20th with a 0 digit or the Number value for the MV of a literal produced by replacing each
+ significant digit after the 20th with a 0 digit and then incrementing the literal at the 20th digit position. A digit is
+ significant if it is not part of an <span class="nt">ExponentPart</span> and</p>
+
+ <ul>
+ <li>it is not <code>0</code>; or</li>
+ <li>there is a nonzero digit to its left and there is a nonzero digit, not in the <span
+ class="nt">ExponentPart</span>, to its right.</li>
+ </ul>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-tointeger">
+ <h1><span class="secnum" id="sec-7.1.4"><a href="#sec-tointeger" title="link to this section">7.1.4</a></span> ToInteger (
+ argument )</h1>
+
+ <p>The abstract operation ToInteger converts <var>argument</var> to an integral numeric value. This abstract operation
+ functions as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, return <b>+0</b>.</li>
+ <li>If <i>number</i> is <b>+0</b>, <b>−0</b>, <b>+∞,</b> or <b>−∞</b>, return <i>number</i>.</li>
+ <li>Return the number value that is the same sign as <i>number</i> and whose magnitude is <a
+ href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>number</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-toint32">
+ <h1><span class="secnum" id="sec-7.1.5"><a href="#sec-toint32" title="link to this section">7.1.5</a></span> ToInt32 (
+ argument )</h1>
+
+ <p>The abstract operation ToInt32 converts <var>argument</var> to one of <span style="font-family: Times New
+ Roman">2<sup>32</sup></span> integer values in the range <span style="font-family: Times New
+ Roman">−2<sup>31</sup></span> through <span style="font-family: Times New Roman">2<sup>31</sup>−1</span>,
+ inclusive. This abstract operation functions as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+0</b>, <b>−0</b>, <b>+∞</b>, or <b>−∞</b>, return
+ <b>+0</b>.</li>
+ <li>Let <i>int</i> be the mathematical value that is the same sign as <i>number</i> and whose magnitude is <a
+ href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>number</i>)).</li>
+ <li>Let <i>int32bit</i> be <i>int</i> <a href="#sec-algorithm-conventions">modulo</a> 2<sup>32</sup>.</li>
+ <li>If <i>int32bit</i> ≥ 2<sup>31</sup>, return <i>int32bit</i> − 2<sup>32</sup>, otherwise return
+ <i>int32bit</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Given the above definition of ToInt32:</p>
+
+ <ul>
+ <li>
+ <p>The ToInt32 abstract operation is idempotent: if applied to a result that it produced, the second application
+ leaves that value unchanged.</p>
+ </li>
+
+ <li>
+ <p><i>ToInt32(<a href="#sec-touint32">ToUint32</a>(x))</i> is equal to ToInt32(<i>x</i>) for all values of <i>x</i>.
+ (It is to preserve this latter property that +<b>∞</b> and −<b>∞</b> are mapped to <b>+0</b>.)</p>
+ </li>
+
+ <li>
+ <p>ToInt32 maps <b>−0</b> to <b>+0</b>.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-touint32">
+ <h1><span class="secnum" id="sec-7.1.6"><a href="#sec-touint32" title="link to this section">7.1.6</a></span> ToUint32 (
+ argument )</h1>
+
+ <p>The abstract operation ToUint32 converts <var>argument</var> to one of <span style="font-family: Times New
+ Roman">2<sup>32</sup></span> integer values in the range <span style="font-family: Times New Roman">0</span> through <span
+ style="font-family: Times New Roman">2<sup>32</sup>−1</span>, inclusive. This abstract operation functions as
+ follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+0</b>, <b>−0</b>, <b>+∞</b>, or <b>−∞</b>, return
+ <b>+0</b>.</li>
+ <li>Let <i>int</i> be the mathematical value that is the same sign as <i>number</i> and whose magnitude is <a
+ href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>number</i>)).</li>
+ <li>Let <i>int32bit</i> be <i>int</i> <a href="#sec-algorithm-conventions">modulo</a> 2<sup>32</sup>.</li>
+ <li>Return <i>int32bit</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Given the above definition of ToUint32:</p>
+
+ <ul>
+ <li>
+ <p>Step 6 is the only difference between ToUint32 and <a href="#sec-toint32">ToInt32</a>.</p>
+ </li>
+
+ <li>
+ <p>The ToUint32 abstract operation is idempotent: if applied to a result that it produced, the second application
+ leaves that value unchanged.</p>
+ </li>
+
+ <li>
+ <p>ToUint32(<a href="#sec-toint32">ToInt32</a>(<i>x</i>)) is equal to ToUint32(<i>x</i>) for all values of <i>x</i>.
+ (It is to preserve this latter property that <b>+∞</b> and <b>−∞</b> are mapped to <b>+0</b>.)</p>
+ </li>
+
+ <li>
+ <p>ToUint32 maps <b>−0</b> to <b>+0</b>.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-toint16">
+ <h1><span class="secnum" id="sec-7.1.7"><a href="#sec-toint16" title="link to this section">7.1.7</a></span> ToInt16 (
+ argument )</h1>
+
+ <p>The abstract operation ToInt16 converts <var>argument</var> to one of <span style="font-family: Times New
+ Roman">2<sup>16</sup></span> integer values in the range <span style="font-family: Times New Roman">−32768</span>
+ through <span style="font-family: Times New Roman">32767</span>, inclusive. This abstract operation functions as
+ follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+0</b>, <b>−0</b>, <b>+∞</b>, or <b>−∞</b>, return
+ <b>+0</b>.</li>
+ <li>Let <i>int</i> be the mathematical value that is the same sign as <i>number</i> and whose magnitude is <a
+ href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>number</i>)).</li>
+ <li>Let <i>int16bit</i> be <i>int</i> <a href="#sec-algorithm-conventions">modulo</a> 2<sup>16</sup>.</li>
+ <li>If <i>int16bit</i> ≥ 2<sup>15</sup>, return <i>int16bit</i> − 2<sup>16</sup>, otherwise return
+ <i>int16bit</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-touint16">
+ <h1><span class="secnum" id="sec-7.1.8"><a href="#sec-touint16" title="link to this section">7.1.8</a></span> ToUint16 (
+ argument )</h1>
+
+ <p>The abstract operation ToUint16 converts <var>argument</var> to one of <span style="font-family: Times New
+ Roman">2<sup>16</sup></span> integer values in the range <span style="font-family: Times New Roman">0</span> through <span
+ style="font-family: Times New Roman">2<sup>16</sup>−1</span>, inclusive. This abstract operation functions as
+ follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+0</b>, <b>−0</b>, <b>+∞</b>, or <b>−∞</b>, return
+ <b>+0</b>.</li>
+ <li>Let <i>int</i> be the mathematical value that is the same sign as <i>number</i> and whose magnitude is <a
+ href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>number</i>)).</li>
+ <li>Let <i>int16bit</i> be <i>int</i> <a href="#sec-algorithm-conventions">modulo</a> 2<sup>16</sup>.</li>
+ <li>Return <i>int16bit</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Given the above definition of ToUint16:</p>
+
+ <ul>
+ <li>The substitution of 2<sup>16</sup> for 2<sup>32</sup> in step 5 is the only difference between <a
+ href="#sec-touint32">ToUint32</a> and ToUint16.</li>
+ <li>ToUint16 maps <b>−0</b> to <span style="font-family: sans-serif"><b>+0</b></span>.</li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-toint8">
+ <h1><span class="secnum" id="sec-7.1.9"><a href="#sec-toint8" title="link to this section">7.1.9</a></span> ToInt8 (
+ argument )</h1>
+
+ <p>The abstract operation ToInt8 converts <var>argument</var> to one of <span style="font-family: Times New
+ Roman">2<sup>8</sup></span> integer values in the range <span style="font-family: Times New Roman">−128</span> through
+ <span style="font-family: Times New Roman">127</span>, inclusive. This abstract operation functions as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+0</b>, <b>−0</b>, <b>+∞</b>, or <b>−∞</b>, return
+ <b>+0</b>.</li>
+ <li>Let <i>int</i> be the mathematical value that is the same sign as <i>number</i> and whose magnitude is <a
+ href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>number</i>)).</li>
+ <li>Let <i>int8bit</i> be <i>int</i> <a href="#sec-algorithm-conventions">modulo</a> 2<sup>8</sup>.</li>
+ <li>If <i>int8bit</i> ≥ 2<sup>7</sup>, return <i>int8bit</i> − 2<sup>8</sup>, otherwise return
+ <i>int8bit</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-touint8">
+ <h1><span class="secnum" id="sec-7.1.10"><a href="#sec-touint8" title="link to this section">7.1.10</a></span> ToUint8 (
+ argument )</h1>
+
+ <p>The abstract operation ToUint8 converts <var>argument</var> to one of <span style="font-family: Times New
+ Roman">2<sup>8</sup></span> integer values in the range <span style="font-family: Times New Roman">0</span> through <span
+ style="font-family: Times New Roman">255</span>, inclusive. This abstract operation functions as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+0</b>, <b>−0</b>, <b>+∞</b>, or <b>−∞</b>, return
+ <b>+0</b>.</li>
+ <li>Let <i>int</i> be the mathematical value that is the same sign as <i>number</i> and whose magnitude is <a
+ href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>number</i>)).</li>
+ <li>Let <i>int8bit</i> be <i>int</i> <a href="#sec-algorithm-conventions">modulo</a> 2<sup>8</sup>.</li>
+ <li>Return <i>int8bit</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-touint8clamp">
+ <h1><span class="secnum" id="sec-7.1.11"><a href="#sec-touint8clamp" title="link to this section">7.1.11</a></span>
+ ToUint8Clamp ( argument )</h1>
+
+ <p>The abstract operation ToUint8Clamp converts <var>argument</var> to one of <span style="font-family: Times New
+ Roman">2<sup>8</sup></span> integer values in the range <span style="font-family: Times New Roman">0</span> through <span
+ style="font-family: Times New Roman">255</span>, inclusive. This abstract operation functions as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>number</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>number</i>).</li>
+ <li>If <i>number</i> is <b>NaN</b>, return <b>+0</b>.</li>
+ <li>If <i>number</i> ≤ 0, return <b>+0</b>.</li>
+ <li>If <i>number</i> ≥ 255, return 255.</li>
+ <li>Let <i>f</i> be <a href="#sec-algorithm-conventions">floor</a>(<i>number</i>).</li>
+ <li>If <i>f</i> <i>+</i> 0.5 < <i>number</i>, return <i>f</i> + 1.</li>
+ <li>If <i>number</i> < <i>f +</i> 0.5, return <i>f</i>.</li>
+ <li>If <i>f</i> is odd, return <i>f</i> + 1.</li>
+ <li>Return <i>f</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Note that unlike the other ECMAScript integer conversion abstract operation, ToUint8Clamp
+ rounds rather than truncates non-integer values and does not convert +<b>∞</b> to 0. ToUint8Clamp does “round
+ half to even” tie-breaking. This differs from <code><a href="#sec-math.round">Math.round</a></code> which does
+ “round half up” tie-breaking.</p>
+ </div>
+ </section>
+
+ <section id="sec-tostring">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.1.12"><a href="#sec-tostring" title="link to this section">7.1.12</a></span> ToString (
+ argument )</h1>
+
+ <p>The abstract operation ToString converts <var>argument</var> to a value of type String according to <a
+ href="#table-12">Table 12</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-12">Table 12</span> — ToString Conversions</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Argument Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Result</th>
+ </tr>
+ <tr>
+ <td><a href="#sec-completion-record-specification-type">Completion Record</a></td>
+ <td>If <var>argument</var> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <var>argument</var>. Otherwise return ToString(<var>argument</var>.[[value]]).</td>
+ </tr>
+ <tr>
+ <td>Undefined</td>
+ <td>Return <code>"undefined"</code>.</td>
+ </tr>
+ <tr>
+ <td>Null</td>
+ <td>Return <code>"null"</code>.</td>
+ </tr>
+ <tr>
+ <td>Boolean</td>
+
+ <td>
+ <p>If <var>argument</var> is <b>true</b>, return <code>"true"</code>.</p>
+
+ <p>If <var>argument</var> is <b>false</b>, return <b><code>"false"</code>.</b></p>
+ </td>
+ </tr>
+ <tr>
+ <td>Number</td>
+ <td>See <a href="#sec-tostring-applied-to-the-number-type">7.1.12.1</a>.</td>
+ </tr>
+ <tr>
+ <td>String</td>
+ <td>Return <var>argument</var>.</td>
+ </tr>
+ <tr>
+ <td>Symbol</td>
+ <td>Throw a <b>TypeError</b> exception.</td>
+ </tr>
+ <tr>
+ <td>Object</td>
+
+ <td>
+ <p>Apply the following steps:</p>
+
+ <p>1. Let <i>primValue</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>argument</i>, hint String).</p>
+
+ <p>2. Return ToString(<i>primValue</i>).</p>
+ </td>
+ </tr>
+ </table>
+ </figure>
+ </div>
+
+ <section id="sec-tostring-applied-to-the-number-type">
+ <h1><span class="secnum" id="sec-7.1.12.1"><a href="#sec-tostring-applied-to-the-number-type"
+ title="link to this section">7.1.12.1</a></span> ToString Applied to the Number Type</h1>
+
+ <p>The abstract operation <a href="#sec-tostring">ToString</a> converts a Number <var>m</var> to String format as
+ follows:</p>
+
+ <ol class="proc">
+ <li>If <i>m</i> is <b>NaN</b>, return the String <code>"NaN"</code>.</li>
+ <li>If <i>m</i> is <b>+0</b> or <b>−0</b>, return the String <code>"0"</code>.</li>
+ <li>If <i>m</i> is less than zero, return the String concatenation of the String <code>"-"</code> and <a
+ href="#sec-tostring">ToString</a>(−<i>m</i>).</li>
+ <li>If <i>m</i> is +∞, return the String <code>"Infinity"</code>.</li>
+ <li>Otherwise, let <i>n</i>, <i>k</i>, and <i>s</i> be integers such that <i>k</i> ≥ 1, 10<sup><i>k</i>−1</sup>
+ ≤ <i>s</i> < 10<sup><i>k</i></sup>, the Number value for <i>s</i> × 10<sup><i>n−k</i></sup> is
+ <i>m</i>, and <i>k</i> is as small as possible. Note that <i>k</i> is the number of digits in the decimal
+ representation of <i>s</i>, that <i>s</i> is not divisible by 10, and that the least significant digit of <i>s</i>
+ is not necessarily uniquely determined by these criteria.</li>
+ <li>If <i>k</i> ≤ <i>n</i> ≤ 21, return the String consisting of the code units of the <i>k</i> digits of the
+ decimal representation of <i>s</i> (in order, with no leading zeroes), followed by <i>n−k</i> occurrences of
+ the code unit 0x0030 <b>(</b>DIGIT ZERO).</li>
+ <li>If 0 < <i>n</i> ≤ 21, return the String consisting of the code units of the most significant <i>n</i> digits
+ of the decimal representation of <i>s</i>, followed by the code units 0x002E <b>(</b>FULL STOP<b>)</b>, followed by
+ the code units of the remaining <i>k−n</i> digits of the decimal representation of <i>s</i>.</li>
+ <li>If −6 < <i>n</i> ≤ 0, return the String consisting of the code unit 0x0030 (DIGIT ZERO), followed by the
+ code unit 0x002E (FULL STOP), followed by −<i>n</i> occurrences of the code unit 0x0030 (DIGIT ZERO), followed
+ by the code units of the <i>k</i> digits of the decimal representation of <i>s</i>.</li>
+ <li>Otherwise, if <i>k</i> = 1, return the String consisting of the code unit of the single digit of <i>s</i>, followed
+ by code unit 0x0065 (LATIN SMALL LETTER E), followed by the code unit 0x002B <b>(</b>PLUS SIGN<b>)</b> or the code
+ unit 0x002D (HYPHEN-MINUS) according to whether <i>n</i>−1 is positive or negative, followed by the code units
+ of the decimal representation of the integer <a href="#sec-algorithm-conventions">abs</a>(<i>n</i>−1) (with no
+ leading zeroes).</li>
+ <li>Return the String consisting of the code units of the most significant digit of the decimal representation of
+ <i>s</i>, followed by code unit 0x002E (FULL STOP), followed by the code units of the remaining <i>k</i>−1
+ digits of the decimal representation of <i>s</i>, followed by code unit 0x0065 (LATIN SMALL LETTER E), followed by
+ code unit 0x002B (PLUS SIGN) or the code unit 0x002D (HYPHEN-MINUS) according to whether <i>n</i>−1 is
+ positive or negative, followed by the code units of the decimal representation of the integer <a
+ href="#sec-algorithm-conventions">abs</a>(<i>n</i>−1) (with no leading zeroes).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The following observations may be useful as guidelines for implementations, but are
+ not part of the normative requirements of this Standard:</p>
+
+ <ul>
+ <li>
+ <p>If x is any Number value other than <b>−0</b>, then <a href="#sec-tonumber">ToNumber</a>(<a
+ href="#sec-tostring">ToString</a>(x)) is exactly the same Number value as x.</p>
+ </li>
+
+ <li>
+ <p>The least significant digit of s is not always uniquely determined by the requirements listed in step 5.</p>
+ </li>
+ </ul>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> For implementations that provide more accurate conversions than required by the rules
+ above, it is recommended that the following alternative version of step 5 be used as a guideline:</p>
+
+ <p>Otherwise, let <i>n</i>, <i>k</i>, and <i>s</i> be integers such that <i>k</i> ≥ 1, 10<sup><i>k</i>−1</sup>
+ ≤ <i>s</i> < 10<sup><i>k</i></sup>, the Number value for <i>s</i> × 10<sup><i>n</i>−<i>k</i></sup> is
+ <i>m</i>, and <i>k</i> is as small as possible. If there are multiple possibilities for <i>s</i>, choose the value of
+ <i>s</i> for which <i>s</i> × 10<sup><i>n</i>−<i>k</i></sup> is closest in value to <i>m</i>. If there are
+ two such possible values of <i>s</i>, choose the one that is even. Note that <i>k</i> is the number of digits in the
+ decimal representation of <i>s</i> and that <i>s</i> is not divisible by 10.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> Implementers of ECMAScript may find useful the paper and code written by David M. Gay
+ for binary-to-decimal conversion of floating-point numbers:</p>
+
+ <p>Gay, David M. Correctly Rounded Binary-Decimal and Decimal-Binary Conversions. Numerical Analysis, Manuscript 90-10.
+ AT&T Bell Laboratories (Murray Hill, New Jersey). November 30, 1990. Available as<br><span style="font-family:
+ sans-serif"><a
+ href="http://cm.bell-labs.com/cm/cs/doc/90/4-10.ps.gz">http://cm.bell-labs.com/cm/cs/doc/90/4-10.ps.gz</a></span>.
+ Associated code available as<br><span style="font-family: sans-serif"><a
+ href="http://netlib.sandia.gov/fp/dtoa.c">http://netlib.sandia.gov/fp/dtoa.c</a></span> and as<br><span
+ style="font-family: sans-serif"><a
+ href="http://netlib.sandia.gov/fp/g_fmt.c">http://netlib.sandia.gov/fp/g_fmt.c</a></span> and may also be found at the
+ various <code>netlib</code> mirror sites.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-toobject">
+ <h1><span class="secnum" id="sec-7.1.13"><a href="#sec-toobject" title="link to this section">7.1.13</a></span> ToObject (
+ argument )</h1>
+
+ <p>The abstract operation ToObject converts <var>argument</var> to a value of type Object according to <a
+ href="#table-13">Table 13</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-13">Table 13</span> — ToObject Conversions</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Argument Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Result</th>
+ </tr>
+ <tr>
+ <td><a href="#sec-completion-record-specification-type">Completion Record</a></td>
+ <td>If <i>argument</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <i>argument</i>. Otherwise return ToObject(<i>argument</i>.[[value]]).</td>
+ </tr>
+ <tr>
+ <td>Undefined</td>
+ <td>Throw a <b>TypeError</b> exception.</td>
+ </tr>
+ <tr>
+ <td>Null</td>
+ <td>Throw a <b>TypeError</b> exception.</td>
+ </tr>
+ <tr>
+ <td>Boolean</td>
+ <td>Return a new Boolean object whose [[BooleanData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is set to the value of <i>argument</i>. See <a href="#sec-boolean-objects">19.3</a> for a description of Boolean objects.</td>
+ </tr>
+ <tr>
+ <td>Number</td>
+ <td>Return a new Number object whose [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is set to the value of <i>argument</i>. See <a href="#sec-number-objects">20.1</a> for a description of Number objects.</td>
+ </tr>
+ <tr>
+ <td>String</td>
+ <td>Return a new String object whose [[StringData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is set to the value of <i>argument</i>. See <a href="#sec-string-objects">21.1</a> for a description of String objects.</td>
+ </tr>
+ <tr>
+ <td>Symbol</td>
+ <td>Return a new Symbol object whose [[SymbolData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is set to the value of <i>argument</i>. See <a href="#sec-symbol-objects">19.4</a> for a description of Symbol objects.</td>
+ </tr>
+ <tr>
+ <td>Object</td>
+ <td>Return <i>argument</i>.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-topropertykey">
+ <h1><span class="secnum" id="sec-7.1.14"><a href="#sec-topropertykey" title="link to this section">7.1.14</a></span>
+ ToPropertyKey ( argument )</h1>
+
+ <p>The abstract operation ToPropertyKey converts <var>argument</var> to a value that can be used as a <a
+ href="#sec-object-type">property key</a> by performing the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>key</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>argument</i>, hint String).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>key</i>) is Symbol, then
+ <ol class="block">
+ <li>Return <i>key</i>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-tostring">ToString</a>(<i>key</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-tolength">
+ <h1><span class="secnum" id="sec-7.1.15"><a href="#sec-tolength" title="link to this section">7.1.15</a></span> ToLength (
+ argument )</h1>
+
+ <p>The abstract operation ToLength converts <var>argument</var> to an integer suitable for use as the length of an
+ array-like object. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argument</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tointeger">ToInteger</a>(<i>argument</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <i>len</i> ≤ +0, return +0.</li>
+ <li>If <i>len</i> is <b>+∞</b>, return 2<sup>53</sup>-1.</li>
+ <li>Return min(<i>len</i>, 2<sup>53</sup>-1).</li>
+ </ol>
+ </section>
+
+ <section id="sec-canonicalnumericindexstring">
+ <h1><span class="secnum" id="sec-7.1.16"><a href="#sec-canonicalnumericindexstring"
+ title="link to this section">7.1.16</a></span> CanonicalNumericIndexString ( argument )</h1>
+
+ <p>The abstract operation CanonicalNumericIndexString returns <var>argument</var> converted to a numeric value if it is a
+ String representation of a Number that would be produced by <a href="#sec-tostring">ToString</a>, or the string
+ <code>"-0"</code>. Otherwise, it returns <span class="value">undefined.</span> This abstract operation functions as
+ follows:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is String.</li>
+ <li>If <i>argument</i> is <code>"-0"</code>, return −0.</li>
+ <li>Let <i>n</i> be <a href="#sec-tonumber">ToNumber</a>(<i>argument</i>).</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<a href="#sec-tostring">ToString</a>(<i>n</i>), <i>argument</i>) is
+ <b>false</b>, return <b>undefined</b>.</li>
+ <li>Return <i>n</i>.</li>
+ </ol>
+
+ <p>A <i>canonical numeric string</i> is any String value for which the CanonicalNumericIndexString abstract operation does
+ not return <span class="value">undefined</span>.</p>
+ </section>
+ </section>
+
+ <section id="sec-testing-and-comparison-operations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.2"><a href="#sec-testing-and-comparison-operations"
+ title="link to this section">7.2</a></span> Testing and Comparison Operations</h1>
+ </div>
+
+ <section id="sec-requireobjectcoercible">
+ <h1><span class="secnum" id="sec-7.2.1"><a href="#sec-requireobjectcoercible" title="link to this section">7.2.1</a></span>
+ RequireObjectCoercible ( argument )</h1>
+
+ <p>The abstract operation RequireObjectCoercible throws an error if <var>argument</var> is a value that cannot be converted
+ to an Object using <a href="#sec-toobject">ToObject</a>. It is defined by <a href="#table-14">Table 14</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-14">Table 14</span> — RequireObjectCoercible Results</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Argument Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Result</th>
+ </tr>
+ <tr>
+ <td><a href="#sec-completion-record-specification-type">Completion Record</a></td>
+ <td>If <var>argument</var> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <var>argument</var>. Otherwise return RequireObjectCoercible(<var>argument</var>.[[value]]).</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Undefined</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Throw a <b>TypeError</b> exception.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Null</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Throw a <b>TypeError</b> exception.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Boolean</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return <var>argument</var>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Number</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return <var>argument</var>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">String</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return <var>argument</var>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Symbol</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return <var>argument</var>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Object</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return <var>argument</var>.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-isarray">
+ <h1><span class="secnum" id="sec-7.2.2"><a href="#sec-isarray" title="link to this section">7.2.2</a></span> IsArray (
+ argument )</h1>
+
+ <p>The abstract operation IsArray takes one argument <var>argument</var>, and performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is not Object, return <b>false</b>.</li>
+ <li>If <i>argument</i> is an <a href="#sec-array-exotic-objects">Array exotic object</a>, return <b>true</b>.</li>
+ <li>If <i>argument</i> is a Proxy exotic object, then
+ <ol class="block">
+ <li>If the value of the [[ProxyHandler]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ of <i>argument</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>argument</i>.</li>
+ <li>Return IsArray(<i>target</i>).</li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-iscallable">
+ <h1><span class="secnum" id="sec-7.2.3"><a href="#sec-iscallable" title="link to this section">7.2.3</a></span> IsCallable (
+ argument )</h1>
+
+ <p>The abstract operation IsCallable determines if <var>argument</var>, which must be an <a
+ href="#sec-ecmascript-language-types">ECMAScript language value</a> or a <a
+ href="#sec-completion-record-specification-type">Completion Record</a>, is a callable function with a [[Call]] internal
+ method.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argument</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is not Object, return <b>false</b>.</li>
+ <li>If <i>argument</i> has a [[Call]] internal method, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isconstructor">
+ <h1><span class="secnum" id="sec-7.2.4"><a href="#sec-isconstructor" title="link to this section">7.2.4</a></span>
+ IsConstructor ( argument )</h1>
+
+ <p>The abstract operation IsConstructor determines if <var>argument</var>, which must be an <a
+ href="#sec-ecmascript-language-types">ECMAScript language value</a> or a <a
+ href="#sec-completion-record-specification-type">Completion Record</a>, is a function object with a [[Construct]] internal
+ method.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argument</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is not Object, return <b>false</b>.</li>
+ <li>If <i>argument</i> has a [[Construct]] internal method, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isextensible-o">
+ <h1><span class="secnum" id="sec-7.2.5"><a href="#sec-isextensible-o" title="link to this section">7.2.5</a></span>
+ IsExtensible (O)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">IsExtensible</span> is used to determine whether
+ additional properties can be added to the object that is <var>O</var>. A Boolean value is returned. This abstract operation
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li>Return <i>O</i>.[[IsExtensible]]().</li>
+ </ol>
+ </section>
+
+ <section id="sec-isinteger">
+ <h1><span class="secnum" id="sec-7.2.6"><a href="#sec-isinteger" title="link to this section">7.2.6</a></span> IsInteger (
+ argument )</h1>
+
+ <p>The abstract operation IsInteger determines if <var>argument</var> is a finite integer numeric value.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argument</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is not Number, return <b>false</b>.</li>
+ <li>If <i>argument</i> is <b>NaN</b>, <b>+∞</b>, or <b>−∞</b>, return <b>false</b>.</li>
+ <li>If <a href="#sec-algorithm-conventions">floor</a>(<a href="#sec-algorithm-conventions">abs</a>(<i>argument</i>)) ≠
+ <a href="#sec-algorithm-conventions">abs</a>(<i>argument</i>), return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ispropertykey">
+ <h1><span class="secnum" id="sec-7.2.7"><a href="#sec-ispropertykey" title="link to this section">7.2.7</a></span>
+ IsPropertyKey ( argument )</h1>
+
+ <p>The abstract operation IsPropertyKey determines if <var>argument</var>, which must be an <a
+ href="#sec-ecmascript-language-types">ECMAScript language value</a> or a <a
+ href="#sec-completion-record-specification-type">Completion Record</a>, is a value that may be used as a <a
+ href="#sec-object-type">property key</a>.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argument</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is String, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is Symbol, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isregexp">
+ <h1><span class="secnum" id="sec-7.2.8"><a href="#sec-isregexp" title="link to this section">7.2.8</a></span> IsRegExp (
+ argument )</h1>
+
+ <p>The abstract operation IsRegExp with argument <var>argument</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>argument</i>) is not Object, return <b>false</b>.</li>
+ <li>Let <i>isRegExp</i> be <a href="#sec-get-o-p">Get</a>(<i>argument</i>, @@match).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isRegExp</i>).</li>
+ <li>If <i>isRegExp</i> is not <b>undefined</b>, return <a href="#sec-toboolean">ToBoolean</a>(<i>isRegExp</i>).</li>
+ <li>If <i>argument</i> has a [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-samevalue">
+ <h1><span class="secnum" id="sec-7.2.9"><a href="#sec-samevalue" title="link to this section">7.2.9</a></span> SameValue(x,
+ y)</h1>
+
+ <p>The internal comparison abstract operation SameValue(<var>x</var>, <var>y</var>), where <var>x</var> and <var>y</var> are
+ <a href="#sec-ecmascript-language-types">ECMAScript language values</a>, produces <b>true</b> or <b>false</b>. Such a
+ comparison is performed as follows:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is different from <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>), return <b>false</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Undefined, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Null, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Number, then
+ <ol class="block">
+ <li>If <i>x</i> is NaN and <i>y</i> is NaN, return <b>true</b>.</li>
+ <li>If <i>x</i> is +0 and <i>y</i> is -0, return <b>false</b>.</li>
+ <li>If <i>x</i> is -0 and <i>y</i> is +0, return <b>false</b>.</li>
+ <li>If <i>x</i> is the same Number value as <i>y</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is String, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are exactly the same sequence of code units (same length and same code units at
+ corresponding indices) return <b>true</b>; otherwise, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Boolean, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are both <b>true</b> or both <b>false</b>, return <b>true</b>; otherwise, return
+ <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Symbol, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are both the same Symbol value, return <b>true</b>; otherwise, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b> if <i>x</i> and <i>y</i> are the same Object value. Otherwise, return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-samevaluezero">
+ <h1><span class="secnum" id="sec-7.2.10"><a href="#sec-samevaluezero" title="link to this section">7.2.10</a></span>
+ SameValueZero(x, y)</h1>
+
+ <p>The internal comparison abstract operation SameValueZero(<var>x</var>, <var>y</var>), where <var>x</var> and <var>y</var>
+ are <a href="#sec-ecmascript-language-types">ECMAScript language values</a>, produces <b>true</b> or <b>false</b>. Such a
+ comparison is performed as follows:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is different from <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>), return <b>false</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Undefined, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Null, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Number, then
+ <ol class="block">
+ <li>If <i>x</i> is NaN and <i>y</i> is NaN, return <b>true</b>.</li>
+ <li>If <i>x</i> is +0 and <i>y</i> is -0, return <b>true</b>.</li>
+ <li>If <i>x</i> is -0 and <i>y</i> is +0, return <b>true</b>.</li>
+ <li>If <i>x</i> is the same Number value as <i>y</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is String, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are exactly the same sequence of code units (same length and same code units at
+ corresponding indices) return <b>true</b>; otherwise, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Boolean, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are both <b>true</b> or both <b>false</b>, return <b>true</b>; otherwise, return
+ <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Symbol, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are both the same Symbol value, return <b>true</b>; otherwise, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b> if <i>x</i> and <i>y</i> are the same Object value. Otherwise, return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> SameValueZero differs from SameValue only in its treatment of +0 and -0.</p>
+ </div>
+ </section>
+
+ <section id="sec-abstract-relational-comparison">
+ <h1><span class="secnum" id="sec-7.2.11"><a href="#sec-abstract-relational-comparison"
+ title="link to this section">7.2.11</a></span> Abstract Relational Comparison</h1>
+
+ <p>The comparison <var>x</var> < <var>y</var>, where <var>x</var> and <var>y</var> are values, produces <b>true</b>,
+ <b>false</b>, or <b>undefined</b> (which indicates that at least one operand is <b>NaN</b>). In addition to <var>x</var> and
+ <var>y</var> the algorithm takes a Boolean flag named <span class="nt">LeftFirst</span> as a parameter. The flag is used to
+ control the order in which operations with potentially visible side-effects are performed upon <var>x</var> and
+ <var>y</var>. It is necessary because ECMAScript specifies left to right evaluation of expressions. The default value of
+ <span class="nt">LeftFirst</span> is <b>true</b> and indicates that the <var>x</var> parameter corresponds to an expression
+ that occurs to the left of the <var>y</var> parameter’s corresponding expression. If <span class="nt">LeftFirst</span>
+ is <b>false</b>, the reverse is the case and operations must be performed upon <var>y</var> before <var>x</var>. Such a
+ comparison is performed as follows:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>If the <i>LeftFirst</i> flag is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>px</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>x</i>, hint Number).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>px</i>).</li>
+ <li>Let <i>py</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>y</i>, hint Number).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>py</i>).</li>
+ </ol>
+ </li>
+ <li>Else the order of evaluation needs to be reversed to preserve left to right evaluation
+ <ol class="block">
+ <li>Let <i>py</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>y</i>, hint Number).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>py</i>).</li>
+ <li>Let <i>px</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>x</i>, hint Number).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>px</i>).</li>
+ </ol>
+ </li>
+ <li>If both <i>px</i> and <i>py</i> are Strings, then
+ <ol class="block">
+ <li>If <i>py</i> is a prefix of <i>px</i>, return <b>false</b>. (A String value <i>p</i> is a prefix of String value
+ <i>q</i> if <i>q</i> can be the result of concatenating <i>p</i> and some other String <i>r</i>. Note that any
+ String is a prefix of itself, because <i>r</i> may be the empty String.)</li>
+ <li>If <i>px</i> is a prefix of <i>py</i>, return <b>true</b>.</li>
+ <li>Let <i>k</i> be the smallest nonnegative integer such that the code unit at index <i>k</i> within <i>px</i> is
+ different from the code unit at index <i>k</i> within <i>py</i>. (There must be such a <i>k</i>, for neither
+ String is a prefix of the other.)</li>
+ <li>Let <i>m</i> be the integer that is the code unit value at index <i>k</i> within <i>px</i>.</li>
+ <li>Let <i>n</i> be the integer that is the code unit value at index <i>k</i> within <i>py</i>.</li>
+ <li>If <i>m</i> < <i>n</i>, return <b>true</b>. Otherwise, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>nx</i> be <a href="#sec-tonumber">ToNumber</a>(<i>px</i>). Because <i>px</i> and <i>py</i> are primitive
+ values evaluation order is not important.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nx</i>).</li>
+ <li>Let <i>ny</i> be <a href="#sec-tonumber">ToNumber</a>(<i>py</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ny</i>).</li>
+ <li>If <i>nx</i> is <b>NaN</b>, return <b>undefined</b>.</li>
+ <li>If <i>ny</i> is <b>NaN</b>, return <b>undefined</b>.</li>
+ <li>If <i>nx</i> and <i>ny</i> are the same Number value, return <b>false</b>.</li>
+ <li>If <i>nx</i> is <b>+0</b> and <i>ny</i> is <b>−0</b>, return <b>false</b>.</li>
+ <li>If <i>nx</i> is <b>−0</b> and <i>ny</i> is <b>+0</b>, return <b>false</b>.</li>
+ <li>If <i>nx</i> is <b>+∞</b>, return <b>false</b>.</li>
+ <li>If <i>ny</i> is <b>+∞</b>, return <b>true</b>.</li>
+ <li>If <i>ny</i> is <b>−∞</b>, return <b>false</b>.</li>
+ <li>If <i>nx</i> is <b>−∞</b>, return <b>true</b>.</li>
+ <li>If the mathematical value of <i>nx</i> is less than the mathematical value of <i>ny</i> —note that these
+ mathematical values are both finite and not both zero—return <b>true</b>. Otherwise, return
+ <b>false</b>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> Step 5 differs from step 11 in the algorithm for the addition operator <code>+</code>
+ (<a href="#sec-addition-operator-plus">12.7.3</a>) in using “and” instead of “or”.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The comparison of Strings uses a simple lexicographic ordering on sequences of code unit
+ values. There is no attempt to use the more complex, semantically oriented definitions of character or string equality and
+ collating order defined in the Unicode specification. Therefore String values that are canonically equal according to the
+ Unicode standard could test as unequal. In effect this algorithm assumes that both Strings are already in normalized form.
+ Also, note that for strings containing supplementary characters, lexicographic ordering on sequences of UTF-16 code unit
+ values differs from that on sequences of code point values.</p>
+ </div>
+ </section>
+
+ <section id="sec-abstract-equality-comparison">
+ <h1><span class="secnum" id="sec-7.2.12"><a href="#sec-abstract-equality-comparison"
+ title="link to this section">7.2.12</a></span> Abstract Equality Comparison</h1>
+
+ <p>The comparison <var>x</var> == <var>y</var>, where <var>x</var> and <var>y</var> are values, produces <b>true</b> or
+ <b>false</b>. Such a comparison is performed as follows:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is the same as <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>), then
+ <ol class="block">
+ <li>Return the result of performing Strict Equality Comparison <i>x</i> === <i>y</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>x</i> is <b>null</b> and <i>y</i> is <b>undefined</b>, return <b>true</b>.</li>
+ <li>If <i>x</i> is <b>undefined</b> and <i>y</i> is <b>null</b>, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Number and <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>) is String,<br>return the result of the comparison
+ <i>x</i> == <a href="#sec-tonumber">ToNumber</a>(<i>y</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is String and <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>) is Number,<br>return the result of the comparison <a
+ href="#sec-tonumber">ToNumber</a>(<i>x</i>) == <i>y</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Boolean, return the result of the comparison
+ <a href="#sec-tonumber">ToNumber</a>(<i>x</i>) == <i>y</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>) is Boolean, return the result of the comparison
+ <i>x</i> == <a href="#sec-tonumber">ToNumber</a>(<i>y</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is either String, Number, or Symbol and <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>) is Object, then<br>return the result of the comparison
+ <i>x</i> == <a href="#sec-toprimitive">ToPrimitive</a>(<i>y</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Object and <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>) is either String, Number, or Symbol, then<br>return
+ the result of the comparison <a href="#sec-toprimitive">ToPrimitive</a>(<i>x</i>) == <i>y</i>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-strict-equality-comparison">
+ <h1><span class="secnum" id="sec-7.2.13"><a href="#sec-strict-equality-comparison"
+ title="link to this section">7.2.13</a></span> Strict Equality Comparison</h1>
+
+ <p>The comparison <var>x</var> === <var>y</var>, where <var>x</var> and <var>y</var> are values, produces <b>true</b> or
+ <b>false</b>. Such a comparison is performed as follows:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is different from <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>), return <b>false</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Undefined, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Null, return <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Number, then
+ <ol class="block">
+ <li>If <i>x</i> is <b>NaN</b>, return <b>false</b>.</li>
+ <li>If <i>y</i> is <b>NaN</b>, return <b>false</b>.</li>
+ <li>If <i>x</i> is the same Number value as <i>y</i>, return <b>true</b>.</li>
+ <li>If <i>x</i> is <b>+0</b> and <i>y</i> is <b>−0</b>, return <b>true</b>.</li>
+ <li>If <i>x</i> is <b>−0</b> and <i>y</i> is <b>+0</b>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is String, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are exactly the same sequence of code units (same length and same code units at
+ corresponding indices), return <b>true</b>.</li>
+ <li>Else, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is Boolean, then
+ <ol class="block">
+ <li>If <i>x</i> and <i>y</i> are both <b>true</b> or both <b>false</b>, return <b>true</b>.</li>
+ <li>Else, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <i>x</i> and <i>y</i> are the same Symbol value, return <b>true</b>.</li>
+ <li>If <i>x</i> and <i>y</i> are the same Object value, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This algorithm differs from <a href="#sec-samevalue">the SameValue Algorithm</a> (<a
+ href="#sec-samevalue">7.2.9</a>) in its treatment of signed zeroes and NaNs.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-operations-on-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.3"><a href="#sec-operations-on-objects" title="link to this section">7.3</a></span>
+ Operations on Objects</h1>
+ </div>
+
+ <section id="sec-get-o-p">
+ <h1><span class="secnum" id="sec-7.3.1"><a href="#sec-get-o-p" title="link to this section">7.3.1</a></span> Get (O, P)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">Get</span> is used to retrieve the value of a specific
+ property of an object. The operation is called with arguments <var>O</var> and <var>P</var> where <var>O</var> is the
+ object and <var>P</var> is the <a href="#sec-object-type">property key</a>. This abstract operation performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Return <i>O</i>.[[Get]](<i>P</i>, <i>O</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-getv">
+ <h1><span class="secnum" id="sec-7.3.2"><a href="#sec-getv" title="link to this section">7.3.2</a></span> GetV (V, P)</h1>
+
+ <p>The abstract operation GetV is used to retrieve the value of a specific property of an <a
+ href="#sec-ecmascript-language-types">ECMAScript language value</a>. If the value is not an object, the property lookup is
+ performed using a wrapper object appropriate for the type of the value. The operation is called with arguments <var>V</var>
+ and <var>P</var> where <var>V</var> is the value and <var>P</var> is the <a href="#sec-object-type">property key</a>. This
+ abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<i>V</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Return <i>O</i>.[[Get]](<i>P</i>, <i>V</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-set-o-p-v-throw">
+ <h1><span class="secnum" id="sec-7.3.3"><a href="#sec-set-o-p-v-throw" title="link to this section">7.3.3</a></span> Set (O,
+ P, V, Throw)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">Set</span> is used to set the value of a specific
+ property of an object. The operation is called with arguments <var>O</var>, <var>P</var>, <var>V</var>, and <span
+ class="nt">Throw</span> where <var>O</var> is the object, <var>P</var> is the <a href="#sec-object-type">property key</a>,
+ <var>V</var> is the new value for the property and <span class="nt">Throw</span> is a Boolean flag. This abstract operation
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>Throw</i>) is Boolean.</li>
+ <li>Let <i>success</i> be <i>O</i>.[[Set]](<i>P</i>, <i>V</i>, <i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>success</i>).</li>
+ <li>If <i>success</i> is <b>false</b> and <i>Throw</i> is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>success</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createdataproperty">
+ <h1><span class="secnum" id="sec-7.3.4"><a href="#sec-createdataproperty" title="link to this section">7.3.4</a></span>
+ CreateDataProperty (O, P, V)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">CreateDataProperty</span> is used to create a new own
+ property of an object. The operation is called with arguments <var>O</var>, <var>P</var>, and <var>V</var> where
+ <var>O</var> is the object, <var>P</var> is the <a href="#sec-object-type">property key</a>, and <var>V</var> is the value
+ for the property. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>newDesc</i> be the PropertyDescriptor{[[Value]]: <i>V</i>, [[Writable]]: <b>true</b>, [[Enumerable]]:
+ <b>true</b>, [[Configurable]]: <b>true</b>}.</li>
+ <li>Return <i>O</i>.[[DefineOwnProperty]](<i>P</i>, <i>newDesc</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This abstract operation creates a property whose attributes are set to the same defaults
+ used for properties created by the ECMAScript language assignment operator. Normally, the property will not already exist.
+ If it does exist and is not configurable or if <i>O</i> is not extensible, [[DefineOwnProperty]] will return
+ <b>false</b>.</p>
+ </div>
+ </section>
+
+ <section id="sec-createmethodproperty">
+ <h1><span class="secnum" id="sec-7.3.5"><a href="#sec-createmethodproperty" title="link to this section">7.3.5</a></span>
+ CreateMethodProperty (O, P, V)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">CreateMethodProperty</span> is used to create a new own
+ property of an object. The operation is called with arguments <var>O</var>, <var>P</var>, and <var>V</var> where
+ <var>O</var> is the object, <var>P</var> is the <a href="#sec-object-type">property key</a>, and <var>V</var> is the value
+ for the property. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>newDesc</i> be the PropertyDescriptor{[[Value]]: <i>V</i>, [[Writable]]: <b>true</b>, [[Enumerable]]:
+ <b>false</b>, [[Configurable]]: <b>true</b>}.</li>
+ <li>Return <i>O</i>.[[DefineOwnProperty]](<i>P</i>, <i>newDesc</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This abstract operation creates a property whose attributes are set to the same defaults
+ used for built-in methods and methods defined using class declaration syntax. Normally, the property will not already
+ exist. If it does exist and is not configurable or if <i>O</i> is not extensible, [[DefineOwnProperty]] will return
+ <b>false</b>.</p>
+ </div>
+ </section>
+
+ <section id="sec-createdatapropertyorthrow">
+ <h1><span class="secnum" id="sec-7.3.6"><a href="#sec-createdatapropertyorthrow"
+ title="link to this section">7.3.6</a></span> CreateDataPropertyOrThrow (O, P, V)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">CreateDataPropertyOrThrow</span> is used to create a
+ new own property of an object. It throws a <span class="value">TypeError</span> exception if the requested property update
+ cannot be performed. The operation is called with arguments <var>O</var>, <var>P</var>, and <var>V</var> where <var>O</var>
+ is the object, <var>P</var> is the <a href="#sec-object-type">property key</a>, and <var>V</var> is the value for the
+ property. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>success</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>O</i>, <i>P</i>, <i>V</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>success</i>).</li>
+ <li>If <i>success</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>success</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This abstract operation creates a property whose attributes are set to the same defaults
+ used for properties created by the ECMAScript language assignment operator. Normally, the property will not already exist.
+ If it does exist and is not configurable or if <i>O</i> is not extensible, [[DefineOwnProperty]] will return <b>false</b>
+ <span style="font-family: sans-serif">causing this operation to throw a</span> <b>TypeError</b> <span style="font-family:
+ sans-serif">exception</span>.</p>
+ </div>
+ </section>
+
+ <section id="sec-definepropertyorthrow">
+ <h1><span class="secnum" id="sec-7.3.7"><a href="#sec-definepropertyorthrow" title="link to this section">7.3.7</a></span>
+ DefinePropertyOrThrow (O, P, desc)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">DefinePropertyOrThrow</span> is used to call the
+ [[DefineOwnProperty]] internal method of an object in a manner that will throw a <b>TypeError</b> exception if the requested
+ property update cannot be performed. The operation is called with arguments <var>O</var>, <var>P</var>, and <var>desc</var>
+ where <var>O</var> is the object, <var>P</var> is the <a href="#sec-object-type">property key</a>, and <var>desc</var> is
+ the <a href="#sec-property-descriptor-specification-type">Property Descriptor</a> for the property. This abstract operation
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>success</i> be <i>O</i>.[[DefineOwnProperty]](<i>P</i>, <i>desc</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>success</i>).</li>
+ <li>If <i>success</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>success</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-deletepropertyorthrow">
+ <h1><span class="secnum" id="sec-7.3.8"><a href="#sec-deletepropertyorthrow" title="link to this section">7.3.8</a></span>
+ DeletePropertyOrThrow (O, P)</h1>
+
+ <p>The abstract operation DeletePropertyOrThrow is used to remove a specific own property of an object. It throws an
+ exception if the property is not configurable. The operation is called with arguments <var>O</var> and <var>P</var> where
+ <var>O</var> is the object and <var>P</var> is the <a href="#sec-object-type">property key</a>. This abstract operation
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>success</i> be <i>O</i>.[[Delete]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>success</i>).</li>
+ <li>If <i>success</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>success</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-getmethod">
+ <h1><span class="secnum" id="sec-7.3.9"><a href="#sec-getmethod" title="link to this section">7.3.9</a></span> GetMethod (O,
+ P)</h1>
+
+ <p>The abstract operation GetMethod is used to get the value of a specific property of an object when the value of the
+ property is expected to be a function. The operation is called with arguments <var>O</var> and <var>P</var> where
+ <var>O</var> is the object, <var>P</var> is the <a href="#sec-object-type">property key</a>. This abstract operation
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>func</i> be <a href="#sec-getv">GetV</a>(<i>O</i>, <i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>func</i>).</li>
+ <li>If <i>func</i> is either <b>undefined</b> or <b>null</b>, return <b>undefined</b>.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>func</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>func</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-hasproperty">
+ <h1><span class="secnum" id="sec-7.3.10"><a href="#sec-hasproperty" title="link to this section">7.3.10</a></span>
+ HasProperty (O, P)</h1>
+
+ <p>The abstract operation HasProperty is used to determine whether an object has a property with the specified <a
+ href="#sec-object-type">property key</a>. The property may be either an own or inherited. A Boolean value is returned. The
+ operation is called with arguments <var>O</var> and <var>P</var> where <var>O</var> is the object and <var>P</var> is the
+ <a href="#sec-object-type">property key</a>. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Return <i>O</i>.[[HasProperty]](<i>P</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-hasownproperty">
+ <h1><span class="secnum" id="sec-7.3.11"><a href="#sec-hasownproperty" title="link to this section">7.3.11</a></span>
+ HasOwnProperty (O, P)</h1>
+
+ <p>The abstract operation HasOwnProperty is used to determine whether an object has an own property with the specified <a
+ href="#sec-object-type">property key</a>. A Boolean value is returned. The operation is called with arguments <var>O</var>
+ and <var>P</var> where <var>O</var> is the object and <var>P</var> is the <a href="#sec-object-type">property key</a>. This
+ abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>desc</i> be <i>O</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>If <i>desc</i> is <b>undefined</b>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-call">
+ <h1><span class="secnum" id="sec-7.3.12"><a href="#sec-call" title="link to this section">7.3.12</a></span> Call(F, V,
+ [argumentsList])</h1>
+
+ <p>The abstract operation Call is used to call the [[Call]] internal method of a function object. The operation is called
+ with arguments <var>F</var>, <var>V</var> , and optionally <var>argumentsList</var> where <var>F</var> is the function
+ object, <var>V</var> is an <a href="#sec-ecmascript-language-types">ECMAScript language value</a> that is the <b>this</b>
+ value of the [[Call]], and <var>argumentsList</var> is the value passed to the corresponding argument of the internal
+ method. If <var>argumentsList</var> is not present, an empty <a href="#sec-list-and-record-specification-type">List</a> is
+ used as its value. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>F</i>).</li>
+ <li>If <i>argumentsList</i> was not passed, let <i>argumentsList</i> be a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>F</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>F</i>.[[Call]](<i>V</i>, <i>argumentsList</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-invoke">
+ <h1><span class="secnum" id="sec-7.3.13"><a href="#sec-invoke" title="link to this section">7.3.13</a></span> Invoke(O,P,
+ [argumentsList])</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">Invoke</span> is used to call a method property of an
+ object. The operation is called with arguments <var>O</var>, <var>P</var> , and optionally <var>argumentsList</var> where
+ <var>O</var> serves as both the lookup point for the property and the <b>this</b> value of the call, <var>P</var> is the <a
+ href="#sec-object-type">property key</a>, and <var>argumentsList</var> is the list of arguments values passed to the method.
+ If <var>argumentsList</var> is not present, an empty <a href="#sec-list-and-record-specification-type">List</a> is used as
+ its value. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>P</i> is a valid <a href="#sec-object-type">property key</a>.</li>
+ <li>If <i>argumentsList</i> was not passed, let <i>argumentsList</i> be a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>func</i> be <a href="#sec-getv">GetV</a>(<i>O</i>, <i>P</i>).</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>func</i>, <i>O</i>, <i>argumentsList</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-construct">
+ <h1><span class="secnum" id="sec-7.3.14"><a href="#sec-construct" title="link to this section">7.3.14</a></span> Construct
+ (F, [argumentsList], [newTarget])</h1>
+
+ <p>The abstract operation Construct is used to call the [[Construct]] internal method of a function object. The operation is
+ called with arguments <var>F</var>, and optionally <span style="font-family: Times New Roman"><i>argumentsList</i>, and
+ <i>newTarget</i></span> where <var>F</var> is the function object. <var>argumentsList</var> and <var>newTarget</var> are the
+ values to be passed as the corresponding arguments of the internal method. If <var>argumentsList</var> is not present, an
+ empty <a href="#sec-list-and-record-specification-type">List</a> is used as its value. If <var>newTarget</var> is not
+ present, <var>F</var> is used as its value. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>newTarget</i> was not passed, let <i>newTarget</i> be <i>F</i>.</li>
+ <li>If <i>argumentsList</i> was not passed, let <i>argumentsList</i> be a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-isconstructor">IsConstructor</a> (<i>F</i>) is
+ <b>true</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-isconstructor">IsConstructor</a> (<i>newTarget</i>) is
+ <b>true</b>.</li>
+ <li>Return <i>F</i>.[[Construct]](<i>argumentsList</i>, <i>newTarget</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>newTarget</i> is not passed, this operation is equivalent to: <code>new
+ F(...argumentsList)</code></p>
+ </div>
+ </section>
+
+ <section id="sec-setintegritylevel">
+ <h1><span class="secnum" id="sec-7.3.15"><a href="#sec-setintegritylevel" title="link to this section">7.3.15</a></span>
+ SetIntegrityLevel (O, level)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">SetIntegrityLevel</span> is used to fix the set of own
+ properties of an object. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>level</i> is either "<code>sealed</code>" or
+ "<code>frozen</code>".</li>
+ <li>Let <i>status</i> be <i>O</i>.[[PreventExtensions]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>Let <i>keys</i> be <i>O</i>.[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keys</i>).</li>
+ <li>If <i>level</i> is "<code>sealed</code>", then
+ <ol class="block">
+ <li>Repeat for each element <i>k</i> of <i>keys</i>,
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>O</i>, <i>k</i>,
+ PropertyDescriptor{ [[Configurable]]: <b>false</b>}).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else <i>level</i> is "<code>frozen</code>",
+ <ol class="block">
+ <li>Repeat for each element <i>k</i> of <i>keys</i>,
+ <ol class="block">
+ <li>Let <i>currentDesc</i> be <i>O</i>.[[GetOwnProperty]](<i>k</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>currentDesc</i>).</li>
+ <li>If <i>currentDesc</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>currentDesc</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>desc</i> be the PropertyDescriptor{[[Configurable]]: <b>false</b>}.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>desc</i> be the PropertyDescriptor { [[Configurable]]: <b>false</b>, [[Writable]]: <b>false</b>
+ }.</li>
+ </ol>
+ </li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>O</i>, <i>k</i>,
+ <i>desc</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-testintegritylevel">
+ <h1><span class="secnum" id="sec-7.3.16"><a href="#sec-testintegritylevel" title="link to this section">7.3.16</a></span>
+ TestIntegrityLevel (O, level)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">TestIntegrityLevel</span> is used to determine if the
+ set of own properties of an object are fixed. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>level</i> is either "<code>sealed</code>" or
+ "<code>frozen</code>".</li>
+ <li>Let <i>status</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>true</b>, return <b>false</b></li>
+ <li>NOTE If the object is extensible, none of its properties are examined.</li>
+ <li>Let <i>keys</i> be <i>O</i>.[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keys</i>).</li>
+ <li>Repeat for each element <i>k</i> of <i>keys</i>,
+ <ol class="block">
+ <li>Let <i>currentDesc</i> be <i>O</i>.[[GetOwnProperty]](<i>k</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>currentDesc</i>).</li>
+ <li>If <i>currentDesc</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>currentDesc</i>.[[Configurable]] is <b>true</b>, return <b>false</b>.</li>
+ <li>If <i>level</i> is "<code>frozen</code>" and <a
+ href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>currentDesc</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>currentDesc</i>.[[Writable]] is <b>true</b>, return <b>false</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createarrayfromlist">
+ <h1><span class="secnum" id="sec-7.3.17"><a href="#sec-createarrayfromlist" title="link to this section">7.3.17</a></span>
+ CreateArrayFromList (elements)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">CreateArrayFromList</span> is used to create an Array
+ object whose elements are provided by a <a href="#sec-list-and-record-specification-type">List</a>. This abstract operation
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>elements</i> is a <a
+ href="#sec-list-and-record-specification-type">List</a> whose elements are all <a
+ href="#sec-ecmascript-language-types">ECMAScript language values</a>.</li>
+ <li>Let <i>array</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0) (<a href="#sec-arraycreate">see 9.4.2.2</a>).</li>
+ <li>Let <i>n</i> be 0.</li>
+ <li>For each element <i>e</i> of <i>elements</i>
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>array</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>), <i>e</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is <b>true</b>.</li>
+ <li>Increment <i>n</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>array</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createlistfromarraylike">
+ <h1><span class="secnum" id="sec-7.3.18"><a href="#sec-createlistfromarraylike"
+ title="link to this section">7.3.18</a></span> CreateListFromArrayLike (obj [, elementTypes] )</h1>
+
+ <p>The abstract operation CreateListFromArrayLike is used to create a List value whose elements are provided by the indexed
+ properties of an array-like object, <var>obj</var>. The optional argument <var>elementTypes</var> is a <a
+ href="#sec-list-and-record-specification-type">List</a> containing the names of ECMAScript Language Types that are allowed
+ for element values of the <a href="#sec-list-and-record-specification-type">List</a> that is created. This abstract
+ operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>If <i>elementTypes</i> was not passed, let <i>elementTypes</i> be (Undefined, Null, Boolean, String, Symbol, Number,
+ Object).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>obj</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>obj</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>list</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>index</i> be 0.</li>
+ <li>Repeat while <i>index</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>indexName</i> be <a href="#sec-tostring">ToString</a>(<i>index</i>).</li>
+ <li>Let <i>next</i> be <a href="#sec-get-o-p">Get</a>(<i>obj</i>, <i>indexName</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>next</i>) is not an element of <i>elementTypes</i>,
+ throw a <b>TypeError</b> exception.</li>
+ <li>Append <i>next</i> as the last element of <i>list</i>.</li>
+ <li>Set <i>index</i> to <i>index</i> + 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>list</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinaryhasinstance">
+ <h1><span class="secnum" id="sec-7.3.19"><a href="#sec-ordinaryhasinstance" title="link to this section">7.3.19</a></span>
+ OrdinaryHasInstance (C, O)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">OrdinaryHasInstance</span> implements the default
+ algorithm for determining if an object <var>O</var> inherits from the instance object inheritance path provided by
+ constructor <var>C</var>. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>C</i>) is <b>false</b>, return <b>false</b>.</li>
+ <li>If <i>C</i> has a <a href="#sec-bound-function-exotic-objects">[[BoundTargetFunction]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li>Let <i>BC</i> be the value of <i>C’s</i> <a
+ href="#sec-bound-function-exotic-objects">[[BoundTargetFunction]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <a href="#sec-instanceofoperator">InstanceofOperator</a>(<i>O</i>,<i>BC</i>) (<a
+ href="#sec-instanceofoperator">see 12.9.4</a>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <b>false</b>.</li>
+ <li>Let <i>P</i> be <a href="#sec-get-o-p">Get</a>(<i>C</i>, <code>"prototype"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>O</i> be <i>O</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <i>O</i> is <code>null</code>, return <b>false</b>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>P</i>, <i>O</i>) is <b>true</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-speciesconstructor">
+ <h1><span class="secnum" id="sec-7.3.20"><a href="#sec-speciesconstructor" title="link to this section">7.3.20</a></span>
+ SpeciesConstructor ( O, defaultConstructor )</h1>
+
+ <p>The abstract operation SpeciesConstructor is used to retrieve the constructor that should be used to create new objects
+ that are derived from the argument object <var>O</var>. The <var>defaultConstructor</var> argument is the constructor to use
+ if <var>O</var> does not have a @@species property. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is
+ Object.</li>
+ <li>Let <i>C</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <code>"constructor"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>If <i>C</i> is <b>undefined</b>, return <i>defaultConstructor</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>C</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-get-o-p">Get</a>(<i>C</i>, @@species).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>If <i>S</i> is either <b>undefined</b> or <b>null</b>, return <i>defaultConstructor</i>.</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>S</i>) is <b>true</b>, return <i>S.</i></li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </section>
+
+ <section id="sec-enumerableownnames">
+ <h1><span class="secnum" id="sec-7.3.21"><a href="#sec-enumerableownnames" title="link to this section">7.3.21</a></span>
+ EnumerableOwnNames (O)</h1>
+
+ <p>When the abstract operation EnumerableOwnNames is called with Object <var>O</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>)
+ is Object.</li>
+ <li>Let <i>ownKeys</i> be <i>O</i>.[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ownKeys</i>).</li>
+ <li>Let <i>names</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Repeat, for each element <i>key</i> of <i>ownKeys</i> in <a href="#sec-list-and-record-specification-type">List</a>
+ order
+ <ol class="block">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>key</i>) is String, then
+ <ol class="block">
+ <li>Let <i>desc</i> be <i>O</i>.[[GetOwnProperty]](<i>key</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>If <i>desc</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>desc.</i>[[Enumerable]] is <b>true</b>, append <i>key</i> to <i>names</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Order the elements of <i>names</i> so they are in the same relative order as would be produced by the Iterator that
+ would be returned if the [[Enumerate]] internal method was invoked on <i>O</i>.</li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The order of elements is returned list is the same as the enumeration order that used by a
+ for-in statement.</p>
+ </div>
+ </section>
+
+ <section id="sec-getfunctionrealm">
+ <h1><span class="secnum" id="sec-7.3.22"><a href="#sec-getfunctionrealm" title="link to this section">7.3.22</a></span>
+ GetFunctionRealm ( obj )</h1>
+
+ <p>The abstract operation GetFunctionRealm with argument <var>obj</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>obj</i> is a callable object.</li>
+ <li>If <i>obj</i> has a [[Realm]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li>Return <i>obj</i>’s [[Realm]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</li>
+ </ol>
+ </li>
+ <li>If <i>obj</i> is a <a href="#sec-bound-function-exotic-objects">Bound Function</a> exotic object, then
+ <ol class="block">
+ <li>Let <i>target</i> be <i>obj</i>’s <a href="#sec-bound-function-exotic-objects">[[BoundTargetFunction]]</a>
+ <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return GetFunctionRealm(<i>target</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>obj</i> is a Proxy exotic object, then
+ <ol class="block">
+ <li>If the value of the [[ProxyHandler]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ of <i>obj</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>proxyTarget</i> be the value of <i>obj</i>’s [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return GetFunctionRealm(<i>proxyTarget</i>).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-code-realms">Realm</a>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Step 5 will only be reached if <i>target</i> is a non-standard exotic function object that
+ does not have a [[Realm]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-operations-on-iterator-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.4"><a href="#sec-operations-on-iterator-objects"
+ title="link to this section">7.4</a></span> Operations on Iterator Objects</h1>
+
+ <p>See Common Iteration Interfaces (<a href="#sec-iteration">25.1</a>).</p>
+ </div>
+
+ <section id="sec-getiterator">
+ <h1><span class="secnum" id="sec-7.4.1"><a href="#sec-getiterator" title="link to this section">7.4.1</a></span> GetIterator
+ ( obj, method )</h1>
+
+ <p>The abstract operation GetIterator with argument <span style="font-family: Times New Roman"><i>obj</i> and</span>
+ optional argument <var>method</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>If <i>method</i> was not passed, then
+ <ol class="block">
+ <li>Let <i>method</i> be <a href="#sec-getmethod">GetMethod</a>(<i>obj</i>, @@iterator).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>method</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>iterator</i> be <a href="#sec-call">Call</a>(<i>method</i>,<i>obj</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>)<i>.</i></li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>iterator</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>iterator</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-iteratornext">
+ <h1><span class="secnum" id="sec-7.4.2"><a href="#sec-iteratornext" title="link to this section">7.4.2</a></span>
+ IteratorNext ( iterator, value )</h1>
+
+ <p>The abstract operation IteratorNext with argument <var>iterator</var> and optional argument <var>value</var> performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>value</i> was not passed, then
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-invoke">Invoke</a>(<i>iterator</i>, <code>"next"</code>, «‍
+ »).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-invoke">Invoke</a>(<i>iterator</i>, <code>"next"</code>,
+ «‍<i>value</i>»).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>result</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-iteratorcomplete">
+ <h1><span class="secnum" id="sec-7.4.3"><a href="#sec-iteratorcomplete" title="link to this section">7.4.3</a></span>
+ IteratorComplete ( iterResult )</h1>
+
+ <p>The abstract operation IteratorComplete with argument <var>iterResult</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>iterResult</i>) is Object.</li>
+ <li>Return <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>iterResult</i>,
+ <code>"done"</code>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-iteratorvalue">
+ <h1><span class="secnum" id="sec-7.4.4"><a href="#sec-iteratorvalue" title="link to this section">7.4.4</a></span>
+ IteratorValue ( iterResult )</h1>
+
+ <p>The abstract operation IteratorValue with argument <var>iterResult</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>iterResult</i>) is Object.</li>
+ <li>Return <a href="#sec-get-o-p">Get</a>(<i>iterResult</i>, <code>"value"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-iteratorstep">
+ <h1><span class="secnum" id="sec-7.4.5"><a href="#sec-iteratorstep" title="link to this section">7.4.5</a></span>
+ IteratorStep ( iterator )</h1>
+
+ <p>The abstract operation IteratorStep with argument <var>iterator</var> requests the next value from <var>iterator</var>
+ and returns either <span class="value">false</span> indicating that the iterator has reached its end or the IteratorResult
+ object if a next value is available. IteratorStep performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>result</i> be <a href="#sec-iteratornext">IteratorNext</a>(<i>iterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>Let <i>done</i> be <a href="#sec-iteratorcomplete">IteratorComplete</a>(<i>result</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>done</i>).</li>
+ <li>If <i>done</i> is <b>true</b>, return <b>false</b>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-iteratorclose">
+ <h1><span class="secnum" id="sec-7.4.6"><a href="#sec-iteratorclose" title="link to this section">7.4.6</a></span>
+ IteratorClose( iterator, completion )</h1>
+
+ <p>The abstract operation IteratorClose with arguments <var>iterator</var> and <var>completion</var> is used to notify an
+ iterator that it should perform any actions it would normally perform when it has reached its completed state:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>iterator</i>) is Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>completion</i> is a <a
+ href="#sec-completion-record-specification-type">Completion Record</a>.</li>
+ <li>Let <i>return</i> be <a href="#sec-getmethod">GetMethod</a>(<i>iterator</i>, <code>"return"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>return</i>).</li>
+ <li>If <i>return</i> is <b>undefined</b>, return <i>completion</i>.</li>
+ <li>Let <i>innerResult</i> be <a href="#sec-call">Call</a>(<i>return</i>, <i>iterator</i>, «‍ »).</li>
+ <li>If <i>completion</i>.[[type]] is <span style="font-family: sans-serif">throw</span>, return <i>completion</i>.</li>
+ <li>If <i>innerResult</i>.[[type]] is <span style="font-family: sans-serif">throw</span>, return <i>innerResult</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>innerResult</i>.[[value]]) is not Object<i>,</i> throw
+ a <b>TypeError</b> exception.</li>
+ <li>Return <i>completion</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createiterresultobject">
+ <h1><span class="secnum" id="sec-7.4.7"><a href="#sec-createiterresultobject" title="link to this section">7.4.7</a></span>
+ CreateIterResultObject ( value, done )</h1>
+
+ <p>The abstract operation CreateIterResultObject with arguments <var>value</var> and <var>done</var> creates an object that
+ supports the IteratorResult interface by performing the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>done</i>)
+ is Boolean.</li>
+ <li>Let <i>obj</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%ObjectPrototype%</span>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>, <code>"value"</code>, <i>value</i>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>, <code>"done"</code>, <i>done</i>).</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createlistiterator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.4.8"><a href="#sec-createlistiterator" title="link to this section">7.4.8</a></span>
+ CreateListIterator ( list )</h1>
+
+ <p>The abstract operation CreateListIterator with argument <var>list</var> creates an Iterator (<a
+ href="#sec-iterator-interface">25.1.1.2</a>) object whose next method returns the successive elements of <var>list</var>.
+ It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%IteratorPrototype%, «[[IteratorNext]],
+ [[IteratedList]], [[ListIteratorNextIndex]]»).</li>
+ <li>Set <i>iterator’s</i> [[IteratedList]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>list</i>.</li>
+ <li>Set <i>iterator’s</i> [[ListIteratorNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to 0.</li>
+ <li>Let <i>next</i> be a new built-in function object as defined in ListIterator <code>next</code> (<a
+ href="#sec-listiterator-next">7.4.8.1</a>).</li>
+ <li>Set <i>iterator’s</i> [[IteratorNext]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>next</i>.</li>
+ <li>Perform <a href="#sec-createmethodproperty">CreateMethodProperty</a>(<i>iterator</i>, <code>"next"</code>,
+ <i>next</i>).</li>
+ <li>Return <i>iterator</i>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-listiterator-next">
+ <h1><span class="secnum" id="sec-7.4.8.1"><a href="#sec-listiterator-next" title="link to this section">7.4.8.1</a></span>
+ ListIterator next( )</h1>
+
+ <p>The ListIterator <code>next</code> method is a standard built-in function object (<a
+ href="#sec-ecmascript-standard-built-in-objects">clause 17</a>) that performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>f</i> be the active function object.</li>
+ <li>If <i>O</i> does not have a [[IteratorNext]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>next</i> be the value of the [[IteratorNext]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>f</i>, <i>next</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[IteratedList]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>list</i> be the value of the [[IteratedList]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>index</i> be the value of the [[ListIteratorNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>len</i> be the number of elements of <i>list</i>.</li>
+ <li>If <i>index</i> ≥ <i>len</i>, then
+ <ol class="block">
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Set the value of the [[ListIteratorNextIndex]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of <i>O</i> to <i>index</i>+1.</li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>list</i>[<i>index</i>],
+ <b>false</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A ListIterator <code>next</code> method will throw an exception if applied to any object
+ other than the one with which it was originally associated.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-createcompounditerator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-7.4.9"><a href="#sec-createcompounditerator"
+ title="link to this section">7.4.9</a></span> CreateCompoundIterator ( iterator1, iterator2 )</h1>
+
+ <p>The abstract operation CreateCompoundIterator with arguments <var>iterator1</var> and <var>iterator2</var> creates an
+ Iterator (<a href="#sec-iterator-interface">25.1.1.2</a>) object whose next method returns the successive elements of
+ <var>iterator1</var> followed by the successive elements of <var>iterator2</var>. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%IteratorPrototype%, «‍[[Iterator1]],
+ [[Iterator2]], [[State]], [[IteratorNext]]»).</li>
+ <li>Set <i>iterator’s</i> [[Iterator1]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>iterator1</i>.</li>
+ <li>Set <i>iterator’s</i> [[Iterator2]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>iterator2</i>.</li>
+ <li>Set <i>iterator’s</i> [[State]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ 1.</li>
+ <li>Let <i>next</i> be a new built-in function object as defined in CompoundIterator <code>next</code> (<a
+ href="#sec-compounditerator-next">7.4.9.1</a>).</li>
+ <li>Set <i>iterator’s</i> [[IteratorNext]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>next</i>.</li>
+ <li>Perform <a href="#sec-createmethodproperty">CreateMethodProperty</a>(<i>iterator</i>, <code>"next"</code>,
+ <i>next</i>).</li>
+ <li>Return <i>iterator</i>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-compounditerator-next">
+ <h1><span class="secnum" id="sec-7.4.9.1"><a href="#sec-compounditerator-next"
+ title="link to this section">7.4.9.1</a></span> CompoundIterator next( )</h1>
+
+ <p>The CompoundIterator <code>next</code> method is a standard built-in function object that performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>f</i> be the active function object.</li>
+ <li>If <i>O</i> does not have a [[IteratorNext]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>next</i> be the value of the [[IteratorNext]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>f</i>, <i>next</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[Iterator1]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an object created and initialized by <a
+ href="#sec-createcompounditerator">CreateCompoundIterator</a>.</li>
+ <li>Let <i>state</i> be the value of <i>O’s</i> [[State]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>state</i> = 1, then
+ <ol class="block">
+ <li>Let <i>iterator1</i> be the value of <i>O’s</i> [[Iterator1]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>result1</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iterator1</i>).</li>
+ <li>If <i>result1</i> is not <b>false</b>, then
+ <ol class="block">
+ <li>Return <i>result1.</i></li>
+ </ol>
+ </li>
+ <li>Set <i>O’s</i> [[State]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ 2.</li>
+ </ol>
+ </li>
+ <li>Let <i>iterator2</i> be the value of <i>O’s</i> [[Iterator2]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <a href="#sec-iteratornext">IteratorNext</a>(<i>iterator2</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A CompoundIterator <code>next</code> method will throw an exception if applied to any
+ object other than the one with which it was originally associated.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+</section>
+
+<section id="sec-executable-code-and-execution-contexts">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8"><a href="#sec-executable-code-and-execution-contexts"
+ title="link to this section">8</a></span> Executable Code and Execution Contexts</h1>
+ </div>
+
+ <section id="sec-lexical-environments">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1"><a href="#sec-lexical-environments" title="link to this section">8.1</a></span>
+ Lexical Environments</h1>
+
+ <p>A <i>Lexical Environment</i> is a specification type used to define the association of <span
+ class="nt">Identifiers</span> to specific variables and functions based upon the lexical nesting structure of ECMAScript
+ code. A Lexical Environment consists of an <a href="#sec-environment-records">Environment Record</a> and a possibly null
+ reference to an <i>outer</i> Lexical Environment. Usually a Lexical Environment is associated with some specific syntactic
+ structure of ECMAScript code such as a <span class="nt">FunctionDeclaration</span>, a <span
+ class="nt">BlockStatement</span>, or a <span class="nt">Catch</span> clause of a <span class="nt">TryStatement</span> and a
+ new Lexical Environment is created each time such code is evaluated.</p>
+
+ <p>An <i><a href="#sec-environment-records">Environment Record</a></i> records the identifier bindings that are created
+ within the scope of its associated Lexical Environment.</p>
+
+ <p>The outer environment reference is used to model the logical nesting of Lexical Environment values. The outer reference
+ of a (inner) Lexical Environment is a reference to the Lexical Environment that logically surrounds the inner Lexical
+ Environment. An outer Lexical Environment may, of course, have its own outer Lexical Environment. A Lexical Environment may
+ serve as the outer environment for multiple inner Lexical Environments. For example, if a <span
+ class="nt">FunctionDeclaration</span> contains two nested <span class="nt">FunctionDeclarations</span> then the Lexical
+ Environments of each of the nested functions will have as their outer Lexical Environment the Lexical Environment of the
+ current evaluation of the surrounding function.</p>
+
+ <p>A <i>global environment</i> is a Lexical Environment which does not have an outer environment. The global
+ environment’s outer environment reference is <b>null</b>. A global environment’s environment record may be
+ prepopulated with identifier bindings and includes an associated <i>global object</i> whose properties provide some of <a
+ href="#sec-global-environment-records">the global environment</a>’s identifier bindings. This global object is the
+ value of a global environment’s <code>this</code> binding. As ECMAScript code is executed, additional properties may
+ be added to the global object and the initial properties may be modified.</p>
+
+ <p>A <i>module environment</i> is a Lexical Environment that contains the bindings for the top level declarations of a <span
+ class="nt">Module</span>. It also contains the bindings that are explicitly imported by the <span class="nt">Module</span>.
+ The outer environment of a module environment is a global environment.</p>
+
+ <p>A <i>function environment</i> is a Lexical Environment that corresponds to the invocation of an <a
+ href="#sec-ecmascript-function-objects">ECMAScript function object</a>. A function environment may establish a new
+ <code>this</code> binding. A function environment also captures the state necessary to support <code>super</code> method
+ invocations.</p>
+
+ <p>Lexical Environments and <a href="#sec-environment-records">Environment Record</a> values are purely specification
+ mechanisms and need not correspond to any specific artefact of an ECMAScript implementation. It is impossible for an
+ ECMAScript program to directly access or manipulate such values.</p>
+ </div>
+
+ <section id="sec-environment-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1.1"><a href="#sec-environment-records" title="link to this section">8.1.1</a></span>
+ Environment Records</h1>
+
+ <p>There are two primary kinds of Environment Record values used in this specification: <i>declarative environment
+ records</i> and <i>object environment records</i>. Declarative environment records are used to define the effect of
+ ECMAScript language syntactic elements such as <span class="nt">FunctionDeclarations</span>, <span
+ class="nt">VariableDeclarations</span>, and <span class="nt">Catch</span> clauses that directly associate identifier
+ bindings with <a href="#sec-ecmascript-language-types">ECMAScript language values</a>. Object environment records are used
+ to define the effect of ECMAScript elements such as <span class="nt">WithStatement</span> that associate identifier
+ bindings with the properties of some object. <a href="#sec-global-environment-records">Global Environment Records</a> and
+ <a href="#sec-function-environment-records">Function Environment Records</a> are specializations that are used for
+ specifically for <span class="nt">Script</span> global declarations and for top-level declarations within functions.</p>
+
+ <p>For specification purposes Environment Record values are values of the Record specification type and can be thought of
+ as existing in a simple object-oriented hierarchy where Environment Record is an abstract class with three concrete
+ subclasses, <a href="#sec-declarative-environment-records">declarative environment record</a>, <a
+ href="#sec-object-environment-records">object environment record</a>, and <a href="#sec-global-environment-records">global
+ environment record</a>. Function environment records and module environment records are subclasses of <a
+ href="#sec-declarative-environment-records">declarative environment record</a>. The abstract class includes the abstract
+ specification methods defined in <a href="#table-15">Table 15</a>. These abstract methods have distinct concrete
+ algorithms for each of the concrete subclasses.</p>
+
+ <figure>
+ <figcaption><span id="table-15">Table 15</span> — Abstract Methods of Environment Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Method</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">HasBinding(N)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Determine if an environment record has a binding for the String value <var>N</var>. Return <b>true</b> if it does and <b>false</b> if it does not</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">CreateMutableBinding(N, D)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Create a new but uninitialized mutable binding in an environment record. The String value <var>N</var> is the text of the bound name. If the optional Boolean argument <var>D</var> is <b>true</b> the binding is may be subsequently deleted.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">CreateImmutableBinding(N, S)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Create a new but uninitialized immutable binding in an environment record. The String value N is the text of the bound name. If <var>S</var> is <b>true</b> then attempts to access the value of the binding before it is initialized or set it after it has been initialized will always throw an exception, regardless of the strict mode setting of operations that reference that binding. <var>S</var> is an optional parameter that defaults to <b>false</b>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">InitializeBinding(N,V)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Set the value of an already existing but uninitialized binding in an environment record. The String value N is the text of the bound name. V is the value for the binding and is a value of any <a href="#sec-ecmascript-language-types">ECMAScript language type</a>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">SetMutableBinding(N,V, S)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Set the value of an already existing mutable binding in an environment record. The String value <var>N</var> is the text of the bound name. <var>V</var> is the value for the binding and may be a value of any <a href="#sec-ecmascript-language-types">ECMAScript language type</a>. <var>S</var> is a Boolean flag. If <var>S</var> is <b>true</b> and the binding cannot be set throw a <b>TypeError</b> exception.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">GetBindingValue(N,S)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Returns the value of an already existing binding from an environment record. The String value <var>N</var> is the text of the bound name. <var>S</var> is used to identify references originating in <a href="#sec-strict-mode-code">strict mode code</a> or that otherwise require strict mode binding reference semantics. If <var>S</var> is <b>true</b> and the binding does not exist throw a <b>ReferenceError</b> exception. If the binding exists but is uninitialized a <b>ReferenceError</b> is thrown, regardless of the value of <i><span style="font-family: Times New Roman">S</span>.</i></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">DeleteBinding(N)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Delete a binding from an environment record. The String value <var>N</var> is the text of the bound name. If a binding for <var>N</var> exists, remove the binding and return <b>true</b>. If the binding exists but cannot be removed return <b>false</b>. If the binding does not exist return <b>true</b>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">HasThisBinding()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Determine if an environment record establishes a <code>this</code> binding. Return <b>true</b> if it does and <b>false</b> if it does not.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">HasSuperBinding()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Determine if an environment record establishes a <code>super</code> method binding. Return <b>true</b> if it does and <b>false</b> if it does not.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">WithBaseObject ()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">If this environment record is associated with a <code>with</code> statement, return the with object. Otherwise, return <span class="value">undefined</span>.</td>
+ </tr>
+ </table>
+ </figure>
+ </div>
+
+ <section id="sec-declarative-environment-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1.1.1"><a href="#sec-declarative-environment-records"
+ title="link to this section">8.1.1.1</a></span> Declarative Environment Records</h1>
+
+ <p>Each declarative environment record is associated with an ECMAScript program scope containing variable, constant,
+ let, class, module, import, and/or function declarations. A declarative environment record binds the set of identifiers
+ defined by the declarations contained within its scope.</p>
+
+ <p>The behaviour of the concrete specification methods for Declarative Environment Records is defined by the following
+ algorithms.</p>
+ </div>
+
+ <section id="sec-declarative-environment-records-hasbinding-n">
+ <h1><span class="secnum" id="sec-8.1.1.1.1"><a href="#sec-declarative-environment-records-hasbinding-n"
+ title="link to this section">8.1.1.1.1</a></span> HasBinding(N)</h1>
+
+ <p>The concrete environment record method HasBinding for declarative environment records simply determines if the
+ argument identifier is one of the identifiers bound by the record:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-declarative-environment-records">declarative environment record</a> for
+ which the method was invoked.</li>
+ <li>If <i>envRec</i> has a binding for the name that is the value of <i>N</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-createmutablebinding-n-d">
+ <h1><span class="secnum" id="sec-8.1.1.1.2"><a href="#sec-declarative-environment-records-createmutablebinding-n-d"
+ title="link to this section">8.1.1.1.2</a></span> CreateMutableBinding (N, D)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateMutableBinding for declarative
+ environment records creates a new mutable binding for the name <var>N</var> that is uninitialized. A binding must not
+ already exist in this <a href="#sec-environment-records">Environment Record</a> for <var>N</var>. If Boolean argument
+ <var>D</var> is provided and has the value <b>true</b> the new binding is marked as being subject to deletion.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-declarative-environment-records">declarative environment record</a> for
+ which the method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> does not already have a binding for <i>N</i>.</li>
+ <li>Create a mutable binding in <i>envRec</i> for <i>N</i> and record that it is uninitialized. If <i>D</i> is
+ <b>true</b> record that the newly created binding may be deleted by a subsequent DeleteBinding call.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-createimmutablebinding-n-s">
+ <h1><span class="secnum" id="sec-8.1.1.1.3"><a href="#sec-declarative-environment-records-createimmutablebinding-n-s"
+ title="link to this section">8.1.1.1.3</a></span> CreateImmutableBinding (N, S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateImmutableBinding for declarative
+ environment records creates a new immutable binding for the name <var>N</var> that is uninitialized. A binding must not
+ already exist in this environment record for <var>N</var>. If Boolean argument <var>S</var> is provided and has the
+ value <b>true</b> the new binding is marked as a strict binding.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-declarative-environment-records">declarative environment record</a> for
+ which the method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> does not already have a binding for <i>N</i>.</li>
+ <li>Create an immutable binding in <i>envRec</i> for <i>N</i> and record that it is uninitialized. If <i>S</i> is
+ <b>true</b> record that the newly created binding is a strict binding.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-initializebinding-n-v">
+ <h1><span class="secnum" id="sec-8.1.1.1.4"><a href="#sec-declarative-environment-records-initializebinding-n-v"
+ title="link to this section">8.1.1.1.4</a></span> InitializeBinding (N,V)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method InitializeBinding for declarative
+ environment records is used to set the bound value of the current binding of the identifier whose name is the value of
+ the argument <var>N</var> to the value of argument <var>V</var>. An uninitialized binding for <var>N</var> must already
+ exist.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-declarative-environment-records">declarative environment record</a> for
+ which the method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> must have an uninitialized binding for
+ <i>N</i>.</li>
+ <li>Set the bound value for <i>N</i> in <i>envRec</i> to <i>V</i>.</li>
+ <li>Record that the binding for <i>N</i> in <i>envRec</i> has been initialized.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-setmutablebinding-n-v-s">
+ <h1><span class="secnum" id="sec-8.1.1.1.5"><a href="#sec-declarative-environment-records-setmutablebinding-n-v-s"
+ title="link to this section">8.1.1.1.5</a></span> SetMutableBinding (N,V,S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method SetMutableBinding for declarative
+ environment records attempts to change the bound value of the current binding of the identifier whose name is the value
+ of the argument <var>N</var> to the value of argument <var>V</var>. A binding for <var>N</var> normally already exist,
+ but in rare cases it may not. If the binding is an immutable binding, a <b>TypeError</b> is thrown if <span
+ style="font-family: Times New Roman">S</span> is <span class="value">true</span>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-declarative-environment-records">declarative environment record</a> for
+ which the method was invoked.</li>
+ <li>If <i>envRec</i> does not have a binding for <i>N</i>, then
+ <ol class="block">
+ <li>If <i>S</i> is <b>true</b> throw a <b>ReferenceError</b> exception.</li>
+ <li>Perform <i>envRec</i>.CreateMutableBinding(<i>N</i>, <b>true</b>).</li>
+ <li>Perform <i>envRec</i>.InitializeBinding(<i>N</i>, <i>V</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </li>
+ <li>If the binding for <i>N</i> in <i>envRec</i> is a strict binding, let <i>S</i> be <b>true</b>.</li>
+ <li>If the binding for <i>N</i> in <i>envRec</i> has not yet been initialized throw a <b>ReferenceError</b>
+ exception.</li>
+ <li>Else if the binding for <i>N</i> in <i>envRec</i> is a mutable binding, change its bound value to <i>V</i>.</li>
+ <li>Else this must be an attempt to change the value of an immutable binding so if <i>S</i> is <b>true</b> throw a
+ <b>TypeError</b> exception.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An example of ECMAScript code that results in a missing binding at step 2 is:</p>
+
+ <pre>function f(){eval("var x; x = (delete x, 0);")}</pre>
+ </div>
+ </section>
+
+ <section id="sec-declarative-environment-records-getbindingvalue-n-s">
+ <h1><span class="secnum" id="sec-8.1.1.1.6"><a href="#sec-declarative-environment-records-getbindingvalue-n-s"
+ title="link to this section">8.1.1.1.6</a></span> GetBindingValue(N,S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method GetBindingValue for declarative
+ environment records simply returns the value of its bound identifier whose name is the value of the argument
+ <var>N</var>. If the binding exists but is uninitialized a <b>ReferenceError</b> is thrown, regardless of the value of
+ <i><span style="font-family: Times New Roman">S</span>.</i></p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-declarative-environment-records">declarative environment record</a> for
+ which the method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> has a binding for <i>N</i>.</li>
+ <li>If the binding for <i>N</i> in <i>envRec</i> is an uninitialized binding, throw a <b>ReferenceError</b>
+ exception.</li>
+ <li>Return the value currently bound to <i>N</i> in <i>envRec</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-deletebinding-n">
+ <h1><span class="secnum" id="sec-8.1.1.1.7"><a href="#sec-declarative-environment-records-deletebinding-n"
+ title="link to this section">8.1.1.1.7</a></span> DeleteBinding (N)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method DeleteBinding for declarative
+ environment records can only delete bindings that have been explicitly designated as being subject to deletion.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-declarative-environment-records">declarative environment record</a> for
+ which the method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> has a binding for the name that is the value of
+ <i>N</i>.</li>
+ <li>If the binding for <i>N</i> in <i>envRec</i> cannot be deleted, return <b>false</b>.</li>
+ <li>Remove the binding for <i>N</i> from <i>envRec</i>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-hasthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.1.8"><a href="#sec-declarative-environment-records-hasthisbinding"
+ title="link to this section">8.1.1.1.8</a></span> HasThisBinding ()</h1>
+
+ <p>Regular Declarative Environment Records do not provide a <code>this</code> binding.</p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-hassuperbinding">
+ <h1><span class="secnum" id="sec-8.1.1.1.9"><a href="#sec-declarative-environment-records-hassuperbinding"
+ title="link to this section">8.1.1.1.9</a></span> HasSuperBinding ()</h1>
+
+ <p>Regular Declarative Environment Records do not provide a <code>super</code> binding.</p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-declarative-environment-records-withbaseobject">
+ <h1><span class="secnum" id="sec-8.1.1.1.10"><a href="#sec-declarative-environment-records-withbaseobject"
+ title="link to this section">8.1.1.1.10</a></span> WithBaseObject()</h1>
+
+ <p>Declarative Environment Records always return <b>undefined</b> as their WithBaseObject.</p>
+
+ <ol class="proc">
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-object-environment-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1.1.2"><a href="#sec-object-environment-records"
+ title="link to this section">8.1.1.2</a></span> Object Environment Records</h1>
+
+ <p>Each object environment record is associated with an object called its <i>binding object</i>. An object environment
+ record binds the set of string identifier names that directly correspond to the property names of its binding object.
+ Property keys that are not strings in the form of an <span class="nt">IdentifierName</span> are not included in the set
+ of bound identifiers. Both own and inherited properties are included in the set regardless of the setting of their
+ [[Enumerable]] attribute. Because properties can be dynamically added and deleted from objects, the set of identifiers
+ bound by an object environment record may potentially change as a side-effect of any operation that adds or deletes
+ properties. Any bindings that are created as a result of such a side-effect are considered to be a mutable binding even
+ if the Writable attribute of the corresponding property has the value <b>false</b>. Immutable bindings do not exist for
+ object environment records.</p>
+
+ <p>Object environment records created for <code>with</code> statements (<a href="#sec-with-statement">13.10</a>) can
+ provide their binding object as an implicit <b>this</b> value for use in function calls. The capability is controlled by
+ a <var>withEnvironment</var> Boolean value that is associated with each object environment record. By default, the value
+ of <var>withEnvironment</var> is <b>false</b> for any object environment record.</p>
+
+ <p>The behaviour of the concrete specification methods for Object Environment Records is defined by the following
+ algorithms.</p>
+ </div>
+
+ <section id="sec-object-environment-records-hasbinding-n">
+ <h1><span class="secnum" id="sec-8.1.1.2.1"><a href="#sec-object-environment-records-hasbinding-n"
+ title="link to this section">8.1.1.2.1</a></span> HasBinding(N)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method HasBinding for object environment
+ records determines if its associated binding object has a property whose name is the value of the argument
+ <var>N</var>:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-object-environment-records">object environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>bindings</i> be the binding object for <i>envRec</i>.</li>
+ <li>Let <i>foundBinding</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>bindings</i>, <i>N</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>foundBinding</i>).</li>
+ <li>If <i>foundBinding</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>If the <i>withEnvironment</i> flag of <i>envRec</i> is <b>false</b>, return <b>true</b>.</li>
+ <li>Let <i>unscopables</i> be <a href="#sec-get-o-p">Get</a>(<i>bindings</i>, @@unscopables).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>unscopables</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>unscopables</i>) is Object, then
+ <ol class="block">
+ <li>Let <i>blocked</i> be <a href="#sec-get-o-p">Get</a>(<i>unscopables</i>, <i>N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>blocked</i>).</li>
+ <li>If <a href="#sec-toboolean">ToBoolean</a>(<i>blocked</i>) is <b>true</b>, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-environment-records-createmutablebinding-n-d">
+ <h1><span class="secnum" id="sec-8.1.1.2.2"><a href="#sec-object-environment-records-createmutablebinding-n-d"
+ title="link to this section">8.1.1.2.2</a></span> CreateMutableBinding (N, D)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateMutableBinding for object
+ environment records creates in an environment record’s associated binding object a property whose name is the
+ String value and initializes it to the value <b>undefined</b>. If Boolean argument <var>D</var> is provided and has the
+ value <b>true</b> the new property’s [[Configurable]] attribute is set to <b>true</b>, otherwise it is set to
+ <b>false</b>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-object-environment-records">object environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>bindings</i> be the binding object for <i>envRec</i>.</li>
+ <li>If <i>D</i> is <b>true</b> then let <i>configValue</i> be <b>true</b> otherwise let <i>configValue</i> be
+ <b>false</b>.</li>
+ <li>Return <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>bindings</i>, <i>N</i>,
+ PropertyDescriptor{[[Value]]:<b>undefined</b>, [[Writable]]: <b>true</b>, [[Enumerable]]: <b>true</b> ,
+ [[Configurable]]: <i>configValue</i>}).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Normally <i>envRec</i> will not have a binding for <i>N</i> but if it does, the
+ semantics of <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a> may result in an existing binding being
+ replaced or shadowed or cause an <a href="#sec-completion-record-specification-type">abrupt completion</a> to be
+ returned.</p>
+ </div>
+ </section>
+
+ <section id="sec-object-environment-records-createimmutablebinding-n-s">
+ <h1><span class="secnum" id="sec-8.1.1.2.3"><a href="#sec-object-environment-records-createimmutablebinding-n-s"
+ title="link to this section">8.1.1.2.3</a></span> CreateImmutableBinding (N, S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateImmutableBinding is never used
+ within this specification in association with Object environment records.</p>
+ </section>
+
+ <section id="sec-object-environment-records-initializebinding-n-v">
+ <h1><span class="secnum" id="sec-8.1.1.2.4"><a href="#sec-object-environment-records-initializebinding-n-v"
+ title="link to this section">8.1.1.2.4</a></span> InitializeBinding (N,V)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method InitializeBinding for object
+ environment records is used to set the bound value of the current binding of the identifier whose name is the value of
+ the argument <var>N</var> to the value of argument <var>V</var>. An uninitialized binding for <var>N</var> must already
+ exist.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-object-environment-records">object environment record</a> for which the
+ method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> must have an uninitialized binding for
+ <i>N</i>.</li>
+ <li>Record that the binding for <i>N</i> in <i>envRec</i> has been initialized.</li>
+ <li>Return <i>envRec</i>.SetMutableBinding(<i>N</i>, <i>V</i>, <b>false</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In this specification, all uses of CreateMutableBinding and CreateImmutableBinding for
+ object environment records are immediately followed by a call to InitializeBinding for the same name. Hence,
+ implementations do not need to explicitly track the initialization state of individual object environment record
+ bindings.</p>
+ </div>
+ </section>
+
+ <section id="sec-object-environment-records-setmutablebinding-n-v-s">
+ <h1><span class="secnum" id="sec-8.1.1.2.5"><a href="#sec-object-environment-records-setmutablebinding-n-v-s"
+ title="link to this section">8.1.1.2.5</a></span> SetMutableBinding (N,V,S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method SetMutableBinding for object
+ environment records attempts to set the value of the environment record’s associated binding object’s
+ property whose name is the value of the argument <var>N</var> to the value of argument <var>V</var>. A property named
+ <var>N</var> normally already exists but if it does not or is not currently writable, error handling is determined by
+ the value of the Boolean argument <var>S</var>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-object-environment-records">object environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>bindings</i> be the binding object for <i>envRec</i>.</li>
+ <li>Return <a href="#sec-set-o-p-v-throw">Set</a>(<i>bindings</i>, <i>N</i>, <i>V</i>, and <i>S</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-environment-records-getbindingvalue-n-s">
+ <h1><span class="secnum" id="sec-8.1.1.2.6"><a href="#sec-object-environment-records-getbindingvalue-n-s"
+ title="link to this section">8.1.1.2.6</a></span> GetBindingValue(N,S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method GetBindingValue for object environment
+ records returns the value of its associated binding object’s property whose name is the String value of the
+ argument identifier <var>N</var>. The property should already exist but if it does not the result depends upon the value
+ of the <var>S</var> argument:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-object-environment-records">object environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>bindings</i> be the binding object for <i>envRec</i>.</li>
+ <li>Let <i>value</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>bindings</i>, <i>N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>If <i>value</i> is <b>false</b>, then
+ <ol class="block">
+ <li>If <i>S</i> is <b>false</b>, return the value <b>undefined</b>, otherwise throw a <b>ReferenceError</b>
+ exception.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-get-o-p">Get</a>(<i>bindings</i>, <i>N</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-environment-records-deletebinding-n">
+ <h1><span class="secnum" id="sec-8.1.1.2.7"><a href="#sec-object-environment-records-deletebinding-n"
+ title="link to this section">8.1.1.2.7</a></span> DeleteBinding (N)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method DeleteBinding for object environment
+ records can only delete bindings that correspond to properties of the environment object whose [[Configurable]]
+ attribute have the value <b>true</b>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-object-environment-records">object environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>bindings</i> be the binding object for <i>envRec</i>.</li>
+ <li>Return <i>bindings</i>.[[Delete]](<i>N</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-environment-records-hasthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.2.8"><a href="#sec-object-environment-records-hasthisbinding"
+ title="link to this section">8.1.1.2.8</a></span> HasThisBinding ()</h1>
+
+ <p>Regular Object Environment Records do not provide a <code>this</code> binding.</p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-environment-records-hassuperbinding">
+ <h1><span class="secnum" id="sec-8.1.1.2.9"><a href="#sec-object-environment-records-hassuperbinding"
+ title="link to this section">8.1.1.2.9</a></span> HasSuperBinding ()</h1>
+
+ <p>Regular Object Environment Records do not provide a <code>super</code> binding.</p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-environment-records-withbaseobject">
+ <h1><span class="secnum" id="sec-8.1.1.2.10"><a href="#sec-object-environment-records-withbaseobject"
+ title="link to this section">8.1.1.2.10</a></span> WithBaseObject()</h1>
+
+ <p>Object Environment Records return <b>undefined</b> as their WithBaseObject unless their <var>withEnvironment</var>
+ flag is <b>true</b>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-object-environment-records">object environment record</a> for which the
+ method was invoked.</li>
+ <li>If the <i>withEnvironment</i> flag of <i>envRec</i> is <b>true</b>, return the binding object for
+ <i>envRec</i>.</li>
+ <li>Otherwise, return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-function-environment-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1.1.3"><a href="#sec-function-environment-records"
+ title="link to this section">8.1.1.3</a></span> Function Environment Records</h1>
+
+ <p>A function environment record is a <a href="#sec-declarative-environment-records">declarative environment record</a>
+ that is used to represent the top-level scope of a function and, if the function is not an <span
+ class="nt">ArrowFunction</span>, provides a <code>this</code> binding. If a function is not an <span
+ class="nt">ArrowFunction</span> function and references <code>super</code>, its function environment record also
+ contains the state that is used to perform <code>super</code> method invocations from within the function.</p>
+
+ <p>Function environment records have the additional state fields listed in <a href="#table-16">Table 16</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-16">Table 16</span> — Additional Fields of Function Environment Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">[[thisValue]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Any</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">This is the <span class="value">this</span> value used for this invocation of the function.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">[[thisBindingStatus]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><code>"lexical"</code> | <code>"initialized"</code> | <code>"uninitialized"</code></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">If the value is <code>"lexical"</code>, this is an <span class="nt">ArrowFunction</span> and does not have a local this value.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">[[FunctionObject]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Object</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">The Function Object whose invocation caused this environment record to be created.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">[[HomeObject]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Object | <b>undefined</b></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">If the associated function has <code>super</code> property accesses and is not an <span class="nt">ArrowFunction</span>, [[HomeObject]] is the object that the function is bound to as a method. The default value for [[HomeObject]] is <span class="value">undefined</span>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">[[NewTarget]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Object | <b>undefined</b></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">If this environment record was created by the [[Construct]] internal method, [[NewTarget]] is the value of the [[Construct]] <var>newTarget</var> parameter. Otherwise, its value is <span class="value">undefined</span>.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>Function environment records support all of <a href="#sec-declarative-environment-records">Declarative Environment
+ Record</a> methods listed in <a href="#table-15">Table 15</a> and share the same specifications for all of those methods
+ except for HasThisBinding and HasSuperBinding. In addition, Function Environment Records support the methods listed in
+ <a href="#table-17">Table 17</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-17">Table 17</span> — Additional Methods of Function Environment Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Method</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-bindthisvalue">BindThisValue</a>(V)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Set the [[thisValue]] and record that it has been initialized.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">GetThisBinding()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return the value of this environment record’s <code>this</code> binding. Throws a <span class="value">ReferenceError</span> if the <code>this</code> binding has not been initialized.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-getsuperbase">GetSuperBase</a>()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return the object that is the base for <code>super</code> property accesses bound in this environment record. The object is derived from this environment record’s [[HomeObject]] field. The value <span class="value">undefined</span> indicates that <code>super</code> property accesses will produce runtime errors.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The behaviour of the additional concrete specification methods for Function Environment Records is defined by the
+ following algorithms:</p>
+ </div>
+
+ <section id="sec-bindthisvalue">
+ <h1><span class="secnum" id="sec-8.1.1.3.1"><a href="#sec-bindthisvalue"
+ title="link to this section">8.1.1.3.1</a></span> BindThisValue(V)</h1>
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-function-environment-records">function environment record</a> for which the
+ method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i>.[[thisBindingStatus]] is not
+ <code>"lexical"</code>.</li>
+ <li>If <i>envRec</i>.[[thisBindingStatus]] is <code>"initialized"</code>, throw a <b>ReferenceError</b>
+ exception.</li>
+ <li>Set <i>envRec</i>.[[thisValue]] to <i>V</i>.</li>
+ <li>Set <i>envRec</i>.[[thisBindingStatus]] to <code>"initialized"</code>.</li>
+ <li>Return <i>V</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-environment-records-hasthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.3.2"><a href="#sec-function-environment-records-hasthisbinding"
+ title="link to this section">8.1.1.3.2</a></span> HasThisBinding ()</h1>
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-function-environment-records">function environment record</a> for which the
+ method was invoked.</li>
+ <li>If <i>envRec</i>.[[thisBindingStatus]] is <code>"lexical"</code>, return <b>false</b>; otherwise, return
+ <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-environment-records-hassuperbinding">
+ <h1><span class="secnum" id="sec-8.1.1.3.3"><a href="#sec-function-environment-records-hassuperbinding"
+ title="link to this section">8.1.1.3.3</a></span> HasSuperBinding ()</h1>
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-function-environment-records">function environment record</a> for which the
+ method was invoked.</li>
+ <li>If <i>envRec</i>.[[thisBindingStatus]] is <code>"lexical"</code>, return <b>false</b>.</li>
+ <li>If <i>envRec</i>.[[HomeObject]] has the value <b>undefined</b>, return <b>false</b>, otherwise, return
+ <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-environment-records-getthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.3.4"><a href="#sec-function-environment-records-getthisbinding"
+ title="link to this section">8.1.1.3.4</a></span> GetThisBinding ()</h1>
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-function-environment-records">function environment record</a> for which the
+ method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i>.[[thisBindingStatus]] is not
+ <code>"lexical"</code>.</li>
+ <li>If <i>envRec</i>.[[thisBindingStatus]] is <code>"uninitialized"</code>, throw a <b>ReferenceError</b>
+ exception.</li>
+ <li>Return <i>envRec</i>.[[thisValue]].</li>
+ </ol>
+ </section>
+
+ <section id="sec-getsuperbase">
+ <h1><span class="secnum" id="sec-8.1.1.3.5"><a href="#sec-getsuperbase"
+ title="link to this section">8.1.1.3.5</a></span> GetSuperBase ()</h1>
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the <a href="#sec-function-environment-records">function environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>home</i> be the value of <i>envRec</i>.[[HomeObject]].</li>
+ <li>If <i>home</i> has the value <b>undefined</b>, return <b>undefined</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>home</i>) is Object.</li>
+ <li>Return <i>home.</i>[[GetPrototypeOf]]().</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-global-environment-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1.1.4"><a href="#sec-global-environment-records"
+ title="link to this section">8.1.1.4</a></span> Global Environment Records</h1>
+
+ <p>A global environment record is used to represent the outer most scope that is shared by all of the ECMAScript <span
+ class="nt">Script</span> elements that are processed in a common <a href="#sec-code-realms">Realm</a> (<a
+ href="#sec-code-realms">8.2</a>). A global environment record provides the bindings for built-in globals (<a
+ href="#sec-global-object">clause 18</a>), properties of the global object, and for all declarations that are not
+ function code and that occur within <span class="nt">Script</span> productions.</p>
+
+ <p>A global environment record is logically a single record but it is specified as a composite encapsulating an <a
+ href="#sec-object-environment-records">object environment record</a> and a <a
+ href="#sec-declarative-environment-records">declarative environment record</a>. The <a
+ href="#sec-object-environment-records">object environment record</a> has as its base object the global object of the
+ associated <a href="#sec-code-realms">Realm</a>. This global object is the value returned by the global environment
+ record’s GetThisBinding concrete method. The <a href="#sec-object-environment-records">object environment
+ record</a> component of a global environment record contains the bindings for all built-in globals (<a
+ href="#sec-global-object">clause 18</a>) and all bindings introduced by a <span style="font-family: Times New
+ Roman"><i>FunctionDeclaration</i>, <i>GeneratorDeclaration</i></span>, or <span class="nt">VariableStatement</span>
+ contained in global code. The bindings for all other ECMAScript declarations in global code are contained in the <a
+ href="#sec-declarative-environment-records">declarative environment record</a> component of the global environment
+ record.</p>
+
+ <p>Properties may be created directly on a global object. Hence, the <a href="#sec-object-environment-records">object
+ environment record</a> component of a global environment record may contain both bindings created explicitly by <span
+ style="font-family: Times New Roman"><i>FunctionDeclaration</i>, <i>GeneratorDeclaration</i></span>, or <span
+ class="nt">VariableDeclaration</span> declarations and binding created implicitly as properties of the global object. In
+ order to identify which bindings were explicitly created using declarations, a global environment record maintains a
+ list of the names bound using its CreateGlobalVarBindings and CreateGlobalFunctionBindings concrete methods.</p>
+
+ <p>Global environment records have the additional fields listed in <a href="#table-18">Table 18</a> and the additional
+ methods listed in <a href="#table-19">Table 19</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-18">Table 18</span> — Additional Fields of Global Environment Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">[[ObjectRecord]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><a href="#sec-object-environment-records">Object Environment Record</a></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Binding object is the global object. It contains global built-in bindings as well as <span style="font-family: Times New Roman"><i>FunctionDeclaration</i>, <i>GeneratorDeclaration</i></span>, and <span class="nt">VariableDeclaration</span> bindings in global code for the associated <a href="#sec-code-realms">Realm</a>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">[[DeclarativeRecord]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-declarative-environment-records">Declarative Environment Record</a></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Contains bindings for all declarations in global code for the associated <a href="#sec-code-realms">Realm</a> code except for <span style="font-family: Times New Roman"><i>FunctionDeclaration</i>, <i>GeneratorDeclaration</i></span>, and <span class="nt">VariableDeclaration</span> <var>bindings</var>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">[[VarNames]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-list-and-record-specification-type">List</a> of String</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">The string names bound by <span style="font-family: Times New Roman"><i>FunctionDeclaration</i>, <i>GeneratorDeclaration</i></span>, and <span class="nt">VariableDeclaration</span> declarations in global code for the associated <a href="#sec-code-realms">Realm</a>.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <figure>
+ <figcaption><span id="table-19">Table 19</span> — Additional Methods of Global Environment Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Method</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">GetThisBinding()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return the value of this environment record’s <code>this</code> binding.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-hasvardeclaration">HasVarDeclaration</a> (N)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Determines if the argument identifier has a binding in this environment record that was created using a <span style="font-family: Times New Roman"><i>VariableDeclaration</i>,</span> <span class="nt">FunctionDeclaration</span>, or <span style="font-family: Times New Roman"><i>GeneratorDeclaration</i>.</span></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-haslexicaldeclaration">HasLexicalDeclaration</a> (N)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Determines if the argument identifier has a binding in this environment record that was created using a lexical declaration such as a <span class="nt">LexicalDeclaration</span> or a <span class="nt">ClassDeclaration</span>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-hasrestrictedglobalproperty">HasRestrictedGlobalProperty</a> (N)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Determines if the argument is the name of a global object property that may not be shadowed by a global lexically binding.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-candeclareglobalvar">CanDeclareGlobalVar</a> (N)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Determines if a corresponding <a href="#sec-createglobalvarbinding">CreateGlobalVarBinding</a> call would succeed if called for the same argument <var>N</var>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-candeclareglobalfunction">CanDeclareGlobalFunction</a> (N)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Determines if a corresponding <a href="#sec-createglobalfunctionbinding">CreateGlobalFunctionBinding</a> call would succeed if called for the same argument <var>N</var>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-createglobalvarbinding">CreateGlobalVarBinding</a>(N, D)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Used to create and initialize to <b>undefined</b> a global <code>var</code> binding in the [[ObjectRecord]] component of a global environment record. The binding will be a mutable binding. The corresponding global object property will have attribute values appropriate for a <code>var</code>. The String value <var>N</var> is the bound name. If <var>D</var> is <b>true</b> the binding may be deleted. Logically equivalent to CreateMutableBinding followed by a SetMutableBinding but it allows var declarations to receive special treatment.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-createglobalfunctionbinding">CreateGlobalFunctionBinding</a>(N, V, D)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Create and initialize a global <code>function</code> binding in the [[ObjectRecord]] component of a global environment record. The binding will be a mutable binding. The corresponding global object property will have attribute values appropriate for a <code>function</code>. The String value <var>N</var> is the bound name. <i>V</i> is the initialization value. If the optional Boolean argument <var>D</var> is <b>true</b> the binding is may be deleted. Logically equivalent to CreateMutableBinding followed by a SetMutableBinding but it allows function declarations to receive special treatment.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The behaviour of the concrete specification methods for Global Environment Records is defined by the following
+ algorithms.</p>
+ </div>
+
+ <section id="sec-global-environment-records-hasbinding-n">
+ <h1><span class="secnum" id="sec-8.1.1.4.1"><a href="#sec-global-environment-records-hasbinding-n"
+ title="link to this section">8.1.1.4.1</a></span> HasBinding(N)</h1>
+
+ <p>The concrete environment record method HasBinding for global environment records simply determines if the argument
+ identifier is one of the identifiers bound by the record:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>If <i>DclRec.</i>HasBinding(<i>N</i>) is <b>true</b>, return <b>true</b>.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Return <i>ObjRec.</i>HasBinding(<i>N</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-createmutablebinding-n-d">
+ <h1><span class="secnum" id="sec-8.1.1.4.2"><a href="#sec-global-environment-records-createmutablebinding-n-d"
+ title="link to this section">8.1.1.4.2</a></span> CreateMutableBinding (N, D)</h1>
+
+ <p>The concrete environment record method CreateMutableBinding for global environment records creates a new mutable
+ binding for the name <var>N</var> that is uninitialized. The binding is created in the associated DeclarativeRecord. A
+ binding for <var>N</var> must not already exist in the DeclarativeRecord. If Boolean argument <var>D</var> is provided
+ and has the value <b>true</b> the new binding is marked as being subject to deletion.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>If <i>DclRec</i>.HasBinding(<i>N</i>) is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>DclRec</i>.CreateMutableBinding(<i>N</i>, <i>D</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-createimmutablebinding-n-s">
+ <h1><span class="secnum" id="sec-8.1.1.4.3"><a href="#sec-global-environment-records-createimmutablebinding-n-s"
+ title="link to this section">8.1.1.4.3</a></span> CreateImmutableBinding (N, S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateImmutableBinding for global
+ environment records creates a new immutable binding for the name <var>N</var> that is uninitialized. A binding must not
+ already exist in this environment record for <var>N</var>. If Boolean argument <var>S</var> is provided and has the
+ value <b>true</b> the new binding is marked as a strict binding.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>If <i>DclRec</i>.HasBinding(<i>N</i>) is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>DclRec</i>.CreateImmutableBinding(<i>N</i>, <i>S</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-initializebinding-n-v">
+ <h1><span class="secnum" id="sec-8.1.1.4.4"><a href="#sec-global-environment-records-initializebinding-n-v"
+ title="link to this section">8.1.1.4.4</a></span> InitializeBinding (N,V)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method InitializeBinding for global
+ environment records is used to set the bound value of the current binding of the identifier whose name is the value of
+ the argument <var>N</var> to the value of argument <var>V</var>. An uninitialized binding for <var>N</var> must already
+ exist.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>If <i>DclRec.</i>HasBinding(<i>N</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Return <i>DclRec</i>.InitializeBinding(<i>N</i>, <i>V</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If the binding exists it must be in the <a
+ href="#sec-object-environment-records">object environment record</a>.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Return <i>ObjRec.</i>InitializeBinding(<i>N</i>, <i>V</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-setmutablebinding-n-v-s">
+ <h1><span class="secnum" id="sec-8.1.1.4.5"><a href="#sec-global-environment-records-setmutablebinding-n-v-s"
+ title="link to this section">8.1.1.4.5</a></span> SetMutableBinding (N,V,S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method SetMutableBinding for global
+ environment records attempts to change the bound value of the current binding of the identifier whose name is the value
+ of the argument <var>N</var> to the value of argument <var>V</var>. If the binding is an immutable binding, a
+ <b>TypeError</b> is thrown if <span style="font-family: Times New Roman">S</span> is <span class="value">true</span>. A
+ property named <var>N</var> normally already exists but if it does not or is not currently writable, error handling is
+ determined by the value of the Boolean argument <var>S</var>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>If <i>DclRec.</i>HasBinding(<i>N</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Return <i>DclRec.</i>SetMutableBinding(<i>N</i>, <i>V</i>, <i>S</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Return <i>ObjRec</i>.SetMutableBinding(<i>N</i>, <i>V</i>, <i>S</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-getbindingvalue-n-s">
+ <h1><span class="secnum" id="sec-8.1.1.4.6"><a href="#sec-global-environment-records-getbindingvalue-n-s"
+ title="link to this section">8.1.1.4.6</a></span> GetBindingValue(N,S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method GetBindingValue for global environment
+ records returns the value of its bound identifier whose name is the value of the argument <var>N</var>. If the binding
+ is an uninitialized binding throw a <b>ReferenceError</b> exception. A property named <var>N</var> normally already
+ exists but if it does not or is not currently writable, error handling is determined by the value of the Boolean
+ argument <var>S</var>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>If <i>DclRec.</i>HasBinding(<i>N</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Return <i>DclRec.</i>GetBindingValue(<i>N</i>, <i>S</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Return <i>ObjRec</i>.GetBindingValue(<i>N</i>, <i>S</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-deletebinding-n">
+ <h1><span class="secnum" id="sec-8.1.1.4.7"><a href="#sec-global-environment-records-deletebinding-n"
+ title="link to this section">8.1.1.4.7</a></span> DeleteBinding (N)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method DeleteBinding for global environment
+ records can only delete bindings that have been explicitly designated as being subject to deletion.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>If <i>DclRec.</i>HasBinding(<i>N</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Return <i>DclRec.</i>DeleteBinding(<i>N</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Let <i>globalObject</i> be the binding object for <i>ObjRec</i>.</li>
+ <li>Let <i>existingProp</i> be <i>globalObject</i>.[[GetOwnProperty]](<i>N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>existingProp</i>).</li>
+ <li>If <i>existingProp</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>ObjRec.</i>DeleteBinding(<i>N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>varNames</i> be <i>envRec</i>.[[VarNames]].</li>
+ <li>If <i>N</i> is an element of <i>varNames</i>, remove that element from the <i>varNames</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-hasthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.4.8"><a href="#sec-global-environment-records-hasthisbinding"
+ title="link to this section">8.1.1.4.8</a></span> HasThisBinding ()</h1>
+
+ <p><a href="#sec-global-environment-records">Global Environment Records</a> always provide a <code>this</code> binding
+ whose value is the associated global object.</p>
+
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-hassuperbinding">
+ <h1><span class="secnum" id="sec-8.1.1.4.9"><a href="#sec-global-environment-records-hassuperbinding"
+ title="link to this section">8.1.1.4.9</a></span> HasSuperBinding ()</h1>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-withbaseobject">
+ <h1><span class="secnum" id="sec-8.1.1.4.10"><a href="#sec-global-environment-records-withbaseobject"
+ title="link to this section">8.1.1.4.10</a></span> WithBaseObject()</h1>
+
+ <p><a href="#sec-global-environment-records">Global Environment Records</a> always return <b>undefined</b> as their
+ WithBaseObject.</p>
+
+ <ol class="proc">
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-global-environment-records-getthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.4.11"><a href="#sec-global-environment-records-getthisbinding"
+ title="link to this section">8.1.1.4.11</a></span> GetThisBinding ()</h1>
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Let <i>bindings</i> be the binding object for <i>ObjRec</i>.</li>
+ <li>Return <i>bindings</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-hasvardeclaration">
+ <h1><span class="secnum" id="sec-8.1.1.4.12"><a href="#sec-hasvardeclaration"
+ title="link to this section">8.1.1.4.12</a></span> HasVarDeclaration (N)</h1>
+
+ <p>The concrete environment record method HasVarDeclaration for global environment records determines if the argument
+ identifier has a binding in this record that was created using a <span class="nt">VariableStatement</span> or a <span
+ class="prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span></span></p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>varDeclaredNames</i> be <i>envRec</i>.[[VarNames]].</li>
+ <li>If <i>varDeclaredNames</i> contains the value of <i>N</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-haslexicaldeclaration">
+ <h1><span class="secnum" id="sec-8.1.1.4.13"><a href="#sec-haslexicaldeclaration"
+ title="link to this section">8.1.1.4.13</a></span> HasLexicalDeclaration (N)</h1>
+
+ <p>The concrete environment record method HasLexicalDeclaration for global environment records determines if the
+ argument identifier has a binding in this record that was created using a lexical declaration such as a <span
+ class="nt">LexicalDeclaration</span> or a <span class="prod"><span class="nt">ClassDeclaration</span> <span
+ class="geq">:</span></span></p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>DclRec</i> be <i>envRec</i>.[[DeclarativeRecord]].</li>
+ <li>Return <i>DclRec.</i>HasBinding(<i>N</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-hasrestrictedglobalproperty">
+ <h1><span class="secnum" id="sec-8.1.1.4.14"><a href="#sec-hasrestrictedglobalproperty"
+ title="link to this section">8.1.1.4.14</a></span> HasRestrictedGlobalProperty (N)</h1>
+
+ <p>The concrete environment record method HasRestrictedGlobalProperty for global environment records determines if the
+ argument identifier is the name of a property of the global object that must not be shadowed by a global lexically
+ binding:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Let <i>globalObject</i> be the binding object for <i>ObjRec</i>.</li>
+ <li>Let <i>existingProp</i> be <i>globalObject</i>.[[GetOwnProperty]](<i>N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>existingProp</i>).</li>
+ <li>If <i>existingProp</i> is <b>undefined</b>, return <b>false</b>.</li>
+ <li>If <i>existingProp</i>.[[Configurable]] is <b>true</b>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Properties may exist upon a global object that were directly created rather than being
+ declared using a var or function declaration. A global lexical binding may not be created that has the same name as a
+ non-configurable property of the global object. The global property <code>undefined</code> is an example of such a
+ property.</p>
+ </div>
+ </section>
+
+ <section id="sec-candeclareglobalvar">
+ <h1><span class="secnum" id="sec-8.1.1.4.15"><a href="#sec-candeclareglobalvar"
+ title="link to this section">8.1.1.4.15</a></span> CanDeclareGlobalVar (N)</h1>
+
+ <p>The concrete environment record method CanDeclareGlobalVar for global environment records determines if a
+ corresponding <a href="#sec-createglobalvarbinding">CreateGlobalVarBinding</a> call would succeed if called for the same
+ argument <var>N</var>. Redundant var declarations and var declarations for pre-existing global object properties are
+ allowed.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Let <i>globalObject</i> be the binding object for <i>ObjRec</i>.</li>
+ <li>Let <i>hasProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>globalObject, N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasProperty</i>).</li>
+ <li>If <i>hasProperty</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Let <i>extensible</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>globalObject</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensible</i>).</li>
+ <li>Return <i>extensible</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-candeclareglobalfunction">
+ <h1><span class="secnum" id="sec-8.1.1.4.16"><a href="#sec-candeclareglobalfunction"
+ title="link to this section">8.1.1.4.16</a></span> CanDeclareGlobalFunction (N)</h1>
+
+ <p>The concrete environment record method CanDeclareGlobalFunction for global environment records determines if a
+ corresponding <a href="#sec-createglobalfunctionbinding">CreateGlobalFunctionBinding</a> call would succeed if called
+ for the same argument <var>N</var>.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Let <i>globalObject</i> be the binding object for <i>ObjRec</i>.</li>
+ <li>Let <i>existingProp</i> be <i>globalObject</i>.[[GetOwnProperty]](<i>N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>existingProp</i>).</li>
+ <li>If <i>existingProp</i> is <b>undefined</b>, return <a
+ href="#sec-isextensible-o">IsExtensible</a>(<i>globalObject</i>).</li>
+ <li>If <i>existingProp</i>.[[Configurable]] is <b>true</b>, return <b>true</b>.</li>
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>existingProp</i>) is <b>true</b> and
+ <i>existingProp</i> has attribute values {.[[Writable]]: <b>true</b>, [[Enumerable]]: <b>true</b>}, return
+ <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createglobalvarbinding">
+ <h1><span class="secnum" id="sec-8.1.1.4.17"><a href="#sec-createglobalvarbinding"
+ title="link to this section">8.1.1.4.17</a></span> CreateGlobalVarBinding (N, D)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateGlobalVarBinding for global
+ environment records creates and initializes a mutable binding in the associated <a
+ href="#sec-object-environment-records">object environment record</a> and records the bound name in the associated
+ [[VarNames]] <a href="#sec-list-and-record-specification-type">List</a>. If a binding already exists, it is reused and
+ assumed to be initialized.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Let <i>globalObject</i> be the binding object for <i>ObjRec</i>.</li>
+ <li>Let <i>hasProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>globalObject, N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasProperty</i>).</li>
+ <li>Let <i>extensible</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>globalObject</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensible</i>).</li>
+ <li>If <i>hasProperty</i> is <b>false</b> and <i>extensible</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>ObjRec.</i>CreateMutableBinding(<i>N</i>, <i>D</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Let <i>status</i> be <i>ObjRec.</i>InitializeBinding(<i>N</i>, <b>undefined</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>varDeclaredNames</i> be <i>envRec</i>.[[VarNames]].</li>
+ <li>If <i>varDeclaredNames</i> does not contain the value of <i>N</i>, then
+ <ol class="block">
+ <li>Append <i>N</i> to <i>varDeclaredNames</i>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-createglobalfunctionbinding">
+ <h1><span class="secnum" id="sec-8.1.1.4.18"><a href="#sec-createglobalfunctionbinding"
+ title="link to this section">8.1.1.4.18</a></span> CreateGlobalFunctionBinding (N, V, D)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateGlobalFunctionBinding for global
+ environment records creates and initializes a mutable binding in the associated <a
+ href="#sec-object-environment-records">object environment record</a> and records the bound name in the associated
+ [[VarNames]] <a href="#sec-list-and-record-specification-type">List</a>. If a binding already exists, it is
+ replaced.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-global-environment-records">the global environment record</a> for which the
+ method was invoked.</li>
+ <li>Let <i>ObjRec</i> be <i>envRec</i>.[[ObjectRecord]].</li>
+ <li>Let <i>globalObject</i> be the binding object for <i>ObjRec</i>.</li>
+ <li>Let <i>existingProp</i> be <i>globalObject</i>.[[GetOwnProperty]](<i>N</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>existingProp</i>).</li>
+ <li>If <i>existingProp</i> is <b>undefined</b> or <i>existingProp</i>.[[Configurable]] is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>desc</i> be the PropertyDescriptor{[[Value]]:<i>V</i>, [[Writable]]: <b>true</b>, [[Enumerable]]:
+ <b>true</b> , [[Configurable]]: <i>D</i>}.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>desc</i> be the PropertyDescriptor{[[Value]]:<i>V</i> }.</li>
+ </ol>
+ </li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>globalObject</i>, <i>N</i>,
+ <i>desc</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Let <i>status</i> be Put(<i>globalObject</i>, <i>V</i>).</li>
+ <li>Record that the binding for <i>N</i> in <i>ObjRec</i> has been initialized.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Let <i>varDeclaredNames</i> be <i>envRec</i>.[[VarNames]].</li>
+ <li>If <i>varDeclaredNames</i> does not contain the value of <i>N</i>, then
+ <ol class="block">
+ <li>Append <i>N</i> to <i>varDeclaredNames</i>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Global function declarations are always represented as own properties of the global
+ object. If possible, an existing own property is reconfigured to have a standard set of attribute values. Steps 10-12
+ are equivalent to what calling the InitializeBinding concrete method would do and if <i>globalObject</i> is a Proxy
+ will produce the same sequence of Proxy trap calls.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-module-environment-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1.1.5"><a href="#sec-module-environment-records"
+ title="link to this section">8.1.1.5</a></span> Module Environment Records</h1>
+
+ <p>A module environment record is a <a href="#sec-declarative-environment-records">declarative environment record</a>
+ that is used to represent the outer scope of an ECMAScript <span class="nt">Module</span>. In additional to normal
+ mutable and immutable bindings, module environment records also provide immutable import bindings which are bindings
+ that provide indirect access to a target binding that exists in another environment record.</p>
+
+ <p>Module environment records support all of the <a href="#sec-declarative-environment-records">Declarative Environment
+ Record</a> methods listed in <a href="#table-15">Table 15</a> and share the same specifications for all of those methods
+ except for GetBindingValue, DeleteBinding, HasThisBinding and GetThisBinding. In addition, module environment records
+ support the methods listed in <a href="#table-20">Table 20</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-20">Table 20</span> — Additional Methods of Module Environment Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Method</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-createimportbinding">CreateImportBinding</a>(N, M, N2 )</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Create an immutable indirect binding in a module environment record. The String value <var>N</var> is the text of the bound name. <var>M</var> is a Module Record (<a href="#sec-abstract-module-records">see 15.2.1.15</a>), and <var>N2</var> is a binding that exists in M’s module environment record.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">GetThisBinding()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return the value of this environment record’s <code>this</code> binding.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The behaviour of the additional concrete specification methods for Module Environment Records is defined by the
+ following algorithms:</p>
+ </div>
+
+ <section id="sec-module-environment-records-getbindingvalue-n-s">
+ <h1><span class="secnum" id="sec-8.1.1.5.1"><a href="#sec-module-environment-records-getbindingvalue-n-s"
+ title="link to this section">8.1.1.5.1</a></span> GetBindingValue(N,S)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method GetBindingValue for module environment
+ records returns the value of its bound identifier whose name is the value of the argument <var>N</var>. However, if the
+ binding is an indirect binding the value of the target binding is returned. If the binding exists but is uninitialized a
+ <span class="value">ReferenceError</span> is thrown, regardless of the value of <i><span style="font-family: Times New
+ Roman">S</span>.</i></p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the module environment record for which the method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> has a binding for <i>N</i>.</li>
+ <li>If the binding for <i>N</i> is an indirect binding, then
+ <ol class="block">
+ <li>Let <i>M</i> and <i>N2</i> be the indirection values provided when this binding for <i>N</i> was created.</li>
+ <li>If <i>M</i> is <b>undefined</b>, throw a <b>ReferenceError</b> exception.</li>
+ <li>Let <i>targetER</i> be <i>M</i>.[[Environment]]’s environment record.</li>
+ <li>Return <i>targetER</i>.GetBindingValue(<i>N2</i>, <i>S</i>).</li>
+ </ol>
+ </li>
+ <li>If the binding for <i>N</i> in <i>envRec</i> is an uninitialized binding, throw a <b>ReferenceError</b>
+ exception.</li>
+ <li>Return the value currently bound to <i>N</i> in <i>envRec</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Because a <i>Module</i> is always <a href="#sec-strict-mode-code">strict mode
+ code</a>, calls to GetBindingValue should always pass <b>true</b> <span style="font-family: sans-serif">as</span>
+ <span style="font-family: sans-serif">the value of</span> <i>S</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-module-environment-records-deletebinding-n">
+ <h1><span class="secnum" id="sec-8.1.1.5.2"><a href="#sec-module-environment-records-deletebinding-n"
+ title="link to this section">8.1.1.5.2</a></span> DeleteBinding (N)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method DeleteBinding for module environment
+ records refuses to delete bindings.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the module environment record for which the method was invoked.</li>
+ <li>If <i>envRec</i> does not have a binding for the name that is the value of <i>N</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Because the bindings of a module environment record are not deletable.</p>
+ </div>
+ </section>
+
+ <section id="sec-module-environment-records-hasthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.5.3"><a href="#sec-module-environment-records-hasthisbinding"
+ title="link to this section">8.1.1.5.3</a></span> HasThisBinding ()</h1>
+
+ <p>Module Environment Records provide a <code>this</code> binding.</p>
+
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-environment-records-getthisbinding">
+ <h1><span class="secnum" id="sec-8.1.1.5.4"><a href="#sec-module-environment-records-getthisbinding"
+ title="link to this section">8.1.1.5.4</a></span> GetThisBinding ()</h1>
+ <ol class="proc">
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createimportbinding">
+ <h1><span class="secnum" id="sec-8.1.1.5.5"><a href="#sec-createimportbinding"
+ title="link to this section">8.1.1.5.5</a></span> CreateImportBinding (N, M, N2)</h1>
+
+ <p>The concrete <a href="#sec-environment-records">Environment Record</a> method CreateImportBinding for module
+ environment records creates a new initialized immutable indirect binding for the name <var>N</var>. A binding must not
+ already exist in this environment record for <var>N</var>. <var>M</var> is a Module Record (<a
+ href="#sec-abstract-module-records">see 15.2.1.15</a>), and <var>N2</var> is the name of a binding that exists in
+ M’s module environment record. Accesses to the value of the new binding will indirectly access the bound value of
+ value of the target binding.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be the module environment record for which the method was invoked.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> does not already have a binding for <i>N</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>M</i> is a Module Record.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: When <i>M</i>.[[Environment]] is instantiated it will have a
+ direct binding for <i>N2</i>.</li>
+ <li>Create an immutable indirect binding in <i>envRec</i> for <i>N</i> that references <i>M</i> and <i>N2</i> as its
+ target binding and record that the binding is initialized.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-lexical-environment-operations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.1.2"><a href="#sec-lexical-environment-operations"
+ title="link to this section">8.1.2</a></span> Lexical Environment Operations</h1>
+
+ <p>The following abstract operations are used in this specification to operate upon lexical environments:</p>
+ </div>
+
+ <section id="sec-getidentifierreference">
+ <h1><span class="secnum" id="sec-8.1.2.1"><a href="#sec-getidentifierreference"
+ title="link to this section">8.1.2.1</a></span> GetIdentifierReference (lex, name, strict)</h1>
+
+ <p>The abstract operation GetIdentifierReference is called with a <a href="#sec-lexical-environments">Lexical
+ Environment</a> <var>lex</var>, a String <var>name</var>, and a Boolean flag <var>strict.</var> The value of
+ <var>lex</var> may be <b>null</b>. When called, the following steps are performed:</p>
+
+ <ol class="proc">
+ <li>If <i>lex</i> is the value <b>null</b>, then
+ <ol class="block">
+ <li>Return a value of type <a href="#sec-reference-specification-type">Reference</a> whose base value is
+ <b>undefined</b>, whose referenced name is <i>name</i>, and whose strict reference flag is <i>strict</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>envRec</i> be <i>lex</i>’s environment record.</li>
+ <li>Let <i>exists</i> be <i>envRec</i>.HasBinding(<i>name</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exists</i>).</li>
+ <li>If <i>exists</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Return a value of type <a href="#sec-reference-specification-type">Reference</a> whose base value is
+ <i>envRec</i>, whose referenced name is <i>name</i>, and whose strict reference flag is <i>strict.</i></li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>outer</i> be the value of <i>lex’s</i> <a href="#sec-lexical-environments">outer environment
+ reference</a>.</li>
+ <li>Return GetIdentifierReference(<i>outer</i>, <i>name</i>, <i>strict</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-newdeclarativeenvironment">
+ <h1><span class="secnum" id="sec-8.1.2.2"><a href="#sec-newdeclarativeenvironment"
+ title="link to this section">8.1.2.2</a></span> NewDeclarativeEnvironment (E)</h1>
+
+ <p>When the abstract operation NewDeclarativeEnvironment is called with either a <a
+ href="#sec-lexical-environments">Lexical Environment</a> or <b>null</b> as argument <var>E</var> the following steps are
+ performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>env</i> be a new <a href="#sec-lexical-environments">Lexical Environment</a>.</li>
+ <li>Let <i>envRec</i> be a new <a href="#sec-declarative-environment-records">declarative environment record</a>
+ containing no bindings.</li>
+ <li>Set <i>env’s</i> environment record to be <i>envRec</i>.</li>
+ <li>Set the <a href="#sec-lexical-environments">outer lexical environment reference</a> of <i>env</i> to <i>E</i>.</li>
+ <li>Return <i>env</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-newobjectenvironment">
+ <h1><span class="secnum" id="sec-8.1.2.3"><a href="#sec-newobjectenvironment"
+ title="link to this section">8.1.2.3</a></span> NewObjectEnvironment (O, E)</h1>
+
+ <p>When the abstract operation NewObjectEnvironment is called with an Object <var>O</var> and a <a
+ href="#sec-lexical-environments">Lexical Environment</a> <var>E</var> (or <b>null)</b> as arguments, the following steps
+ are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>env</i> be a new <a href="#sec-lexical-environments">Lexical Environment</a>.</li>
+ <li>Let <i>envRec</i> be a new <a href="#sec-object-environment-records">object environment record</a> containing
+ <i>O</i> as the binding object.</li>
+ <li>Set <i>env’s</i> environment record to <i>envRec</i>.</li>
+ <li>Set the <a href="#sec-lexical-environments">outer lexical environment reference</a> of <i>env</i> to <i>E</i>.</li>
+ <li>Return <i>env</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-newfunctionenvironment">
+ <h1><span class="secnum" id="sec-8.1.2.4"><a href="#sec-newfunctionenvironment"
+ title="link to this section">8.1.2.4</a></span> NewFunctionEnvironment ( F, newTarget )</h1>
+
+ <p>When the abstract operation NewFunctionEnvironment is called with arguments <var>F</var> and <var>newTarget</var> the
+ following steps are performed:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an ECMAScript function.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>newTarget</i>) is Undefined or Object.</li>
+ <li>Let <i>env</i> be a new <a href="#sec-lexical-environments">Lexical Environment</a>.</li>
+ <li>Let <i>envRec</i> be a new <a href="#sec-function-environment-records">Function environment record</a> containing no
+ bindings.</li>
+ <li>Set <i>envRec</i>.[[FunctionObject]] to <i>F</i>.</li>
+ <li>If <i>F’s</i> [[ThisMode]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is
+ <span style="font-family: sans-serif">lexical</span>, set <i>envRec</i>.[[thisBindingStatus]] to
+ <code>"lexical"</code>.</li>
+ <li>Else, Set <i>envRec</i>.[[thisBindingStatus]] to <code>"uninitialized"</code>.</li>
+ <li>Let <i>home</i> be the value of <i>F’s</i> [[HomeObject]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Set <i>envRec</i>.[[HomeObject]] to <i>home</i>.</li>
+ <li>Set <i>envRec</i>.[[NewTarget]] to <i>newTarget</i>.</li>
+ <li>Set <i>env’s</i> environment record to be <i>envRec</i>.</li>
+ <li>Set the <a href="#sec-lexical-environments">outer lexical environment reference</a> of <i>env</i> to the value of
+ <i>F’s</i> [[Environment]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>env</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-newglobalenvironment">
+ <h1><span class="secnum" id="sec-8.1.2.5"><a href="#sec-newglobalenvironment"
+ title="link to this section">8.1.2.5</a></span> NewGlobalEnvironment ( G )</h1>
+
+ <p>When the abstract operation NewGlobalEnvironment is called with an ECMAScript Object <var>G</var> as its argument, the
+ following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>env</i> be a new <a href="#sec-lexical-environments">Lexical Environment</a>.</li>
+ <li>Let <i>objRec</i> be a new <a href="#sec-object-environment-records">object environment record</a> containing
+ <i>G</i> as the binding object.</li>
+ <li>Let <i>dclRec</i> be a new <a href="#sec-declarative-environment-records">declarative environment record</a>
+ containing no bindings.</li>
+ <li>Let <i>globalRec</i> be a new <a href="#sec-global-environment-records">global environment record</a>.</li>
+ <li>Set <i>globalRec</i>.[[ObjectRecord]] to <i>objRec</i>.</li>
+ <li>Set <i>globalRec</i>.[[DeclarativeRecord]] to <i>dclRec</i>.</li>
+ <li>Set <i>globalRec</i>.[[VarNames]] to a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Set <i>env’s</i> environment record to <i>globalRec</i>.</li>
+ <li>Set the <a href="#sec-lexical-environments">outer lexical environment reference</a> of <i>env</i> to
+ <b>null</b></li>
+ <li>Return <i>env</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-newmoduleenvironment">
+ <h1><span class="secnum" id="sec-8.1.2.6"><a href="#sec-newmoduleenvironment"
+ title="link to this section">8.1.2.6</a></span> NewModuleEnvironment (E)</h1>
+
+ <p>When the abstract operation NewModuleEnvironment is called with a <a href="#sec-lexical-environments">Lexical
+ Environment</a> argument <var>E</var> the following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>env</i> be a new <a href="#sec-lexical-environments">Lexical Environment</a>.</li>
+ <li>Let <i>envRec</i> be a new module environment record containing no bindings.</li>
+ <li>Set <i>env’s</i> environment record to be <i>envRec</i>.</li>
+ <li>Set the <a href="#sec-lexical-environments">outer lexical environment reference</a> of <i>env</i> to <i>E</i>.</li>
+ <li>Return <i>env</i>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-code-realms">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.2"><a href="#sec-code-realms" title="link to this section">8.2</a></span> Code
+ Realms</h1>
+
+ <p>Before it is evaluated, all ECMAScript code must be associated with a <i>Realm</i>. Conceptually, a realm consists of a
+ set of intrinsic objects, an ECMAScript global environment, all of the ECMAScript code that is loaded within the scope of
+ that global environment, and other associated state and resources.</p>
+
+ <p>A Realm is specified as a Record with the fields specified in <a href="#table-21">Table 21</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-21">Table 21</span> — Realm Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[intrinsics]]</td>
+ <td>Record whose field names are intrinsic keys and whose values are objects</td>
+ <td>These are the intrinsic values used by code associated with this Realm</td>
+ </tr>
+ <tr>
+ <td>[[globalThis]]</td>
+ <td>Object</td>
+ <td>The global object for this Realm</td>
+ </tr>
+ <tr>
+ <td>[[globalEnv]]</td>
+ <td><a href="#sec-lexical-environments">Lexical Environment</a></td>
+ <td>The global environment for this Realm</td>
+ </tr>
+ <tr>
+ <td>[[templateMap]]</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of Record{ [[strings]]: <a href="#sec-list-and-record-specification-type">List</a>, [[array]]: Object}.</td>
+ <td>Template objects are canonicalized separately for each Realm using its [[templateMap]]. Each [[strings]] value is a <a href="#sec-list-and-record-specification-type">List</a> containing, in source text order, the raw string values of a <span class="nt">TemplateLiteral</span> that has been evaluated. The associated [[array]] value is the corresponding template object that is passed to a tag function.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>An implementation may define other, implementation specific fields.</p>
+ </div>
+
+ <section id="sec-createrealm">
+ <h1><span class="secnum" id="sec-8.2.1"><a href="#sec-createrealm" title="link to this section">8.2.1</a></span> CreateRealm
+ ( )</h1>
+
+ <p>The abstract operation CreateRealm with no arguments performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>realmRec</i> be a new Record.</li>
+ <li>Perform <a href="#sec-createintrinsics">CreateIntrinsics</a>(<i>realmRec</i>).</li>
+ <li>Set <i>realmRec</i>.[[globalThis]] to <b>undefined</b>.</li>
+ <li>Set <i>realmRec</i>.[[globalEnv]] to <b>undefined</b>.</li>
+ <li>Set <i>realmRec</i>.[[templateMap]] to a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return <i>realmRec</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createintrinsics">
+ <h1><span class="secnum" id="sec-8.2.2"><a href="#sec-createintrinsics" title="link to this section">8.2.2</a></span>
+ CreateIntrinsics ( realmRec )</h1>
+
+ <p>When the abstract operation CreateIntrinsics with argument <var>realmRec</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>intrinsics</i> be a new Record.</li>
+ <li>Set <i>realmRec</i>.[[intrinsics]] to <i>intrinsics</i>.</li>
+ <li>Let <i>objProto</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<b>null</b>).</li>
+ <li>Set <i>intrinsics</i>.[[%ObjectPrototype%]] to <i>objProto</i>.</li>
+ <li>Let <i>throwerSteps</i> be the algorithm steps specifed in <a href="#sec-%throwtypeerror%">9.2.8.1</a> for the <a
+ href="#sec-%throwtypeerror%">%ThrowTypeError%</a> function.</li>
+ <li>Let <i>thrower</i> be <a href="#sec-createbuiltinfunction">CreateBuiltinFunction</a>(<i>realmRec</i>,
+ <i>throwerSteps</i>, <b>null</b>).</li>
+ <li>Set <i>intrinsics</i>.[[<span style="font-family: sans-serif"><a
+ href="#sec-%throwtypeerror%">%ThrowTypeError%</a></span>]] to <i>thrower</i>.</li>
+ <li>Let <i>noSteps</i> be an empty sequence of algorithm steps.</li>
+ <li>Let <i>funcProto</i> be <a href="#sec-createbuiltinfunction">CreateBuiltinFunction</a>(<i>realmRec</i>,
+ <i>noSteps</i>, <i>objProto</i>).</li>
+ <li>Set <i>intrinsics</i>.[[%FunctionPrototype%]] to <i>funcProto</i>.</li>
+ <li><a href="#sec-call">Call</a> <i>thrower</i>.[[SetPrototypeOf]](<i>funcProto</i>).</li>
+ <li>Perform <a href="#sec-addrestrictedfunctionproperties">AddRestrictedFunctionProperties</a>(<i>funcProto</i>,
+ <i>realmRec</i>).</li>
+ <li>Set fields of <i>intrinsics</i> with the values listed in <a href="#table-7">Table 7</a> that have not already been
+ handled above. The field names are the names listed in column one of the table. The value of each field is a new
+ object value fully and recursively populated with property values as defined by the specification of each object in
+ clauses 18-26. All object property values are newly created object values. All values that are built-in function
+ objects are created by performing <a href="#sec-createbuiltinfunction">CreateBuiltinFunction</a>(<i>realmRec</i>,
+ <steps>, <prototype>, <slots>) where <steps> is the definition of that function provided by
+ this specification, <prototype> is the specified value of the function’s [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> and <slots> is a list of the names, if
+ any, of the functions specified internal slots. The creation of the intrinsics and their properties must be ordered to
+ avoid any dependencies upon objects that have not yet been created.</li>
+ <li>Return <i>intrinsics</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-setrealmglobalobject">
+ <h1><span class="secnum" id="sec-8.2.3"><a href="#sec-setrealmglobalobject" title="link to this section">8.2.3</a></span>
+ SetRealmGlobalObject ( realmRec, globalObj )</h1>
+
+ <p>The abstract operation SetRealmGlobalObject with arguments <var>realmRec</var> and <var>globalObj</var> performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>globalObj</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>intrinsics</i> be <i>realmRec</i>.[[intrinsics]].</li>
+ <li>Let <i>globalObj</i> be <a
+ href="#sec-objectcreate">ObjectCreate</a>(<i>intrinsics</i>.[[%ObjectPrototype%]]).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>globalObj</i>) is Object.</li>
+ <li>Set <i>realmRec</i>.[[globalThis]] to <i>globalObj</i>.</li>
+ <li>Let <i>newGlobalEnv</i> be <a href="#sec-newglobalenvironment">NewGlobalEnvironment</a>(<i>globalObj</i>).</li>
+ <li>Set <i>realmRec</i>.[[globalEnv]] to <i>newGlobalEnv</i>.</li>
+ <li>Return <i>realmRec</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-setdefaultglobalbindings">
+ <h1><span class="secnum" id="sec-8.2.4"><a href="#sec-setdefaultglobalbindings"
+ title="link to this section">8.2.4</a></span> SetDefaultGlobalBindings ( realmRec )</h1>
+
+ <p>The abstract operation SetDefaultGlobalBindings with argument <var>realmRec</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>global</i> be <i>realmRec</i>.[[globalThis]].</li>
+ <li>For each property of the Global Object specified in <a href="#sec-global-object">clause 18</a>, do
+ <ol class="block">
+ <li>Let <i>name</i> be the string value of the property name.</li>
+ <li>Let <i>desc</i> be the fully populated data property descriptor for the property containing the specified
+ attributes for the property. For properties whose values are functions, the value of the [[Value]] attribute is
+ the corresponding intrinsic function object from <i>realmRec</i>.</li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>global</i>, <i>name</i>,
+ <i>desc</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>global</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-execution-contexts">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.3"><a href="#sec-execution-contexts" title="link to this section">8.3</a></span>
+ Execution Contexts</h1>
+
+ <p>An <i>execution context</i> is a specification device that is used to track the runtime evaluation of code by an
+ ECMAScript implementation. At any point in time, there is at most one execution context that is actually executing code.
+ This is known as the <i>running</i> execution context. A stack is used to track execution contexts. The running execution
+ context is always the top element of this stack. A new execution context is created whenever control is transferred from the
+ executable code associated with the currently running execution context to executable code that is not associated with that
+ execution context. The newly created execution context is pushed onto the stack and becomes the running execution
+ context.</p>
+
+ <p>An execution context contains whatever implementation specific state is necessary to track the execution progress of its
+ associated code. Each execution context has at least the state components listed in <a href="#table-22">Table 22</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-22">Table 22</span> —State Components for All Execution Contexts</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Component</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">code evaluation state</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Any state needed to perform, suspend, and resume evaluation of the code associated with this execution context.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Function</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">If this execution context is evaluating the code of a function object, then the value of this component is that function object. If the context is evaluating the code of a <span class="nt">Script</span> or <span class="nt">Module</span>, the value is <span class="value">null</span>.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><a href="#sec-code-realms">Realm</a></td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The <a href="#sec-code-realms">Realm</a> from which associated code accesses ECMAScript resources.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>Evaluation of code by the running execution context may be suspended at various points defined within this specification.
+ Once the running execution context has been suspended a different execution context may become the running execution context
+ and commence evaluating its code. At some later time a suspended execution context may again become the running execution
+ context and continue evaluating its code at the point where it had previously been suspended. Transition of the running
+ execution context status among execution contexts usually occurs in stack-like last-in/first-out manner. However, some
+ ECMAScript features require non-LIFO transitions of the running execution context.</p>
+
+ <p>The value of the <a href="#sec-code-realms">Realm</a> component of the running execution context is also called the
+ <i>current <a href="#sec-code-realms">Realm</a></i>. The value of the Function component of the running execution context is
+ also called the <i>active function object.</i></p>
+
+ <p>Execution contexts for ECMAScript code have the additional state components listed in <a href="#table-23">Table
+ 23</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-23">Table 23</span> — Additional State Components for ECMAScript Code Execution Contexts</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Component</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">LexicalEnvironment</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Identifies the <a href="#sec-lexical-environments">Lexical Environment</a> used to resolve identifier references made by code within this execution context.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">VariableEnvironment</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Identifies the <a href="#sec-lexical-environments">Lexical Environment</a> whose environment record holds bindings created by <span class="nt">VariableStatements</span> within this execution context.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The LexicalEnvironment and VariableEnvironment components of an execution context are always Lexical Environments. When
+ an execution context is created its LexicalEnvironment and VariableEnvironment components initially have the same value.</p>
+
+ <p>Execution contexts representing the evaluation of generator objects have the additional state components listed in <a
+ href="#table-24">Table 24</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-24">Table 24</span> — Additional State Components for Generator Execution Contexts</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Component</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Generator</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">The GeneratorObject that this execution context is evaluating.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>In most situations only the running execution context (the top of the execution context stack) is directly manipulated by
+ algorithms within this specification. Hence when the terms “LexicalEnvironment”, and
+ “VariableEnvironment” are used without qualification they are in reference to those components of the running
+ execution context.</p>
+
+ <p>An execution context is purely a specification mechanism and need not correspond to any particular artefact of an
+ ECMAScript implementation. It is impossible for ECMAScript code to directly access or observe an execution context.</p>
+ </div>
+
+ <section id="sec-resolvebinding">
+ <h1><span class="secnum" id="sec-8.3.1"><a href="#sec-resolvebinding" title="link to this section">8.3.1</a></span>
+ ResolveBinding ( name )</h1>
+
+ <p>The ResolveBinding abstract operation is used to determine the binding of <var>name</var> passed as a string value using
+ the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <a href="#sec-execution-contexts">the running execution
+ context</a>. During execution of ECMAScript code, ResolveBinding is performed using the following algorithm:</p>
+
+ <ol class="proc">
+ <li>Let <i>env</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>If the code matching the syntactic production that is being evaluated is contained in <a
+ href="#sec-strict-mode-code">strict mode code</a>, let <i>strict</i> be <b>true</b>, else let <i>strict</i> be
+ <b>false</b>.</li>
+ <li>Return <a href="#sec-getidentifierreference">GetIdentifierReference</a>(<i>env</i>, <i>name</i>, <i>strict</i> ).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The result of ResolveBinding is always a <a
+ href="#sec-reference-specification-type">Reference</a> value with its referenced name component equal to the <i>name</i>
+ argument.</p>
+ </div>
+ </section>
+
+ <section id="sec-getthisenvironment">
+ <h1><span class="secnum" id="sec-8.3.2"><a href="#sec-getthisenvironment" title="link to this section">8.3.2</a></span>
+ GetThisEnvironment ( )</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">GetThisEnvironment</span> finds the environment record
+ that currently supplies the binding of the keyword <code>this</code>. <span style="font-family: Times New
+ Roman">GetThisEnvironment</span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>lex</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>envRec</i> be <i>lex</i>’s environment record.</li>
+ <li>Let <i>exists</i> be <i>envRec</i>.HasThisBinding().</li>
+ <li>If <i>exists</i> is <b>true</b>, return <i>envRec</i>.</li>
+ <li>Let <i>outer</i> be the value of <i>lex’s</i> <a href="#sec-lexical-environments">outer environment
+ reference</a>.</li>
+ <li>Let <i>lex</i> be <i>outer</i>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The loop in step 2 will always terminate because the list of environments always ends with
+ <a href="#sec-global-environment-records">the global environment</a> which has a <code>this</code> binding.</p>
+ </div>
+ </section>
+
+ <section id="sec-resolvethisbinding">
+ <h1><span class="secnum" id="sec-8.3.3"><a href="#sec-resolvethisbinding" title="link to this section">8.3.3</a></span>
+ ResolveThisBinding ( )</h1>
+
+ <p>The abstract operation ResolveThisBinding determines the binding of the keyword <code>this</code> using the <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> of <a href="#sec-execution-contexts">the running execution
+ context</a>. ResolveThisBinding performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-getthisenvironment">GetThisEnvironment</a>( ).</li>
+ <li>Return <i>envRec</i>.GetThisBinding().</li>
+ </ol>
+ </section>
+
+ <section id="sec-getnewtarget">
+ <h1><span class="secnum" id="sec-8.3.4"><a href="#sec-getnewtarget" title="link to this section">8.3.4</a></span>
+ GetNewTarget ( )</h1>
+
+ <p>The abstract operation GetNewTarget determines the NewTarget value using the <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> of <a href="#sec-execution-contexts">the running execution
+ context</a>. GetNewTarget performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-getthisenvironment">GetThisEnvironment</a>( ).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> has a [[NewTarget]] field.</li>
+ <li>Return <i>envRec</i>.[[NewTarget]].</li>
+ </ol>
+ </section>
+
+ <section id="sec-getglobalobject">
+ <h1><span class="secnum" id="sec-8.3.5"><a href="#sec-getglobalobject" title="link to this section">8.3.5</a></span>
+ GetGlobalObject ( )</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">GetGlobalObject</span> returns the global object used
+ by <a href="#sec-execution-contexts">the currently running execution context</a>. <span style="font-family: Times New
+ Roman">GetGlobalObject</span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>ctx</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>currentRealm</i> be <i>ctx’s</i> <a href="#sec-code-realms">Realm</a>.</li>
+ <li>Return <i>currentRealm</i>.[[globalThis]].</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-jobs-and-job-queues">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.4"><a href="#sec-jobs-and-job-queues" title="link to this section">8.4</a></span> Jobs
+ and Job Queues</h1>
+
+ <p>A Job is an abstract operation that initiates an ECMAScript computation when no other ECMAScript computation is currently
+ in progress. A Job abstract operation may be defined to accept an arbitrary set of job parameters.</p>
+
+ <p>Execution of a Job can be initiated only when there is no running <a href="#sec-execution-contexts">execution context</a>
+ and <a href="#sec-execution-contexts">the execution context stack</a> is empty. A PendingJob is a request for the future
+ execution of a Job. A PendingJob is an internal Record whose fields are specified in <a href="#table-25">Table 25</a>. Once
+ execution of a Job is initiated, the Job always executes to completion. No other Job may be initiated until the currently
+ running Job completes. However, the currently running Job or external events may cause the enqueuing of additional
+ PendingJobs that may be initiated sometime after completion of the currently running Job.</p>
+
+ <figure>
+ <figcaption><span id="table-25">Table 25</span> — PendingJob Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[Job]]</td>
+ <td>The name of a Job abstract operation</td>
+ <td>This is the abstract operation that is performed when execution of this PendingJob is initiated. Jobs are abstract operations that use NextJob rather than Return to indicate that they have completed.</td>
+ </tr>
+ <tr>
+ <td>[[Arguments]]</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a></td>
+ <td>The <a href="#sec-list-and-record-specification-type">List</a> of argument values that are to be passed to [[Job]] when it is activated.</td>
+ </tr>
+ <tr>
+ <td>[[Realm]]</td>
+ <td>A <a href="#sec-code-realms">Realm</a> Record</td>
+ <td>The <a href="#sec-code-realms">Realm</a> for the initial <a href="#sec-execution-contexts">execution context</a> when this Pending Job is initiated.</td>
+ </tr>
+ <tr>
+ <td>[[HostDefined]]</td>
+ <td>Any, default value is <span class="value">undefined</span>.</td>
+ <td>Field reserved for use by host environments that need to associate additional information with a pending Job.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>A Job Queue is a FIFO queue of PendingJob records. Each Job Queue has a name and the full set of available Job Queues are
+ defined by an ECMAScript implementation. Every ECMAScript implementation has at least the Job Queues defined in <a
+ href="#table-26">Table 26</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-26">Table 26</span> — Required Job Queues</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Name</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">ScriptJobs</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Jobs that validate and evaluate ECMAScript <span class="nt">Script</span> and <span class="nt">Module</span> source text. See clauses 10 and 15.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">PromiseJobs</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Jobs that are responses to the settlement of a Promise (<a href="#sec-promise-objects">see 25.4</a>).</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>A request for the future execution of a Job is made by enqueueing, on a Job Queue, a PendingJob record that includes a
+ Job abstract operation name and any necessary argument values. When there is no running <a
+ href="#sec-execution-contexts">execution context</a> and <a href="#sec-execution-contexts">the execution context stack</a>
+ is empty, the ECMAScript implementation removes the first PendingJob from a Job Queue and uses the information contained in
+ it to create an <a href="#sec-execution-contexts">execution context</a> and starts execution of the associated Job abstract
+ operation.</p>
+
+ <p>The PendingJob records from a single Job Queue are always initiated in FIFO order. This specification does not define the
+ order in which multiple Job Queues are serviced. An ECMAScript implementation may interweave the FIFO evaluation of the
+ PendingJob records of a Job Queue with the evaluation of the PendingJob records of one or more other Job Queues. An
+ implementation must define what occurs when there are no running <a href="#sec-execution-contexts">execution context</a> and
+ all Job Queues are empty.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Typically an ECMAScript implementation will have its Job Queues pre-initialized with at
+ least one PendingJob and one of those Jobs will be the first to be executed. An implementation might choose to free all
+ resources and terminate if the current Job completes and all Job Queues are empty. Alternatively, it might choose to wait
+ for a some implementation specific agent or mechanism to enqueue new PendingJob requests.</p>
+ </div>
+
+ <p>The following abstract operations are used to create and manage Jobs and Job Queues:</p>
+ </div>
+
+ <section id="sec-enqueuejob">
+ <h1><span class="secnum" id="sec-8.4.1"><a href="#sec-enqueuejob" title="link to this section">8.4.1</a></span> EnqueueJob (
+ queueName, job, arguments)</h1>
+
+ <p>The EnqueueJob abstract operation requires three arguments: <var>queueName</var>, <var>job</var>, and
+ <var>arguments</var>. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>queueName</i>) is String and its value is the name of a Job
+ Queue recognized by this implementation.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>job</i> is the name of a Job.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>arguments</i> is a <a
+ href="#sec-list-and-record-specification-type">List</a> that has the same number of elements as the number of
+ parameters required by <i>job</i>.</li>
+ <li>Let <i>callerContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>callerRealm</i> be <i>callerContext’s</i> <a href="#sec-code-realms">Realm</a>.</li>
+ <li>Let <i>pending</i> be PendingJob{ [[Job]]: <i>job</i>, [[Arguments]]: <i>arguments</i>, [[Realm]]: <i>callerRealm</i>,
+ [[HostDefined]]: <b>undefined</b> }.</li>
+ <li>Perform any implementation or host environment defined processing of <i>pending</i>. This may include modifying the
+ [[HostDefined]] field or any other field of <i>pending</i>.</li>
+ <li>Add <i>pending</i> at the back of the Job Queue named by <i>queueName</i>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-nextjob-result">
+ <h1><span class="secnum" id="sec-8.4.2"><a href="#sec-nextjob-result" title="link to this section">8.4.2</a></span> NextJob
+ result</h1>
+
+ <p>An algorithm step such as:</p>
+
+ <ol class="proc">
+ <li>NextJob <i>result</i>.</li>
+ </ol>
+
+ <p>is used in Job abstract operations in place of:</p>
+
+ <ol class="proc">
+ <li>Return <i>result</i>.</li>
+ </ol>
+
+ <p>Job abstract operations must not contain a Return step or a <a href="#sec-returnifabrupt">ReturnIfAbrupt</a> step. The
+ NextJob <var>result</var> operation is equivalent to the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>result</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, perform
+ implementation defined unhandled exception processing.</li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <a href="#sec-execution-contexts">the running execution context</a> and
+ remove it from <a href="#sec-execution-contexts">the execution context stack</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The <a href="#sec-execution-contexts">execution context stack</a> is
+ now empty.</li>
+ <li>Let <i>nextQueue</i> be a non-empty Job Queue chosen in an implementation defined manner. If all Job Queues are empty,
+ the result is implementation defined.</li>
+ <li>Let <i>nextPending</i> be the PendingJob record at the front of <i>nextQueue</i>. Remove that record from
+ <i>nextQueue</i>.</li>
+ <li>Let <i>newContext</i> be a new <a href="#sec-execution-contexts">execution context</a>.</li>
+ <li>Set <i>newContext</i>’s <a href="#sec-code-realms">Realm</a> to <i>nextPending</i>.[[Realm]].</li>
+ <li>Push <i>newContext</i> onto <a href="#sec-execution-contexts">the execution context stack</a>; <i>newContext</i> is
+ now <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Perform any implementation or host environment defined job initialization using <i>nextPending</i>.</li>
+ <li>Perform the abstract operation named by <i>nextPending</i>.[[Job]] using the elements of
+ <i>nextPending</i>.[[Arguments]] as its arguments.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-initialization">
+ <div class="front">
+ <h1><span class="secnum" id="sec-8.5"><a href="#sec-initialization" title="link to this section">8.5</a></span>
+ Initialization()</h1>
+
+ <p>An ECMAScript implementation performs the following steps prior to the execution of any Jobs or the evaluation of any
+ ECMAScript code:</p>
+
+ <ol class="proc">
+ <li>Let <i>realm</i> be <a href="#sec-createrealm">CreateRealm</a>().</li>
+ <li>Let <i>newContext</i> be a new <a href="#sec-execution-contexts">execution context</a>.</li>
+ <li>Set the Function of <i>newContext</i> to <b>null</b>.</li>
+ <li>Set the <a href="#sec-code-realms">Realm</a> of <i>newContext</i> to <i>realm</i>.</li>
+ <li>Push <i>newContext</i> onto <a href="#sec-execution-contexts">the execution context stack</a>; <i>newContext</i> is
+ now <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>status</i> be <a href="#sec-initializehostdefinedrealm">InitializeHostDefinedRealm</a>(<i>realm</i>).</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The first realm could not be created.</li>
+ <li>Terminate ECMAScript execution.</li>
+ </ol>
+ </li>
+ <li>In an implementation dependent manner, obtain the ECMAScript source text strings (see <a
+ href="#sec-ecmascript-language-source-code">clause 10</a>) for zero or more ECMAScript scripts and/or ECMAScript
+ modules. For each such <i>sourceText</i> do,
+ <ol class="block">
+ <li>If <i>sourceText</i> is the source code of a script, then
+ <ol class="block">
+ <li>Perform <a href="#sec-enqueuejob">EnqueueJob</a>(<code>"ScriptJobs"</code>, <a
+ href="#sec-scriptevaluationjob">ScriptEvaluationJob</a>, « <i>sourceText</i> »).</li>
+ </ol>
+ </li>
+ <li>Else <i>sourceText</i> is the source code of a module,
+ <ol class="block">
+ <li>Perform <a href="#sec-enqueuejob">EnqueueJob</a>(<code>"ScriptJobs"</code>, <a
+ href="#sec-toplevelmoduleevaluationjob">TopLevelModuleEvaluationJob</a>, « <i>sourceText</i>
+ »).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>NextJob <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-initializehostdefinedrealm">
+ <h1><span class="secnum" id="sec-8.5.1"><a href="#sec-initializehostdefinedrealm"
+ title="link to this section">8.5.1</a></span> InitializeHostDefinedRealm ( realm )</h1>
+
+ <p>The abstract operation InitializeFirstRealm with parameter <var>realm</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If this implementation requires use of an exotic object to serve as <i>realm</i>’s global object, let
+ <i>global</i> be such an object created in an implementation defined manner. Otherwise, let <i>global</i> be
+ <b>undefined</b> indicating that an ordinary object should be created as the global object.</li>
+ <li>Perform <a href="#sec-setrealmglobalobject">SetRealmGlobalObject</a>(<i>realm</i>, <i>global</i>).</li>
+ <li>Let <i>globalObj</i> be <a href="#sec-setdefaultglobalbindings">SetDefaultGlobalBindings</a>(<i>realm</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>globalObj</i>).</li>
+ <li>Create any implementation defined global object properties on <i>globalObj</i>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </section>
+ </section>
+</section>
+
+<section id="sec-ordinary-and-exotic-objects-behaviours">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9"><a href="#sec-ordinary-and-exotic-objects-behaviours"
+ title="link to this section">9</a></span> Ordinary and Exotic Objects Behaviours</h1>
+ </div>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.1"><a href="#sec-ordinary-object-internal-methods-and-internal-slots"
+ title="link to this section">9.1</a></span> Ordinary Object Internal Methods and Internal Slots</h1>
+
+ <p>All ordinary objects have an <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> called
+ [[Prototype]]. The value of this <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is either
+ <b>null</b> or an object and is used for implementing inheritance. Data properties of the [[Prototype]] object are inherited
+ (are visible as properties of the child object) for the purposes of get access, but not for set access. Accessor properties
+ are inherited for both get access and set access.</p>
+
+ <p>Every ordinary object has a Boolean-valued [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> that controls whether or not properties may be
+ added to the object. If the value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> is <b>false</b> then additional properties may not be added to the object. In addition, if [[Extensible]] is
+ <b>false</b> the value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ the object may not be modified. Once the value of an object’s [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> has been set to <b>false</b> it may not be
+ subsequently changed to <b>true</b>.</p>
+
+ <p>In the following algorithm descriptions, assume <var>O</var> is an ordinary object, <var>P</var> is a <a
+ href="#sec-object-type">property key value</a>, <var>V</var> is any <a href="#sec-ecmascript-language-types">ECMAScript
+ language value</a>, and <span class="nt">Desc</span> is a <a href="#sec-property-descriptor-specification-type">Property
+ Descriptor</a> record.</p>
+ </div>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-getprototypeof">
+ <h1><span class="secnum" id="sec-9.1.1"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-getprototypeof"
+ title="link to this section">9.1.1</a></span> [[GetPrototypeOf]] ( )</h1>
+
+ <p>When the [[GetPrototypeOf]] internal method of <var>O</var> is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return the value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-setprototypeof-v">
+ <h1><span class="secnum" id="sec-9.1.2"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-setprototypeof-v"
+ title="link to this section">9.1.2</a></span> [[SetPrototypeOf]] (V)</h1>
+
+ <p>When the [[SetPrototypeOf]] internal method of <var>O</var> is called with argument <var>V</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: Either <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is Object or <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is Null.</li>
+ <li>Let <i>extensible</i> be the value of the [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>current</i> be the value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>V</i>, <i>current</i>), return <b>true.</b></li>
+ <li>If <i>extensible</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>Let <i>p</i> be <i>V</i>.</li>
+ <li>Let <i>done</i> be <b>false</b>.</li>
+ <li>Repeat while <i>done</i> is <b>false</b>,
+ <ol class="block">
+ <li>If <i>p</i> is <b>null</b>, let <i>done</i> be <b>true</b>.</li>
+ <li>Else, if <a href="#sec-samevalue">SameValue</a>(<i>p</i>, <i>O</i>) is <b>true</b>, return <b>false</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>If the [[GetPrototypeOf]] internal method of <i>p</i> is not the ordinary object internal method defined in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-getprototypeof">9.1.1</a>, let <i>done</i> be
+ <b>true</b>.</li>
+ <li>Else, let <i>p</i> be the value of <i>p</i>’s [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set the value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>O</i> to <i>V</i>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The loop in step 8 guarantees that there will be no circularities in any prototype chain
+ that only includes objects that use the ordinary object definitions for [[GetPrototypeOf]] and [[SetPrototypeOf]].</p>
+ </div>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-isextensible">
+ <h1><span class="secnum" id="sec-9.1.3"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-isextensible"
+ title="link to this section">9.1.3</a></span> [[IsExtensible]] ( )</h1>
+
+ <p>When the [[IsExtensible]] internal method of <var>O</var> is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return the value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-preventextensions">
+ <h1><span class="secnum" id="sec-9.1.4"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-preventextensions"
+ title="link to this section">9.1.4</a></span> [[PreventExtensions]] ( )</h1>
+
+ <p>When the [[PreventExtensions]] internal method of <var>O</var> is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Set the value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>O</i> to <b>false</b>.</li>
+ <li>Return <b>true.</b></li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-getownproperty-p">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.1.5"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-getownproperty-p"
+ title="link to this section">9.1.5</a></span> [[GetOwnProperty]] (P)</h1>
+
+ <p>When the [[GetOwnProperty]] internal method of <var>O</var> is called with <a href="#sec-object-type">property key</a>
+ <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>O</i>, <i>P</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-ordinarygetownproperty">
+ <h1><span class="secnum" id="sec-9.1.5.1"><a href="#sec-ordinarygetownproperty"
+ title="link to this section">9.1.5.1</a></span> OrdinaryGetOwnProperty (O, P)</h1>
+
+ <p>When the abstract operation OrdinaryGetOwnProperty is called with Object <var>O</var> and with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>If <i>O</i> does not have an own property with key <i>P</i>, return <b>undefined</b>.</li>
+ <li>Let <i>D</i> be a newly created <a href="#sec-property-descriptor-specification-type">Property Descriptor</a> with
+ no fields.</li>
+ <li>Let <i>X</i> be <i>O</i>’s own property whose key is <i>P</i>.</li>
+ <li>If <i>X</i> is a data property, then
+ <ol class="block">
+ <li>Set <i>D</i>.[[Value]] to the value of <i>X</i>’s [[Value]] attribute.</li>
+ <li>Set <i>D</i>.[[Writable]] to the value of <i>X</i>’s [[Writable]] attribute</li>
+ </ol>
+ </li>
+ <li>Else <i>X</i> is an accessor property, so
+ <ol class="block">
+ <li>Set <i>D</i>.[[Get]] to the value of <i>X</i>’s [[Get]] attribute.</li>
+ <li>Set <i>D</i>.[[Set]] to the value of <i>X</i>’s [[Set]] attribute.</li>
+ </ol>
+ </li>
+ <li>Set <i>D</i>.[[Enumerable]] to the value of <i>X</i>’s [[Enumerable]] attribute.</li>
+ <li>Set <i>D</i>.[[Configurable]] to the value of <i>X</i>’s [[Configurable]] attribute.</li>
+ <li>Return <i>D</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-defineownproperty-p-desc">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.1.6"><a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-defineownproperty-p-desc"
+ title="link to this section">9.1.6</a></span> [[DefineOwnProperty]] (P, Desc)</h1>
+
+ <p>When the [[DefineOwnProperty]] internal method of <var>O</var> is called with <a href="#sec-object-type">property
+ key</a> <var>P</var> and <a href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span
+ class="nt">Desc</span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>O</i>, <i>P</i>, <i>Desc</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-ordinarydefineownproperty">
+ <h1><span class="secnum" id="sec-9.1.6.1"><a href="#sec-ordinarydefineownproperty"
+ title="link to this section">9.1.6.1</a></span> OrdinaryDefineOwnProperty (O, P, Desc)</h1>
+
+ <p>When the abstract operation <span style="font-family: Times New Roman">OrdinaryDefineOwnProperty</span> is called with
+ Object <var>O</var>, <a href="#sec-object-type">property key</a> <span style="font-family: Times New
+ Roman"><i>P</i>,</span> and <a href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span
+ class="nt">Desc</span> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>current</i> be <i>O</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>current</i>).</li>
+ <li>Let <i>extensible</i> be the value of the [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Return <a href="#sec-validateandapplypropertydescriptor">ValidateAndApplyPropertyDescriptor</a>(<i>O</i>, <i>P</i>,
+ <i>extensible</i>, <i>Desc</i>, <i>current</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-iscompatiblepropertydescriptor">
+ <h1><span class="secnum" id="sec-9.1.6.2"><a href="#sec-iscompatiblepropertydescriptor"
+ title="link to this section">9.1.6.2</a></span> IsCompatiblePropertyDescriptor (Extensible, Desc, Current)</h1>
+
+ <p>When the abstract operation <span style="font-family: Times New Roman">IsCompatiblePropertyDescriptor</span> is called
+ with Boolean value <span class="nt">Extensible</span>, and Property Descriptors <span class="nt">Desc</span>, and <span
+ class="nt">Current</span> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-validateandapplypropertydescriptor">ValidateAndApplyPropertyDescriptor</a>(<b>undefined</b>,
+ <b>undefined</b>, <i>Extensible</i>, <i>Desc</i>, <i>Current</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-validateandapplypropertydescriptor">
+ <h1><span class="secnum" id="sec-9.1.6.3"><a href="#sec-validateandapplypropertydescriptor"
+ title="link to this section">9.1.6.3</a></span> ValidateAndApplyPropertyDescriptor (O, P, extensible, Desc,
+ current)</h1>
+
+ <p>When the abstract operation <span style="font-family: Times New Roman">ValidateAndApplyPropertyDescriptor</span> is
+ called with Object <var>O</var>, <a href="#sec-object-type">property key</a> <span style="font-family: Times New
+ Roman"><i>P</i>,</span> Boolean value <var>extensible</var>, and Property Descriptors <span class="nt">Desc</span>, and
+ <var>current</var> the following steps are taken:</p>
+
+ <p>This algorithm contains steps that test various fields of the <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span> for specific
+ values. The fields that are tested in this manner need not actually exist in <span class="nt">Desc</span>. If a field is
+ absent then its value is considered to be <b>false</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <b>undefined</b> is passed as the <i>O</i> argument only validation is performed and
+ no object updates are performed.</p>
+ </div>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If <i>O</i> is not <b>undefined</b> then <i>P</i> is a valid <a
+ href="#sec-object-type">property key</a>.</li>
+ <li>If <i>current</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>extensible</i> is <b>false</b>, return <b>false</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>extensible</i> is <b>true</b>.</li>
+ <li>If <a href="#sec-isgenericdescriptor">IsGenericDescriptor</a>(<i>Desc</i>) or <a
+ href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>Desc</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>O</i> is not <b>undefined</b>, create an own data property named <i>P</i> of object <i>O</i> whose
+ [[Value]], [[Writable]], [[Enumerable]] and [[Configurable]] attribute values are described by <i>Desc</i>.
+ If the value of an attribute field of <i>Desc</i> is absent, the attribute of the newly created property is
+ set to its default value.</li>
+ </ol>
+ </li>
+ <li>Else <i>Desc</i> must be an accessor <a href="#sec-property-descriptor-specification-type">Property
+ Descriptor</a>,
+ <ol class="block">
+ <li>If <i>O</i> is not <b>undefined</b>, create an own accessor property named <i>P</i> of object <i>O</i> whose
+ [[Get]], [[Set]], [[Enumerable]] and [[Configurable]] attribute values are described by <i>Desc</i>. If the
+ value of an attribute field of <i>Desc</i> is absent, the attribute of the newly created property is set to
+ its default value.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>, if every field in <i>Desc</i> is absent.</li>
+ <li>Return <b>true</b>, if every field in <i>Desc</i> also occurs in <i>current</i> and the value of every field in
+ <i>Desc</i> is the same value as the corresponding field in <i>current</i> when compared using <a
+ href="#sec-samevalue">the SameValue algorithm</a>.</li>
+ <li>If the [[Configurable]] field of <i>current</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return <b>false</b>, if the [[Configurable]] field of <i>Desc</i> is <b>true</b>.</li>
+ <li>Return <b>false</b>, if the [[Enumerable]] field of <i>Desc</i> is present and the [[Enumerable]] fields of
+ <i>current</i> and <i>Desc</i> are the Boolean negation of each other.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-isgenericdescriptor">IsGenericDescriptor</a>(<i>Desc</i>) is <b>true</b>, no further validation is
+ required.</li>
+ <li>Else if <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>current</i>) and <a
+ href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>Desc</i>) have different results, then
+ <ol class="block">
+ <li>Return <b>false</b>, if the [[Configurable]] field of <i>current</i> is <b>false</b>.</li>
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>current</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>O</i> is not <b>undefined</b>, convert the property named <i>P</i> of object <i>O</i> from a data
+ property to an accessor property. Preserve the existing values of the converted property’s
+ [[Configurable]] and [[Enumerable]] attributes and set the rest of the property’s attributes to their
+ default values.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>If <i>O</i> is not <b>undefined</b>, convert the property named <i>P</i> of object <i>O</i> from an accessor
+ property to a data property. Preserve the existing values of the converted property’s [[Configurable]]
+ and [[Enumerable]] attributes and set the rest of the property’s attributes to their default
+ values.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else if <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>current</i>) and <a
+ href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>Desc</i>) are both <b>true</b>, then
+ <ol class="block">
+ <li>If the [[Configurable]] field of <i>current</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return <b>false</b>, if the [[Writable]] field of <i>current</i> is <b>false</b> and the [[Writable]] field
+ of <i>Desc</i> is <b>true</b>.</li>
+ <li>If the [[Writable]] field of <i>current</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return <b>false</b>, if the [[Value]] field of <i>Desc</i> is present and <a
+ href="#sec-samevalue">SameValue</a>(<i>Desc</i>.[[Value]], <i>current</i>.[[Value]]) is
+ <b>false</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else the [[Configurable]] field of <i>current</i> is <b>true</b>, so any change is acceptable.</li>
+ </ol>
+ </li>
+ <li>Else <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>current</i>) and <a
+ href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>Desc</i>) are both <b>true</b>,
+ <ol class="block">
+ <li>If the [[Configurable]] field of <i>current</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return <b>false</b>, if the [[Set]] field of <i>Desc</i> is present and <a
+ href="#sec-samevalue">SameValue</a>(<i>Desc</i>.[[Set]], <i>current</i>.[[Set]]) is <b>false</b>.</li>
+ <li>Return <b>false</b>, if the [[Get]] field of <i>Desc</i> is present and <a
+ href="#sec-samevalue">SameValue</a>(<i>Desc</i>.[[Get]], <i>current</i>.[[Get]]) is <b>false</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>O</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>For each field of <i>Desc</i> that is present, set the corresponding attribute of the property named <i>P</i> of
+ object <i>O</i> to the value of the field.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Step 8.b allows any field of Desc to be different from the corresponding field of
+ current if current’s [[Configurable]] field is <b>true</b>. This even permits changing the [[Value]] of a property
+ whose [[Writable]] attribute is <b>false</b>. This is allowed because a <b>true</b> [[Configurable]] attribute would
+ permit an equivalent sequence of calls where [[Writable]] is first set to <b>true</b>, a new [[Value]] is set, and then
+ [[Writable]] is set to <b>false</b>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-hasproperty-p">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.1.7"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-hasproperty-p"
+ title="link to this section">9.1.7</a></span> [[HasProperty]](P)</h1>
+
+ <p>When the [[HasProperty]] internal method of <var>O</var> is called with <a href="#sec-object-type">property key</a>
+ <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-ordinaryhasproperty">OrdinaryHasProperty</a>(<i>O</i>, <i>P</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-ordinaryhasproperty">
+ <h1><span class="secnum" id="sec-9.1.7.1"><a href="#sec-ordinaryhasproperty"
+ title="link to this section">9.1.7.1</a></span> OrdinaryHasProperty (O, P)</h1>
+
+ <p>When the abstract operation OrdinaryHasProperty is called with Object <var>O</var> and with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>hasOwn</i> be <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>O</i>, <i>P</i>).</li>
+ <li>If <i>hasOwn</i> is not <b>undefined</b>, return <b>true</b>.</li>
+ <li>Let <i>parent</i> be <i>O</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>parent</i>).</li>
+ <li>If <i>parent</i> is not <b>null</b>, then
+ <ol class="block">
+ <li>Return <i>parent</i>.[[HasProperty]](<i>P</i>).</li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver">
+ <h1><span class="secnum" id="sec-9.1.8"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver"
+ title="link to this section">9.1.8</a></span> [[Get]] (P, Receiver)</h1>
+
+ <p>When the [[Get]] internal method of <var>O</var> is called with <a href="#sec-object-type">property key</a> <var>P</var>
+ and <a href="#sec-ecmascript-language-types">ECMAScript language value</a> <span class="nt">Receiver</span> the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>desc</i> be <i>O</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>If <i>desc</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>parent</i> be <i>O</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>parent</i>).</li>
+ <li>If <i>parent</i> is <b>null</b>, return <b>undefined.</b></li>
+ <li>Return <i>parent</i>.[[Get]](<i>P</i>, <i>Receiver</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>desc</i>) is <b>true</b>, return
+ <i>desc</i>.[[Value]].</li>
+ <li>Otherwise, <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>desc</i>) must be <b>true</b> so, let
+ <i>getter</i> be <i>desc</i>.[[Get]].</li>
+ <li>If <i>getter</i> is <b>undefined</b>, return <b>undefined</b>.</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>getter,</i> <i>Receiver</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-set-p-v-receiver">
+ <h1><span class="secnum" id="sec-9.1.9"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-set-p-v-receiver"
+ title="link to this section">9.1.9</a></span> [[Set]] ( P, V, Receiver)</h1>
+
+ <p>When the [[Set]] internal method of <var>O</var> is called with <a href="#sec-object-type">property key</a> <var>P</var>,
+ value <var>V</var>, and <a href="#sec-ecmascript-language-types">ECMAScript language value</a> <span
+ class="nt">Receiver</span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>ownDesc</i> be <i>O</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ownDesc</i>).</li>
+ <li>If <i>ownDesc</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>parent</i> be <i>O</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>parent</i>).</li>
+ <li>If <i>parent</i> is not <b>null</b>, then
+ <ol class="block">
+ <li>Return <i>parent</i>.[[Set]](<i>P</i>, <i>V</i>, <i>Receiver</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>ownDesc</i> be the PropertyDescriptor{[[Value]]: <b>undefined</b>, [[Writable]]: <b>true</b>,
+ [[Enumerable]]: <b>true</b>, [[Configurable]]: <b>true</b>}.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>ownDesc</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>ownDesc</i>.[[Writable]] is <b>false</b>, return <b>false</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>Receiver</i>) is not Object, return
+ <b>false</b>.</li>
+ <li>Let <i>existingDescriptor</i> be <i>Receiver</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>existingDescriptor</i>).</li>
+ <li>If <i>existingDescriptor</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>valueDesc</i> be the PropertyDescriptor{[[Value]]: <i>V</i>}.</li>
+ <li>Return <i>Receiver</i>.[[DefineOwnProperty]](<i>P</i>, <i>valueDesc</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>Receiver</i> does not currently have a property <i>P</i>,
+ <ol class="block">
+ <li>Return <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>Receiver</i>, <i>P</i>, <i>V</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>ownDesc</i>) is <b>true</b>.</li>
+ <li>Let <i>setter</i> be <i>ownDesc</i>.[[Set]].</li>
+ <li>If <i>setter</i> is <b>undefined</b>, return <b>false</b>.</li>
+ <li>Let <i>setterResult</i> be <a href="#sec-call">Call</a>(<i>setter</i>, <i>Receiver</i>, «<i>V</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setterResult</i>).</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-delete-p">
+ <h1><span class="secnum" id="sec-9.1.10"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-delete-p"
+ title="link to this section">9.1.10</a></span> [[Delete]] (P)</h1>
+
+ <p>When the [[Delete]] internal method of <var>O</var> is called with <a href="#sec-object-type">property key</a>
+ <var>P</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>desc</i> be <i>O</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>If <i>desc</i> is <b>undefined</b>, return <b>true</b>.</li>
+ <li>If <i>desc</i>.[[Configurable]] is <b>true</b>, then
+ <ol class="block">
+ <li>Remove the own property with name <i>P</i> from <i>O</i>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-enumerate">
+ <h1><span class="secnum" id="sec-9.1.11"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-enumerate"
+ title="link to this section">9.1.11</a></span> [[Enumerate]] ()</h1>
+
+ <p>When the [[Enumerate]] internal method of <var>O</var> is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return an Iterator object (<a href="#sec-iterator-interface">25.1.1.2</a>) whose <code>next</code> method iterates
+ over all the String-valued keys of enumerable properties of <i>O</i>. The Iterator object must inherit from
+ %IteratorPrototype% (<a href="#sec-%iteratorprototype%-object">25.1.2</a>). The mechanics and order of enumerating the
+ properties is not specified but must conform to the rules specified below.</li>
+ </ol>
+
+ <p>The iterator’s <code>next</code> method processes object properties to determine whether the <a
+ href="#sec-object-type">property key</a> should be returned as an iterator value. Processed properties do not include
+ properties whose <a href="#sec-object-type">property key</a> is a Symbol. Properties of the object being enumerated may be
+ deleted during enumeration. A property that is deleted before it is processed by the iterator’s <code>next</code>
+ method is ignored. If new properties are added to the object being enumerated during enumeration, the newly added properties
+ are not guaranteed to be processed in the active enumeration. A property name will be returned by the iterator’s
+ <code>next</code> method at most once in any enumeration.</p>
+
+ <p>Enumerating the properties of an object includes enumerating properties of its prototype, and the prototype of the
+ prototype, and so on, recursively; but a property of a prototype is not processed if it has the same name as a property that
+ has already been processed by the iterator’s <code>next</code> method. The values of [[Enumerable]] attributes are not
+ considered when determining if a property of a prototype object has already been processed. The enumerable properties of
+ prototype objects must be accessed by invoking the prototype object’s [[Enumerate]] internal method.</p>
+
+ <p class="Note">The following is an informative definition of an ECMAScript generator function that conforms to these
+ rules:</p>
+
+ <pre>function* enumerate(obj) {</pre>
+ <pre>let visited=new Set;</pre>
+ <pre>for (let name of <a href="#sec-object.getownpropertynames">Object.getOwnPropertyNames</a>(obj)) {</pre>
+ <pre>let desc = <a href="#sec-object.getownpropertydescriptor">Object.getOwnPropertyDescriptor</a>(obj,name);</pre>
+ <pre>if (desc) {</pre>
+ <pre>visited.add(name);</pre>
+ <pre>if (desc.enumerable) yield name;</pre>
+ <pre>}</pre>
+ <pre>}</pre>
+ <pre>let proto = <a href="#sec-object.getprototypeof">Object.getPrototypeOf</a>(obj)</pre>
+ <pre>if (proto === null) return;</pre>
+ <pre>for (let protoName of <a href="#sec-reflect.enumerate">Reflect.enumerate</a>(proto){</pre>
+ <pre>if (!visited.has(protoName)) yield protoName;</pre>
+ <pre>}</pre>
+ <pre>}</pre>
+ </section>
+
+ <section id="sec-ordinary-object-internal-methods-and-internal-slots-ownpropertykeys">
+ <h1><span class="secnum" id="sec-9.1.12"><a href="#sec-ordinary-object-internal-methods-and-internal-slots-ownpropertykeys"
+ title="link to this section">9.1.12</a></span> [[OwnPropertyKeys]] ( )</h1>
+
+ <p>When the [[OwnPropertyKeys]] internal method of <var>O</var> is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>keys</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> that is an integer index, in ascending
+ numeric index order
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> that is a String but is not an integer
+ index, in property creation order
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> that is a Symbol, in property creation
+ order
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>keys</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-objectcreate">
+ <h1><span class="secnum" id="sec-9.1.13"><a href="#sec-objectcreate" title="link to this section">9.1.13</a></span>
+ ObjectCreate(proto, internalSlotsList)</h1>
+
+ <p>The abstract operation ObjectCreate with argument <i>proto</i> (an object or null) is used to specify the runtime
+ creation of new ordinary objects. The optional argument <var>internalSlotsList</var> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of the names of additional internal slots that must be defined as
+ part of the object. If the list is not provided, an empty <a href="#sec-list-and-record-specification-type">List</a> is
+ used. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>internalSlotsList</i> was not provided, let <i>internalSlotsList</i> be an empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>obj</i> be a newly created object with an <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> for each name in <i>internalSlotsList</i>.</li>
+ <li>Set <i>obj</i>’s essential internal methods to the default ordinary object definitions specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to
+ <i>proto</i>.</li>
+ <li>Set the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to
+ <b>true</b>.</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinarycreatefromconstructor">
+ <h1><span class="secnum" id="sec-9.1.14"><a href="#sec-ordinarycreatefromconstructor"
+ title="link to this section">9.1.14</a></span> OrdinaryCreateFromConstructor ( constructor, intrinsicDefaultProto,
+ internalSlotsList )</h1>
+
+ <p>The abstract operation OrdinaryCreateFromConstructor creates an ordinary object whose [[Prototype]] value is retrieved
+ from a constructor’s <code>prototype</code> property, if it exists. Otherwise the intrinsic named by
+ <var>intrinsicDefaultProto</var> is used for [[Prototype]]. The optional <var>internalSlotsList</var> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of the names of additional internal slots that must be defined as
+ part of the object. If the list is not provided, an empty <a href="#sec-list-and-record-specification-type">List</a> is
+ used. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>intrinsicDefaultProto</i> is a string value that is this
+ specification’s name of an intrinsic object. The corresponding object must be an intrinsic that is intended to
+ be used as the [[Prototype]] value of an object.</li>
+ <li>Let <i>proto</i> be <a href="#sec-getprototypefromconstructor">GetPrototypeFromConstructor</a>(<i>constructor</i>,
+ <i>intrinsicDefaultProto</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>Return <a href="#sec-objectcreate">ObjectCreate</a>(<i>proto</i>, <i>internalSlotsList</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-getprototypefromconstructor">
+ <h1><span class="secnum" id="sec-9.1.15"><a href="#sec-getprototypefromconstructor"
+ title="link to this section">9.1.15</a></span> GetPrototypeFromConstructor ( constructor, intrinsicDefaultProto )</h1>
+
+ <p>The abstract operation GetPrototypeFromConstructor determines the [[Prototype]] value that should be used to create an
+ object corresponding to a specific constructor. The value is retrieved from the constructor’s <code>prototype</code>
+ property, if it exists. Otherwise the intrinsic named by <var>intrinsicDefaultProto</var> is used for [[Prototype]]. This
+ abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>intrinsicDefaultProto</i> is a string value that is this
+ specification’s name of an intrinsic object. The corresponding object must be an intrinsic that is intended to
+ be used as the [[Prototype]] value of an object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-isconstructor">IsConstructor</a> (<i>constructor</i>)
+ is <b>true</b>.</li>
+ <li>Let <i>proto</i> be <a href="#sec-get-o-p">Get</a>(<i>constructor</i>, <code>"prototype"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>proto</i>) is not Object, then
+ <ol class="block">
+ <li>Let <i>realm</i> be <a href="#sec-getfunctionrealm">GetFunctionRealm</a>(<i>constructor</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>realm</i>).</li>
+ <li>Let <i>proto</i> be <i>realm’s</i> intrinsic object named <i>intrinsicDefaultProto</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>proto</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>constructor</i> does not supply a [[Prototype]] value, the default value that is
+ used is obtained from the <a href="#sec-code-realms">Code Realm</a> of the <i>constructor</i> function rather than from <a
+ href="#sec-execution-contexts">the running execution context</a>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-ecmascript-function-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.2"><a href="#sec-ecmascript-function-objects" title="link to this section">9.2</a></span>
+ ECMAScript Function Objects</h1>
+
+ <p>ECMAScript function objects encapsulate parameterized ECMAScript code closed over a <a
+ href="#sec-lexical-environments">lexical environment</a> and support the dynamic evaluation of that code. An ECMAScript
+ function object is an ordinary object and has the same internal slots and (except as noted below) and the same internal
+ methods as other ordinary objects. The code of an ECMAScript function object may be either <a
+ href="#sec-strict-mode-code">strict mode code</a> (<a href="#sec-strict-mode-code">10.2.1</a>) or non-<a
+ href="#sec-strict-mode-code">strict mode code</a>.</p>
+
+ <p>ECMAScript function objects have the additional internal slots listed in <a href="#table-27">Table 27</a>.</p>
+
+ <p>ECMAScript function objects whose code is not <a href="#sec-strict-mode-code">strict mode code</a> (<a
+ href="#sec-strict-mode-code">10.2.1</a>) provide an alternative definition for the [[GetOwnProperty]] internal method. This
+ alternative prevents the value of strict mode function from being revealed as the value of a function object property named
+ "<code>caller</code>". The alternative definition exist solely to preclude a non-standard legacy feature of some ECMAScript
+ implementations from revealing information about strict mode callers. If an implementation does not provide such a feature,
+ it need not implement this alternative internal method for ECMAScript function objects. ECMAScript function objects are
+ considered to be ordinary objects even though they may use the alternative definition of [[GetOwnProperty]].</p>
+
+ <figure>
+ <figcaption><span id="table-27">Table 27</span> — Internal Slots of ECMAScript Function Objects</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[Environment]]</td>
+ <td><a href="#sec-lexical-environments">Lexical Environment</a></td>
+ <td>The <a href="#sec-lexical-environments">Lexical Environment</a> that the function was closed over. Used as the outer environment when evaluating the code of the function.</td>
+ </tr>
+ <tr>
+ <td>[[FormalParameters]]</td>
+ <td>Parse Node</td>
+ <td>The root parse node of the source text that defines the function’s formal parameter list.</td>
+ </tr>
+ <tr>
+ <td>[[FunctionKind]]</td>
+ <td>String</td>
+ <td>Either "<code>normal</code>", "<code>classConstructor</code>" or "<code>generator</code>".</td>
+ </tr>
+ <tr>
+ <td>[[ECMAScriptCode]]</td>
+ <td>Parse Node</td>
+ <td>The root parse node of the source text that defines the function’s body.</td>
+ </tr>
+ <tr>
+ <td>[[ConstructorKind]]</td>
+ <td>String</td>
+ <td>Either "<code>base</code>" or "<code>derived</code>".</td>
+ </tr>
+ <tr>
+ <td>[[Realm]]</td>
+ <td><a href="#sec-code-realms">Realm</a> Record</td>
+ <td>The <a href="#sec-code-realms">Code Realm</a> in which the function was created and which provides any intrinsic objects that are accessed when evaluating the function.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">[[ThisMode]]</td>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">(lexical, strict, global)</td>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">Defines how <code>this</code> references are interpreted within the formal parameters and code body of the function. <b>lexical</b> means that <code>this</code> refers to the <b>this</b> value of a lexically enclosing function. <b>strict</b> means that the <b>this</b> value is used exactly as provided by an invocation of the function. <b>global</b> means that a <b>this</b> value of <span class="value">undefined</span> is interpreted as a reference to the global object.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">[[Strict]]</td>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">Boolean</td>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080"><span class="value">true</span> if this is a strict mode function, <span class="value">false</span> if this is not a strict mode function.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 0px solid black">[[HomeObject]]</td>
+ <td style="border-bottom: 0px solid black">Object</td>
+ <td style="border-bottom: 0px solid black">If the function uses <code>super</code>, this is the object whose [[GetPrototypeOf]] provides the object where <code>super</code> property lookups begin.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>All ECMAScript function objects have the [[Call]] internal method defined here. ECMAScript functions that are also
+ constructors in addition have the [[Construct]] internal method. ECMAScript function objects whose code is not <a
+ href="#sec-strict-mode-code">strict mode code</a> have the [[GetOwnProperty]] internal method defined here.</p>
+ </div>
+
+ <section id="sec-ecmascript-function-objects-getownproperty-p">
+ <h1><span class="secnum" id="sec-9.2.1"><a href="#sec-ecmascript-function-objects-getownproperty-p"
+ title="link to this section">9.2.1</a></span> [[GetOwnProperty]] (P)</h1>
+
+ <p>When the [[GetOwnProperty]] internal method of a non-strict mode <a href="#sec-ecmascript-function-objects">ECMAScript
+ function object</a> <var>F</var> is called with <a href="#sec-object-type">property key</a> <var>P</var>, the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>F</i>, <i>P</i>).</li>
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>v</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>P</i> is <code>"caller"</code>, then
+ <ol class="block">
+ <li>Let <i>callerValue</i> be <i>v</i>.[[Value]].</li>
+ <li>If <i>callerValue</i> is an <a href="#sec-ecmascript-function-objects">ECMAScript Function object</a>, then
+ <ol class="block">
+ <li>If <i>callerValue</i>’s [[Strict]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <b>true</b>, set
+ <i>v</i>.[[Value]] to <b>null</b>.</li>
+ </ol>
+ </li>
+ <li>Else if <a href="#sec-iscallable">IsCallable</a>(<i>callerValue</i>) is <b>true</b>, set <i>v</i>.[[Value]] to
+ <b>null</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+
+ <p>If an implementation extends non-strict mode ECMAScript function or built-in function objects with a built-in
+ <code>caller</code> own property then it must use this definition of [[GetOwnProperty]]. If an implementation does not
+ provide such an extension, the ordinary object [[GetOwnProperty]] internal method must be used.</p>
+ </section>
+
+ <section id="sec-ecmascript-function-objects-call-thisargument-argumentslist">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.2.2"><a href="#sec-ecmascript-function-objects-call-thisargument-argumentslist"
+ title="link to this section">9.2.2</a></span> [[Call]] ( thisArgument, argumentsList)</h1>
+
+ <p>The [[Call]] internal method for an <a href="#sec-ecmascript-function-objects">ECMAScript function object</a>
+ <var>F</var> is called with parameters <var>thisArgument</var> and <var>argumentsList</var>, a <a
+ href="#sec-list-and-record-specification-type">List</a> of <a href="#sec-ecmascript-language-types">ECMAScript language
+ values</a>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an <a
+ href="#sec-ecmascript-function-objects">ECMAScript function object</a>.</li>
+ <li>If <i>F</i>’s [[FunctionKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is
+ "<code>classConstructor</code>", throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>callerContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>calleeContext</i> be <a href="#sec-prepareforordinarycall">PrepareForOrdinaryCall</a>(<i>F</i>,
+ <b>null</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>calleeContext</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-ordinarycallbindthis">OrdinaryCallBindThis</a>(<i>F</i>, <i>calleeContext</i>,
+ <i>thisArgument</i>).</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Remove <i>calleeContext</i> from <a href="#sec-execution-contexts">the execution context stack</a> and restore
+ <i>callerContext</i> as <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>result</i> be <a href="#sec-ordinarycallevaluatebody">OrdinaryCallEvaluateBody</a>(<i>F</i>,
+ <i>argumentsList</i>).</li>
+ <li>Remove <i>calleeContext</i> from <a href="#sec-execution-contexts">the execution context stack</a> and restore
+ <i>callerContext</i> as <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>If <i>result</i>.[[type]] is <span style="font-family: sans-serif">return</span>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>result</i>.[[value]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When <i>calleeContext</i> is removed from <a href="#sec-execution-contexts">the
+ execution context stack</a> in step 9 it must not be destroyed if it is <a href="#sec-execution-contexts">suspended</a>
+ and retained for later resumption by an accessible generator object<i>.</i></p>
+ </div>
+ </div>
+
+ <section id="sec-prepareforordinarycall">
+ <h1><span class="secnum" id="sec-9.2.2.1"><a href="#sec-prepareforordinarycall"
+ title="link to this section">9.2.2.1</a></span> PrepareForOrdinaryCall( F, newTarget )</h1>
+
+ <p>When the abstract operation PrepareForOrdinaryCall is called with function object <var>F</var> <span
+ style="font-family: Times New Roman">and <a href="#sec-ecmascript-language-types">ECMAScript language value</a>
+ <i>newTarget</i></span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>newTarget</i>) is Undefined or Object.</li>
+ <li>Let <i>callerContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>calleeContext</i> be a new <a href="#sec-execution-contexts">ECMAScript code execution context</a>.</li>
+ <li>Set the Function of <i>calleeContext</i> to <i>F</i>.</li>
+ <li>Let <i>calleeRealm</i> be the value of <i>F’s</i> [[Realm]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Set the <a href="#sec-code-realms">Realm</a> of <i>calleeContext</i> to <i>calleeRealm</i>.</li>
+ <li>Let <i>localEnv</i> be <a href="#sec-newfunctionenvironment">NewFunctionEnvironment</a>(<i>F</i>,
+ <i>newTarget</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>localEnv</i>).</li>
+ <li><span style="font-family: sans-serif">NOTE Any exception objects produced by <a
+ href="#sec-newfunctionenvironment">NewFunctionEnvironment</a> are associated with</span> <i>callerRealm</i>.</li>
+ <li>Set the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>calleeContext</i> to <i>localEnv</i>.</li>
+ <li>Set the <a href="#sec-execution-contexts">VariableEnvironment</a> of <i>calleeContext</i> to <i>localEnv</i>.</li>
+ <li>If <i>callerContext</i> is not already <a href="#sec-execution-contexts">suspended</a>, <a
+ href="#sec-execution-contexts">Suspend</a> <i>callerContext</i>.</li>
+ <li>Push <i>calleeContext</i> onto <a href="#sec-execution-contexts">the execution context stack</a>;
+ <i>calleeContext</i> is now <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Return <i>calleeContext</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinarycallbindthis">
+ <h1><span class="secnum" id="sec-9.2.2.2"><a href="#sec-ordinarycallbindthis"
+ title="link to this section">9.2.2.2</a></span> OrdinaryCallBindThis ( F, calleeContext, thisArgument )</h1>
+
+ <p>When the abstract operation OrdinaryCallBindThis is called with function object <var>F</var>, <a
+ href="#sec-execution-contexts">execution context</a> <var>calleeContext</var>, and ECMAScript value
+ <var>thisArgument</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>thisMode</i> be the value of <i>F</i>’s [[ThisMode]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>thisMode</i> is <span style="font-family: sans-serif">lexical</span>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>Let <i>calleeRealm</i> be the value of <i>F’s</i> [[Realm]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>localEnv</i> be the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>calleeContext</i>.</li>
+ <li>If <i>thisMode</i> is <span style="font-family: sans-serif">strict</span>, let <i>thisValue</i> be
+ <i>thisArgument</i>.</li>
+ <li>Else
+ <ol class="block">
+ <li>if <i>thisArgument</i> is <b>null</b> or <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>thisValue</i> be <i>calleeRealm</i>.[[globalThis]].</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>thisValue</i> be <a href="#sec-toobject">ToObject</a>(<i>thisArgument</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>thisValue</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><span style="font-family: sans-serif">NOTE <a href="#sec-toobject">ToObject</a> produces</span> <span
+ style="font-family: sans-serif">wrapper objects using</span> <i>calleeRealm</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>envRec</i> be <i>localEnv</i>’s environment record.</li>
+ <li>Return <i>envRec</i>.<a href="#sec-bindthisvalue">BindThisValue</a>(<i>thisValue</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-ordinarycallevaluatebody">
+ <h1><span class="secnum" id="sec-9.2.2.3"><a href="#sec-ordinarycallevaluatebody"
+ title="link to this section">9.2.2.3</a></span> OrdinaryCallEvaluateBody ( F, argumentsList )</h1>
+
+ <p>When the abstract operation OrdinaryCallEvaluateBody is called with function object <var>F</var> and <a
+ href="#sec-list-and-record-specification-type">List</a> <var>argumentsList</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>status</i> be <a href="#sec-functiondeclarationinstantiation">FunctionDeclarationInstantiation</a>(<i>F</i>,
+ <i>argumentsList</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>)</li>
+ <li>Return the result of EvaluateBody of the parsed code that is the value of <i>F</i>'s [[ECMAScriptCode]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> passing <i>F</i> as the argument.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-ecmascript-function-objects-construct-argumentslist-newtarget">
+ <h1><span class="secnum" id="sec-9.2.3"><a href="#sec-ecmascript-function-objects-construct-argumentslist-newtarget"
+ title="link to this section">9.2.3</a></span> [[Construct]] ( argumentsList, newTarget)</h1>
+
+ <p>The [[Construct]] internal method for an <a href="#sec-ecmascript-function-objects">ECMAScript Function object</a>
+ <var>F</var> is called with parameters <var>argumentsList</var> and <span style="font-family: Times New
+ Roman"><i>newTarget</i>. <i>argumentsList</i></span> is a possibly empty <a
+ href="#sec-list-and-record-specification-type">List</a> of <a href="#sec-ecmascript-language-types">ECMAScript language
+ values</a>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an <a href="#sec-ecmascript-function-objects">ECMAScript
+ function object</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>newTarget</i>) is Object.</li>
+ <li>Let <i>callerContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>kind</i> be <i>F</i>’s [[ConstructorKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>kind</i> is <code>"base"</code>, then
+ <ol class="block">
+ <li>Let <i>thisArgument</i> be <a
+ href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(<i>newTarget</i>,
+ <code>"%ObjectPrototype%"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>thisArgument</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>calleeContext</i> be <a href="#sec-prepareforordinarycall">PrepareForOrdinaryCall</a>(<i>F</i>,
+ <i>newTarget</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>calleeContext</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>calleeContext</i> is now <a href="#sec-execution-contexts">the
+ running execution context</a>.</li>
+ <li>If <i>kind</i> is <code>"base"</code>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-ordinarycallbindthis">OrdinaryCallBindThis</a>(<i>F</i>, <i>calleeContext</i>,
+ <i>thisArgument</i>).</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Remove <i>calleeContext</i> from <a href="#sec-execution-contexts">the execution context stack</a> and restore
+ <i>callerContext</i> as <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>constructorEnv</i> be the <a href="#sec-execution-contexts">LexicalEnvironment</a> of
+ <i>calleeContext</i>.</li>
+ <li>Let <i>envRec</i> be <i>constructorEnv</i>’s environment record.</li>
+ <li>Let <i>result</i> be <a href="#sec-ordinarycallevaluatebody">OrdinaryCallEvaluateBody</a>(<i>F</i>,
+ <i>argumentsList</i>).</li>
+ <li>Remove <i>calleeContext</i> from <a href="#sec-execution-contexts">the execution context stack</a> and restore
+ <i>callerContext</i> as <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>If <i>result</i>.[[type]] is <span style="font-family: sans-serif">return</span>, then
+ <ol class="block">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>result</i>.[[value]]) is Object, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>result</i>.[[value]]).</li>
+ <li>If <i>kind</i> is <code>"base"</code>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>thisArgument</i>).</li>
+ <li>If <i>result</i>.[[value]] is not <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Else, <a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>Return <i>envRec</i>.GetThisBinding().</li>
+ </ol>
+ </section>
+
+ <section id="sec-functionallocate">
+ <h1><span class="secnum" id="sec-9.2.4"><a href="#sec-functionallocate" title="link to this section">9.2.4</a></span>
+ FunctionAllocate (functionPrototype, strict [,functionKind] )</h1>
+
+ <p>The abstract operation FunctionAllocate requires the two arguments <span style="font-family: Times New
+ Roman"><i>functionPrototype</i> and <i>strict</i>.</span> It also accepts one optional argument, <var>functionKind</var>.
+ FunctionAllocate performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>functionPrototype</i>) is Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If <i>functionKind</i> is present, its value is either
+ "<code>normal</code>", "<code>non-constructor</code>" or "<code>generator</code>".</li>
+ <li>If <i>functionKind</i> is not present, let <i>functionKind</i> be "<code>normal</code>".</li>
+ <li>If <i>functionKind</i> is "<code>non-constructor</code>", then
+ <ol class="block">
+ <li>Let <i>functionKind</i> be "<code>normal</code>".</li>
+ <li>Let <i>needsConstruct</i> be <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Else let <i>needsConstruct</i> be <b>true</b>.</li>
+ <li>Let <i>F</i> be a newly created <a href="#sec-ecmascript-function-objects">ECMAScript function object</a> with the
+ internal slots listed in <a href="#table-27">Table 27</a>. All of those internal slots are initialized to
+ <b>undefined</b>.</li>
+ <li>Set <i>F</i>’s essential internal methods except for [[GetOwnProperty]] to the default ordinary object
+ definitions specified in <a href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</li>
+ <li>If <i>strict</i> is <b>true</b>, set <i>F</i>’s [[GetOwnProperty]] internal method to the default ordinary
+ object definition specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-getownproperty-p">9.1.5</a>.</li>
+ <li>Else, set <i>F</i>’s [[GetOwnProperty]] internal method as specified in <a
+ href="#sec-ecmascript-function-objects-getownproperty-p">9.2.1</a>.</li>
+ <li>Set <i>F</i>’s [[Call]] internal method to the definition specified in <a
+ href="#sec-ecmascript-function-objects-call-thisargument-argumentslist">9.2.2</a>.</li>
+ <li>If <i>needsConstruct</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>F</i>’s [[Construct]] internal method to the definition specified in <a
+ href="#sec-ecmascript-function-objects-construct-argumentslist-newtarget">9.2.3</a>.</li>
+ <li>If <i>functionKind</i> is "<code>generator</code>", set the [[ConstructorKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ "<code>derived</code>".</li>
+ <li>Else, set the [[ConstructorKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>F</i> to "<code>base</code>".</li>
+ <li>NOTE Generator functions are tagged as <span style="font-family: Times New
+ Roman">"</span><code>derived</code><span style="font-family: Times New Roman">"</span> constructors to prevent
+ [[Construct]] from preallocating a generator instance. Generator instance objects are allocated when EvaluateBody
+ is applied to the <span class="nt">GeneratorBody</span> of a generator function.</li>
+ </ol>
+ </li>
+ <li>Set the [[Strict]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ <i>strict</i>.</li>
+ <li>Set the [[FunctionKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ <i>functionKind</i>.</li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ <i>functionPrototype</i>.</li>
+ <li>Set the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ <b>true</b>.</li>
+ <li>Set the [[Realm]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to <a
+ href="#sec-execution-contexts">the running execution context</a>’s <a href="#sec-code-realms">Realm</a>.</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-functioninitialize">
+ <h1><span class="secnum" id="sec-9.2.5"><a href="#sec-functioninitialize" title="link to this section">9.2.5</a></span>
+ FunctionInitialize (F, kind, ParameterList, Body, Scope)</h1>
+
+ <p>The abstract operation FunctionInitialize requires the arguments: a function object <var>F</var>, <var>kind</var> which
+ is one of (Normal, Method, Arrow), a parameter list production specified by <span class="nt">ParameterList</span>, a body
+ production specified by <span class="nt">Body</span>, a <a href="#sec-lexical-environments">Lexical Environment</a>
+ specified by <span style="font-family: Times New Roman"><i>Scope</i>.</span> FunctionInitialize performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an extensible object that does not have a
+ <code>length</code> own property.</li>
+ <li>Let <i>len</i> be the ExpectedArgumentCount of <i>ParameterList</i>.</li>
+ <li>Let <i>realm</i> be the value of <i>F’s</i> [[Realm]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>F</i>, <code>"length"</code>,
+ PropertyDescriptor{[[Value]]: <i>len</i>, [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>true</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Let <i>Strict</i> be the value of the [[Strict]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of <i>F</i>.</li>
+ <li>Set the [[Environment]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to the
+ value of <i>Scope</i>.</li>
+ <li>Set the [[FormalParameters]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i>
+ to <i>ParameterList</i> .</li>
+ <li>Set the [[ECMAScriptCode]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ <i>Body</i>.</li>
+ <li>If <i>kind</i> is <span style="font-family: sans-serif">Arrow</span>, set the [[ThisMode]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to <span style="font-family:
+ sans-serif">lexical</span>.</li>
+ <li>Else if <i>Strict</i> is <b>true</b>, set the [[ThisMode]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to <span style="font-family:
+ sans-serif">strict</span>.</li>
+ <li>Else set the [[ThisMode]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ <span style="font-family: sans-serif">global</span>.</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-functioncreate">
+ <h1><span class="secnum" id="sec-9.2.6"><a href="#sec-functioncreate" title="link to this section">9.2.6</a></span>
+ FunctionCreate (kind, ParameterList, Body, Scope, Strict, prototype)</h1>
+
+ <p>The abstract operation FunctionCreate requires the arguments: <var>kind</var> which is one of (Normal, Method, Arrow), a
+ parameter list production specified by <span class="nt">ParameterList</span>, a body production specified by <span
+ class="nt">Body</span>, a <a href="#sec-lexical-environments">Lexical Environment</a> specified by <span
+ class="nt">Scope</span>, a Boolean flag <span class="nt">Strict</span>, and optionally, an object <span style="font-family:
+ Times New Roman"><i>prototype</i>.</span> FunctionCreate performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If the <i>prototype</i> argument was not passed, then
+ <ol class="block">
+ <li>Let <i>prototype</i> be the intrinsic object %FunctionPrototype%.</li>
+ </ol>
+ </li>
+ <li>If <i>kind</i> is not <span style="font-family: sans-serif">Normal</span>, let <i>allocKind</i> be
+ "<code>non-constructor</code>".</li>
+ <li>Else let <i>allocKind</i> be "<code>normal</code>".</li>
+ <li>Let <i>F</i> be <a href="#sec-functionallocate">FunctionAllocate</a>(<i>prototype</i>, <i>Strict</i>,
+ <i>allocKind</i>).</li>
+ <li>Return <a href="#sec-functioninitialize">FunctionInitialize</a>(<i>F</i>, <i>kind</i>, <i>ParameterList</i>,
+ <i>Body</i>, <i>Scope</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-generatorfunctioncreate">
+ <h1><span class="secnum" id="sec-9.2.7"><a href="#sec-generatorfunctioncreate" title="link to this section">9.2.7</a></span>
+ GeneratorFunctionCreate (kind, ParameterList, Body, Scope, Strict)</h1>
+
+ <p>The abstract operation GeneratorFunctionCreate requires the arguments: <var>kind</var> which is one of (Normal, Method),
+ a parameter list production specified by <span class="nt">ParameterList</span>, a body production specified by <span
+ class="nt">Body</span>, a <a href="#sec-lexical-environments">Lexical Environment</a> specified by <span
+ class="nt">Scope</span>, and a Boolean flag <span class="nt">Strict</span>. GeneratorFunctionCreate performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>functionPrototype</i> be the intrinsic object %Generator%.</li>
+ <li>Let <i>F</i> be <a href="#sec-functionallocate">FunctionAllocate</a>(<i>functionPrototype</i>, <i>Strict</i>,
+ <code>"generator"</code>).</li>
+ <li>Return <a href="#sec-functioninitialize">FunctionInitialize</a>(<i>F</i>, <i>kind</i>, <i>ParameterList</i>,
+ <i>Body</i>, <i>Scope</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-addrestrictedfunctionproperties">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.2.8"><a href="#sec-addrestrictedfunctionproperties"
+ title="link to this section">9.2.8</a></span> AddRestrictedFunctionProperties ( F, realm )</h1>
+
+ <p>The abstract operation AddRestrictedFunctionProperties is called with a function object <var>F</var> and <a
+ href="#sec-code-realms">Realm</a> Record <var>realm</var> as its argument. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>realm</i>.[[intrinsics]].[[<span style="font-family:
+ sans-serif">%ThrowTypeError%]] exists and has been initialized.</span></li>
+ <li>Let <i>thrower</i> be <i>realm</i>.[[intrinsics]].[[<span style="font-family:
+ sans-serif">%ThrowTypeError%]].</span></li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>F</i>, <code>"caller"</code>,
+ PropertyDescriptor {[[Get]]: <i>thrower</i>, [[Set]]: <i>thrower</i>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>true</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>F</i> , <code>"arguments"</code>,
+ PropertyDescriptor {[[Get]]: <i>thrower</i>, [[Set]]: <i>thrower</i>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>true</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above returned value is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-%throwtypeerror%">
+ <h1><span class="secnum" id="sec-9.2.8.1"><a href="#sec-%throwtypeerror%" title="link to this section">9.2.8.1</a></span>
+ %ThrowTypeError% ( )</h1>
+
+ <p>The %ThrowTypeError% intrinsic is an anonymous built-in function object that is defined once for each <a
+ href="#sec-code-realms">Realm</a>. When %ThrowTypeError% is called it performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+
+ <p>The value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of a
+ %ThrowTypeError% function is <span class="value">false</span>.</p>
+
+ <p>The <code>length</code> property of a %ThrowTypeError% function has the attributes { [[Writable]]: <b>false</b>,
+ [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-makeconstructor">
+ <h1><span class="secnum" id="sec-9.2.9"><a href="#sec-makeconstructor" title="link to this section">9.2.9</a></span>
+ MakeConstructor (F, writablePrototype, prototype)</h1>
+
+ <p>The abstract operation MakeConstructor requires a Function argument <var>F</var> and optionally, a Boolean
+ <var>writablePrototype</var> and an object <var>prototype</var>. If <var>prototype</var> is provided it is assumed to
+ already contain, if needed, a <code>"constructor"</code> property whose value is <var>F</var>. This operation converts
+ <var>F</var> into a constructor by performing the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an <a href="#sec-ecmascript-function-objects">ECMAScript
+ function object</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> has a [[Construct]] internal method.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an extensible object that does not have a
+ <code>prototype</code> own property.</li>
+ <li>Let <i>installNeeded</i> be <b>false</b>.</li>
+ <li>If the <i>prototype</i> argument was not provided, then
+ <ol class="block">
+ <li>Let <i>installNeeded</i> be <b>true</b>.</li>
+ <li>Let <i>prototype</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%ObjectPrototype%</span>).</li>
+ </ol>
+ </li>
+ <li>If the <i>writablePrototype</i> argument was not provided, then
+ <ol class="block">
+ <li>Let <i>writablePrototype</i> be <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>If <i>installNeeded</i>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>prototype</i>,
+ <code>"constructor"</code>, PropertyDescriptor{[[Value]]: <i>F</i>, [[Writable]]: <i>writablePrototype</i>,
+ [[Enumerable]]: <b>false</b>, [[Configurable]]: <i>writablePrototype</i> }).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>F</i>,
+ <code>"prototype"</code>, PropertyDescriptor{[[Value]]: <i>prototype</i>, [[Writable]]: <i>writablePrototype</i>,
+ [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-makeclassconstructor">
+ <h1><span class="secnum" id="sec-9.2.10"><a href="#sec-makeclassconstructor" title="link to this section">9.2.10</a></span>
+ MakeClassConstructor ( F)</h1>
+
+ <p>The abstract operation MakeClassConstructor with argument <var>F</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an <a href="#sec-ecmascript-function-objects">ECMAScript
+ function object</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i>’s [[FunctionKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is "<code>normal</code>".</li>
+ <li>Set <i>F</i>’s [[FunctionKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ "<code>classConstructor</code>".</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-makemethod">
+ <h1><span class="secnum" id="sec-9.2.11"><a href="#sec-makemethod" title="link to this section">9.2.11</a></span> MakeMethod
+ ( F, homeObject)</h1>
+
+ <p>The abstract operation MakeMethod with arguments <var>F</var> and <var>homeObject</var> configures <var>F</var> as a
+ method by performing the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an <a href="#sec-ecmascript-function-objects">ECMAScript
+ function object</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>homeObject</i> ) is Object.</li>
+ <li>Set the [[HomeObject]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>F</i> to
+ <i>homeObject</i>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-setfunctionname">
+ <h1><span class="secnum" id="sec-9.2.12"><a href="#sec-setfunctionname" title="link to this section">9.2.12</a></span>
+ SetFunctionName (F, name, prefix)</h1>
+
+ <p>The abstract operation SetFunctionName requires a Function argument <var>F</var>, a String or Symbol argument
+ <var>name</var> and optionally a String argument <var>prefix</var>. This operation adds a <code>name</code> property to
+ <var>F</var> by performing the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> is an extensible object that does not have a
+ <code>name</code> own property.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>name</i>)
+ is either Symbol or String.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If <i>prefix</i> was passed then <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>prefix</i>) is String.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>name</i>) is Symbol, then
+ <ol class="block">
+ <li>Let <i>description</i> be <i>name</i>’s [[Description]] value.</li>
+ <li>If <i>description</i> is <b>undefined</b>, let <i>name</i> be the empty String.</li>
+ <li>Else, let <i>name</i> be the concatenation of <code>"["</code>, <i>description</i>, and <code>"]"</code>.</li>
+ </ol>
+ </li>
+ <li>If <i>prefix</i> was passed, then
+ <ol class="block">
+ <li>Let <i>name</i> be the concatenation of <i>prefix</i>, Unicode code unit 0x0020 (Space) , and <i>name</i>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>F</i>, <code>"name"</code>,
+ PropertyDescriptor{[[Value]]: <i>name</i>, [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>true</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: the result is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-functiondeclarationinstantiation">
+ <h1><span class="secnum" id="sec-9.2.13"><a href="#sec-functiondeclarationinstantiation"
+ title="link to this section">9.2.13</a></span> FunctionDeclarationInstantiation(func, argumentsList)</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When an <a href="#sec-execution-contexts">execution context</a> is established for
+ evaluating an ECMAScript function a new <a href="#sec-function-environment-records">Function Environment Record</a> is
+ created and bindings for each formal parameter are instantiated in that environment record. Each declaration in the
+ function body is also instantiated. If the function’s formal parameters do not include any default value
+ initializers then the body declarations are instantiated in the same environment record as the parameters. If default
+ value parameter initializers exist, a second environment record is created for the body declarations. Formal parameters
+ and functions are initialized as part of FunctionDeclarationInstantiation. All other bindings are initialized during
+ evaluation of the function body.</p>
+ </div>
+
+ <p>FunctionDeclarationInstantiation is performed as follows using arguments <var>func</var> and <var>argumentsList</var>.
+ <var>func</var> is the function object for which the <a href="#sec-execution-contexts">execution context</a> is being
+ established.</p>
+
+ <ol class="proc">
+ <li>Let <i>calleeContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>env</i> be the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>calleeContext</i>.</li>
+ <li>Let <i>envRec</i> be <i>env</i>’s environment record.</li>
+ <li>Let <i>code</i> be the value of the [[ECMAScriptCode]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>func</i>.</li>
+ <li>Let <i>strict</i> be the value of the [[Strict]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of <i>func</i>.</li>
+ <li>Let <i>formals</i> be the value of the [[FormalParameters]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>func</i>.</li>
+ <li>Let <i>parameterNames</i> be the BoundNames of <i>formals</i>.</li>
+ <li>If <i>parameterNames</i> has any duplicate entries, let <i>hasDuplicates</i> be <b>true</b>. Otherwise, let
+ <i>hasDuplicates</i> be <b>false</b>.</li>
+ <li>Let <i>simpleParameterList</i> be IsSimpleParameterList of <i>formals</i>.</li>
+ <li>Let <i>hasParameterExpressions</i> be ContainsExpression of <i>formals.</i></li>
+ <li>Let <i>varNames</i> be the VarDeclaredNames of <i>code</i>.</li>
+ <li>Let <i>varDeclarations</i> be the VarScopedDeclarations of <i>code</i>.</li>
+ <li>Let <i>lexicalNames</i> be the LexicallyDeclaredNames of <i>code</i>.</li>
+ <li>Let <i>functionNames</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>functionsToInitialize</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each <i>d</i> in <i>varDeclarations</i>, in reverse list order do
+ <ol class="block">
+ <li>If <i>d</i> is neither a <i>VariableDeclaration</i> or a <i>ForBinding</i>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>d</i> is either a <i>FunctionDeclaration</i> or a
+ <i>GeneratorDeclaration</i>.</li>
+ <li>Let <i>fn</i> be the sole element of the BoundNames of <i>d.</i></li>
+ <li>If <i>fn</i> is not an element of <i>functionNames</i>, then
+ <ol class="block">
+ <li>Insert <i>fn</i> as the first element of <i>functionNames</i>.</li>
+ <li>NOTE If there are multiple <span style="font-family: Times New Roman"><i>FunctionDeclarations</i> or
+ <i>GeneratorDeclarations</i></span> for the same name, the last declaration is used.</li>
+ <li>Insert <i>d</i> as the first element of <i>functionsToInitialize</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>argumentsObjectNeeded</i> be <b>true</b>.</li>
+ <li>If the value of the [[ThisMode]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>func</i> is <span style="font-family: sans-serif">lexical</span>, then
+ <ol class="block">
+ <li>NOTE Arrow functions never have an arguments objects.</li>
+ <li>Let <i>argumentsObjectNeeded</i> be <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Else if "<code>arguments</code>" is an element of <i>parameterNames</i>, then
+ <ol class="block">
+ <li>Let <i>argumentsObjectNeeded</i> be <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Else if <i>hasParameterExpressions</i> is <b>false</b>, then
+ <ol class="block">
+ <li>If "<code>arguments</code>" is an element of <i>functionNames</i> or if "<code>arguments</code>" is an element of
+ <i>lexicalNames</i>, then
+ <ol class="block">
+ <li>Let <i>argumentsObjectNeeded</i> be <b>false</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>For each String <i>paramName</i> in <i>parameterNames</i>, do
+ <ol class="block">
+ <li>Let <i>alreadyDeclared</i> be <i>envRec</i>.HasBinding(<i>paramName</i>).</li>
+ <li>NOTE Early errors ensure that duplicate parameter names can only occur in non-strict mode functions that do not
+ have parameter default values or rest parameters.</li>
+ <li>If <i>alreadyDeclared</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateMutableBinding(<i>paramName</i>).</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.InitializeBinding(<i>paramName</i>, <b>undefined</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a> for either of the above
+ operations.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>argumentsObjectNeeded</i> is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>strict</i> is <b>true</b> or if <i>simpleParameterList</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>ao</i> be <a
+ href="#sec-createunmappedargumentsobject">CreateUnmappedArgumentsObject</a>(<i>argumentsList</i>)<i>.</i></li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>NOTE mapped argument object is only provided for non-strict mode functions that don’t have a rest
+ parameter, any parameter default value initializers, or any destructured parameters .</li>
+ <li>Let <i>ao</i> be <a href="#sec-createmappedargumentsobject">CreateMappedArgumentsObject</a>(<i>func</i>,
+ <i>formals</i>, <i>argumentsList</i>, <i>env</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ao</i>).</li>
+ <li>If <i>strict</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateImmutableBinding("<code>arguments</code>").</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateMutableBinding("<code>arguments</code>").</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><a href="#sec-call">Call</a> <i>envRec</i>.InitializeBinding("<code>arguments</code>", <i>ao</i>).</li>
+ <li>Append "<code>arguments</code>" to <i>parameterNames</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <a
+ href="#sec-createlistiterator">CreateListIterator</a>(<i>argumentsList</i>), [[done]]: <b>false</b>}.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>formalStatus</i> be IteratorBindingInitialization for <i>formals</i> with <i>iteratorRecord</i> and
+ <b>undefined</b> as arguments.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>formalStatus</i> be IteratorBindingInitialization for <i>formals</i> with <i>iteratorRecord</i> and
+ <i>envRec</i> as arguments.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>formalStatus</i>).</li>
+ <li>If <i>hasParameterExpressions</i> is <b>false</b>, then
+ <ol class="block">
+ <li>NOTE Only a single <a href="#sec-lexical-environments">lexical environment</a> is needed for the parameters and
+ top-level vars.</li>
+ <li>Let <i>instantiatedVarNames</i> be a copy of the <a href="#sec-list-and-record-specification-type">List</a>
+ <i>parameterNames</i>.</li>
+ <li>For each <i>n</i> in <i>varNames</i>, do
+ <ol class="block">
+ <li>If <i>n</i> is not an element of <i>instantiatedVarNames</i>, then
+ <ol class="block">
+ <li>Append <i>n</i> to <i>instantiatedVarNames</i>.</li>
+ <li>Let <i>status</i> be <i>envRec</i>.CreateMutableBinding(<i>n</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><a href="#sec-call">Call</a> <i>envRec</i>.InitializeBinding(<i>n</i>, <b>undefined</b>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>varEnv</i> be <i>env</i>.</li>
+ <li>Let <i>varEnvRec</i> be <i>envRec</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>NOTE A separate environment record is needed to ensure that closures created by expressions in the formal
+ parameter list do not have visibility of declarations in the function body.</li>
+ <li>Let <i>varEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>env</i>).</li>
+ <li>Let <i>varEnvRec</i> be <i>varEnv</i>’s environment record.</li>
+ <li>Set the <a href="#sec-execution-contexts">VariableEnvironment</a> of <i>calleeContext</i> to <i>varEnv</i>.</li>
+ <li>Let <i>instantiatedVarNames</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each <i>n</i> in <i>varNames</i>, do
+ <ol class="block">
+ <li>If <i>n</i> is not an element of <i>instantiatedVarNames</i>, then
+ <ol class="block">
+ <li>Append <i>n</i> to <i>instantiatedVarNames</i>.</li>
+ <li>Let <i>status</i> be <i>varEnvRec</i>.CreateMutableBinding(<i>n</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>n</i> is not an element of <i>parameterNames</i> or if <i>n</i> is an element of
+ <i>functionNames</i>, let <i>initialValue</i> be <b>undefined</b>.</li>
+ <li>else,
+ <ol class="block">
+ <li>Let <i>initialValue</i> be <i>envRec.</i>GetBindingValue(<i>n</i>, <b>false</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>initialValue</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-call">Call</a> <i>varEnvRec</i>.InitializeBinding(<i>n</i>,
+ <i>initialValue</i><b>)</b>.</li>
+ <li>NOTE vars whose names are the same as a formal parameter, initially have the same value as the
+ corresponding initialized parameter.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>NOTE: Annex <a href="#sec-block-level-function-declarations-web-legacy-compatibility-semantics">B.3.3</a> adds
+ additional steps at this point.</li>
+ <li>If <i>strict</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>lexEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>varEnv</i>).</li>
+ <li>NOTE: Non-strict mode functions use a separate <a href="#sec-lexical-environments">lexical environment</a> record
+ for top-level lexical declarations so that a direct <code>eval</code> (<a
+ href="#sec-function-calls-runtime-semantics-evaluation">see 12.3.4.1</a>) can determine whether any var scoped
+ declarations introduced by the eval code conflict with pre-existing top-level lexically scoped declarations. This
+ is not needed for strict mode functions because a strict direct <code>eval</code> always places all declarations
+ into a new environment record.</li>
+ </ol>
+ </li>
+ <li>Else, let <i>lexEnv</i> be <i>varEnv</i>.</li>
+ <li>Let <i>lexEnvRec</i> be <i>lexEnv</i>’s environment record.</li>
+ <li>Set the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>calleeContext</i> to <i>lexEnv</i>.</li>
+ <li>Let <i>lexDeclarations</i> be the LexicallyScopedDeclarations of <i>code</i>.</li>
+ <li>For each element <i>d</i> in <i>lexDeclarations</i> do
+ <ol class="block">
+ <li>NOTE A lexically declared name cannot be the same as a function/generator declaration, formal parameter, or a var
+ name. Lexically declared names are only instantiated here but not initialized.</li>
+ <li>For each element <i>dn</i> of the BoundNames of <i>d</i> do
+ <ol class="block">
+ <li>If IsConstantDeclaration of <i>d</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>lexEnvRec</i>.CreateImmutableBinding(<i>dn</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>lexEnvRec</i>.CreateMutableBinding(<i>dn</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>For each parsed grammar phase <i>f</i> in <i>functionsToInitialize</i>, do
+ <ol class="block">
+ <li>Let <i>fn</i> be the sole element of the BoundNames of <i>f.</i></li>
+ <li>Let <i>fo</i> be the result of performing InstantiateFunctionObject for <i>f</i> with argument <i>lexEnv</i>.</li>
+ <li>Let <i>status</i> be <i>varEnvRec</i>.SetMutableBinding(<i>fn</i>, <i>fo</i>, <b>false</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> <a
+ href="#sec-block-level-function-declarations-web-legacy-compatibility-semantics">B.3.3</a> provides an extension to the
+ above algorithm that is necessary for backwards compatibility with web browser implementations of ECMAScript that predate
+ the sixth edition of ECMA-262.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Parameter <i>Initializers</i> may contain direct eval expressions (<a
+ href="#sec-function-calls-runtime-semantics-evaluation">12.3.4.1</a>). Any top level declarations of such evals are only
+ visible to the eval code (<a href="#sec-types-of-source-code">10.2</a>). The creation of the environment for such
+ declarations is described in <a
+ href="#sec-function-definitions-runtime-semantics-iteratorbindinginitialization">14.1.19</a>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-built-in-function-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.3"><a href="#sec-built-in-function-objects" title="link to this section">9.3</a></span>
+ Built-in Function Objects</h1>
+
+ <p>The built-in function objects defined in this specification may be implemented as either ECMAScript function objects (<a
+ href="#sec-ecmascript-function-objects">9.2</a>) whose behaviour is provided using ECMAScript code or as implementation
+ provided exotic function objects whose behaviour is provided in some other manner. In either case, the effect of calling
+ such functions must conform to their specifications. An implementation may also provide additional built-in function objects
+ that are not defined in this specification.</p>
+
+ <p>If a built-in function object is implemented as an exotic object it must have the ordinary object behaviour specified in
+ <a href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a> except [[GetOwnProperty]] which must be as
+ specified in <a href="#sec-ecmascript-function-objects-getownproperty-p">9.2.1</a>. All such exotic function objects also
+ have [[Prototype]], [[Extensible]], and [[Realm]] internal slots.</p>
+
+ <p>Unless otherwise specified every built-in function object initially has the %FunctionPrototype% object (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>) as the initial value of its [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The behaviour specified for each built-in function via algorithm steps or other means is the specification of the
+ function body behaviour for both [[Call]] and [[Construct]] invocations of the function. However, [[Construct]] invocation
+ is not supported by all built-in functions. For each built-in function, when invoked with [[Call]], the [[Call]]
+ <var>thisArgument</var> provides the <span class="value">this</span> value, the [[Call]] <var>argumentsList</var> provides
+ the named parameters, and the NewTarget value is <span class="value">undefined</span>. When invoked with [[Construct]], the
+ <span class="value">this</span> value is uninitialized, the [[Construct]] <var>argumentsList</var> provides the named
+ parameters, and the [[Construct]] <var>newTarget</var> parameter provides the NewTarget value. If the built-in function is
+ implemented as an <a href="#sec-ecmascript-function-objects">ECMAScript function object</a> then this specified behaviour
+ must be implemented by the ECMAScript code that is the body of the function. Built-in functions that are ECMAScript function
+ objects must be strict mode functions. If a built-in constructor has any [[Call]] behaviour other than throwing a <span
+ class="value">TypeError</span> exception, an ECMAScript implementation of the function must be done in a manner that does
+ not cause the function’s [[FunctionKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ to have the value "<code>classConstructor</code>".</p>
+
+ <p>Built-in function objects that are not identified as constructors do not implement the [[Construct]] internal method
+ unless otherwise specified in the description of a particular function. When a built-in constructor is called as part of a
+ <code>new</code> expression the <var>argumentsList</var> parameter of the invoked [[Construct]] internal method provides the
+ values for the built-in constructor’s named parameters.</p>
+
+ <p>Built-in functions that are not constructors do not have a <code>prototype</code> property unless otherwise specified in
+ the description of a particular function.</p>
+
+ <p>If a built-in function object is not implemented as an ECMAScript function it must provide [[Call]] and [[Construct]]
+ internal methods that conform to the following definitions:</p>
+ </div>
+
+ <section id="sec-built-in-function-objects-call-thisargument-argumentslist">
+ <h1><span class="secnum" id="sec-9.3.1"><a href="#sec-built-in-function-objects-call-thisargument-argumentslist"
+ title="link to this section">9.3.1</a></span> [[Call]] ( thisArgument, argumentsList)</h1>
+
+ <p>The [[Call]] internal method for a built-in function object <var>F</var> is called with parameters
+ <var>thisArgument</var> and <var>argumentsList</var>, a <a href="#sec-list-and-record-specification-type">List</a> of <a
+ href="#sec-ecmascript-language-types">ECMAScript language values</a>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>callerContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>If <i>callerContext</i> is not already <a href="#sec-execution-contexts">suspended</a>, <a
+ href="#sec-execution-contexts">Suspend</a> <i>callerContext</i>.</li>
+ <li>Let <i>calleeContext</i> be a new <a href="#sec-execution-contexts">ECMAScript code execution context</a>.</li>
+ <li>Set the Function of <i>calleeContext</i> to <i>F</i>.</li>
+ <li>Let <i>calleeRealm</i> be the value of <i>F’s</i> [[Realm]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Set the <a href="#sec-code-realms">Realm</a> of <i>calleeContext</i> to <i>calleeRealm</i>.</li>
+ <li>Perform any necessary implementation defined initialization of <i>calleeContext</i>.</li>
+ <li>Push <i>calleeContext</i> onto <a href="#sec-execution-contexts">the execution context stack</a>; <i>calleeContext</i>
+ is now <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>result</i> be the <a href="#sec-completion-record-specification-type">Completion Record</a> that is the result
+ of evaluating <i>F</i> in an implementation defined manner that conforms to the specification of <i>F</i>.
+ <i>thisArgument</i> is the <b>this</b> value, <i>argumentsList</i> provides the named parameters, and the NewTarget
+ value is <b>undefined</b>.</li>
+ <li>Remove <i>calleeContext</i> from <a href="#sec-execution-contexts">the execution context stack</a> and restore
+ <i>callerContext</i> as <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> When <i>calleeContext</i> is removed from <a href="#sec-execution-contexts">the
+ execution context stack</a> it must not be destroyed if it has been <a href="#sec-execution-contexts">suspended</a> and
+ retained by an accessible generator object for later resumption<i>.</i></p>
+ </div>
+ </section>
+
+ <section id="sec-built-in-function-objects-construct-argumentslist-newtarget">
+ <h1><span class="secnum" id="sec-9.3.2"><a href="#sec-built-in-function-objects-construct-argumentslist-newtarget"
+ title="link to this section">9.3.2</a></span> [[Construct]] (argumentsList, newTarget)</h1>
+
+ <p>The [[Construct]] internal method for built-in function object <var>F</var> is called with parameters
+ <var>argumentsList</var> and <var>newTarget</var>. The steps performed are the same as [[Call]] (<a
+ href="#sec-built-in-function-objects-call-thisargument-argumentslist">see 9.3.1</a>) except that step 9 is replaced by:</p>
+
+ <ol class="proc">
+ <li>Let <i>result</i> be the <a href="#sec-completion-record-specification-type">Completion Record</a> that is the result
+ of evaluating <i>F</i> in an implementation defined manner that conforms to the specification of <i>F</i>. The
+ <b>this</b> value is uninitialized, <i>argumentsList</i> provides the named parameters, and <i>newTarget</i> provides
+ the NewTarget value.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createbuiltinfunction">
+ <h1><span class="secnum" id="sec-9.3.3"><a href="#sec-createbuiltinfunction" title="link to this section">9.3.3</a></span>
+ CreateBuiltinFunction(realm, steps, prototype, internalSlotsList)</h1>
+
+ <p>The abstract operation CreateBuiltinFunction takes arguments <span style="font-family: Times New Roman"><i>realm</i>,
+ <i>prototype</i>,</span> and <var>steps</var>. The optional argument <var>internalSlotsList</var> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of the names of additional internal slots that must be defined as
+ part of the object. If the list is not provided, an empty <a href="#sec-list-and-record-specification-type">List</a> is
+ used. CreateBuiltinFunction returns a built-in function object created by the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>realm</i> is a <a href="#sec-code-realms">Realm</a> Record.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>steps</i> is either a set of algorithm steps or other definition
+ of a functions behaviour provided in this specification.</li>
+ <li>Let <i>func</i> be a new built-in function object that when called performs the action described by <i>steps</i>. The
+ new function object has internal slots whose names are the elements of <i>internalSlotsList</i>. The initial value of
+ each of those internal slots is <b>undefined<i>.</i></b></li>
+ <li>Set the [[Realm]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>func</i> to
+ <i>realm</i>.</li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>func</i> to
+ <i>prototype</i>.</li>
+ <li>Return <i>func</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-built-in-exotic-object-internal-methods-and-slots">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4"><a href="#sec-built-in-exotic-object-internal-methods-and-slots"
+ title="link to this section">9.4</a></span> Built-in Exotic Object Internal Methods and Slots</h1>
+
+ <p>This specification defines several kinds of built-in exotic objects. These objects generally behave similar to ordinary
+ objects except for a few specific situations. The following exotic objects use the ordinary object internal methods except
+ where it is explicitly specified otherwise below:</p>
+ </div>
+
+ <section id="sec-bound-function-exotic-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.1"><a href="#sec-bound-function-exotic-objects"
+ title="link to this section">9.4.1</a></span> Bound Function Exotic Objects</h1>
+
+ <p>A <i>bound function</i> is an exotic object that wraps another function object. A bound function is callable (it has a
+ [[Call]] internal method and may have a [[Construct]] internal method). Calling a bound function generally results in a
+ call of its wrapped function.</p>
+
+ <p>Bound function objects do not have the internal slots of ECMAScript function objects defined in <a
+ href="#table-27">Table 27</a>. Instead they have the internal slots defined in <a href="#table-28">Table 28</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-28">Table 28</span> — Internal Slots of Exotic Bound Function Objects</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[BoundTargetFunction]]</td>
+ <td>Callable Object</td>
+ <td>The wrapped function object.</td>
+ </tr>
+ <tr>
+ <td>[[BoundThis]]</td>
+ <td>Any</td>
+ <td>The value that is always passed as the <b>this</b> value when calling the wrapped function.</td>
+ </tr>
+ <tr>
+ <td>[[BoundArguments]]</td>
+ <td><a href="#sec-list-and-record-specification-type">List</a> of Any</td>
+ <td>A list of values whose elements are used as the first arguments to any call to the wrapped function.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>Unlike ECMAScript function objects, bound function objects do not use an alternative definition of the
+ [[GetOwnProperty]] internal methods. Bound function objects provide all of the essential internal methods as specified in
+ <a href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>. However, they use the following definitions
+ for the essential internal methods of function objects.</p>
+ </div>
+
+ <section id="sec-bound-function-exotic-objects-call-thisargument-argumentslist">
+ <h1><span class="secnum" id="sec-9.4.1.1"><a href="#sec-bound-function-exotic-objects-call-thisargument-argumentslist"
+ title="link to this section">9.4.1.1</a></span> [[Call]] ( thisArgument, argumentsList)</h1>
+
+ <p>When the [[Call]] internal method of an exotic <a href="#sec-bound-function-exotic-objects">bound function</a> object,
+ <var>F</var>, which was created using the bind function is called with parameters <var>thisArgument</var> and
+ <var>argumentsList</var>, a <a href="#sec-list-and-record-specification-type">List</a> of <a
+ href="#sec-ecmascript-language-types">ECMAScript language values</a>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>target</i> be the value of <i>F’s</i> <a
+ href="#sec-bound-function-exotic-objects">[[BoundTargetFunction]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>boundThis</i> be the value of <i>F’s</i> <a href="#sec-bound-function-exotic-objects">[[BoundThis]]</a>
+ <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>boundArgs</i> be the value of <i>F’s</i> <a
+ href="#sec-bound-function-exotic-objects">[[BoundArguments]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>args</i> be a new list containing the same values as the list <i>boundArgs</i> in the same order followed by
+ the same values as the list <i>argumentsList</i> in the same order.</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>target</i>, <i>boundThis</i>, <i>args</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-bound-function-exotic-objects-construct-argumentslist-newtarget">
+ <h1><span class="secnum" id="sec-9.4.1.2"><a href="#sec-bound-function-exotic-objects-construct-argumentslist-newtarget"
+ title="link to this section">9.4.1.2</a></span> [[Construct]] (argumentsList, newTarget)</h1>
+
+ <p>When the [[Construct]] internal method of an exotic <a href="#sec-bound-function-exotic-objects">bound function</a>
+ object, <var>F</var> that was created using the bind function is called with a list of arguments <span style="font-family:
+ Times New Roman"><i>argumentsList</i> and <i>newTarget</i></span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>target</i> be the value of <i>F’s</i> <a
+ href="#sec-bound-function-exotic-objects">[[BoundTargetFunction]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>target</i> has a [[Construct]] internal method.</li>
+ <li>Let <i>boundArgs</i> be the value of <i>F’s</i> <a
+ href="#sec-bound-function-exotic-objects">[[BoundArguments]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>args</i> be a new list containing the same values as the list <i>boundArgs</i> in the same order followed by
+ the same values as the list <i>argumentsList</i> in the same order.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>F</i>, <i>newTarget</i>) is <b>true</b>, let <i>newTarget</i> be
+ <i>target</i>.</li>
+ <li>Return <a href="#sec-construct">Construct</a>(<i>target</i>, <i>args</i>, <i>newTarget</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-boundfunctioncreate">
+ <h1><span class="secnum" id="sec-9.4.1.3"><a href="#sec-boundfunctioncreate"
+ title="link to this section">9.4.1.3</a></span> BoundFunctionCreate (targetFunction, boundThis, boundArgs)</h1>
+
+ <p>The abstract operation BoundFunctionCreate with arguments <var>targetFunction</var>, <var>boundThis</var> and
+ <var>boundArgs</var> is used to specify the creation of new <a href="#sec-bound-function-exotic-objects">Bound
+ Function</a> exotic objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>targetFunction</i>) is Object.</li>
+ <li>Let <i>proto</i> be <i>targetFunction</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>Let <i>obj</i> be a newly created object.</li>
+ <li>Set <i>obj</i>’s essential internal methods to the default ordinary object definitions specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</li>
+ <li>Set the [[Call]] internal method of <i>obj</i> as described in <a
+ href="#sec-bound-function-exotic-objects-call-thisargument-argumentslist">9.4.1.1</a>.</li>
+ <li>If <i>targetFunction</i> has a [[Construct]] internal method, then
+ <ol class="block">
+ <li>Set the [[Construct]] internal method of <i>obj</i> as described in <a
+ href="#sec-bound-function-exotic-objects-construct-argumentslist-newtarget">9.4.1.2</a>.</li>
+ </ol>
+ </li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to
+ <i>proto</i>.</li>
+ <li>Set the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to
+ <b>true</b>.</li>
+ <li>Set the <a href="#sec-bound-function-exotic-objects">[[BoundTargetFunction]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to
+ <i>targetFunction</i>.</li>
+ <li>Set the <a href="#sec-bound-function-exotic-objects">[[BoundThis]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to the value of
+ <i>boundThis</i>.</li>
+ <li>Set the <a href="#sec-bound-function-exotic-objects">[[BoundArguments]]</a> <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to <i>boundArgs</i>.</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-array-exotic-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.2"><a href="#sec-array-exotic-objects" title="link to this section">9.4.2</a></span>
+ Array Exotic Objects</h1>
+
+ <p>An <i>Array object</i> is an exotic object that gives special treatment to array index property keys (<a
+ href="#sec-object-type">see 6.1.7</a>). A property whose property name is an array index is also called an <i>element</i>.
+ Every Array object has a <code>length</code> property whose value is always a nonnegative integer less than <span
+ style="font-family: Times New Roman">2<sup>32</sup></span>. The value of the <code>length</code> property is numerically
+ greater than the name of every own property whose name is an array index; whenever an own property of an Array object is
+ created or changed, other properties are adjusted as necessary to maintain this invariant. Specifically, whenever an own
+ property is added whose name is an array index, the value of the <code>length</code> property is changed, if necessary, to
+ be one more than the numeric value of that array index; and whenever the value of the <code>length</code> property is
+ changed, every own property whose name is an array index whose value is not smaller than the new length is deleted. This
+ constraint applies only to own properties of an Array object and is unaffected by <code>length</code> or array index
+ properties that may be inherited from its prototypes.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A String property name <i>P</i> is an <i>array index</i> if and only if <a
+ href="#sec-tostring">ToString</a>(<a href="#sec-touint32">ToUint32</a>(<i>P</i>)) is equal to <i>P</i> and <a
+ href="#sec-touint32">ToUint32</a>(<i>P</i>) is not equal to 2<sup>32</sup>−1.</p>
+ </div>
+
+ <p>Array exotic objects always have a non-configurable property named <b>"<code>length</code>"</b>.</p>
+
+ <p>Array exotic objects provide an alternative definition for the [[DefineOwnProperty]] internal method. Except for that
+ internal method, Array exotic objects provide all of the other essential internal methods as specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</p>
+ </div>
+
+ <section id="sec-array-exotic-objects-defineownproperty-p-desc">
+ <h1><span class="secnum" id="sec-9.4.2.1"><a href="#sec-array-exotic-objects-defineownproperty-p-desc"
+ title="link to this section">9.4.2.1</a></span> [[DefineOwnProperty]] ( P, Desc)</h1>
+
+ <p>When the [[DefineOwnProperty]] internal method of an <a href="#sec-array-exotic-objects">Array exotic object</a>
+ <var>A</var> is called with <a href="#sec-object-type">property key</a> <var>P</var>, and <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span> the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>If <i>P</i> is <code>"length"</code>, then
+ <ol class="block">
+ <li>Return <a href="#sec-arraysetlength">ArraySetLength</a>(<i>A</i>, <i>Desc</i>).</li>
+ </ol>
+ </li>
+ <li>Else if <i>P</i> is an array index, then
+ <ol class="block">
+ <li>Let <i>oldLenDesc</i> be <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>A</i>,
+ <code>"length"</code>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>oldLenDesc</i> will never be <b>undefined</b> or an accessor
+ descriptor because Array objects are created with a length data property that cannot be deleted or
+ reconfigured.</li>
+ <li>Let <i>oldLen</i> be <i>oldLenDesc</i>.[[Value]].</li>
+ <li>Let <i>index</i> be <a href="#sec-touint32">ToUint32</a>(<i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>index</i> will never be an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>index</i> ≥ <i>oldLen</i> and <i>oldLenDesc</i>.[[Writable]] is <b>false</b>, return <b>false</b>.</li>
+ <li>Let <i>succeeded</i> be <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>,
+ <i>P</i>, <i>Desc</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>succeeded</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>succeeded</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>If <i>index</i> ≥ <i>oldLen</i>
+ <ol class="block">
+ <li>Set <i>oldLenDesc</i>.[[Value]] to <i>index</i> + 1.</li>
+ <li>Let <i>succeeded</i> be <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>,
+ <b>"<code>length</code>"</b>, <i>oldLenDesc</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>succeeded</i> is <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>, <i>P</i>, <i>Desc</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-arraycreate">
+ <h1><span class="secnum" id="sec-9.4.2.2"><a href="#sec-arraycreate" title="link to this section">9.4.2.2</a></span>
+ ArrayCreate(length, proto)</h1>
+
+ <p>The abstract operation ArrayCreate with argument <var>length</var> (a positive integer) and optional argument
+ <var>proto</var> is used to specify the creation of new Array exotic objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>length</i> is an integer Number ≥ 0.</li>
+ <li>If <i>length</i> is −0, let <i>length</i> be +0.</li>
+ <li>If <i>length</i>>2<sup>32</sup>-1, throw a <b>RangeError</b> exception.</li>
+ <li>If the <i>proto</i> argument was not passed, let <i>proto</i> be the intrinsic object <span style="font-family:
+ sans-serif">%ArrayPrototype%</span>.</li>
+ <li>Let <i>A</i> be a newly created <a href="#sec-array-exotic-objects">Array exotic object</a>.</li>
+ <li>Set <i>A</i>’s essential internal methods except for [[DefineOwnProperty]] to the default ordinary object
+ definitions specified in <a href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</li>
+ <li>Set the [[DefineOwnProperty]] internal method of <i>A</i> as specified in <a
+ href="#sec-array-exotic-objects-defineownproperty-p-desc">9.4.2.1</a>.</li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>A</i> to
+ <i>proto</i>.</li>
+ <li>Set the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>A</i> to
+ <b>true</b>.</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a> with arguments
+ <i>A</i>, <code>"length"</code> and PropertyDescriptor{[[Value]]: <i>length</i>, [[Writable]]: <b>true</b>,
+ [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b>}.</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrayspeciescreate">
+ <h1><span class="secnum" id="sec-9.4.2.3"><a href="#sec-arrayspeciescreate"
+ title="link to this section">9.4.2.3</a></span> ArraySpeciesCreate(originalArray, length)</h1>
+
+ <p>The abstract operation ArraySpeciesCreate with arguments <var>originalArray</var> and <var>length</var> is used to
+ specify the creation of a new Array object using a constructor function that is derived from <var>originalArray</var>. It
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>length</i> is an integer Number ≥ 0.</li>
+ <li>If <i>length</i> is −0, let <i>length</i> be +0.</li>
+ <li>Let <i>C</i> be <b>undefined</b>.</li>
+ <li>Let <i>isArray</i> be <a href="#sec-isarray">IsArray</a>(<i>originalArray</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isArray</i>).</li>
+ <li>If <i>isArray</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>C</i> be <a href="#sec-get-o-p">Get</a>(<i>originalArray</i>, <code>"constructor"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>thisRealm</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-code-realms">Realm</a>.</li>
+ <li>Let <i>realmC</i> be <a href="#sec-getfunctionrealm">GetFunctionRealm</a>(<i>C</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>realmC</i>).</li>
+ <li>If <i>thisRealm</i> and <i>realmC</i> are not the same <a href="#sec-code-realms">Realm</a> Record, then
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>C</i>, <i>realmC</i>.[[intrinsics]].[[%Array%]]) is
+ <b>true</b>, let <i>C</i> be <b>undefined</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(C) is Object, then
+ <ol class="block">
+ <li>Let <i>C</i> be <a href="#sec-get-o-p">Get</a>(<i>C</i>, @@species).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>If <i>C</i> is <b>null</b>, let <i>C</i> be <b>undefined</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>C</i> is <b>undefined</b>, return <a href="#sec-arraycreate">ArrayCreate</a>(<i>length</i>).</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception<i>.</i></li>
+ <li>Return <a href="#sec-construct">Construct</a>(<i>C</i>, «<i>length</i>»).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>originalArray</i> was created using the standard built-in Array constructor for a
+ <a href="#sec-code-realms">Realm</a> that is not the <a href="#sec-code-realms">Realm</a> of <a
+ href="#sec-execution-contexts">the running execution context</a>, then a new Array is created using the <a
+ href="#sec-code-realms">Realm</a> of <a href="#sec-execution-contexts">the running execution context</a>. This maintains
+ compatibility with Web browsers that have historically had that behaviour for the Array.prototype methods that now are
+ defined using ArraySpeciesCreate.</p>
+ </div>
+ </section>
+
+ <section id="sec-arraysetlength">
+ <h1><span class="secnum" id="sec-9.4.2.4"><a href="#sec-arraysetlength" title="link to this section">9.4.2.4</a></span>
+ ArraySetLength(A, Desc)</h1>
+
+ <p>When the abstract operation ArraySetLength is called with an <a href="#sec-array-exotic-objects">Array exotic
+ object</a> <span style="font-family: Times New Roman"><i>A</i>,</span> and <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> <span class="nt">Desc</span> the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>If the [[Value]] field of <i>Desc</i> is absent, then
+ <ol class="block">
+ <li>Return <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>,
+ <b>"<code>length</code>"</b>, <i>Desc</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>newLenDesc</i> be a copy of <i>Desc</i>.</li>
+ <li>Let <i>newLen</i> be <a href="#sec-touint32">ToUint32</a>(<i>Desc</i>.[[Value]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>newLen</i>).</li>
+ <li>Let <i>numberLen</i> be <a href="#sec-tonumber">ToNumber</a>(<i>Desc</i>.[[Value]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>newLen</i>).</li>
+ <li>If <i>newLen</i> ≠ <i>numberLen</i>, throw a <b>RangeError</b> exception.</li>
+ <li>Set <i>newLenDesc</i>.[[Value]] to <i>newLen</i>.</li>
+ <li>Let <i>oldLenDesc</i> be <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>A</i>,
+ <code>"length"</code>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>oldLenDesc</i> will never be <b>undefined</b> or an accessor
+ descriptor because Array objects are created with a length data property that cannot be deleted or
+ reconfigured.</li>
+ <li>Let <i>oldLen</i> be <i>oldLenDesc</i>.[[Value]].</li>
+ <li>If <i>newLen</i> ≥<i>oldLen</i>, then
+ <ol class="block">
+ <li>Return <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>,
+ <b>"<code>length</code>"</b>, <i>newLenDesc</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>oldLenDesc</i>.[[Writable]] is <b>false</b>, return <b>false</b>.</li>
+ <li>If <i>newLenDesc</i>.[[Writable]] is absent or has the value <b>true</b>, let <i>newWritable</i> be
+ <b>true</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Need to defer setting the [[Writable]] attribute to <b>false</b> in case any elements cannot be deleted.</li>
+ <li>Let <i>newWritable</i> be <b>false</b>.</li>
+ <li>Set <i>newLenDesc</i>.[[Writable]] to <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>succeeded</i> be <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>,
+ <b>"<code>length</code>"</b>, <i>newLenDesc</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>:<i>succeeded</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>succeeded</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>While <i>newLen</i> < <i>oldLen</i> repeat,
+ <ol class="block">
+ <li>Set <i>oldLen</i> to <i>oldLen</i> – 1.</li>
+ <li>Let <i>deleteSucceeded</i> be <i>A</i>.[[Delete]](<a href="#sec-tostring">ToString</a>(<i>oldLen</i>)).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>deleteSucceeded</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>deleteSucceeded</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Set <i>newLenDesc</i>.[[Value]] to <i>oldLen+1</i>.</li>
+ <li>If <i>newWritable</i> is <b>false</b>, set <i>newLenDesc</i>.[[Writable]] to <b>false</b>.</li>
+ <li>Let <i>succeeded</i> be <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>,
+ <b>"<code>length</code>"</b>, <i>newLenDesc</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>:<i>succeeded</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>newWritable</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>A</i>,
+ <b>"<code>length</code>"</b>, PropertyDescriptor{[[Writable]]: <b>false</b>}). This call will always return
+ <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In steps 3 and 4, if <i>Desc</i>.[[Value]] is an object then its <code>valueOf</code>
+ method is called twice. This is legacy behaviour that was specified with this effect starting with the 2<sup>nd</sup>
+ Edition of this specification.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-string-exotic-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.3"><a href="#sec-string-exotic-objects" title="link to this section">9.4.3</a></span>
+ String Exotic Objects</h1>
+
+ <p>A <i>String object</i> is an exotic object that encapsulates a String value and exposes virtual integer indexed data
+ properties corresponding to the individual code unit elements of the string value. Exotic String objects always have a
+ data property named <b>"<code>length</code>"</b> whose value is the number of code unit elements in the encapsulated
+ String value. Both the code unit data properties and the <b>"<code>length</code>"</b> property are non-writable and
+ non-configurable.</p>
+
+ <p>Exotic String objects have the same internal slots as ordinary objects. They also have a [[StringData]] internal
+ slot.</p>
+
+ <p>Exotic String objects provide alternative definitions for the following internal methods. All of the other exotic
+ String object essential internal methods that are not defined below are as specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</p>
+ </div>
+
+ <section id="sec-string-exotic-objects-getownproperty-p">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.3.1"><a href="#sec-string-exotic-objects-getownproperty-p"
+ title="link to this section">9.4.3.1</a></span> [[GetOwnProperty]] ( P )</h1>
+
+ <p>When the [[GetOwnProperty]] internal method of an exotic String object <var>S</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>desc</i> be <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>S</i>, <i>P</i>).</li>
+ <li>If <i>desc</i> is not <b>undefined</b> return <i>desc</i>.</li>
+ <li>Return <a href="#sec-stringgetindexproperty">StringGetIndexProperty</a>(<i>S</i>, <i>P</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-stringgetindexproperty">
+ <h1><span class="secnum" id="sec-9.4.3.1.1"><a href="#sec-stringgetindexproperty"
+ title="link to this section">9.4.3.1.1</a></span> StringGetIndexProperty (S, P)</h1>
+
+ <p>When the abstract operation StringGetIndexProperty is called with an exotic String object <var>S</var> and with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is not String, return <b>undefined</b>.</li>
+ <li>Let <i>index</i> be <a href="#sec-canonicalnumericindexstring">CanonicalNumericIndexString</a> (<i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>index</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>index</i> is <b>undefined</b>, return <b>undefined</b>.</li>
+ <li>If <a href="#sec-isinteger">IsInteger</a>(<i>index</i>) is <b>false</b>, return <b>undefined</b>.</li>
+ <li>If <i>index</i> = −0, return <b>undefined</b>.</li>
+ <li>Let <i>str</i> be the String value of the [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>S</i>.</li>
+ <li>Let <i>len</i> be the number of elements in <i>str</i>.</li>
+ <li>If <i>index</i> < 0 or <i>len</i> ≤ <i>index</i>, return <b>undefined</b>.</li>
+ <li>Let <i>resultStr</i> be a String value of length 1, containing one code unit from <i>str</i>, specifically the
+ code unit at index <i>index</i>.</li>
+ <li>Return a PropertyDescriptor{ [[Value]]: <i>resultStr</i>, [[Enumerable]]: <b>true</b>, [[Writable]]: <b>false</b>,
+ [[Configurable]]: <b>false</b> }.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-string-exotic-objects-hasproperty-p">
+ <h1><span class="secnum" id="sec-9.4.3.2"><a href="#sec-string-exotic-objects-hasproperty-p"
+ title="link to this section">9.4.3.2</a></span> [[HasProperty]](P)</h1>
+
+ <p>When the [[HasProperty]] internal method of an exotic String object <var>S</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>hasOrdinary</i> be <a href="#sec-ordinaryhasproperty">OrdinaryHasProperty</a>(<i>S</i>, <i>P</i>).</li>
+ <li>If <i>hasOrdinary</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Let <i>desc</i> be <a href="#sec-stringgetindexproperty">StringGetIndexProperty</a>(<i>S</i>, <i>P</i>).</li>
+ <li>If <i>desc</i> is <b>undefined</b>, return <b>false</b>; otherwise, return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-string-exotic-objects-enumerate">
+ <h1><span class="secnum" id="sec-9.4.3.3"><a href="#sec-string-exotic-objects-enumerate"
+ title="link to this section">9.4.3.3</a></span> [[Enumerate]] ()</h1>
+
+ <p>When the [[Enumerate]] internal method of an exotic String object <var>O</var> is called the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>indexKeys</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>str</i> be the String value of the [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>len</i> be the number of elements in <i>str</i>.</li>
+ <li>For each integer <i>i</i> starting with 0 such that <i>i</i> < <i>len</i>, in ascending order,
+ <ol class="block">
+ <li>Add <a href="#sec-tostring">ToString</a>(<i>i</i>) as the last element of <i>indexKeys</i></li>
+ </ol>
+ </li>
+ <li>Let <i>ordinary</i> be the result of calling the default ordinary object [[Enumerate]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-enumerate">9.1.11</a>) on <i>O</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ordinary</i>).</li>
+ <li>Return <a href="#sec-createcompounditerator">CreateCompoundIterator</a>(<a
+ href="#sec-createlistiterator">CreateListIterator</a>(<i>indexKeys</i>), <i>ordinary</i>)<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-string-exotic-objects-ownpropertykeys">
+ <h1><span class="secnum" id="sec-9.4.3.4"><a href="#sec-string-exotic-objects-ownpropertykeys"
+ title="link to this section">9.4.3.4</a></span> [[OwnPropertyKeys]] ( )</h1>
+
+ <p>When the [[OwnPropertyKeys]] internal method of a <a href="#sec-string-exotic-objects">String exotic object</a>
+ <var>O</var> is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>keys</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>str</i> be the String value of the [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>len</i> be the number of elements in <i>str</i>.</li>
+ <li>For each integer <i>i</i> starting with 0 such that <i>i</i> < <i>len</i>, in ascending order,
+ <ol class="block">
+ <li>Add <a href="#sec-tostring">ToString</a>(<i>i</i>) as the last element of <i>keys</i></li>
+ </ol>
+ </li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> such that <i>P</i> is an integer index
+ and <a href="#sec-tointeger">ToInteger</a>(<i>P</i>) ≥ <i>len</i>, in ascending numeric index order,
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> such that <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is String and <i>P</i> is not an integer index, in
+ property creation order,
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> such that <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is Symbol, in property creation order,
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>keys</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-stringcreate">
+ <h1><span class="secnum" id="sec-9.4.3.5"><a href="#sec-stringcreate" title="link to this section">9.4.3.5</a></span>
+ StringCreate( value, prototype)</h1>
+
+ <p>The abstract operation StringCreate with arguments <var>value</var> and <var>prototype</var> is used to specify the
+ creation of new exotic String objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>prototype</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is String.</li>
+ <li>Let <i>S</i> be a newly created <a href="#sec-string-exotic-objects">String exotic object</a>.</li>
+ <li>Set the [[StringData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>S</i> to
+ <i>value</i>.</li>
+ <li>Set <i>S</i>’s essential internal methods to the default ordinary object definitions specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</li>
+ <li>Set the [[GetOwnProperty]] internal method of <i>S</i> as specified in <a
+ href="#sec-string-exotic-objects-getownproperty-p">9.4.3.1</a>.</li>
+ <li>Set the [[HasProperty]] internal method of <i>S</i> as specified in <a
+ href="#sec-string-exotic-objects-hasproperty-p">9.4.3.2</a>.</li>
+ <li>Set the [[Enumerate]] internal method of <i>S</i> as specified in <a
+ href="#sec-string-exotic-objects-enumerate">9.4.3.3</a></li>
+ <li>Set the [[OwnPropertyKeys]] internal method of <i>S</i> as specified in <a
+ href="#sec-string-exotic-objects-ownpropertykeys">9.4.3.4</a>.</li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>S</i> to
+ <i>prototype</i>.</li>
+ <li>Set the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>S</i> to
+ <b>true</b>.</li>
+ <li>Let <i>length</i> be the number of code unit elements in <i>value.</i></li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>S</i>, <code>"length"</code>,
+ PropertyDescriptor{[[Value]]: <i>length</i>, [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>false</b> }).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>S</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-arguments-exotic-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.4"><a href="#sec-arguments-exotic-objects"
+ title="link to this section">9.4.4</a></span> Arguments Exotic Objects</h1>
+
+ <p>Most ECMAScript functions make an arguments objects available to their code. Depending upon the characteristics of the
+ function definition, its argument object is either an ordinary object or an <i>arguments exotic object</i>. An arguments
+ exotic object is an exotic object whose array index properties map to the formal parameters bindings of an invocation of
+ its associated ECMAScript function.</p>
+
+ <p>Arguments exotic objects have the same internal slots as ordinary objects. They also have a [[ParameterMap]] internal
+ slot. Ordinary arguments objects also have a [[ParameterMap]] internal slot whose value is always undefined. For ordinary
+ argument objects the [[ParameterMap]] internal slot is only used by <code><a
+ href="#sec-object.prototype.tostring">Object.prototype.toString</a></code> (<a
+ href="#sec-object.prototype.tostring">19.1.3.6</a>) to identify them as such.</p>
+
+ <p>Arguments exotic objects provide alternative definitions for the following internal methods. All of the other exotic
+ arguments object essential internal methods that are not defined below are as specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a></p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> For non-strict mode functions the integer indexed data properties of an arguments
+ object whose numeric name values are less than the number of formal parameters of the corresponding function object
+ initially share their values with the corresponding argument bindings in the function’s <a
+ href="#sec-execution-contexts">execution context</a>. This means that changing the property changes the corresponding
+ value of the argument binding and vice-versa. This correspondence is broken if such a property is deleted and then
+ redefined or if the property is changed into an accessor property. For strict mode functions, the values of the
+ arguments object’s properties are simply a copy of the arguments passed to the function and there is no dynamic
+ linkage between the property values and the formal parameter values.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The ParameterMap object and its property values are used as a device for specifying
+ the arguments object correspondence to argument bindings. The ParameterMap object and the objects that are the values of
+ its properties are not directly observable from ECMAScript code. An ECMAScript implementation does not need to actually
+ create or use such objects to implement the specified semantics.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> Arguments objects for strict mode functions define non-configurable accessor
+ properties named "<code>caller</code>" and "<code>callee</code>" which throw a <b>TypeError</b> exception on access. The
+ "<code>callee</code>" property has a more specific meaning for non-strict mode functions and a "<code>caller</code>"
+ property has historically been provided as an implementation-defined extension by some ECMAScript implementations. The
+ strict mode definition of these properties exists to ensure that neither of them is defined in any other manner by
+ conforming ECMAScript implementations.</p>
+ </div>
+ </div>
+
+ <section id="sec-arguments-exotic-objects-getownproperty-p">
+ <h1><span class="secnum" id="sec-9.4.4.1"><a href="#sec-arguments-exotic-objects-getownproperty-p"
+ title="link to this section">9.4.4.1</a></span> [[GetOwnProperty]] (P)</h1>
+
+ <p>The [[GetOwnProperty]] internal method of an arguments exotic object when called with a <a
+ href="#sec-object-type">property key</a> <var>P</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>args</i> be the arguments object.</li>
+ <li>Let <i>desc</i> be <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>args</i>, <i>P</i>).</li>
+ <li>If <i>desc</i> is <b>undefined</b>, return <i>desc</i>.</li>
+ <li>Let <i>map</i> be the value of the [[ParameterMap]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the arguments object.</li>
+ <li>Let <i>isMapped</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>map</i>, <i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>isMapped</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If the value of <i>isMapped</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>desc</i>.[[Value]] to <a href="#sec-get-o-p">Get</a>(<i>map</i>, <i>P</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>desc</i>) is <b>true</b> and <i>P</i> is
+ <code>"caller"</code> and <i>desc</i>.[[Value]] is a strict mode Function object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>desc</i>.</li>
+ </ol>
+
+ <p>If an implementation does not provide a built-in <code>caller</code> property for argument exotic objects then step 8
+ of this algorithm is must be skipped.</p>
+ </section>
+
+ <section id="sec-arguments-exotic-objects-defineownproperty-p-desc">
+ <h1><span class="secnum" id="sec-9.4.4.2"><a href="#sec-arguments-exotic-objects-defineownproperty-p-desc"
+ title="link to this section">9.4.4.2</a></span> [[DefineOwnProperty]] (P, Desc)</h1>
+
+ <p>The [[DefineOwnProperty]] internal method of an arguments exotic object when called with a <a
+ href="#sec-object-type">property key</a> <var>P</var> and <a href="#sec-property-descriptor-specification-type">Property
+ Descriptor</a> <span class="nt">Desc</span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>args</i> be the arguments object.</li>
+ <li>Let <i>map</i> be the value of the [[ParameterMap]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the arguments object.</li>
+ <li>Let <i>isMapped</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>map</i>, <i>P</i>).</li>
+ <li>Let <i>allowed</i> be <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>args</i>, <i>P</i>,
+ <i>Desc</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>allowed</i>).</li>
+ <li>If <i>allowed</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>If the value of <i>isMapped</i> is <b>true</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>Desc</i>) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> the [[Delete]] internal method of <i>map</i> passing <i>P</i> as the
+ argument.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>If <i>Desc</i>.[[Value]] is present, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>map</i>, <i>P</i>,
+ <i>Desc</i>.[[Value]], <b>false</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>setStatus</i> is <b>true</b> because formal
+ parameters mapped by argument objects are always writable.</li>
+ </ol>
+ </li>
+ <li>If <i>Desc</i>.[[Writable]] is present and its value is <b>false</b>, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> the [[Delete]] internal method of <i>map</i> passing <i>P</i> as the
+ argument.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arguments-exotic-objects-get-p-receiver">
+ <h1><span class="secnum" id="sec-9.4.4.3"><a href="#sec-arguments-exotic-objects-get-p-receiver"
+ title="link to this section">9.4.4.3</a></span> [[Get]] (P, Receiver)</h1>
+
+ <p>The [[Get]] internal method of an arguments exotic object when called with a <a href="#sec-object-type">property
+ key</a> <var>P</var> and <a href="#sec-ecmascript-language-types">ECMAScript language value</a> <span
+ class="nt">Receiver</span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>args</i> be the arguments object.</li>
+ <li>Let <i>map</i> be the value of the [[ParameterMap]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the arguments object.</li>
+ <li>Let <i>isMapped</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>map</i>, <i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>isMapped</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If the value of <i>isMapped</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>v</i> be the result of calling the default ordinary object [[Get]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver">9.1.8</a>) on <i>args</i> passing
+ <i>P</i> and <i>Receiver</i> as the arguments.</li>
+ </ol>
+ </li>
+ <li>Else <i>map</i> contains a formal parameter mapping for <i>P</i>,
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-get-o-p">Get</a>(<i>map</i>, <i>P</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arguments-exotic-objects-set-p-v-receiver">
+ <h1><span class="secnum" id="sec-9.4.4.4"><a href="#sec-arguments-exotic-objects-set-p-v-receiver"
+ title="link to this section">9.4.4.4</a></span> [[Set]] ( P, V, Receiver)</h1>
+
+ <p>The [[Set]] internal method of an arguments exotic object when called with <a href="#sec-object-type">property key</a>
+ <var>P</var>, value <var>V</var>, and <a href="#sec-ecmascript-language-types">ECMAScript language value</a> <span
+ class="nt">Receiver</span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>args</i> be the arguments object.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>args</i>, <i>Receiver</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>isMapped</i> be <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>map</i> be the value of the [[ParameterMap]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the arguments object.</li>
+ <li>Let <i>isMapped</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>map</i>, <i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>isMapped</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>If the value of <i>isMapped</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return the result of calling the default ordinary object [[Set]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-set-p-v-receiver">9.1.9</a>) on <i>args</i>
+ passing <i>P</i>, <i>V</i> and <i>Receiver</i> as the arguments.</li>
+ </ol>
+ </li>
+ <li>Else <i>map</i> contains a formal parameter mapping for <i>P</i>,
+ <ol class="block">
+ <li>Return <a href="#sec-set-o-p-v-throw">Set</a>(<i>map</i>, <i>P</i>, <i>V</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-arguments-exotic-objects-delete-p">
+ <h1><span class="secnum" id="sec-9.4.4.5"><a href="#sec-arguments-exotic-objects-delete-p"
+ title="link to this section">9.4.4.5</a></span> [[Delete]] (P)</h1>
+
+ <p>The [[Delete]] internal method of an arguments exotic object when called with a <a href="#sec-object-type">property
+ key</a> <var>P</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>map</i> be the value of the [[ParameterMap]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the arguments object.</li>
+ <li>Let <i>isMapped</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>map</i>, <i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>isMapped</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Let <i>result</i> be the result of calling the default [[Delete]] internal method for ordinary objects (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-delete-p">9.1.10</a>) on the arguments object passing
+ <i>P</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>If <i>result</i> is <b>true</b> and the value of <i>isMapped</i> is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> the [[Delete]] internal method of <i>map</i> passing <i>P</i> as the argument.</li>
+ </ol>
+ </li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-createunmappedargumentsobject">
+ <h1><span class="secnum" id="sec-9.4.4.6"><a href="#sec-createunmappedargumentsobject"
+ title="link to this section">9.4.4.6</a></span> CreateUnmappedArgumentsObject(argumentsList)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">CreateUnmappedArgumentsObject</span> called with an
+ argument <var>argumentsList</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>len</i> be the number of elements in <i>argumentsList</i>.</li>
+ <li>Let <i>obj</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%ObjectPrototype%,
+ «‍[[ParameterMap]]»).</li>
+ <li>Set <i>obj</i>’s [[ParameterMap]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ to <b>undefined</b>.</li>
+ <li>Perform <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>, <b>"<code>length</code>"</b>,
+ PropertyDescriptor{[[Value]]: <i>len</i>, [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>true</b>}).</li>
+ <li>Let <i>index</i> be 0.</li>
+ <li>Repeat while <i>index</i> < <i>len</i>,
+ <ol class="block">
+ <li>Let <i>val</i> be <i>argumentsList</i>[<i>index</i>].</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>, <a
+ href="#sec-tostring">ToString</a>(<i>index</i>), <i>val</i>).</li>
+ <li>Let <i>index</i> be <i>index</i> + 1</li>
+ </ol>
+ </li>
+ <li>Perform <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>, @@iterator, PropertyDescriptor
+ {[[Value]]:%ArrayProto_values%, [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>true</b>}).</li>
+ <li>Perform <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>, <code>"caller"</code>,
+ PropertyDescriptor {[[Get]]: <a href="#sec-%throwtypeerror%">%ThrowTypeError%</a>, [[Set]]: <a
+ href="#sec-%throwtypeerror%">%ThrowTypeError%</a>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b>}).</li>
+ <li>Perform <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>, <code>"callee"</code>,
+ PropertyDescriptor {[[Get]]: <a href="#sec-%throwtypeerror%">%ThrowTypeError%</a>, [[Set]]: <a
+ href="#sec-%throwtypeerror%">%ThrowTypeError%</a>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: the above property definitions will not produce an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>obj</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-createmappedargumentsobject">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.4.7"><a href="#sec-createmappedargumentsobject"
+ title="link to this section">9.4.4.7</a></span> CreateMappedArgumentsObject ( func, formals, argumentsList, env
+ )</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">CreateMappedArgumentsObject</span> is called with
+ object <var>func</var>, parsed grammar phrase <var>formals</var>, <a
+ href="#sec-list-and-record-specification-type">List</a> <var>argumentsList</var>, and environment record <span
+ style="font-family: Times New Roman"><i>env</i>.</span> The following steps are performed:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>formals</i> does not contain a rest parameter, any binding
+ patterns, or any initializers. It may contain duplicate identifiers.</li>
+ <li>Let <i>len</i> be the number of elements in <i>argumentsList</i>.</li>
+ <li>Let <i>obj</i> be a newly created arguments exotic object with a [[ParameterMap]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Set the [[GetOwnProperty]] internal method of <i>obj</i> as specified in <a
+ href="#sec-arguments-exotic-objects-getownproperty-p">9.4.4.1</a>.</li>
+ <li>Set the [[DefineOwnProperty]] internal method of <i>obj</i> as specified in <a
+ href="#sec-arguments-exotic-objects-defineownproperty-p-desc">9.4.4.2</a>.</li>
+ <li>Set the [[Get]] internal method of <i>obj</i> as specified in <a
+ href="#sec-arguments-exotic-objects-get-p-receiver">9.4.4.3</a>.</li>
+ <li>Set the [[Set]] internal method of <i>obj</i> as specified in <a
+ href="#sec-arguments-exotic-objects-set-p-v-receiver">9.4.4.4</a>.</li>
+ <li>Set the [[Delete]] internal method of <i>obj</i> as specified in <a
+ href="#sec-arguments-exotic-objects-delete-p">9.4.4.5</a>.</li>
+ <li>Set the remainder of <i>obj</i>’s essential internal methods to the default ordinary object definitions
+ specified in <a href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> to
+ %ObjectPrototype%.</li>
+ <li>Set the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i>
+ to <b>true</b>.</li>
+ <li>Let <i>parameterNames</i> be the BoundNames of <i>formals</i>.</li>
+ <li>Let <i>numberOfParameters</i> be the number of elements in <i>parameterNames</i></li>
+ <li>Let <i>index</i> be 0.</li>
+ <li>Repeat while <i>index</i> < <i>len</i> ,
+ <ol class="block">
+ <li>Let <i>val</i> be <i>argumentsList</i>[<i>index</i>].</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>obj</i>, <a
+ href="#sec-tostring">ToString</a>(<i>index</i>), <i>val</i>).</li>
+ <li>Let <i>index</i> be <i>index</i> + 1</li>
+ </ol>
+ </li>
+ <li>Perform <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>, <b>"<code>length</code>"</b>,
+ PropertyDescriptor{[[Value]]: <i>len</i>, [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>true</b>}).</li>
+ <li>Let <i>map</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<b>null</b>).</li>
+ <li>Let <i>mappedNames</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>index</i> be <i>numberOfParameters</i> − 1.</li>
+ <li>Repeat while <i>index</i> ≥ 0 ,
+ <ol class="block">
+ <li>Let <i>name</i> be <i>parameterNames</i>[<i>index</i>].</li>
+ <li>If <i>name</i> is not an element of <i>mappedNames</i>, then
+ <ol class="block">
+ <li>Add <i>name</i> as an element of the list <i>mappedNames</i>.</li>
+ <li>If <i>index</i> < <i>len</i>, then
+ <ol class="block">
+ <li>Let <i>g</i> be <a href="#sec-makearggetter">MakeArgGetter</a>(<i>name</i>, <i>env</i>).</li>
+ <li>Let <i>p</i> be <a href="#sec-makeargsetter">MakeArgSetter</a>(<i>name</i>, <i>env</i>).</li>
+ <li><a href="#sec-call">Call</a> the [[DefineOwnProperty]] internal method of <i>map</i> passing <a
+ href="#sec-tostring">ToString</a>(<i>index</i>) and the PropertyDescriptor{[[Set]]: <i>p</i>, [[Get]]:
+ <i>g,</i> [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>true</b>} as arguments.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>index</i> be <i>index</i> − 1</li>
+ </ol>
+ </li>
+ <li>Set the [[ParameterMap]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i>
+ to <i>map</i>.</li>
+ <li>Perform <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>, @@iterator, PropertyDescriptor
+ {[[Value]]:%ArrayProto_values%, [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>true</b>}).</li>
+ <li>Perform <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>, <code>"callee"</code>,
+ PropertyDescriptor {[[Value]]: <i>func</i>, [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>true</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: the above property definitions will not produce an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>obj</i></li>
+ </ol>
+ </div>
+
+ <section id="sec-makearggetter">
+ <h1><span class="secnum" id="sec-9.4.4.7.1"><a href="#sec-makearggetter"
+ title="link to this section">9.4.4.7.1</a></span> MakeArgGetter ( name, env)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">MakeArgGetter</span> called with String
+ <var>name</var> and environment record <var>env</var> creates a built-in function object that when executed returns the
+ value bound for <var>name</var> in <var>env</var>. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>realm</i> be <a href="#sec-execution-contexts">the current Realm</a>.</li>
+ <li>Let <i>steps</i> be the steps of an ArgGetter function as specified below.</li>
+ <li>Let <i>getter</i> be <a href="#sec-createbuiltinfunction">CreateBuiltinFunction</a>(<i>realm</i>, <i>steps</i>,
+ %FunctionPrototype%, «‍[[name]], [[env]]» ).</li>
+ <li>Set <i>getter’s</i> [[name]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>name</i>.</li>
+ <li>Set <i>getter’s</i> [[env]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>env</i>.</li>
+ <li>Return <i>getter</i>.</li>
+ </ol>
+
+ <p>An ArgGetter function is an anonymous built-in function with [[name]] and [[env]] internal slots. When an ArgGetter
+ function <var>f</var> that expects no arguments is called it performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>name</i> be the value of <i>f’s</i> [[name]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>env</i> be the value of <i>f’s</i> [[env]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a></li>
+ <li>Return <i>env</i>.GetBindingValue(<i>name</i>, <b>false</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> ArgGetter functions are never directly accessible to ECMAScript code.</p>
+ </div>
+ </section>
+
+ <section id="sec-makeargsetter">
+ <h1><span class="secnum" id="sec-9.4.4.7.2"><a href="#sec-makeargsetter"
+ title="link to this section">9.4.4.7.2</a></span> MakeArgSetter ( name, env)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">MakeArgSetter</span> called with String
+ <var>name</var> and environment record <var>env</var> creates a built-in function object that when executed sets the
+ value bound for <var>name</var> in <var>env</var>. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>realm</i> be <a href="#sec-execution-contexts">the current Realm</a>.</li>
+ <li>Let <i>steps</i> be the steps of an ArgSetter function as specified below.</li>
+ <li>Let <i>setter</i> be <a href="#sec-createbuiltinfunction">CreateBuiltinFunction</a>(<i>realm</i>, <i>steps</i>,
+ %FunctionPrototype%, «‍[[name]], [[env]]» ).</li>
+ <li>Set <i>setter’s</i> [[name]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>name</i>.</li>
+ <li>Set <i>setter’s</i> [[env]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>env</i>.</li>
+ <li>Return <i>setter</i>.</li>
+ </ol>
+
+ <p>An ArgSetter function is an anonymous built-in function with [[name]] and [[env]] internal slots. When an ArgSetter
+ function <var>f</var> is called with argument <var>value</var> it performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>name</i> be the value of <i>f’s</i> [[name]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>env</i> be the value of <i>f’s</i> [[env]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a></li>
+ <li>Return <i>env</i>.SetMutableBinding(<i>name</i>, <i>value</i>, <b>false</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> ArgSetter functions are never directly accessible to ECMAScript code.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-integer-indexed-exotic-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.5"><a href="#sec-integer-indexed-exotic-objects"
+ title="link to this section">9.4.5</a></span> Integer Indexed Exotic Objects</h1>
+
+ <p>An <i>Integer Indexed object</i> is an exotic object that performs special handling of integer index property keys.</p>
+
+ <p>Integer Indexed exotic objects have the same internal slots as ordinary objects additionally [[ViewedArrayBuffer]],
+ [[ArrayLength]], [[ByteOffset]], and [[TypedArrayName]] internal slots.</p>
+
+ <p>Integer Indexed Exotic objects provide alternative definitions for the following internal methods. All of the other
+ Integer Indexed exotic object essential internal methods that are not defined below are as specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</p>
+ </div>
+
+ <section id="sec-integer-indexed-exotic-objects-getownproperty-p">
+ <h1><span class="secnum" id="sec-9.4.5.1"><a href="#sec-integer-indexed-exotic-objects-getownproperty-p"
+ title="link to this section">9.4.5.1</a></span> [[GetOwnProperty]] ( P )</h1>
+
+ <p>When the [[GetOwnProperty]] internal method of an Integer Indexed exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an Object that has a [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is String, then
+ <ol class="block">
+ <li>Let <i>numericIndex</i> be <a
+ href="#sec-canonicalnumericindexstring">CanonicalNumericIndexString</a>(<i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numericIndex</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>numericIndex</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-integerindexedelementget">IntegerIndexedElementGet</a> (<i>O</i>,
+ <i>numericIndex</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>If <i>value</i> is <b>undefined</b>, return <b>undefined</b>.</li>
+ <li>Return a PropertyDescriptor{ [[Value]]: <i>value</i>, [[Enumerable]]: <b>true</b>, [[Writable]]:
+ <b>true</b>, [[Configurable]]: <b>false</b> }.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>O</i>, <i>P</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-integer-indexed-exotic-objects-hasproperty-p">
+ <h1><span class="secnum" id="sec-9.4.5.2"><a href="#sec-integer-indexed-exotic-objects-hasproperty-p"
+ title="link to this section">9.4.5.2</a></span> [[HasProperty]](P)</h1>
+
+ <p>When the [[HasProperty]] internal method of an Integer Indexed exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an Object that has a [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is String, then
+ <ol class="block">
+ <li>Let <i>numericIndex</i> be <a
+ href="#sec-canonicalnumericindexstring">CanonicalNumericIndexString</a>(<i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numericIndex</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>numericIndex</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-isinteger">IsInteger</a>(<i>numericIndex</i>) is <b>false</b>, return <b>false</b></li>
+ <li>If <i>numericIndex</i> = −0, return <b>false</b>.</li>
+ <li>If <i>numericIndex</i> < 0, return <b>false</b>.</li>
+ <li>If <i>numericIndex</i> ≥ the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-ordinaryhasproperty">OrdinaryHasProperty</a>(<i>O</i>, <i>P</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-integer-indexed-exotic-objects-defineownproperty-p-desc">
+ <h1><span class="secnum" id="sec-9.4.5.3"><a href="#sec-integer-indexed-exotic-objects-defineownproperty-p-desc"
+ title="link to this section">9.4.5.3</a></span> [[DefineOwnProperty]] ( P, Desc)</h1>
+
+ <p>When the [[DefineOwnProperty]] internal method of an Integer Indexed exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, and <a href="#sec-property-descriptor-specification-type">Property
+ Descriptor</a> <span class="nt">Desc</span> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an Object that has a [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is String, then
+ <ol class="block">
+ <li>Let <i>numericIndex</i> be <a href="#sec-canonicalnumericindexstring">CanonicalNumericIndexString</a>
+ (<i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numericIndex</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>numericIndex</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isinteger">IsInteger</a>(<i>numericIndex</i>) is <b>false</b>, return <b>false</b></li>
+ <li>Let <i>intIndex</i> be <i>numericIndex</i>.</li>
+ <li>If <i>intIndex</i> = −0, return <b>false</b>.</li>
+ <li>If <i>intIndex</i> < 0, return <b>false</b>.</li>
+ <li>Let <i>length</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>intIndex</i> ≥ <i>length</i>, return <b>false</b>.</li>
+ <li>If <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>Desc</i>) is <b>true</b>, return
+ <b>false.</b></li>
+ <li>If <i>Desc</i> has a [[Configurable]] field and if <i>Desc</i>.[[Configurable]] is <b>true</b>, return
+ <b>false<i>.</i></b></li>
+ <li>If <i>Desc</i> has an [[Enumerable]] field and if <i>Desc</i>.[[Enumerable]] is <b>false</b>, return
+ <b>false<i>.</i></b></li>
+ <li>If <i>Desc</i> has a [[Writable]] field and if <i>Desc</i>.[[Writable]] is <b>false</b>, return
+ <b>false</b>.</li>
+ <li>If <i>Desc</i> has a [[Value]] field, then
+ <ol class="block">
+ <li>Let <i>value</i> be <i>Desc</i>.[[Value]].</li>
+ <li>Let <i>status</i> be <a href="#sec-integerindexedelementset">IntegerIndexedElementSet</a> (<i>O</i>,
+ <i>intIndex</i>, <i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-ordinarydefineownproperty">OrdinaryDefineOwnProperty</a>(<i>O</i>, <i>P</i>, <i>Desc</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-integer-indexed-exotic-objects-get-p-receiver">
+ <h1><span class="secnum" id="sec-9.4.5.4"><a href="#sec-integer-indexed-exotic-objects-get-p-receiver"
+ title="link to this section">9.4.5.4</a></span> [[Get]] (P, Receiver)</h1>
+
+ <p>When the [[Get]] internal method of an Integer Indexed exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> and <a href="#sec-ecmascript-language-types">ECMAScript language
+ value</a> <span class="nt">Receiver</span> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is String and if <a
+ href="#sec-samevalue">SameValue</a>(<i>O</i>, <i>Receiver</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>numericIndex</i> be <a href="#sec-canonicalnumericindexstring">CanonicalNumericIndexString</a>
+ (<i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numericIndex</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>numericIndex</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-integerindexedelementget">IntegerIndexedElementGet</a> (<i>O</i>,
+ <i>numericIndex</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return the result of calling the default ordinary object [[Get]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver">9.1.8</a>) on <i>O</i> passing
+ <i>P</i> and <i>Receiver</i> as arguments.</li>
+ </ol>
+ </section>
+
+ <section id="sec-integer-indexed-exotic-objects-set-p-v-receiver">
+ <h1><span class="secnum" id="sec-9.4.5.5"><a href="#sec-integer-indexed-exotic-objects-set-p-v-receiver"
+ title="link to this section">9.4.5.5</a></span> [[Set]] ( P, V, Receiver)</h1>
+
+ <p>When the [[Set]] internal method of an Integer Indexed exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, value <var>V</var>, and <a
+ href="#sec-ecmascript-language-types">ECMAScript language value</a> <span class="nt">Receiver</span>, the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is String and if <a
+ href="#sec-samevalue">SameValue</a>(<i>O</i>, <i>Receiver</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>numericIndex</i> be <a href="#sec-canonicalnumericindexstring">CanonicalNumericIndexString</a>
+ (<i>P</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numericIndex</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>numericIndex</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-integerindexedelementset">IntegerIndexedElementSet</a> (<i>O</i>, <i>numericIndex</i>,
+ <i>V</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return the result of calling the default ordinary object [[Set]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver">9.1.8</a>) on <i>O</i> passing
+ <i>P</i>, <i>V</i>, and <i>Receiver</i> as arguments.</li>
+ </ol>
+ </section>
+
+ <section id="sec-integer-indexed-exotic-objects-enumerate">
+ <h1><span class="secnum" id="sec-9.4.5.6"><a href="#sec-integer-indexed-exotic-objects-enumerate"
+ title="link to this section">9.4.5.6</a></span> [[Enumerate]] ()</h1>
+
+ <p>When the [[Enumerate]] internal method of an Integer Indexed exotic object <var>O</var> is called the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>indexKeys</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an Object that has [[ViewedArrayBuffer]],
+ [[ArrayLength]], [[ByteOffset]], and [[TypedArrayName]] internal slots.</li>
+ <li>Let <i>len</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>For each integer <i>i</i> starting with 0 such that <i>i</i> < <i>len</i>, in ascending order,
+ <ol class="block">
+ <li>Add <a href="#sec-tostring">ToString</a>(<i>i</i>) as the last element of <i>indexKeys</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>ordinary</i> be the result of calling the default ordinary object [[Enumerate]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-enumerate">9.1.11</a>) on <i>O</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ordinary</i>).</li>
+ <li>Return <a href="#sec-createcompounditerator">CreateCompoundIterator</a>(<a
+ href="#sec-createlistiterator">CreateListIterator</a>(<i>indexKeys</i>), <i>ordinary</i>)<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-integer-indexed-exotic-objects-ownpropertykeys">
+ <h1><span class="secnum" id="sec-9.4.5.7"><a href="#sec-integer-indexed-exotic-objects-ownpropertykeys"
+ title="link to this section">9.4.5.7</a></span> [[OwnPropertyKeys]] ()</h1>
+
+ <p>When the [[OwnPropertyKeys]] internal method of an Integer Indexed exotic object <var>O</var> is called the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>keys</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an Object that has [[ViewedArrayBuffer]],
+ [[ArrayLength]], [[ByteOffset]], and [[TypedArrayName]] internal slots.</li>
+ <li>Let <i>len</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>For each integer <i>i</i> starting with 0 such that <i>i</i> < <i>len</i>, in ascending order,
+ <ol class="block">
+ <li>Add <a href="#sec-tostring">ToString</a>(<i>i</i>) as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> such that <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is String and <i>P</i> is not an integer index, in
+ property creation order
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>For each own <a href="#sec-object-type">property key</a> <i>P</i> of <i>O</i> such that <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is Symbol, in property creation order
+ <ol class="block">
+ <li>Add <i>P</i> as the last element of <i>keys</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>keys</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-integerindexedobjectcreate">
+ <h1><span class="secnum" id="sec-9.4.5.8"><a href="#sec-integerindexedobjectcreate"
+ title="link to this section">9.4.5.8</a></span> IntegerIndexedObjectCreate <span style="font-family:
+ sans-serif">(prototype, internalSlotsList)</span></h1>
+
+ <p>The abstract operation IntegerIndexedObjectCreate with arguments <var>prototype</var> and <var>internalSlotsList</var>
+ is used to specify the creation of new Integer Indexed exotic objects. The argument <var>internalSlotsList</var> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of the names of additional internal slots that must be defined as
+ part of the object. IntegerIndexedObjectCreate performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>A</i> be a newly created object with an <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> for each name in <i>internalSlotsList</i>.</li>
+ <li>Set <i>A</i>’s essential internal methods to the default ordinary object definitions specified in <a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots">9.1</a>.</li>
+ <li>Set the [[GetOwnProperty]] internal method of <i>A</i> as specified in <a
+ href="#sec-integer-indexed-exotic-objects-getownproperty-p">9.4.5.1</a>.</li>
+ <li>Set the [[HasProperty]] internal method of <i>A</i> as specified in <a
+ href="#sec-integer-indexed-exotic-objects-hasproperty-p">9.4.5.2</a>.</li>
+ <li>Set the [[DefineOwnProperty]] internal method of <i>A</i> as specified in <a
+ href="#sec-integer-indexed-exotic-objects-defineownproperty-p-desc">9.4.5.3</a>.</li>
+ <li>Set the [[Get]] internal method of <i>A</i> as specified in <a
+ href="#sec-integer-indexed-exotic-objects-get-p-receiver">9.4.5.4</a>.</li>
+ <li>Set the [[Set]] internal method of <i>A</i> as specified in <a
+ href="#sec-integer-indexed-exotic-objects-set-p-v-receiver">9.4.5.5</a>.</li>
+ <li>Set the [[Enumerate]] internal method of <i>A</i> as specified in <a
+ href="#sec-integer-indexed-exotic-objects-enumerate">9.4.5.6</a>.</li>
+ <li>Set the [[OwnPropertyKeys]] internal method of <i>A</i> as specified in <a
+ href="#sec-integer-indexed-exotic-objects-ownpropertykeys">9.4.5.7</a>.</li>
+ <li>Set the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>A</i> to
+ <i>prototype</i>.</li>
+ <li>Set the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>A</i> to
+ <b>true</b>.</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-integerindexedelementget">
+ <h1><span class="secnum" id="sec-9.4.5.9"><a href="#sec-integerindexedelementget"
+ title="link to this section">9.4.5.9</a></span> IntegerIndexedElementGet ( O, index )</h1>
+
+ <p>The abstract operation IntegerIndexedElementGet with arguments <var>O</var> and <var>index</var> performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>index</i>) is Number.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an Object that has [[ViewedArrayBuffer]],
+ [[ArrayLength]], [[ByteOffset]], and [[TypedArrayName]] internal slots.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <a href="#sec-isinteger">IsInteger</a>(<i>index</i>) is <b>false</b>, return <b>undefined</b></li>
+ <li>If <i>index</i> = −0, return <b>undefined</b>.</li>
+ <li>Let <i>length</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>index</i> < 0 or <i>index</i> ≥ <i>length</i>, return <b>undefined</b>.</li>
+ <li>Let <i>offset</i> be the value of <i>O</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>arrayTypeName</i> be the string value of <i>O</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table 49</a>
+ for <i>arrayTypeName</i>.</li>
+ <li>Let <i>indexedPosition</i> = (<i>index</i> × <i>elementSize</i>) + <i>offset</i>.</li>
+ <li>Let <i>elementType</i> be the string value of the Element Type value in<a href="#table-49">Table 49</a> for
+ <i>arrayTypeName</i>.</li>
+ <li>Return <a href="#sec-getvaluefrombuffer">GetValueFromBuffer</a>(<i>buffer</i>, <i>indexedPosition</i>,
+ <i>elementType</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-integerindexedelementset">
+ <h1><span class="secnum" id="sec-9.4.5.10"><a href="#sec-integerindexedelementset"
+ title="link to this section">9.4.5.10</a></span> IntegerIndexedElementSet ( O, index, value )</h1>
+
+ <p>The abstract operation IntegerIndexedElementSet with arguments <var>O</var>, <var>index</var>, and <var>value</var>
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>index</i>) is Number.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> is an Object that has [[ViewedArrayBuffer]],
+ [[ArrayLength]], [[ByteOffset]], and [[TypedArrayName]] internal slots.</li>
+ <li>Let <i>numValue</i> be <a href="#sec-tonumber">ToNumber</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>numValue</i>).</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <a href="#sec-isinteger">IsInteger</a>(<i>index</i>) is <b>false</b>, return <b>false</b></li>
+ <li>If <i>index</i> = −0, return <b>false</b>.</li>
+ <li>Let <i>length</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>index</i> < 0 or <i>index</i> ≥ <i>length</i>, return <b>false</b>.</li>
+ <li>Let <i>offset</i> be the value of <i>O</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>arrayTypeName</i> be the string value of <i>O</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table 49</a>
+ for <i>arrayTypeName</i>.</li>
+ <li>Let <i>indexedPosition</i> = (<i>index</i> × <i>elementSize</i>) + <i>offset</i>.</li>
+ <li>Let <i>elementType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>arrayTypeName</i>.</li>
+ <li>Let <i>status</i> be <a href="#sec-setvalueinbuffer">SetValueInBuffer</a>(<i>buffer</i>, <i>indexedPosition</i>,
+ <i>elementType</i>, <i>numValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.4.6"><a href="#sec-module-namespace-exotic-objects"
+ title="link to this section">9.4.6</a></span> Module Namespace Exotic Objects</h1>
+
+ <p>A <i>module namespace object</i> is an exotic object that exposes the bindings exported from an ECMAScript <span
+ class="nt">Module</span> <var>(See <a href="#sec-exports">15.2.3</a>)</var>. There is a one-to-one correspondence between
+ the String-keyed own properties of a module namespace exotic object and the binding names exported by the <span
+ class="nt">Module</span>. The exported bindings include any bindings that are indirectly exported using <code>export
+ *</code> export items. Each String-valued own <a href="#sec-object-type">property key</a> is the StringValue of the
+ corresponding exported binding name. These are the only String-keyed properties of a module namespace exotic object. Each
+ such property has the attributes {[[Configurable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">true</span>}. Module namespace objects are not extensible.</p>
+
+ <p>Module namespace objects have the internal slots defined in <a href="#table-29">Table 29</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-29">Table 29</span> — Internal Slots of Module Namespace Exotic Objects</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[Module]]</td>
+ <td>Module Record</td>
+ <td>The Module Record whose exports this namespace exposes.</td>
+ </tr>
+ <tr>
+ <td>[[Exports]]</td>
+ <td><a href="#sec-list-and-record-specification-type">List</a> of String</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> containing the String values of the exported names exposed as own properties of this object. The list is ordered as if an Array of those string values had been sorted using <code><a href="#sec-array.prototype.sort">Array.prototype.sort</a></code> using <a href="#sec-sortcompare">SortCompare</a> as <i><span style="font-family: Times New Roman">comparefn</span>.</i></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>Module namespace exotic objects provide alternative definitions for all of the internal methods.</p>
+ </div>
+
+ <section id="sec-module-namespace-exotic-objects-getprototypeof">
+ <h1><span class="secnum" id="sec-9.4.6.1"><a href="#sec-module-namespace-exotic-objects-getprototypeof"
+ title="link to this section">9.4.6.1</a></span> [[GetPrototypeOf]] ( )</h1>
+
+ <p>When the [[GetPrototypeOf]] internal method of a module namespace exotic object <var>O</var> is called the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <b>null</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-setprototypeof-v">
+ <h1><span class="secnum" id="sec-9.4.6.2"><a href="#sec-module-namespace-exotic-objects-setprototypeof-v"
+ title="link to this section">9.4.6.2</a></span> [[SetPrototypeOf]] (V)</h1>
+
+ <p>When the [[SetPrototypeOf]] internal method of a module namespace exotic object <var>O</var> is called with argument
+ <i>V</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: Either <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is Object or <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is Null.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-isextensible">
+ <h1><span class="secnum" id="sec-9.4.6.3"><a href="#sec-module-namespace-exotic-objects-isextensible"
+ title="link to this section">9.4.6.3</a></span> [[IsExtensible]] ( )</h1>
+
+ <p>When the [[IsExtensible]] internal method of a module namespace exotic object <var>O</var> is called the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-preventextensions">
+ <h1><span class="secnum" id="sec-9.4.6.4"><a href="#sec-module-namespace-exotic-objects-preventextensions"
+ title="link to this section">9.4.6.4</a></span> [[PreventExtensions]] ( )</h1>
+
+ <p>When the [[PreventExtensions]] internal method of a module namespace exotic object <var>O</var> is called the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-getownproperty-p">
+ <h1><span class="secnum" id="sec-9.4.6.5"><a href="#sec-module-namespace-exotic-objects-getownproperty-p"
+ title="link to this section">9.4.6.5</a></span> [[GetOwnProperty]] (P)</h1>
+
+ <p>When the [[GetOwnProperty]] internal method of a module namespace exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is Symbol, return <a
+ href="#sec-ordinarygetownproperty">OrdinaryGetOwnProperty</a>(<i>O</i>, <i>P</i>).</li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-defineownproperty-p-desc">
+ <h1><span class="secnum" id="sec-9.4.6.6"><a href="#sec-module-namespace-exotic-objects-defineownproperty-p-desc"
+ title="link to this section">9.4.6.6</a></span> [[DefineOwnProperty]] (P, Desc)</h1>
+
+ <p>When the [[DefineOwnProperty]] internal method of a module namespace exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> and <a href="#sec-property-descriptor-specification-type">Property
+ Descriptor</a> <span class="nt">Desc</span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-hasproperty-p">
+ <h1><span class="secnum" id="sec-9.4.6.7"><a href="#sec-module-namespace-exotic-objects-hasproperty-p"
+ title="link to this section">9.4.6.7</a></span> [[HasProperty]] (P)</h1>
+
+ <p>When the [[HasProperty]] internal method of a module namespace exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is Symbol, return <a
+ href="#sec-ordinaryhasproperty">OrdinaryHasProperty</a>(<i>O</i>, <i>P</i>).</li>
+ <li>Let <i>exports</i> be the value of <i>O</i>’s [[Exports]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>P</i> is an element of <i>exports</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-get-p-receiver">
+ <h1><span class="secnum" id="sec-9.4.6.8"><a href="#sec-module-namespace-exotic-objects-get-p-receiver"
+ title="link to this section">9.4.6.8</a></span> [[Get]] (P, Receiver)</h1>
+
+ <p>When the [[Get]] internal method of a module namespace exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> and <a href="#sec-ecmascript-language-types">ECMAScript language
+ value</a> <span class="nt">Receiver</span> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>P</i>) is Symbol, then
+ <ol class="block">
+ <li>Return the result of calling the default ordinary object [[Get]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver">9.1.8</a>) on <i>O</i> passing
+ <i>P</i> and <i>Receiver</i> as arguments.</li>
+ </ol>
+ </li>
+ <li>Let <i>exports</i> be the value of <i>O</i>’s [[Exports]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>P</i> is not an element of <i>exports</i>, return <b>undefined</b>.</li>
+ <li>Let <i>m</i> be the value of <i>O</i>’s [[Module]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>binding</i> be <i>m</i>.<a href="#sec-resolveexport">ResolveExport</a>(<i>P</i>, «»,
+ «»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>binding</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>binding</i> is neither <b>null</b> nor
+ <code>"ambiguous"</code>.</li>
+ <li>Let <i>targetModule</i> be <i>binding</i>.[[module]],</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>targetModule</i> is not <b>undefined</b>.</li>
+ <li>Let <i>targetEnv</i> be <i>targetModule</i>.[[Environment]].</li>
+ <li>If <i>targetEnv</i> is <b>undefined</b>, throw a <b>ReferenceError</b> exception.</li>
+ <li>Let <i>targetEnvRec</i> be <i>targetEnv</i>’s environment record.</li>
+ <li>Return <i>targetEnvRec</i>.GetBindingValue(<i>binding.</i>[[bindingName]], <b>true</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <a href="#sec-resolveexport">ResolveExport</a> is idempotent and side-effect free. An
+ implementation might choose to pre-compute or cache the <a href="#sec-resolveexport">ResolveExport</a> results for the
+ [[Exports]] of each module namespace exotic object.</p>
+ </div>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-set-p-v-receiver">
+ <h1><span class="secnum" id="sec-9.4.6.9"><a href="#sec-module-namespace-exotic-objects-set-p-v-receiver"
+ title="link to this section">9.4.6.9</a></span> [[Set]] ( P, V, Receiver)</h1>
+
+ <p>When the [[Set]] internal method of <span style="font-family: Times New Roman">a</span> module namespace exotic object
+ <var>O</var> is called with <a href="#sec-object-type">property key</a> <var>P</var>, value <var>V</var>, and <a
+ href="#sec-ecmascript-language-types">ECMAScript language value</a> <span class="nt">Receiver</span>, the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-delete-p">
+ <h1><span class="secnum" id="sec-9.4.6.10"><a href="#sec-module-namespace-exotic-objects-delete-p"
+ title="link to this section">9.4.6.10</a></span> [[Delete]] (P)</h1>
+
+ <p>When the [[Delete]] internal method of a module namespace exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>exports</i> be the value of <i>O</i>’s [[Exports]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>P</i> is an element of <i>exports</i>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-enumerate">
+ <h1><span class="secnum" id="sec-9.4.6.11"><a href="#sec-module-namespace-exotic-objects-enumerate"
+ title="link to this section">9.4.6.11</a></span> [[Enumerate]] ()</h1>
+
+ <p>When the [[Enumerate]] internal method of a module namespace exotic object <var>O</var> is called the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>exports</i> be the value of <i>O</i>’s [[Exports]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <a href="#sec-createlistiterator">CreateListIterator</a>(<i>exports</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-namespace-exotic-objects-ownpropertykeys">
+ <h1><span class="secnum" id="sec-9.4.6.12"><a href="#sec-module-namespace-exotic-objects-ownpropertykeys"
+ title="link to this section">9.4.6.12</a></span> [[OwnPropertyKeys]] ( )</h1>
+
+ <p>When the [[OwnPropertyKeys]] internal method of a module namespace exotic object <var>O</var> is called the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>exports</i> be a copy of the value of <i>O</i>’s [[Exports]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>symbolKeys</i> be the result of calling the default ordinary object [[OwnPropertyKeys]] internal method (<a
+ href="#sec-ordinary-object-internal-methods-and-internal-slots-ownpropertykeys">9.1.12</a>) on <i>O</i> passing no
+ arguments.</li>
+ <li>Append all the entries of <i>symbolKeys</i> to the end of <i>exports</i>.</li>
+ <li>Return <i>exports</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-modulenamespacecreate">
+ <h1><span class="secnum" id="sec-9.4.6.13"><a href="#sec-modulenamespacecreate"
+ title="link to this section">9.4.6.13</a></span> ModuleNamespaceCreate (module, exports)</h1>
+
+ <p>The abstract operation ModuleNamespaceCreate with arguments <var>module</var>, and <var>exports</var> is used to
+ specify the creation of new module namespace exotic objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i> is a Module Record (<a
+ href="#sec-abstract-module-records">see 15.2.1.15</a>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i>.[[Namespace]] is <b>undefined</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>exports</i> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of string values.</li>
+ <li>Let <i>M</i> be a newly created object.</li>
+ <li>Set <i>M</i>’s essential internal methods to the definitions specified in <a
+ href="#sec-module-namespace-exotic-objects">9.4.6</a>.</li>
+ <li>Set <i>M</i>’s [[Module]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>module</i>.</li>
+ <li>Set <i>M</i>’s [[Exports]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>exports</i>.</li>
+ <li>Create own properties of <i>M</i> corresponding to the definitions in <a
+ href="#sec-module-namespace-objects">26.3</a>.</li>
+ <li>Set <i>module</i>.[[Namespace]] to <i>M</i>.</li>
+ <li>Return <i>M</i>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots">
+ <div class="front">
+ <h1><span class="secnum" id="sec-9.5"><a href="#sec-proxy-object-internal-methods-and-internal-slots"
+ title="link to this section">9.5</a></span> Proxy Object Internal Methods and Internal Slots</h1>
+
+ <p>A proxy object is an exotic object whose essential internal methods are partially implemented using ECMAScript code.
+ Every proxy objects has an <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> called
+ [[ProxyHandler]]. The value of [[ProxyHandler]] is an object, called the proxy’s <i>handler object</i>, or <span
+ class="value">null</span>. Methods (see <a href="#table-30">Table 30</a>) of a handler object may be used to augment the
+ implementation for one or more of the proxy object’s internal methods. Every proxy object also has an <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> called [[ProxyTarget]] whose value is either an
+ object or the <b>null</b> value. This object is called the proxy’s <i>target object</i>.</p>
+
+ <figure>
+ <figcaption><span id="table-30">Table 30</span> — Proxy Handler Methods</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Method</th>
+ <th style="border-bottom: 1px solid #000000; border-top: 2px solid #000000">Handler Method</th>
+ </tr>
+ <tr>
+ <td>[[GetPrototypeOf]]</td>
+ <td><code>getPrototypeOf</code></td>
+ </tr>
+ <tr>
+ <td>[[SetPrototypeOf]]</td>
+ <td><code>setPrototypeOf</code></td>
+ </tr>
+ <tr>
+ <td>[[IsExtensible]]</td>
+ <td><code>isExtensible</code></td>
+ </tr>
+ <tr>
+ <td>[[PreventExtensions]]</td>
+ <td><code>preventExtensions</code></td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080">[[GetOwnProperty]]</td>
+ <td style="border-bottom: 1px solid #808080; border-left: 1px solid #808080; border-right: 1px solid #808080; border-top: 1px solid #808080"><code>getOwnPropertyDescriptor</code></td>
+ </tr>
+ <tr>
+ <td>[[HasProperty]]</td>
+ <td><code>has</code></td>
+ </tr>
+ <tr>
+ <td>[[Get]]</td>
+ <td><code>get</code></td>
+ </tr>
+ <tr>
+ <td>[[Set]]</td>
+ <td><code>set</code></td>
+ </tr>
+ <tr>
+ <td>[[Delete]]</td>
+ <td><code>deleteProperty</code></td>
+ </tr>
+ <tr>
+ <td>[[DefineOwnProperty]]</td>
+ <td><code>defineProperty</code></td>
+ </tr>
+ <tr>
+ <td>[[Enumerate]]</td>
+ <td><code>enumerate</code></td>
+ </tr>
+ <tr>
+ <td>[[OwnPropertyKeys]]</td>
+ <td><code>ownKeys</code></td>
+ </tr>
+ <tr>
+ <td>[[Call]]</td>
+ <td><code>apply</code></td>
+ </tr>
+ <tr>
+ <td>[[Construct]]</td>
+ <td><code>construct</code></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>When a handler method is called to provide the implementation of a proxy object internal method, the handler method is
+ passed the proxy’s target object as a parameter. A proxy’s handler object does not necessarily have a method
+ corresponding to every essential internal method. Invoking an internal method on the proxy results in the invocation of the
+ corresponding internal method on the proxy’s target object if the handler object does not have a method corresponding
+ to the internal trap.</p>
+
+ <p>The [[ProxyHandler]] and [[ProxyTarget]] internal slots of a proxy object are always initialized when the object is
+ created and typically may not be modified. Some proxy objects are created in a manner that permits them to be subsequently
+ <i>revoked</i>. When a proxy is revoked, its [[ProxyHander]] and [[ProxyTarget]] internal slots are set to <b>null</b>
+ causing subsequent invocations of internal methods on that proxy object to throw a <span class="value">TypeError</span>
+ exception.</p>
+
+ <p>Because proxy objects permit the implementation of internal methods to be provided by arbitrary ECMAScript code, it is
+ possible to define a proxy object whose handler methods violates the invariants defined in <a
+ href="#sec-invariants-of-the-essential-internal-methods">6.1.7.3</a>. Some of the internal method invariants defined in <a
+ href="#sec-invariants-of-the-essential-internal-methods">6.1.7.3</a> are essential integrity invariants. These invariants
+ are explicitly enforced by the proxy object internal methods specified in this section. An ECMAScript implementation must be
+ robust in the presence of all possible invariant violations.</p>
+
+ <p>In the following algorithm descriptions, assume <var>O</var> is an ECMAScript proxy object, <var>P</var> is a <a
+ href="#sec-object-type">property key value</a>, <var>V</var> is any <a href="#sec-ecmascript-language-types">ECMAScript
+ language value</a> and <span style="font-family: Times New Roman">Desc</span> is a <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> record.</p>
+ </div>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-getprototypeof">
+ <h1><span class="secnum" id="sec-9.5.1"><a href="#sec-proxy-object-internal-methods-and-internal-slots-getprototypeof"
+ title="link to this section">9.5.1</a></span> [[GetPrototypeOf]] ( )</h1>
+
+ <p>When the [[GetPrototypeOf]] internal method of a Proxy exotic object <var>O</var> is called the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>getPrototypeOf</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[GetPrototypeOf]]().</li>
+ </ol>
+ </li>
+ <li>Let <i>handlerProto</i> be <a href="#sec-call">Call</a>(<i>trap</i>, <i>handler</i>,
+ «<i>target</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>handlerProto</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handlerProto</i>) is neither Object nor Null, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Let <i>extensibleTarget</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensibleTarget</i>).</li>
+ <li>If <i>extensibleTarget</i> is <b>true</b>, return <i>handlerProto</i>.</li>
+ <li>Let <i>targetProto</i> be <i>target</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetProto</i>).</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>handlerProto</i>, <i>targetProto</i>) is <b>false</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Return <i>handlerProto</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[GetPrototypeOf]] for proxy objects enforces the following invariant:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[GetPrototypeOf]] must be either an Object or <b>null</b>.</p>
+ </li>
+
+ <li>
+ <p>If the target object is not extensible, [[GetPrototypeOf]] applied to the proxy object must return the same value
+ as [[GetPrototypeOf]] applied to the proxy object’s target object.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-setprototypeof-v">
+ <h1><span class="secnum" id="sec-9.5.2"><a href="#sec-proxy-object-internal-methods-and-internal-slots-setprototypeof-v"
+ title="link to this section">9.5.2</a></span> [[SetPrototypeOf]] (V)</h1>
+
+ <p>When the [[SetPrototypeOf]] internal method of a Proxy exotic object <var>O</var> is called with argument <i>V</i> the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: Either <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is Object or <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is Null.</li>
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>setPrototypeOf</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[SetPrototypeOf]](<i>V</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>booleanTrapResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>trap</i>,
+ <i>handler</i>, «<i>target</i>, <i>V</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>booleanTrapResult</i>).</li>
+ <li>Let <i>extensibleTarget</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensibleTarget</i>).</li>
+ <li>If <i>extensibleTarget</i> is <b>true</b>, return <i>booleanTrapResult</i>.</li>
+ <li>Let <i>targetProto</i> be <i>target</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetProto</i>).</li>
+ <li>If <i>booleanTrapResult</i> is <b>true</b> and <a href="#sec-samevalue">SameValue</a>(<i>V</i>, <i>targetProto</i>) is
+ <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>booleanTrapResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[SetPrototypeOf]] for proxy objects enforces the following invariant:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[SetPrototypeOf]] is a Boolean value.</p>
+ </li>
+
+ <li>
+ <p>If the target object is not extensible, the argument value must be the same as the result of [[GetPrototypeOf]]
+ applied to target object.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-isextensible">
+ <h1><span class="secnum" id="sec-9.5.3"><a href="#sec-proxy-object-internal-methods-and-internal-slots-isextensible"
+ title="link to this section">9.5.3</a></span> [[IsExtensible]] ( )</h1>
+
+ <p>When the [[IsExtensible]] internal method of a Proxy exotic object <var>O</var> is called the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>isExtensible</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[IsExtensible]]().</li>
+ </ol>
+ </li>
+ <li>Let <i>booleanTrapResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>trap</i>,
+ <i>handler</i>, «<i>target</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>booleanTrapResult</i>).</li>
+ <li>Let <i>targetResult</i> be <i>target</i>.[[IsExtensible]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetResult</i>).</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>booleanTrapResult</i>, <i>targetResult</i>) is <b>false</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Return <i>booleanTrapResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[IsExtensible]] for proxy objects enforces the following invariant:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[IsExtensible]] is a Boolean value.</p>
+ </li>
+
+ <li>
+ <p>[[IsExtensible]] applied to the proxy object must return the same value as [[IsExtensible]] applied to the proxy
+ object’s target object with the same argument.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-preventextensions">
+ <h1><span class="secnum" id="sec-9.5.4"><a href="#sec-proxy-object-internal-methods-and-internal-slots-preventextensions"
+ title="link to this section">9.5.4</a></span> [[PreventExtensions]] ( )</h1>
+
+ <p>When the [[PreventExtensions]] internal method of a Proxy exotic object <var>O</var> is called the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>preventExtensions</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[PreventExtensions]]().</li>
+ </ol>
+ </li>
+ <li>Let <i>booleanTrapResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>trap</i>,
+ <i>handler</i>, «<i>target</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>booleanTrapResult</i>).</li>
+ <li>If <i>booleanTrapResult</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>targetIsExtensible</i> be <i>target</i>.[[IsExtensible]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetIsExtensible</i>).</li>
+ <li>If <i>targetIsExtensible</i> is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Return <i>booleanTrapResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[PreventExtensions]] for proxy objects enforces the following invariant:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[PreventExtensions]] is a Boolean value.</p>
+ </li>
+
+ <li>
+ <p>[[PreventExtensions]] applied to the proxy object only returns <b>true</b> if [[IsExtensible]] applied to the proxy
+ object’s target object is <b>false</b>.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-getownproperty-p">
+ <h1><span class="secnum" id="sec-9.5.5"><a href="#sec-proxy-object-internal-methods-and-internal-slots-getownproperty-p"
+ title="link to this section">9.5.5</a></span> [[GetOwnProperty]] (P)</h1>
+
+ <p>When the [[GetOwnProperty]] internal method of a Proxy exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>,
+ "<code>getOwnPropertyDescriptor</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>trapResultObj</i> be <a href="#sec-call">Call</a>(<i>trap</i>, <i>handler</i>, «<i>target</i>,
+ <i>P</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trapResultObj</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>trapResultObj</i>) is neither Object nor Undefined,
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>targetDesc</i> be <i>target</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetDesc</i>).</li>
+ <li>If <i>trapResultObj</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>targetDesc</i> is <b>undefined</b>, return <b>undefined</b>.</li>
+ <li>If <i>targetDesc</i>.[[Configurable]] is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>extensibleTarget</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensibleTarget</i>).</li>
+ <li>If <a href="#sec-toboolean">ToBoolean</a>(<i>extensibleTarget</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>extensibleTarget</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensibleTarget</i>).</li>
+ <li>Let <i>resultDesc</i> be <a href="#sec-topropertydescriptor">ToPropertyDescriptor</a>(<i>trapResultObj</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resultDesc</i>).</li>
+ <li><a href="#sec-call">Call</a> <a
+ href="#sec-completepropertydescriptor">CompletePropertyDescriptor</a>(<i>resultDesc</i>).</li>
+ <li>Let <i>valid</i> be <a href="#sec-iscompatiblepropertydescriptor">IsCompatiblePropertyDescriptor</a>
+ (<i>extensibleTarget</i>, <i>resultDesc</i>, <i>targetDesc</i>).</li>
+ <li>If <i>valid</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <i>resultDesc</i>.[[Configurable]] is <b>false</b>, then
+ <ol class="block">
+ <li>If <i>targetDesc</i> is <b>undefined</b> or <i>targetDesc</i>.[[Configurable]] is <b>true</b><i>,</i> then
+ <ol class="block">
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>resultDesc</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[GetOwnProperty]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[GetOwnProperty]] must be either an Object or <b>undefined</b>.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be reported as non-existent, if it exists as a non-configurable own property of the target
+ object.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be reported as non-existent, if it exists as an own property of the target object and the target
+ object is not extensible.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be reported as existent, if it does not exists as an own property of the target object and the
+ target object is not extensible.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be reported as non-configurable, if it does not exists as an own property of the target object or
+ if it exists as a configurable own property of the target object.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-defineownproperty-p-desc">
+ <h1><span class="secnum" id="sec-9.5.6"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-defineownproperty-p-desc"
+ title="link to this section">9.5.6</a></span> [[DefineOwnProperty]] (P, Desc)</h1>
+
+ <p>When the [[DefineOwnProperty]] internal method of a Proxy exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> and <a href="#sec-property-descriptor-specification-type">Property
+ Descriptor</a> <span class="nt">Desc</span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>defineProperty</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[DefineOwnProperty]](<i>P</i>, <i>Desc</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>descObj</i> be <a href="#sec-frompropertydescriptor">FromPropertyDescriptor</a>(<i>Desc</i>).</li>
+ <li>Let <i>booleanTrapResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>trap</i>,
+ <i>handler</i>, «<i>target</i>, <i>P</i>, <i>descObj</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>booleanTrapResult</i>).</li>
+ <li>If <i>booleanTrapResult</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>Let <i>targetDesc</i> be <i>target</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetDesc</i>).</li>
+ <li>Let <i>extensibleTarget</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensibleTarget</i>).</li>
+ <li>If <i>Desc</i> has a [[Configurable]] field and if <i>Desc</i>.[[Configurable]] is <b>false,</b> then
+ <ol class="block">
+ <li>Let <i>settingConfigFalse</i> be <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Else let <i>settingConfigFalse</i> be <b>false</b>.</li>
+ <li>If <i>targetDesc</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>extensibleTarget</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <i>settingConfigFalse</i> is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Else <i>targetDesc</i> is not <b>undefined<i>,</i></b>
+ <ol class="block">
+ <li>If <a href="#sec-iscompatiblepropertydescriptor">IsCompatiblePropertyDescriptor</a>(<i>extensibleTarget</i>,
+ <i>Desc</i> , <i>targetDesc</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <i>settingConfigFalse</i> is <b>true</b> and <i>targetDesc</i>.[[Configurable]] is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[DefineOwnProperty]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[DefineOwnProperty]] is a Boolean value.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be added, if the target object is not extensible.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be non-configurable, unless there exists a corresponding non-configurable own property of the
+ target object.</p>
+ </li>
+
+ <li>
+ <p>If a property has a corresponding target object property then applying the <a
+ href="#sec-property-descriptor-specification-type">Property Descriptor</a> of the property to the target object using
+ [[DefineOwnProperty]] will not throw an exception.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-hasproperty-p">
+ <h1><span class="secnum" id="sec-9.5.7"><a href="#sec-proxy-object-internal-methods-and-internal-slots-hasproperty-p"
+ title="link to this section">9.5.7</a></span> [[HasProperty]] (P)</h1>
+
+ <p>When the [[HasProperty]] internal method of a Proxy exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>has</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[HasProperty]](<i>P</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>booleanTrapResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>trap</i>,
+ <i>handler</i>, «<i>target</i>, <i>P</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>booleanTrapResult</i>).</li>
+ <li>If <i>booleanTrapResult</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>targetDesc</i> be <i>target</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetDesc</i>).</li>
+ <li>If <i>targetDesc</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>targetDesc</i>.[[Configurable]] is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>extensibleTarget</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensibleTarget</i>).</li>
+ <li>If <i>extensibleTarget</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>booleanTrapResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[HasProperty]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[HasProperty]] is a Boolean value.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be reported as non-existent, if it exists as a non-configurable own property of the target
+ object.</p>
+ </li>
+
+ <li>
+ <p>A property cannot be reported as non-existent, if it exists as an own property of the target object and the target
+ object is not extensible.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver">
+ <h1><span class="secnum" id="sec-9.5.8"><a href="#sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver"
+ title="link to this section">9.5.8</a></span> [[Get]] (P, Receiver)</h1>
+
+ <p>When the [[Get]] internal method of a Proxy exotic object <var>O</var> is called with <a href="#sec-object-type">property
+ key</a> <var>P</var> and <a href="#sec-ecmascript-language-types">ECMAScript language value</a> <span
+ class="nt">Receiver</span> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>get</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[Get]](<i>P</i>, <i>Receiver</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>trapResult</i> be <a href="#sec-call">Call</a>(<i>trap</i>, <i>handler</i>, «<i>target</i>, <i>P</i>,
+ <i>Receiver</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trapResult</i>).</li>
+ <li>Let <i>targetDesc</i> be <i>target</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetDesc</i>).</li>
+ <li>If <i>targetDesc</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>targetDesc</i>) and <i>targetDesc</i>.[[Configurable]]
+ is <b>false</b> and <i>targetDesc</i>.[[Writable]] is <b>false</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>trapResult</i>, <i>targetDesc</i>.[[Value]]) is <b>false</b>,
+ throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>targetDesc</i>) and
+ <i>targetDesc</i>.[[Configurable]] is <b>false</b> and <i>targetDesc</i>.[[Get]] is <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>trapResult</i> is not <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>trapResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[Get]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>
+ <p>The value reported for a property must be the same as the value of the corresponding target object property if the
+ target object property is a non-writable, non-configurable own data property.</p>
+ </li>
+
+ <li>
+ <p>The value reported for a property must be <b>undefined</b> if the corresponding target object property is a
+ non-configurable own accessor property that has <b>undefined</b> as its [[Get]] attribute.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-set-p-v-receiver">
+ <h1><span class="secnum" id="sec-9.5.9"><a href="#sec-proxy-object-internal-methods-and-internal-slots-set-p-v-receiver"
+ title="link to this section">9.5.9</a></span> [[Set]] ( P, V, Receiver)</h1>
+
+ <p>When the [[Set]] internal method of a Proxy exotic object <var>O</var> is called with <a href="#sec-object-type">property
+ key</a> <var>P</var>, value <var>V</var>, and <a href="#sec-ecmascript-language-types">ECMAScript language value</a> <span
+ class="nt">Receiver</span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>set</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[Set]](<i>P</i>, <i>V</i>, <i>Receiver</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>booleanTrapResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>trap</i>,
+ <i>handler</i>, «<i>target</i>, <i>P</i>, <i>V</i>, <i>Receiver</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>booleanTrapResult</i>).</li>
+ <li>If <i>booleanTrapResult</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>Let <i>targetDesc</i> be <i>target</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetDesc</i>).</li>
+ <li>If <i>targetDesc</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isdatadescriptor">IsDataDescriptor</a>(<i>targetDesc</i>) and <i>targetDesc</i>.[[Configurable]]
+ is <b>false</b> and <i>targetDesc</i>.[[Writable]] is <b>false</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>V</i>, <i>targetDesc</i>.[[Value]]) is <b>false</b>, throw a
+ <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-isaccessordescriptor">IsAccessorDescriptor</a>(<i>targetDesc</i>) and
+ <i>targetDesc</i>.[[Configurable]] is <b>false</b>, then
+ <ol class="block">
+ <li>If <i>targetDesc</i>.[[Set]] is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[Set]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[Set]] is a Boolean value.</p>
+ </li>
+
+ <li>
+ <p>Cannot change the value of a property to be different from the value of the corresponding target object property if
+ the corresponding target object property is a non-writable, non-configurable own data property.</p>
+ </li>
+
+ <li>
+ <p>Cannot set the value of a property if the corresponding target object property is a non-configurable own accessor
+ property that has <b>undefined</b> as its [[Set]] attribute.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-delete-p">
+ <h1><span class="secnum" id="sec-9.5.10"><a href="#sec-proxy-object-internal-methods-and-internal-slots-delete-p"
+ title="link to this section">9.5.10</a></span> [[Delete]] (P)</h1>
+
+ <p>When the [[Delete]] internal method of a Proxy exotic object <var>O</var> is called with <a
+ href="#sec-object-type">property key</a> <var>P</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispropertykey">IsPropertyKey</a>(<i>P</i>) is
+ <b>true</b>.</li>
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>deleteProperty</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[Delete]](<i>P</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>booleanTrapResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>trap</i>,
+ <i>handler</i>, «<i>target</i>, <i>P</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>booleanTrapResult</i>).</li>
+ <li>If <i>booleanTrapResult</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>Let <i>targetDesc</i> be <i>target</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetDesc</i>).</li>
+ <li>If <i>targetDesc</i> is <b>undefined</b>, return <b>true</b>.</li>
+ <li>If <i>targetDesc</i>.[[Configurable]] is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[Delete]] for proxy objects enforces the following invariant:</p>
+
+ <ul>
+ <li>The result of [[Delete]] is a Boolean value.</li>
+ <li>A property cannot be reported as deleted, if it exists as a non-configurable own property of the target object.</li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-enumerate">
+ <h1><span class="secnum" id="sec-9.5.11"><a href="#sec-proxy-object-internal-methods-and-internal-slots-enumerate"
+ title="link to this section">9.5.11</a></span> [[Enumerate]] ()</h1>
+
+ <p>When the [[Enumerate]] internal method of a Proxy exotic object <var>O</var> is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>enumerate</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[Enumerate]]().</li>
+ </ol>
+ </li>
+ <li>Let <i>trapResult</i> be <a href="#sec-call">Call</a>(<i>trap</i>, <i>handler</i>, «<i>target</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trapResult</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>trapResult</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>trapResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[Enumerate]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>The result of [[Enumerate]] must be an Object.</li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-ownpropertykeys">
+ <h1><span class="secnum" id="sec-9.5.12"><a href="#sec-proxy-object-internal-methods-and-internal-slots-ownpropertykeys"
+ title="link to this section">9.5.12</a></span> [[OwnPropertyKeys]] ( )</h1>
+
+ <p>When the [[OwnPropertyKeys]] internal method of a Proxy exotic object <var>O</var> is called the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>ownKeys</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <i>target</i>.[[OwnPropertyKeys]]().</li>
+ </ol>
+ </li>
+ <li>Let <i>trapResultArray</i> be <a href="#sec-call">Call</a>(<i>trap</i>, <i>handler</i>,
+ «<i>target</i>»).</li>
+ <li>Let <i>trapResult</i> be <a href="#sec-createlistfromarraylike">CreateListFromArrayLike</a>(<i>trapResultArray</i>,
+ «‍String, Symbol»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trapResult</i>).</li>
+ <li>Let <i>extensibleTarget</i> be <a href="#sec-isextensible-o">IsExtensible</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>extensibleTarget</i>).</li>
+ <li>Let <i>targetKeys</i> be <i>target</i>.[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetKeys</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>targetKeys</i> is a <a
+ href="#sec-list-and-record-specification-type">List</a> containing only String and Symbol values.</li>
+ <li>Let <i>targetConfigurableKeys</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>targetNonconfigurableKeys</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Repeat, for each element <i>key</i> of <i>targetKeys</i>,
+ <ol class="block">
+ <li>Let <i>desc</i> be <i>target</i>.[[GetOwnProperty]](<i>key</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>If <i>desc</i> is not <b>undefined</b> and <i>desc.</i>[[Configurable]] is <b>false</b>, then
+ <ol class="block">
+ <li>Append <i>key</i> as an element of <i>targetNonconfigurableKeys</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Append <i>key</i> as an element of <i>targetConfigurableKeys</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>extensibleTarget</i> is <b>true</b> and <i>targetNonconfigurableKeys</i> is empty, then
+ <ol class="block">
+ <li>Return <i>trapResult</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>uncheckedResultKeys</i> be a new <a href="#sec-list-and-record-specification-type">List</a> which is a copy of
+ <i>trapResult</i>.</li>
+ <li>Repeat, for each <i>key</i> that is an element of <i>targetNonconfigurableKeys</i>,
+ <ol class="block">
+ <li>If <i>key</i> is not an element of <i>uncheckedResultKeys</i>, throw a <b>TypeError</b> exception.</li>
+ <li>Remove <i>key</i> from <i>uncheckedResultKeys</i></li>
+ </ol>
+ </li>
+ <li>If <i>extensibleTarget</i> is <b>true</b>, return <i>trapResult</i>.</li>
+ <li>Repeat, for each <i>key</i> that is an element of <i>targetConfigurableKeys</i>,
+ <ol class="block">
+ <li>If <i>key</i> is not an element of <i>uncheckedResultKeys</i>, throw a <b>TypeError</b> exception.</li>
+ <li>Remove <i>key</i> from <i>uncheckedResultKeys</i></li>
+ </ol>
+ </li>
+ <li>If <i>uncheckedResultKeys</i> is not empty, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>trapResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> [[OwnPropertyKeys]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>
+ <p>The result of [[OwnPropertyKeys]] is a <a href="#sec-list-and-record-specification-type">List</a>.</p>
+ </li>
+
+ <li>
+ <p>The Type of each result <a href="#sec-list-and-record-specification-type">List</a> element is either String or
+ Symbol.</p>
+ </li>
+
+ <li>
+ <p>The result <a href="#sec-list-and-record-specification-type">List</a> must contain the keys of all non-configurable
+ own properties of the target object.</p>
+ </li>
+
+ <li>
+ <p>If the target object is not extensible, then the result <a href="#sec-list-and-record-specification-type">List</a>
+ must contain all the keys of the own properties of the target object and no other values.</p>
+ </li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-call-thisargument-argumentslist">
+ <h1><span class="secnum" id="sec-9.5.13"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-call-thisargument-argumentslist"
+ title="link to this section">9.5.13</a></span> [[Call]] (thisArgument, argumentsList)</h1>
+
+ <p>The [[Call]] internal method of a Proxy exotic object <var>O</var> is called with parameters <var>thisArgument</var> and
+ <var>argumentsList</var>, a <a href="#sec-list-and-record-specification-type">List</a> of <a
+ href="#sec-ecmascript-language-types">ECMAScript language values</a>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>apply</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-call">Call</a>(<i>target</i>, <i>thisArgument</i>, <i>argumentsList</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>argArray</i> be <a href="#sec-createarrayfromlist">CreateArrayFromList</a>(<i>argumentsList</i>).</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>trap</i>, <i>handler</i>, «<i>target</i>, <i>thisArgument</i>,
+ <i>argArray</i>»).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A Proxy exotic object only has a [[Call]] internal method if the initial value of its
+ [[ProxyTarget]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is an object that has a
+ [[Call]] internal method.</p>
+ </div>
+ </section>
+
+ <section id="sec-proxy-object-internal-methods-and-internal-slots-construct-argumentslist-newtarget">
+ <h1><span class="secnum" id="sec-9.5.14"><a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-construct-argumentslist-newtarget"
+ title="link to this section">9.5.14</a></span> [[Construct]] ( argumentsList, newTarget)</h1>
+
+ <p>The [[Construct]] internal method of a Proxy exotic object <var>O</var> is called with parameters
+ <var>argumentsList</var> which is a possibly empty <a href="#sec-list-and-record-specification-type">List</a> of <a
+ href="#sec-ecmascript-language-types">ECMAScript language values</a> and <var>newTarget</var>. The following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>handler</i> be the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>handler</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is Object.</li>
+ <li>Let <i>target</i> be the value of the [[ProxyTarget]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>trap</i> be <a href="#sec-getmethod">GetMethod</a>(<i>handler</i>, "<code>construct</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>trap</i>).</li>
+ <li>If <i>trap</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>target</i> has a [[Construct]] internal method.</li>
+ <li>Return <a href="#sec-construct">Construct</a>(<i>target</i>, <i>argumentsList</i>, <i>newTarget</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>argArray</i> be <a href="#sec-createarrayfromlist">CreateArrayFromList</a>(<i>argumentsList</i>).</li>
+ <li>Let <i>newObj</i> be <a href="#sec-call">Call</a>(<i>trap</i>, <i>handler</i>, «<i>target</i>, <i>argArray</i>,
+ <i>newTarget</i> »).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>newObj</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>newObj</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>newObj</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> A Proxy exotic object only has a [[Construct]] internal method if the initial value of
+ its [[ProxyTarget]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is an object that has a
+ [[Construct]] internal method.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> [[Construct]] for proxy objects enforces the following invariants:</p>
+
+ <ul>
+ <li>The result of [[Construct]] must be an Object.</li>
+ </ul>
+ </div>
+ </section>
+
+ <section id="sec-proxycreate">
+ <h1><span class="secnum" id="sec-9.5.15"><a href="#sec-proxycreate" title="link to this section">9.5.15</a></span>
+ ProxyCreate(target, handler)</h1>
+
+ <p>The abstract operation ProxyCreate with arguments <var>target</var> and <var>handler</var> is used to specify the
+ creation of new Proxy exotic objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ Exception.</li>
+ <li>If <i>target</i> is a Proxy exotic object and the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>target</i> is <b>null</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>handler</i>) is not Object, throw a <b>TypeError</b>
+ Exception.</li>
+ <li>If <i>handler</i> is a Proxy exotic object and the value of the [[ProxyHandler]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>handler</i> is <b>null</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Let <i>P</i> be a newly created object.</li>
+ <li>Set <i>P</i>’s essential internal methods (except for [[Call]] and [[Construct]]) to the definitions specified
+ in <a href="#sec-proxy-object-internal-methods-and-internal-slots">9.5</a>.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>target</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Set the [[Call]] internal method of <i>P</i> as specified in <a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-call-thisargument-argumentslist">9.5.13</a>.</li>
+ <li>If <i>target</i> has a [[Construct]] internal method, then
+ <ol class="block">
+ <li>Set the [[Construct]] internal method of <i>P</i> as specified in <a
+ href="#sec-proxy-object-internal-methods-and-internal-slots-construct-argumentslist-newtarget">9.5.14</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set the [[ProxyTarget]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>P</i> to
+ <i>target</i>.</li>
+ <li>Set the [[ProxyHandler]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>P</i> to
+ <i>handler</i>.</li>
+ <li>Return <i>P</i>.</li>
+ </ol>
+ </section>
+ </section>
+</section>
+
+<section id="sec-ecmascript-language-source-code">
+ <div class="front">
+ <h1><span class="secnum" id="sec-10"><a href="#sec-ecmascript-language-source-code" title="link to this section">10</a></span>
+ ECMAScript Language: Source Code</h1>
+ </div>
+
+ <section id="sec-source-text">
+ <div class="front">
+ <h1><span class="secnum" id="sec-10.1"><a href="#sec-source-text" title="link to this section">10.1</a></span> Source
+ Text</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SourceCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="gprose">any Unicode code point</span></div>
+ </div>
+
+ <p>ECMAScript code is expressed using Unicode, version 5.1 or later. ECMAScript source text is a sequence of code points.
+ All Unicode code point values from U+0000 to U+10FFFF, including surrogate code points, may occur in source text where
+ permitted by the ECMAScript grammars. The actual encodings used to store and interchange ECMAScript source text is not
+ relevant to this specification. Regardless of the external source text encoding, a conforming ECMAScript implementation
+ processes the source text as if it was an equivalent sequence of <span class="nt">SourceCharacter</span> values. Each <span
+ class="nt">SourceCharacter</span> being a Unicode code point. Conforming ECMAScript implementations are not required to
+ perform any normalization of source text, or behave as though they were performing normalization of source text.</p>
+
+ <p>The components of a combining character sequence are treated as individual Unicode code points even though a user might
+ think of the whole sequence as a single character.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In string literals, regular expression literals, template literals and identifiers, any
+ Unicode code point may also be expressed using Unicode escape sequences that explicitly express a code point’s
+ numeric value. Within a comment, such an escape sequence is effectively ignored as part of the comment.</p>
+
+ <p>ECMAScript differs from the Java programming language in the behaviour of Unicode escape sequences. In a Java program,
+ if the Unicode escape sequence <code>\u000A</code>, for example, occurs within a single-line comment, it is interpreted as
+ a line terminator (Unicode code point U+000A is line feed (lf)) and therefore the next code point is not part of the
+ comment. Similarly, if the Unicode escape sequence <code>\u000A</code> occurs within a string literal in a Java program,
+ it is likewise interpreted as a line terminator, which is not allowed within a string literal—one must write
+ <code>\n</code> instead of <code>\u000A</code> to cause a line feed (lf) to be part of the string value of a string
+ literal. In an ECMAScript program, a Unicode escape sequence occurring within a comment is never interpreted and therefore
+ cannot contribute to termination of the comment. Similarly, a Unicode escape sequence occurring within a string literal in
+ an ECMAScript program always contributes to the literal and is never interpreted as a line terminator or as a code point
+ that might terminate the string literal.</p>
+ </div>
+ </div>
+
+ <section id="sec-utf16encoding">
+ <h1><span class="secnum" id="sec-10.1.1"><a href="#sec-utf16encoding" title="link to this section">10.1.1</a></span> Static
+ Semantics: <i>UTF16Encoding ( cp )</i></h1>
+
+ <p>The UTF16Encoding of a numeric code point value, <var>cp</var>, is determined as follows:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: 0 ≤ <i>cp</i> ≤ 0x10FFFF.</li>
+ <li>If <i>cp</i> ≤ 65535, return <i>cp</i>.</li>
+ <li>Let <i>cu1</i> be <a href="#sec-algorithm-conventions">floor</a>((<i>cp</i> – 65536) / 1024) + 0xD800.</li>
+ <li>Let <i>cu2</i> be ((<i>cp</i> – 65536) <a href="#sec-algorithm-conventions">modulo</a> 1024) + 0xDC00.</li>
+ <li>Return the code unit sequence consisting of <i>cu1</i> followed by <i>cu2</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-utf16decode">
+ <h1><span class="secnum" id="sec-10.1.2"><a href="#sec-utf16decode" title="link to this section">10.1.2</a></span> Static
+ Semantics: UTF16Decode( lead, trail )</h1>
+
+ <p>Two code units, <var>lead</var> and <var>trail</var>, that form a UTF-16 surrogate pair are converted to a code point by
+ performing the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: 0xD800 ≤ <i>lead</i> ≤ 0xDBFF and 0xDC00 ≤ <i>trail</i> ≤
+ 0xDFFF.</li>
+ <li>Let <i>cp</i> be (<i>lead</i> – 0xD800) × 1024 + (<i>trail</i> – 0xDC00) + 0x10000.</li>
+ <li>Return the code point <i>cp</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-types-of-source-code">
+ <div class="front">
+ <h1><span class="secnum" id="sec-10.2"><a href="#sec-types-of-source-code" title="link to this section">10.2</a></span>
+ Types of Source Code</h1>
+
+ <p>There are four types of ECMAScript code:</p>
+
+ <ul>
+ <li>
+ <p><i>Global code</i> is source text that is treated as an ECMAScript <i>Script</i>. The global code of a particular
+ <i>Script</i> does not include any source text that is parsed as part of a <i>FunctionDeclaration</i>,
+ <i>FunctionExpression</i>, <i>GeneratorDeclaration</i>, <i>GeneratorExpression</i>, <i>MethodDefinition</i>,
+ <i>ArrowFunction, ClassDeclaration</i>, or <i>ClassExpression</i>.</p>
+ </li>
+
+ <li>
+ <p><i>Eval code</i> is the source text supplied to the built-in <code>eval</code> function. More precisely, if the
+ parameter to the built-in <code>eval</code> function is a String, it is treated as an ECMAScript <i>Script</i>. The eval
+ code for a particular invocation of <code>eval</code> is the global code portion of that <i>Script</i>.</p>
+ </li>
+
+ <li>
+ <p><i>Function code</i> is source text that is parsed to supply the value of the [[ECMAScriptCode]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> (<a href="#sec-ecmascript-function-objects">see
+ 9.2</a>) of function and generator objects. It also includes the code that defines and initializes the formal parameters
+ of the function. The <i>function code</i> of a particular function or generator does not include any source text that is
+ parsed as the function code of a nested <i>FunctionDeclaration</i>, <i>FunctionExpression</i>,
+ <i>GeneratorDeclaration</i>, <i>GeneratorExpression</i>, <i>MethodDefinition</i>, <i>ArrowFunction,
+ ClassDeclaration</i>, or <i>ClassExpression</i>.</p>
+ </li>
+
+ <li>
+ <p><i>Module code</i> is source text that is code that is provided as a <i>ModuleBody</i>. It is the code that is
+ directly evaluated when a module is initialized. The module code of a particular module does not include any source text
+ that is parsed as part of a nested <i>FunctionDeclaration</i>, <i>FunctionExpression</i>, <i>GeneratorDeclaration</i>,
+ <i>GeneratorExpression</i>, <i>MethodDefinition</i>, <i>ArrowFunction, ClassDeclaration</i>, or
+ <i>ClassExpression</i>.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Function code is generally provided as the bodies of Function Definitions (<a
+ href="#sec-function-definitions">14.1</a>), Arrow Function Definitions (<a
+ href="#sec-arrow-function-definitions">14.2</a>), Method Definitions (<a href="#sec-method-definitions">14.3</a>) and
+ Generator Definitions (<a href="#sec-generator-function-definitions">14.4</a>). Function code is also derived from the
+ last argument to the Function constructor (<a href="#sec-function-p1-p2-pn-body">19.2.1.1</a>) and the GeneratorFunction
+ constructor (<a href="#sec-generatorfunction">25.2.1.1</a>).</p>
+ </div>
+ </div>
+
+ <section id="sec-strict-mode-code">
+ <h1><span class="secnum" id="sec-10.2.1"><a href="#sec-strict-mode-code" title="link to this section">10.2.1</a></span>
+ Strict Mode Code</h1>
+
+ <p>An ECMAScript <span class="nt">Script</span> syntactic unit may be processed using either unrestricted or strict mode
+ syntax and semantics. Code is interpreted as strict mode code in the following situations:</p>
+
+ <ul>
+ <li>
+ <p>Global code is strict mode code if it begins with a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Directive Prologue</a> that contains a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Use Strict Directive</a> (see <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">14.1.1</a>).</p>
+ </li>
+
+ <li>
+ <p>Module code is always strict mode code.</p>
+ </li>
+
+ <li>
+ <p>All parts of a <span class="nt">ClassDeclaration</span> or a <span class="nt">ClassExpression</span> are strict mode
+ code.</p>
+ </li>
+
+ <li>
+ <p>Eval code is strict mode code if it begins with a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Directive Prologue</a> that contains a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Use Strict Directive</a> or if the call to eval is a direct
+ call (<a href="#sec-function-calls-runtime-semantics-evaluation">see 12.3.4.1</a>) to the eval function that is
+ contained in strict mode code.</p>
+ </li>
+
+ <li>
+ <p>Function code is strict mode code if its <span class="nt">FunctionDeclaration</span>, <span
+ class="nt">FunctionExpression</span>, <span class="nt">GeneratorDeclaration</span>, <span
+ class="nt">GeneratorExpression</span>, <span class="nt">MethodDefinition</span>, or <span
+ class="nt">ArrowFunction</span> is contained in strict mode code or if it is within a <span
+ class="nt">FunctionBody</span> that begins with a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Directive Prologue</a> that contains a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Use Strict Directive</a>.</p>
+ </li>
+
+ <li>
+ <p>Function code that is supplied as the last argument to the built-in Function constructor is strict mode code if the
+ last argument is a String that when processed as a <span class="nt">FunctionBody</span> begins with a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Directive Prologue</a> that contains a <a
+ href="#sec-directive-prologues-and-the-use-strict-directive">Use Strict Directive</a>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-non-ecmascript-functions">
+ <h1><span class="secnum" id="sec-10.2.2"><a href="#sec-non-ecmascript-functions"
+ title="link to this section">10.2.2</a></span> Non-ECMAScript Functions</h1>
+
+ <p>An ECMAScript implementation may support the evaluation of exotic function objects whose evaluative behaviour is
+ expressed in some implementation defined form of executable code other than via ECMAScript code. Whether a function object
+ is an ECMAScript code function or a non-ECMAScript function is not semantically observable from the perspective of an
+ ECMAScript code function that calls or is called by such a non-ECMAScript function.</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-ecmascript-language-lexical-grammar">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11"><a href="#sec-ecmascript-language-lexical-grammar"
+ title="link to this section">11</a></span> ECMAScript Language: Lexical Grammar</h1>
+
+ <p>The source text of an ECMAScript <span class="nt">Script</span> or <span class="nt">Module</span> is first converted into a
+ sequence of input elements, which are tokens, line terminators, comments, or white space. The source text is scanned from left
+ to right, repeatedly taking the longest possible sequence of code units as the next input element.</p>
+
+ <p>There are several situations where the identification of lexical input elements is sensitive to the syntactic grammar
+ context that is consuming the input elements. This requires multiple goal symbols for the lexical grammar. The <span
+ class="nt">InputElementRegExpOrTemplateTail</span> goal is used in syntactic grammar contexts where a
+ <var>RegularExpressionLiteral,</var> a <var>TemplateMiddle,</var> or a <span class="nt">TemplateTail</span> is permitted. The
+ <span class="nt">InputElementRegExp</span> goal symbol is used in all syntactic grammar contexts where a <span
+ class="nt">RegularExpressionLiteral</span> is permitted but neither a <var>TemplateMiddle,</var> nor a <span
+ class="nt">TemplateTail</span> is permitted. The <span class="nt">InputElementTemplateTail</span> goal is used in all
+ syntactic grammar contexts where a <span class="nt">TemplateMiddle</span> or a <span class="nt">TemplateTail</span> is
+ permitted but a <span class="nt">RegularExpressionLiteral</span> is not permitted. In all other contexts, <span
+ class="nt">InputElementDiv</span> is used as the lexical goal symbol.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The use of multiple lexical goals ensures that there are no lexical ambiguities that would
+ affect <a href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a>. For example, there are no syntactic
+ grammar contexts where both a leading division or division-assignment, and a leading <i>RegularExpressionLiteral</i> are
+ permitted. This is not affected by semicolon insertion (<a href="#sec-automatic-semicolon-insertion">see 11.9</a>); in
+ examples such as the following:</p>
+
+ <pre>a = b<br>/hi/g.exec(c).map(d);</pre>
+
+ <p>where the first non-whitespace, non-comment code point after a <i>LineTerminator</i> is SOLIDUS (<code>/</code>) and the
+ syntactic context allows division or division-assignment, no semicolon is inserted at the <i>LineTerminator</i>. That is,
+ the above example is interpreted in the same way as:</p>
+
+ <pre>a = b / hi / g.exec(c).map(d);</pre>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">InputElementDiv</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">DivPunctuator</span></div>
+ <div class="rhs"><span class="nt">RightBracePunctuator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">InputElementRegExp</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">RightBracePunctuator</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">InputElementRegExpOrTemplateTail</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateSubstitutionTail</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">InputElementTemplateTail</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">DivPunctuator</span></div>
+ <div class="rhs"><span class="nt">TemplateSubstitutionTail</span></div>
+ </div>
+ </div>
+
+ <section id="sec-unicode-format-control-characters">
+ <h1><span class="secnum" id="sec-11.1"><a href="#sec-unicode-format-control-characters"
+ title="link to this section">11.1</a></span> Unicode Format-Control Characters</h1>
+
+ <p>The Unicode format-control characters (i.e., the characters in category “Cf” in the Unicode Character Database
+ such as left-to-right mark or right-to-left mark) are control codes used to control the formatting of a range of text in the
+ absence of higher-level protocols for this (such as mark-up languages).</p>
+
+ <p>It is useful to allow format-control characters in source text to facilitate editing and display. All format control
+ characters may be used within comments, and within string literals, template literals, and regular expression literals.</p>
+
+ <p>U+200C <span style="font-family: Times New Roman">(</span>Zero width non-joiner<span style="font-family: Times New
+ Roman">)</span> and U+200D <span style="font-family: Times New Roman">(</span>Zero width joiner<span style="font-family: Times
+ New Roman">)</span> are format-control characters that are used to make necessary distinctions when forming words or phrases
+ in certain languages. In ECMAScript source text these code points may also be used in an <span
+ class="nt">IdentifierName</span> (<a href="#sec-identifier-names">see 11.6.1</a>) after the first character.</p>
+
+ <p>U+FEFF <span style="font-family: Times New Roman">(</span>Zero Width no-break space<span style="font-family: Times New
+ Roman">)</span> is a format-control character used primarily at the start of a text to mark it as Unicode and to allow
+ detection of the text's encoding and byte order. <span style="font-family: Times New Roman"><ZWNBSP></span> characters
+ intended for this purpose can sometimes also appear after the start of a text, for example as a result of concatenating files.
+ In ECMAScript source text <ZWNBSP> code points are treated as white space characters (<a href="#sec-white-space">see
+ 11.2</a>).</p>
+
+ <p>The special treatment of certain format-control characters outside of comments, string literals, and regular expression
+ literals is summarized in <a href="#table-31">Table 31</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-31">Table 31</span> — Format-Control Code Point Usage</figcaption>
+ <table class="real-table">
+ <tr>
+ <th>Code Point</th>
+ <th>Name</th>
+ <th>Abbreviation</th>
+ <th>Usage</th>
+ </tr>
+ <tr>
+ <td><code>U+200C</code></td>
+ <td>Zero width non-joiner</td>
+ <td><ZWNJ></td>
+ <td><i>IdentifierPart</i></td>
+ </tr>
+ <tr>
+ <td><code>U+200D</code></td>
+ <td>Zero width joiner</td>
+ <td><ZWJ></td>
+ <td><i>IdentifierPart</i></td>
+ </tr>
+ <tr>
+ <td><code>U+FEFF</code></td>
+ <td>ZERO WIDTH NO-BREAK SPACE</td>
+ <td><ZWNBSP></td>
+ <td><i>Whitespace</i></td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-white-space">
+ <h1><span class="secnum" id="sec-11.2"><a href="#sec-white-space" title="link to this section">11.2</a></span> White
+ Space</h1>
+
+ <p>White space code points are used to improve source text readability and to separate tokens (indivisible lexical units) from
+ each other, but are otherwise insignificant. White space code points may occur between any two tokens and at the start or end
+ of input. White space code points may occur within a <span class="nt">StringLiteral</span>, a <span
+ class="nt">RegularExpressionLiteral</span>, a <span class="nt">Template</span>, or a <span
+ class="nt">TemplateSubstitutionTail</span> where they are considered significant code points forming part of a literal value.
+ They may also occur within a <span class="nt">Comment</span>, but cannot appear within any other kind of token.</p>
+
+ <p>The ECMAScript white space code points are listed in <a href="#table-32">Table 32</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-32">Table 32</span> — Whitespace Code Points</figcaption>
+ <table class="real-table">
+ <tr>
+ <th>Code Point</th>
+ <th>Name</th>
+ <th>Abbreviation</th>
+ </tr>
+ <tr>
+ <td><code>U+0009</code></td>
+ <td>Character Tabulation</td>
+ <td><TAB></td>
+ </tr>
+ <tr>
+ <td><code>U+000B</code></td>
+ <td>LINE TABULATION</td>
+ <td><VT></td>
+ </tr>
+ <tr>
+ <td><code>U+000C</code></td>
+ <td>Form Feed (ff)</td>
+ <td><FF></td>
+ </tr>
+ <tr>
+ <td><code>U+0020</code></td>
+ <td>Space</td>
+ <td><SP></td>
+ </tr>
+ <tr>
+ <td><code>U+00A0</code></td>
+ <td>No-break space</td>
+ <td><NBSP></td>
+ </tr>
+ <tr>
+ <td><code>U+FEFF</code></td>
+ <td>ZERO wIDTH nO-bREAK SPACE</td>
+ <td><ZWNBSP></td>
+ </tr>
+ <tr>
+ <td>Other category “Zs”</td>
+ <td>Any other Unicode “Separator, space” code point</td>
+ <td><USP></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>ECMAScript implementations must recognize as <span class="nt">Whitespace</span> code points listed in the “Separator,
+ space” (Zs) category by Unicode 5.1. ECMAScript implementations may also recognize as <span class="nt">Whitespace</span>
+ additional category Zs code points from subsequent editions of the Unicode Standard.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Other than for the code points listed in <a href="#table-32">Table 32</a>, ECMAScript
+ <i>Whitespace</i> intentionally excludes all code points that have the Unicode “White_Space” property but which
+ are not classified in category “Zs”.</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">WhiteSpace</span> <span class="geq">::</span></div>
+ <div class="rhs"><TAB></div>
+ <div class="rhs"><VT></div>
+ <div class="rhs"><FF></div>
+ <div class="rhs"><SP></div>
+ <div class="rhs"><NBSP></div>
+ <div class="rhs"><zwnbsp></div>
+ <div class="rhs"><USP></div>
+ </div>
+ </section>
+
+ <section id="sec-line-terminators">
+ <h1><span class="secnum" id="sec-11.3"><a href="#sec-line-terminators" title="link to this section">11.3</a></span> Line
+ Terminators</h1>
+
+ <p>Like white space code points, line terminator code points are used to improve source text readability and to separate
+ tokens (indivisible lexical units) from each other. However, unlike white space code points, line terminators have some
+ influence over the behaviour of the syntactic grammar. In general, line terminators may occur between any two tokens, but
+ there are a few places where they are forbidden by the syntactic grammar. Line terminators also affect the process of <a
+ href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a> (<a
+ href="#sec-automatic-semicolon-insertion">11.9</a>). A line terminator cannot occur within any token except a <span
+ class="nt">StringLiteral</span>, <span class="nt">Template</span>, or <span class="nt">TemplateSubstitutionTail</span>. Line
+ terminators may only occur within a <span class="nt">StringLiteral</span> token as part of a <span
+ class="nt">LineContinuation</span>.</p>
+
+ <p>A line terminator can occur within a <span class="nt">MultiLineComment</span> (<a href="#sec-comments">11.4</a>) but cannot
+ occur within a <span class="nt">SingleLineComment</span>.</p>
+
+ <p>Line terminators are included in the set of white space code points that are matched by the <code>\s</code> class in
+ regular expressions.</p>
+
+ <p>The ECMAScript line terminator code points are listed in <a href="#table-33">Table 33</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-33">Table 33</span> — Line Terminator Code Points</figcaption>
+ <table class="real-table">
+ <tr>
+ <th>Code Point</th>
+ <th>Unicode Name</th>
+ <th>Abbreviation</th>
+ </tr>
+ <tr>
+ <td><code>U+000A</code></td>
+ <td>Line Feed (LF)</td>
+ <td><LF></td>
+ </tr>
+ <tr>
+ <td><code>U+000D</code></td>
+ <td>Carriage Return (CR)</td>
+ <td><CR></td>
+ </tr>
+ <tr>
+ <td><code>U+2028</code></td>
+ <td>Line separator</td>
+ <td><LS></td>
+ </tr>
+ <tr>
+ <td><code>U+2029</code></td>
+ <td>Paragraph separator</td>
+ <td><PS></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>Only the Unicode code points in <a href="#table-33">Table 33</a> are treated as line terminators. Other new line or line
+ breaking Unicode code points are not treated as line terminators but are treated as white space if they meet the requirements
+ listed in <a href="#table-32">Table 32</a>. The sequence <CR><LF> is commonly used as a line terminator. It should
+ be considered a single <span class="nt">SourceCharacter</span> for the purpose of reporting line numbers.</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LineTerminator</span> <span class="geq">::</span></div>
+ <div class="rhs"><LF></div>
+ <div class="rhs"><CR></div>
+ <div class="rhs"><LS></div>
+ <div class="rhs"><PS></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LineTerminatorSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><LF></div>
+ <div class="rhs"><CR> <span class="grhsannot">[lookahead ≠ <LF> ]</span></div>
+ <div class="rhs"><LS></div>
+ <div class="rhs"><PS></div>
+ <div class="rhs"><CR> <LF></div>
+ </div>
+ </section>
+
+ <section id="sec-comments">
+ <h1><span class="secnum" id="sec-11.4"><a href="#sec-comments" title="link to this section">11.4</a></span> Comments</h1>
+
+ <p>Comments can be either single or multi-line. Multi-line comments cannot nest.</p>
+
+ <p>Because a single-line comment can contain any Unicode code point except a <span class="nt">LineTerminator</span> code
+ point, and because of the general rule that a token is always as long as possible, a single-line comment always consists of
+ all code points from the <code>//</code> marker to the end of the line. However, the <span class="nt">LineTerminator</span> at
+ the end of the line is not considered to be part of the single-line comment; it is recognized separately by the lexical
+ grammar and becomes part of the stream of input elements for the syntactic grammar. This point is very important, because it
+ implies that the presence or absence of single-line comments does not affect the process of <a
+ href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a> (<a href="#sec-automatic-semicolon-insertion">see
+ 11.9</a>).</p>
+
+ <p>Comments behave like white space and are discarded except that, if a <span class="nt">MultiLineComment</span> contains a
+ line terminator code point, then the entire comment is considered to be a <span class="nt">LineTerminator</span> for purposes
+ of parsing by the syntactic grammar.</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Comment</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">MultiLineComment</span></div>
+ <div class="rhs"><span class="nt">SingleLineComment</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiLineComment</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">/*</code> <span class="nt">MultiLineCommentChars</span><sub>opt</sub> <code class="t">*/</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiLineCommentChars</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">MultiLineNotAsteriskChar</span> <span class="nt">MultiLineCommentChars</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">PostAsteriskCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PostAsteriskCommentChars</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">MultiLineNotForwardSlashOrAsteriskChar</span> <span class="nt">MultiLineCommentChars</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">PostAsteriskCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiLineNotAsteriskChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <code class="t">*</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiLineNotForwardSlashOrAsteriskChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">/</code> <span class="grhsmod">or</span> <code class="t">*</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineComment</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">//</code> <span class="nt">SingleLineCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineCommentChars</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleLineCommentChar</span> <span class="nt">SingleLineCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineCommentChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">LineTerminator</span></div>
+ </div>
+ </section>
+
+ <section id="sec-tokens">
+ <h1><span class="secnum" id="sec-11.5"><a href="#sec-tokens" title="link to this section">11.5</a></span> Tokens</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CommonToken</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">Punctuator</span></div>
+ <div class="rhs"><span class="nt">NumericLiteral</span></div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ <div class="rhs"><span class="nt">Template</span></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <i>DivPunctuator</i>, <i>RegularExpressionLiteral</i>, <i>RightBracePunctuator,</i> and
+ <i>TemplateSubstitutionTail</i> productions define tokens, but are not included in the <i>CommonToken</i> production.</p>
+ </div>
+ </section>
+
+ <section id="sec-names-and-keywords">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.6"><a href="#sec-names-and-keywords" title="link to this section">11.6</a></span> Names
+ and Keywords</h1>
+
+ <p><span class="nt">IdentifierName</span> and <span class="nt">ReservedWord</span> are tokens that are interpreted according
+ to the Default Identifier Syntax given in Unicode Standard Annex #31, Identifier and Pattern Syntax, with some small
+ modifications. <span class="nt">ReservedWord</span> is an enumerated subset of <span style="font-family: Times New
+ Roman"><i>IdentifierName</i>.</span> The syntactic grammar defines <span class="nt">Identifier</span> as an <span
+ class="nt">IdentifierName</span> that is not a <span class="nt">ReservedWord</span> (<a href="#sec-reserved-words">see
+ 11.6.2</a>). The Unicode identifier grammar is based on character properties specified by the Unicode Standard. The Unicode
+ code points in the specified categories in version 5.1.0 of the Unicode standard must be treated as in those categories by
+ all conforming ECMAScript implementations. ECMAScript implementations may recognize identifier code points defined in later
+ editions of the Unicode Standard.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> This standard specifies specific code point additions: <span style="font-family:
+ sans-serif">U+0024</span> (dollar sign) and <span style="font-family: sans-serif">U+005F</span> (<span style="font-family:
+ sans-serif">LOW LINE</span>) are permitted anywhere in an <i>IdentifierName</i><span style="font-family: sans-serif">, and
+ the code points</span> <span style="font-family: sans-serif">U+200C (zero-width non-joiner) and U+200D (zero-width joiner)
+ are permitted anywhere after the first code point</span> <span style="font-family: sans-serif">of an</span>
+ <i>IdentifierName</i>.</p>
+ </div>
+
+ <p>Unicode escape sequences are permitted in an <span class="nt">IdentifierName</span>, where they contribute a single
+ Unicode code point to the <span class="nt">IdentifierName</span>. The code point is expressed by the <span
+ class="nt">HexDigits</span> of the <span class="nt">UnicodeEscapeSequence</span> (<a
+ href="#sec-literals-string-literals">see 11.8.4</a>). The <code>\</code> preceding the <span
+ class="nt">UnicodeEscapeSequence</span> and the <code>u</code> and <code>{ }</code> code units, if they appear, do not
+ contribute code points to the <span class="nt">IdentifierName</span>. A <span class="nt">UnicodeEscapeSequence</span> cannot
+ be used to put a code point into an <span class="nt">IdentifierName</span> that would otherwise be illegal. In other words,
+ if a <code>\</code> <span class="nt">UnicodeEscapeSequence</span> sequence were replaced by the <span
+ class="nt">SourceCharacter</span> it contributes, the result must still be a valid <span class="nt">IdentifierName</span>
+ that has the exact same sequence of <span class="nt">SourceCharacter</span> elements as the original <span
+ class="nt">IdentifierName</span>. All interpretations of <span class="nt">IdentifierName</span> within this specification
+ are based upon their actual code points regardless of whether or not an escape sequence was used to contribute any
+ particular code point.</p>
+
+ <p>Two <span class="nt">IdentifierName</span> that are canonically equivalent according to the Unicode standard are
+ <i>not</i> equal unless they are represented by the exact same sequence of code points (in other words, conforming
+ ECMAScript implementations are only required to do bitwise comparison on <span class="nt">IdentifierName</span> values).</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IdentifierName</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">IdentifierStart</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <span class="nt">IdentifierPart</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IdentifierStart</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">UnicodeIDStart</span></div>
+ <div class="rhs"><code class="t">$</code></div>
+ <div class="rhs"><code class="t">_</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">UnicodeEscapeSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IdentifierPart</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">UnicodeIDContinue</span></div>
+ <div class="rhs"><code class="t">$</code></div>
+ <div class="rhs"><code class="t">_</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">UnicodeEscapeSequence</span></div>
+ <div class="rhs"><ZWNJ></div>
+ <div class="rhs"><ZWJ></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnicodeIDStart</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="gprose">any Unicode code point with the Unicode property “ID_Start” or “Other_ID_Start”</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnicodeIDContinue</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="gprose">any Unicode code point with the Unicode property “ID_Continue”, “Other_ID_Continue”,</span></div>
+ <div class="rhs"><span class="grhsmod">or</span> <code class="t">“Other_ID_Start”</code></div>
+ </div>
+
+ <p>The definitions of the nonterminal <span class="nt">UnicodeEscapeSequence</span> is given in <a
+ href="#sec-literals-string-literals">11.8.4</a>.</p>
+ </div>
+
+ <section id="sec-identifier-names">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.6.1"><a href="#sec-identifier-names" title="link to this section">11.6.1</a></span>
+ Identifier Names</h1>
+ </div>
+
+ <section id="sec-identifier-names-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-11.6.1.1"><a href="#sec-identifier-names-static-semantics-early-errors"
+ title="link to this section">11.6.1.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">IdentifierStart</span> <span class="geq">::</span> <code class="t">\</code> <span class="nt">UnicodeEscapeSequence</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span style="font-family: Times New Roman">SV(<i>UnicodeEscapeSequence</i>)</span> is
+ neither the <a href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of a single
+ Unicode code point with the Unicode property “ID_Start” nor <code>"$"</code> or <code>"_"</code>.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">IdentifierPart</span> <span class="geq">::</span> <code class="t">\</code> <span class="nt">UnicodeEscapeSequence</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span style="font-family: Times New Roman">SV(<i>UnicodeEscapeSequence</i>)</span> is
+ neither the <a href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of a single
+ Unicode code point with the Unicode property “ID_Continue” nor <code>"$"</code> or <code>"_"</code> nor
+ the <a href="#sec-utf16encoding">UTF16Encoding</a> of either <ZWNJ> or <ZWJ>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-identifier-names-static-semantics-stringvalue">
+ <h1><span class="secnum" id="sec-11.6.1.2"><a href="#sec-identifier-names-static-semantics-stringvalue"
+ title="link to this section">11.6.1.2</a></span> Static Semantics<span style="font-family: sans-serif">:</span>
+ <i>StringValue</i></h1>
+
+ <p>See also: <a href="#sec-string-literals-static-semantics-stringvalue">11.8.4.2</a>, <a
+ href="#sec-identifiers-static-semantics-stringvalue">12.1.4</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IdentifierName</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">IdentifierStart</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <span class="nt">IdentifierPart</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return the String value consisting of the sequence of code units corresponding to <i>IdentifierName</i>. In
+ determining the sequence any occurrences of <code>\</code> <i>UnicodeEscapeSequence</i> are first replaced with the
+ code point represented by the <i>UnicodeEscapeSequence</i> and then the code points of the entire
+ <i>IdentifierName</i> are converted to code units by <a href="#sec-utf16encoding">UTF16Encoding</a> (<a
+ href="#sec-utf16encoding">10.1.1</a>) each code point.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-reserved-words">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.6.2"><a href="#sec-reserved-words" title="link to this section">11.6.2</a></span>
+ Reserved Words</h1>
+
+ <p>A reserved word is an <span class="nt">IdentifierName</span> that cannot be used as an <span
+ class="nt">Identifier</span>.</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ReservedWord</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">Keyword</span></div>
+ <div class="rhs"><span class="nt">FutureReservedWord</span></div>
+ <div class="rhs"><span class="nt">NullLiteral</span></div>
+ <div class="rhs"><span class="nt">BooleanLiteral</span></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <i>ReservedWord</i> definitions are specified as literal sequences of specific
+ <i>SourceCharacter</i> elements. A code point in a <i>ReservedWord</i> cannot be expressed by a <code>\</code>
+ <i>UnicodeEscapeSequence</i>.</p>
+ </div>
+ </div>
+
+ <section id="sec-keywords">
+ <h1><span class="secnum" id="sec-11.6.2.1"><a href="#sec-keywords" title="link to this section">11.6.2.1</a></span>
+ Keywords</h1>
+
+ <p>The following tokens are ECMAScript keywords and may not be used as <span class="nt">Identifiers</span> in ECMAScript
+ programs.</p>
+
+ <h2>Syntax</h2>
+ <div class="gp prod"><span class="nt">Keyword</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>break</code></td>
+ <td><code>do</code></td>
+ <td><code>in</code></td>
+ <td><code>typeof</code></td>
+ </tr>
+ <tr>
+ <td><code>case</code></td>
+ <td><code>else</code></td>
+ <td><code>instanceof</code></td>
+ <td><code>var</code></td>
+ </tr>
+ <tr>
+ <td><code>catch</code></td>
+ <td><code>export</code></td>
+ <td><code>new</code></td>
+ <td><code>void</code></td>
+ </tr>
+ <tr>
+ <td><code>class</code></td>
+ <td><code>extends</code></td>
+ <td><code>return</code></td>
+ <td><code>while</code></td>
+ </tr>
+ <tr>
+ <td><code>const</code></td>
+ <td><code>finally</code></td>
+ <td><code>super</code></td>
+ <td><code>with</code></td>
+ </tr>
+ <tr>
+ <td><code>continue</code></td>
+ <td><code>for</code></td>
+ <td><code>switch</code></td>
+ <td><code>yield</code></td>
+ </tr>
+ <tr>
+ <td><code>debugger</code></td>
+ <td><code>function</code></td>
+ <td><code>this</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>default</code></td>
+ <td><code>if</code></td>
+ <td><code>throw</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>delete</code></td>
+ <td><code>import</code></td>
+ <td><code>try</code></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In some contexts <code>yield</code> is given the semantics of an <i>Identifier</i>. See
+ <a href="#sec-identifiers-static-semantics-early-errors">12.1.1</a>. In <a href="#sec-strict-mode-code">strict mode
+ code</a>, <code>let</code> and <code>static</code> are treated as reserved keywords through static semantic restrictions
+ (see <a href="#sec-identifiers-static-semantics-early-errors">12.1.1</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-early-errors">13.2.1.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-early-errors">13.6.4.1</a>, and <a
+ href="#sec-class-definitions-static-semantics-early-errors">14.5.1</a>) rather than the lexical grammar.</p>
+ </div>
+ </section>
+
+ <section id="sec-future-reserved-words">
+ <h1><span class="secnum" id="sec-11.6.2.2"><a href="#sec-future-reserved-words"
+ title="link to this section">11.6.2.2</a></span> Future Reserved Words</h1>
+
+ <p>The following tokens are reserved for used as keywords in future language extensions.</p>
+
+ <h2>Syntax</h2>
+ <div class="gp prod"><span class="nt">FutureReservedWord</span> <span class="geq">::</span></div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>enum<br>await</code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p><code>await</code> is only treated as a <span class="nt">FutureReservedWord</span> when <span class="nt">Module</span>
+ is the goal symbol of the syntactic grammar.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Use of the following tokens within <a href="#sec-strict-mode-code">strict mode code</a>
+ (<a href="#sec-strict-mode-code">see 10.2.1</a>) is also reserved. That usage is restricted using static semantic
+ restrictions (<a href="#sec-identifiers-static-semantics-early-errors">see 12.1.1</a>) rather than the lexical
+ grammar:</p>
+ </div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>implements</code></td>
+ <td><code>package</code></td>
+ <td><code>protected</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>interface</code></td>
+ <td><code>private</code></td>
+ <td><code>public</code></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-punctuators">
+ <h1><span class="secnum" id="sec-11.7"><a href="#sec-punctuators" title="link to this section">11.7</a></span>
+ Punctuators</h1>
+ <h2>Syntax</h2>
+ <div class="gp prod"><span class="nt">Punctuator</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>{</code></td>
+ <td><code>(</code></td>
+ <td><code>)</code></td>
+ <td><code>[</code></td>
+ <td><code>]</code></td>
+ <td><code>.</code></td>
+ </tr>
+ <tr>
+ <td><code>...</code></td>
+ <td><code>;</code></td>
+ <td><code>,</code></td>
+ <td><code><</code></td>
+ <td><code>></code></td>
+ <td><code><=</code></td>
+ </tr>
+ <tr>
+ <td><code>>=</code></td>
+ <td><code>==</code></td>
+ <td><code>!=</code></td>
+ <td><code>===</code></td>
+ <td><code>!==</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>+</code></td>
+ <td><code>-</code></td>
+ <td><code>*</code></td>
+ <td><code>%</code></td>
+ <td><code>++</code></td>
+ <td><code>--</code></td>
+ </tr>
+ <tr>
+ <td><code><<</code></td>
+ <td><code>>></code></td>
+ <td><code>>>></code></td>
+ <td><code>&</code></td>
+ <td><code>|</code></td>
+ <td><code>^</code></td>
+ </tr>
+ <tr>
+ <td><code>!</code></td>
+ <td><code>~</code></td>
+ <td><code>&&</code></td>
+ <td><code>||</code></td>
+ <td><code>?</code></td>
+ <td><code>:</code></td>
+ </tr>
+ <tr>
+ <td><code>=</code></td>
+ <td><code>+=</code></td>
+ <td><code>-=</code></td>
+ <td><code>*=</code></td>
+ <td><code>%=</code></td>
+ <td><code><<=</code></td>
+ </tr>
+ <tr>
+ <td><code>>>=</code></td>
+ <td><code>>>>=</code></td>
+ <td><code>&=</code></td>
+ <td><code>|=</code></td>
+ <td><code>^=</code></td>
+ <td><code>=></code></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp prod"><span class="nt">DivPunctuator</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>/</code></td>
+ <td><code>/=</code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp prod"><span class="nt">RightBracePunctuator</span> <span class="geq">::</span></div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>}</code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-ecmascript-language-lexical-grammar-literals">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.8"><a href="#sec-ecmascript-language-lexical-grammar-literals"
+ title="link to this section">11.8</a></span> Literals</h1>
+ </div>
+
+ <section id="sec-null-literals">
+ <h1><span class="secnum" id="sec-11.8.1"><a href="#sec-null-literals" title="link to this section">11.8.1</a></span> Null
+ Literals</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NullLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">null</code></div>
+ </div>
+ </section>
+
+ <section id="sec-boolean-literals">
+ <h1><span class="secnum" id="sec-11.8.2"><a href="#sec-boolean-literals" title="link to this section">11.8.2</a></span>
+ Boolean Literals</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BooleanLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">true</code></div>
+ <div class="rhs"><code class="t">false</code></div>
+ </div>
+ </section>
+
+ <section id="sec-literals-numeric-literals">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.8.3"><a href="#sec-literals-numeric-literals"
+ title="link to this section">11.8.3</a></span> Numeric Literals</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NumericLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalLiteral</span></div>
+ <div class="rhs"><span class="nt">BinaryIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">OctalIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">HexIntegerLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalIntegerLiteral</span> <code class="t">.</code> <span class="nt">DecimalDigits</span><sub>opt</sub> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">.</code> <span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">DecimalIntegerLiteral</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0</code></div>
+ <div class="rhs"><span class="nt">NonZeroDigit</span> <span class="nt">DecimalDigits</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalDigits</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <span class="nt">DecimalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonZeroDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExponentPart</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">ExponentIndicator</span> <span class="nt">SignedInteger</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExponentIndicator</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">e</code> <code class="t">E</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SignedInteger</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">DecimalDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BinaryIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0b</code> <span class="nt">BinaryDigits</span></div>
+ <div class="rhs"><code class="t">0B</code> <span class="nt">BinaryDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BinaryDigits</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">BinaryDigit</span></div>
+ <div class="rhs"><span class="nt">BinaryDigits</span> <span class="nt">BinaryDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BinaryDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">OctalIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0o</code> <span class="nt">OctalDigits</span></div>
+ <div class="rhs"><code class="t">0O</code> <span class="nt">OctalDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">OctalDigits</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">OctalDigit</span></div>
+ <div class="rhs"><span class="nt">OctalDigits</span> <span class="nt">OctalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">OctalDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">HexIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0x</code> <span class="nt">HexDigits</span></div>
+ <div class="rhs"><code class="t">0X</code> <span class="nt">HexDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">HexDigits</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">HexDigit</span></div>
+ <div class="rhs"><span class="nt">HexDigits</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">HexDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code> <code class="t">a</code> <code class="t">b</code> <code class="t">c</code> <code class="t">d</code> <code class="t">e</code> <code class="t">f</code> <code class="t">A</code> <code class="t">B</code> <code class="t">C</code> <code class="t">D</code> <code class="t">E</code> <code class="t">F</code></div>
+ </div>
+
+ <p>The <span class="nt">SourceCharacter</span> immediately following a <span class="nt">NumericLiteral</span> must not be
+ an <span class="nt">IdentifierStart</span> or <span class="nt">DecimalDigit</span>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For example:</p>
+
+ <pre>3in</pre>
+
+ <p>is an error and not the two input elements <code>3</code> and <code>in</code>.</p>
+ </div>
+
+ <p>A conforming implementation, when processing <a href="#sec-strict-mode-code">strict mode code</a> (<a
+ href="#sec-strict-mode-code">see 10.2.1</a>), must not extend, as described in <a
+ href="#sec-additional-syntax-numeric-literals">B.1.1</a>, the syntax of <span class="nt">NumericLiteral</span> to include
+ <i>Legacy<span style="font-family: Times New Roman">OctalIntegerLiteral</span></i>, nor extend the syntax of <span
+ class="nt">DecimalIntegerLiteral</span> to include <span class="nt">NonOctalDecimalIntegerLiteral</span>.</p>
+ </div>
+
+ <section id="sec-static-semantics-mv-s">
+ <h1><span class="secnum" id="sec-11.8.3.1"><a href="#sec-static-semantics-mv-s"
+ title="link to this section">11.8.3.1</a></span> Static Semantics: MV’s</h1>
+
+ <p>A numeric literal stands for a value of the Number type. This value is determined in two steps: first, a mathematical
+ value (MV) is derived from the literal; second, this mathematical value is rounded as described below.</p>
+
+ <ul>
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NumericLiteral</span> <span class="geq">::</span> <span
+ class="nt">DecimalLiteral</span></span> is the MV of <i>DecimalLiteral</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NumericLiteral</span> <span class="geq">::</span> <span
+ class="nt">BinaryIntegerLiteral</span></span> is the MV of <i>BinaryIntegerLiteral</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NumericLiteral</span> <span class="geq">::</span> <span
+ class="nt">OctalIntegerLiteral</span></span> is the MV of <i>OctalIntegerLiteral</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NumericLiteral</span> <span class="geq">::</span> <span
+ class="nt">HexIntegerLiteral</span></span> is the MV of <i>HexIntegerLiteral</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <span
+ class="nt">DecimalIntegerLiteral</span> <code class="t">.</code></span> is the MV of <i>DecimalIntegerLiteral</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <span
+ class="nt">DecimalIntegerLiteral</span> <code class="t">.</code> <span class="nt">DecimalDigits</span></span> is the
+ MV of <i>DecimalIntegerLiteral</i> plus (the MV of <i>DecimalDigits</i> × 10<sup>–<i>n</i></sup>), where
+ <i>n</i> is the number of code points in <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <span
+ class="nt">DecimalIntegerLiteral</span> <code class="t">.</code> <span class="nt">ExponentPart</span></span> is the MV
+ of <i>DecimalIntegerLiteral</i> × 10<sup><i>e</i></sup>, where <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <span
+ class="nt">DecimalIntegerLiteral</span> <code class="t">.</code> <span class="nt">DecimalDigits</span> <span
+ class="nt">ExponentPart</span></span> is (the MV of <i>DecimalIntegerLiteral</i> plus (the MV of <i>DecimalDigits</i>
+ × 10<sup>–<i>n</i></sup>)) × 10<sup><i>e</i></sup>, where <i>n</i> is the number of code points in
+ <i>DecimalDigits</i> and <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <code
+ class="t">.</code> <span class="nt">DecimalDigits</span></span> is the MV of <i>DecimalDigits</i> ×
+ 10<sup>–<i>n</i></sup>, where <i>n</i> is the number of code points in <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <code
+ class="t">.</code> <span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span></span> is the MV of
+ <i>DecimalDigits</i> × 10<sup><i>e</i>–<i>n</i></sup>, where <i>n</i> is the number of code points in
+ <i>DecimalDigits</i> and <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <span
+ class="nt">DecimalIntegerLiteral</span></span> is the MV of <i>DecimalIntegerLiteral</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> <span
+ class="nt">DecimalIntegerLiteral</span> <span class="nt">ExponentPart</span></span> is the MV of
+ <i>DecimalIntegerLiteral</i> × 10<sup><i>e</i></sup>, where <i>e</i> is the MV of <i>ExponentPart</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0</code></span> is 0.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalIntegerLiteral</span> <span class="geq">::</span> <span
+ class="nt">NonZeroDigit</span></span> is the MV of <i>NonZeroDigit.</i></p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalIntegerLiteral</span> <span class="geq">::</span> <span
+ class="nt">NonZeroDigit</span> <span class="nt">DecimalDigits</span></span> is (the MV of <i>NonZeroDigit</i> ×
+ 10<sup><i>n</i></sup>) plus the MV of <i>DecimalDigits</i>, where <i>n</i> is the number of code points in
+ <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigits</span> <span class="geq">::</span> <span
+ class="nt">DecimalDigit</span></span> is the MV of <i>DecimalDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigits</span> <span class="geq">::</span> <span
+ class="nt">DecimalDigits</span> <span class="nt">DecimalDigit</span></span> is (the MV of <i>DecimalDigits</i> ×
+ 10) plus the MV of <i>DecimalDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">ExponentPart</span> <span class="geq">::</span> <span
+ class="nt">ExponentIndicator</span> <span class="nt">SignedInteger</span></span> is the MV of
+ <i>SignedInteger</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">SignedInteger</span> <span class="geq">::</span> <span
+ class="nt">DecimalDigits</span></span> is the MV of <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">SignedInteger</span> <span class="geq">::</span> <code
+ class="t">+</code> <span class="nt">DecimalDigits</span></span> is the MV of <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">SignedInteger</span> <span class="geq">::</span> <code
+ class="t">-</code> <span class="nt">DecimalDigits</span></span> is the negative of the MV of <i>DecimalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">0</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">0</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span class="geq">::</span>
+ <code class="t">0</code></span> or of <span class="prod"><span class="nt">BinaryDigit</span> <span
+ class="geq">::</span> <code class="t">0</code></span> is 0.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">1</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">1</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">1</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span
+ class="geq">::</span> <code class="t">1</code></span> or<br>of <span class="prod"><span class="nt">BinaryDigit</span>
+ <span class="geq">::</span> <code class="t">1</code></span> is 1.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">2</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">2</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">2</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span
+ class="geq">::</span> <code class="t">2</code></span> is 2.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">3</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">3</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">3</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span
+ class="geq">::</span> <code class="t">3</code></span> is 3.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">4</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">4</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">4</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span
+ class="geq">::</span> <code class="t">4</code></span> is 4.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">5</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">5</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">5</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span
+ class="geq">::</span> <code class="t">5</code></span> is 5.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">6</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">6</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">6</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span
+ class="geq">::</span> <code class="t">6</code></span> is 6.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">7</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">7</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">7</code></span> or of <span class="prod"><span class="nt">OctalDigit</span> <span
+ class="geq">::</span> <code class="t">7</code></span> is 7.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">8</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">8</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">8</code></span> is 8.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <code
+ class="t">9</code></span> or of <span class="prod"><span class="nt">NonZeroDigit</span> <span class="geq">::</span>
+ <code class="t">9</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span>
+ <code class="t">9</code></span> is 9.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">a</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">A</code></span> is 10.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">b</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">B</code></span> is 11.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">c</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">C</code></span> is 12.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">d</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">D</code></span> is 13.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">e</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">E</code></span> is 14.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">f</code></span> or of <span class="prod"><span class="nt">HexDigit</span> <span class="geq">::</span> <code
+ class="t">F</code></span> is 15.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">BinaryIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0b</code> <span class="nt">BinaryDigits</span></span> is the MV of <i>BinaryDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">BinaryIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0B</code> <span class="nt">BinaryDigits</span></span> is the MV of <i>BinaryDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">BinaryDigits</span> <span class="geq">::</span> <span
+ class="nt">BinaryDigit</span></span> is the MV of <i>BinaryDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">BinaryDigits</span> <span class="geq">::</span> <span
+ class="nt">BinaryDigits</span> <span class="nt">BinaryDigit</span></span> is (the MV of <i>BinaryDigits</i> × 2)
+ plus the MV of <i>BinaryDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">OctalIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0o</code> <span class="nt">OctalDigits</span></span> is the MV of <i>OctalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">OctalIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0O</code> <span class="nt">OctalDigits</span></span> is the MV of <i>OctalDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">OctalDigits</span> <span class="geq">::</span> <span
+ class="nt">OctalDigit</span></span> is the MV of <i>OctalDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">OctalDigits</span> <span class="geq">::</span> <span
+ class="nt">OctalDigits</span> <span class="nt">OctalDigit</span></span> is (the MV of <i>OctalDigits</i> × 8)
+ plus the MV of <i>OctalDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0x</code> <span class="nt">HexDigits</span></span> is the MV of <i>HexDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0X</code> <span class="nt">HexDigits</span></span> is the MV of <i>HexDigits</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigits</span> <span class="geq">::</span> <span
+ class="nt">HexDigit</span></span> is the MV of <i>HexDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">HexDigits</span> <span class="geq">::</span> <span
+ class="nt">HexDigits</span> <span class="nt">HexDigit</span></span> is (the MV of <i>HexDigits</i> × 16) plus
+ the MV of <i>HexDigit</i>.</p>
+ </li>
+ </ul>
+
+ <p>Once the exact MV for a numeric literal has been determined, it is then rounded to a value of the Number type. If the
+ MV is 0, then the rounded value is <span class="value">+0</span>; otherwise, the rounded value must be the Number value
+ for the MV (as specified in <a href="#sec-ecmascript-language-types-number-type">6.1.6</a>), unless the literal is a <span
+ class="nt">DecimalLiteral</span> and the literal has more than 20 significant digits, in which case the Number value may
+ be either the Number value for the MV of a literal produced by replacing each significant digit after the 20th with a
+ <code>0</code> digit or the Number value for the MV of a literal produced by replacing each significant digit after the
+ 20th with a <code>0</code> digit and then incrementing the literal at the 20th significant digit position. A digit is
+ <i>significant</i> if it is not part of an <span class="nt">ExponentPart</span> and</p>
+
+ <ul>
+ <li>it is not <code>0</code>; or</li>
+ <li>there is a nonzero digit to its left and there is a nonzero digit, not in the <i>ExponentPart</i>, to its
+ right.</li>
+ </ul>
+ </section>
+ </section>
+
+ <section id="sec-literals-string-literals">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.8.4"><a href="#sec-literals-string-literals"
+ title="link to this section">11.8.4</a></span> String Literals</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A string literal is zero or more Unicode code points enclosed in single or double
+ quotes. Unicode code points may also be represented by an escape sequence. All <span style="font-family:
+ sans-serif">code points</span> may appear literally in a string literal except for the closing quote <span
+ style="font-family: sans-serif">code points</span>, REVERSE SOLIDUS (\), carriage return (CR), line separator, paragraph
+ separator, and line feed (LF). Any <span style="font-family: sans-serif">code points</span> may appear in the form of an
+ escape sequence. String literals evaluate to ECMAScript String values. When generating these string values Unicode code
+ points are UTF-16 encoded as defined in <a href="#sec-utf16encoding">10.1.1</a>. Code points belonging to the Basic
+ Multilingual Plane are encoded as a single code unit element of the string. All other code points are encoded as two
+ code unit elements of the string.</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StringLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">"</code> <span class="nt">DoubleStringCharacters</span><sub>opt</sub> <code class="t">"</code></div>
+ <div class="rhs"><code class="t">'</code> <span class="nt">SingleStringCharacters</span><sub>opt</sub> <code class="t">'</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DoubleStringCharacters</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DoubleStringCharacter</span> <span class="nt">DoubleStringCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleStringCharacters</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleStringCharacter</span> <span class="nt">SingleStringCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DoubleStringCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">"</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">EscapeSequence</span></div>
+ <div class="rhs"><span class="nt">LineContinuation</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleStringCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">'</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">EscapeSequence</span></div>
+ <div class="rhs"><span class="nt">LineContinuation</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LineContinuation</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">LineTerminatorSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EscapeSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">CharacterEscapeSequence</span></div>
+ <div class="rhs"><code class="t">0</code> <span class="grhsannot">[lookahead ∉ <span class="nt">DecimalDigit</span>]</span></div>
+ <div class="rhs"><span class="nt">HexEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">UnicodeEscapeSequence</span></div>
+ </div>
+
+ <p>A conforming implementation, when processing <a href="#sec-strict-mode-code">strict mode code</a> (<a
+ href="#sec-strict-mode-code">see 10.2.1</a>), must not extend the syntax of <span class="nt">EscapeSequence</span> to
+ include <i>Legacy<span style="font-family: Times New Roman">OctalEscapeSequence</span></i> as described in <a
+ href="#sec-additional-syntax-string-literals">B.1.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CharacterEscapeSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleEscapeCharacter</span></div>
+ <div class="rhs"><span class="nt">NonEscapeCharacter</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleEscapeCharacter</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">'</code> <code class="t">"</code> <code class="t">\</code> <code class="t">b</code> <code class="t">f</code> <code class="t">n</code> <code class="t">r</code> <code class="t">t</code> <code class="t">v</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonEscapeCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <span class="nt">EscapeCharacter</span> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EscapeCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleEscapeCharacter</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><code class="t">x</code></div>
+ <div class="rhs"><code class="t">u</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">HexEscapeSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">x</code> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnicodeEscapeSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">u</code> <span class="nt">Hex4Digits</span></div>
+ <div class="rhs"><code class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Hex4Digits</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <p>The definition of the nonterminal <span class="nt">HexDigit</span> is given in <a
+ href="#sec-literals-numeric-literals">11.8.3</a>. <span class="nt">SourceCharacter</span> is defined in <a
+ href="#sec-source-text">10.1</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A line terminator <span style="font-family: sans-serif">code point</span> cannot appear
+ in a string literal, except as part of a <i>LineContinuation</i> to produce the empty <span style="font-family:
+ sans-serif">code points</span> sequence. The proper way to cause a line terminator <span style="font-family:
+ sans-serif">code point</span> to be part of the String value of a string literal is to use an escape sequence such as
+ <code>\n</code> or <code>\u000A</code>.</p>
+ </div>
+ </div>
+
+ <section id="sec-string-literals-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-11.8.4.1"><a href="#sec-string-literals-static-semantics-early-errors"
+ title="link to this section">11.8.4.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">UnicodeEscapeSequence</span> <span class="geq">::</span> <code class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></div>
+ <ul>
+ <li>It is a Syntax Error if the MV of <span class="nt">HexDigits</span> > <span style="font-family: Times New
+ Roman">1114111<i>.</i></span></li>
+ </ul>
+ </section>
+
+ <section id="sec-string-literals-static-semantics-stringvalue">
+ <h1><span class="secnum" id="sec-11.8.4.2"><a href="#sec-string-literals-static-semantics-stringvalue"
+ title="link to this section">11.8.4.2</a></span> Static Semantics<span style="font-family: sans-serif">:</span>
+ <i>StringValue</i></h1>
+
+ <p>See also: <a href="#sec-identifier-names-static-semantics-stringvalue">11.6.1.2</a>, <a
+ href="#sec-identifiers-static-semantics-stringvalue">12.1.4</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StringLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">"</code> <span class="nt">DoubleStringCharacters</span><sub>opt</sub> <code class="t">"</code></div>
+ <div class="rhs"><code class="t">'</code> <span class="nt">SingleStringCharacters</span><sub>opt</sub> <code class="t">'</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return the String value whose elements are the SV of this <i>StringLiteral</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-sv-s">
+ <h1><span class="secnum" id="sec-11.8.4.3"><a href="#sec-static-semantics-sv-s"
+ title="link to this section">11.8.4.3</a></span> Static Semantics: <i>SV’s</i></h1>
+
+ <p>A string literal stands for a value of the String type. The String value (SV) of the literal is described in terms of
+ code unit values contributed by the various parts of the string literal. As part of this process, some Unicode code points
+ within the string literal are interpreted as having a mathematical value (MV), as described below or in <a
+ href="#sec-literals-numeric-literals">11.8.3</a>.</p>
+
+ <ul>
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">StringLiteral</span> <span class="geq">::</span> <code
+ class="t">""</code></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">StringLiteral</span> <span class="geq">::</span> <code
+ class="t">''</code></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">StringLiteral</span> <span class="geq">::</span> <code
+ class="t">"</code> <span class="nt">DoubleStringCharacters</span> <code class="t">"</code></span> is the SV of
+ <i>DoubleStringCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">StringLiteral</span> <span class="geq">::</span> <code
+ class="t">'</code> <span class="nt">SingleStringCharacters</span> <code class="t">'</code></span> is the SV of
+ <i>SingleStringCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">DoubleStringCharacters</span> <span class="geq">::</span> <span
+ class="nt">DoubleStringCharacter</span></span> is a sequence of one or two code units that is the SV of
+ <i>DoubleStringCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">DoubleStringCharacters</span> <span class="geq">::</span> <span
+ class="nt">DoubleStringCharacter</span> <span class="nt">DoubleStringCharacters</span></span> is a sequence of one or
+ two code units that is the SV of <i>DoubleStringCharacter</i> followed by all the code units in the SV of
+ <i>DoubleStringCharacters</i> in order.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">SingleStringCharacters</span> <span class="geq">::</span> <span
+ class="nt">SingleStringCharacter</span></span> is a sequence of one or two code units that is the SV of
+ <i>SingleStringCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">SingleStringCharacters</span> <span class="geq">::</span> <span
+ class="nt">SingleStringCharacter</span> <span class="nt">SingleStringCharacters</span></span> is a sequence of one or
+ two code units that is the SV of <i>SingleStringCharacter</i> followed by all the code units in the SV of
+ <i>SingleStringCharacters</i> in order.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">DoubleStringCharacter</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">"</code> <span
+ class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <span
+ class="nt">LineTerminator</span></span> is the <a href="#sec-utf16encoding">UTF16Encoding</a> (<a
+ href="#sec-utf16encoding">10.1.1</a>) of the code point value of <i>SourceCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">DoubleStringCharacter</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">EscapeSequence</span></span> is the SV of the <i>EscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">DoubleStringCharacter</span> <span class="geq">::</span> <span
+ class="nt">LineContinuation</span></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">SingleStringCharacter</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">'</code> <span
+ class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <span
+ class="nt">LineTerminator</span></span> is the <a href="#sec-utf16encoding">UTF16Encoding</a> (<a
+ href="#sec-utf16encoding">10.1.1</a>) of the code point value of <i>SourceCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">SingleStringCharacter</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">EscapeSequence</span></span> is the SV of the <i>EscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">SingleStringCharacter</span> <span class="geq">::</span> <span
+ class="nt">LineContinuation</span></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">CharacterEscapeSequence</span></span> is the SV of the <i>CharacterEscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <code
+ class="t">0</code></span> is the code unit value 0.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">HexEscapeSequence</span></span> is the SV of the <i>HexEscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">UnicodeEscapeSequence</span></span> is the SV of the <i>UnicodeEscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">CharacterEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">SingleEscapeCharacter</span></span> is the code unit whose value is determined by the
+ <i>SingleEscapeCharacter</i> according to <a href="#table-34">Table 34</a>.</p>
+ </li>
+ </ul>
+
+ <figure>
+ <figcaption><span id="table-34">Table 34</span> — String Single Character Escape Sequences</figcaption>
+ <table class="real-table">
+ <tr>
+ <th>Escape Sequence</th>
+ <th>Code Unit Value</th>
+ <th>Unicode Character Name</th>
+ <th>Symbol</th>
+ </tr>
+ <tr>
+ <td><code>\b</code></td>
+ <td><code>0x0008</code></td>
+ <td>BACKSPACE</td>
+ <td><BS></td>
+ </tr>
+ <tr>
+ <td><code>\t</code></td>
+ <td><code>0x0009</code></td>
+ <td>CHARACTER TABULATION</td>
+ <td><HT></td>
+ </tr>
+ <tr>
+ <td><code>\n</code></td>
+ <td><code>0x000A</code></td>
+ <td>line feed (lf)</td>
+ <td><LF></td>
+ </tr>
+ <tr>
+ <td><code>\v</code></td>
+ <td><code>0x000B</code></td>
+ <td>LINE TABULATION</td>
+ <td><VT></td>
+ </tr>
+ <tr>
+ <td><code>\f</code></td>
+ <td><code>0x000C</code></td>
+ <td>form feed (ff)</td>
+ <td><FF></td>
+ </tr>
+ <tr>
+ <td><code>\r</code></td>
+ <td><code>0x000D</code></td>
+ <td>carriage return (cr)</td>
+ <td><CR></td>
+ </tr>
+ <tr>
+ <td><code>\"</code></td>
+ <td><code>0x0022</code></td>
+ <td>quotation Mark</td>
+ <td><code>"</code></td>
+ </tr>
+ <tr>
+ <td><code>\'</code></td>
+ <td><code>0x0027</code></td>
+ <td>apostrophe</td>
+ <td><code>'</code></td>
+ </tr>
+ <tr>
+ <td><code>\\</code></td>
+ <td><code>0x005C</code></td>
+ <td>REverse Solidus</td>
+ <td><code>\</code></td>
+ </tr>
+ </table>
+ </figure>
+
+ <ul>
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">CharacterEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">NonEscapeCharacter</span></span> is the SV of the <i>NonEscapeCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">NonEscapeCharacter</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <span class="nt">EscapeCharacter</span>
+ <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></span> is the <a
+ href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of the code point value of
+ <i>SourceCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">HexEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">x</code> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></span> is the code unit value
+ that is (16 times the MV of the first <i>HexDigit</i>) plus the MV of the second <i>HexDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">UnicodeEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">u</code> <span class="nt">Hex4Digits</span></span> is the SV of <var>Hex4Digits.</var></p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">Hex4Digits</span> <span class="geq">::</span> <span
+ class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span
+ class="nt">HexDigit</span></span> is the code unit value that is (4096 times the MV of the first <i>HexDigit</i>) plus
+ (256 times the MV of the second <i>HexDigit</i>) plus (16 times the MV of the third <i>HexDigit</i>) plus the MV of
+ the fourth <i>HexDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">UnicodeEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></span> is the <a
+ href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of the MV of
+ <i>HexDigits</i>.</p>
+ </li>
+ </ul>
+ </section>
+ </section>
+
+ <section id="sec-literals-regular-expression-literals">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.8.5"><a href="#sec-literals-regular-expression-literals"
+ title="link to this section">11.8.5</a></span> Regular Expression Literals</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A regular expression literal is an input element that is converted to a RegExp object
+ (<a href="#sec-regexp-regular-expression-objects">see 21.2</a>) each time the literal is evaluated. Two regular
+ expression literals in a program evaluate to regular expression objects that never compare as <code>===</code> to each
+ other even if the two literals' contents are identical. A RegExp object may also be created at runtime by <code>new
+ RegExp</code> or calling the <code>RegExp</code> constructor as a function (<a href="#sec-regexp-constructor">see
+ 21.2.3</a>).</p>
+ </div>
+
+ <p>The productions below describe the syntax for a regular expression literal and are used by the input element scanner to
+ find the end of the regular expression literal. The source text comprising the <span
+ class="nt">RegularExpressionBody</span> and the <span class="nt">RegularExpressionFlags</span> are subsequently parsed
+ again using the more stringent ECMAScript Regular Expression grammar (<a href="#sec-patterns">21.2.1</a>).</p>
+
+ <p>An implementation may extend the ECMAScript Regular Expression grammar defined in <a href="#sec-patterns">21.2.1</a>,
+ but it must not extend the <span class="nt">RegularExpressionBody</span> and <span
+ class="nt">RegularExpressionFlags</span> productions defined below or the productions used by these productions.</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">/</code> <span class="nt">RegularExpressionBody</span> <code class="t">/</code> <span class="nt">RegularExpressionFlags</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionBody</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionFirstChar</span> <span class="nt">RegularExpressionChars</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionChars</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionChars</span> <span class="nt">RegularExpressionChar</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionFirstChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="grhsmod">but not one of</span> <code class="t">*</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">/</code> <span class="grhsmod">or</span> <code class="t">[</code></div>
+ <div class="rhs"><span class="nt">RegularExpressionBackslashSequence</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionClass</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">/</code> <span class="grhsmod">or</span> <code class="t">[</code></div>
+ <div class="rhs"><span class="nt">RegularExpressionBackslashSequence</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionClass</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionBackslashSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">RegularExpressionNonTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionClass</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">RegularExpressionClassChars</span> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionClassChars</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionClassChars</span> <span class="nt">RegularExpressionClassChar</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionClassChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="grhsmod">but not one of</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">\</code></div>
+ <div class="rhs"><span class="nt">RegularExpressionBackslashSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegularExpressionFlags</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionFlags</span> <span class="nt">IdentifierPart</span></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Regular expression literals may not be empty; instead of representing an empty regular
+ expression literal, the code unit sequence <code>//</code> starts a single-line comment. To specify an empty regular
+ expression, use: <code>/(?:)/</code>.</p>
+ </div>
+ </div>
+
+ <section id="sec-literals-regular-expression-literals-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-11.8.5.1"><a
+ href="#sec-literals-regular-expression-literals-static-semantics-early-errors"
+ title="link to this section">11.8.5.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">RegularExpressionFlags</span> <span class="geq">::</span> <span class="nt">RegularExpressionFlags</span> <span class="nt">IdentifierPart</span></div>
+ <ul>
+ <li>It is a Syntax Error if <span class="nt">IdentifierPart</span> contains a Unicode escape sequence<var>.</var></li>
+ </ul>
+ </section>
+
+ <section id="sec-static-semantics-bodytext">
+ <h1><span class="secnum" id="sec-11.8.5.2"><a href="#sec-static-semantics-bodytext"
+ title="link to this section">11.8.5.2</a></span> Static Semantics: <i>BodyText</i></h1>
+ <div class="gp prod"><span class="nt">RegularExpressionLiteral</span> <span class="geq">::</span> <code class="t">/</code> <span class="nt">RegularExpressionBody</span> <code class="t">/</code> <span class="nt">RegularExpressionFlags</span></div>
+ <ol class="proc">
+ <li>Return the source text that was recognized as <i>RegularExpressionBody</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-flagtext">
+ <h1><span class="secnum" id="sec-11.8.5.3"><a href="#sec-static-semantics-flagtext"
+ title="link to this section">11.8.5.3</a></span> Static Semantics: <i>FlagText</i></h1>
+ <div class="gp prod"><span class="nt">RegularExpressionLiteral</span> <span class="geq">::</span> <code class="t">/</code> <span class="nt">RegularExpressionBody</span> <code class="t">/</code> <span class="nt">RegularExpressionFlags</span></div>
+ <ol class="proc">
+ <li>Return the source text that was recognized as <i>RegularExpressionFlags</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-template-literal-lexical-components">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.8.6"><a href="#sec-template-literal-lexical-components"
+ title="link to this section">11.8.6</a></span> Template Literal Lexical Components</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Template</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">NoSubstitutionTemplate</span></div>
+ <div class="rhs"><span class="nt">TemplateHead</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NoSubstitutionTemplate</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">`</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">`</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateHead</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">`</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">${</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateSubstitutionTail</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">TemplateMiddle</span></div>
+ <div class="rhs"><span class="nt">TemplateTail</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateMiddle</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">}</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">${</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateTail</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">}</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">`</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateCharacters</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">TemplateCharacter</span> <span class="nt">TemplateCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">$</code> <span class="grhsannot">[lookahead ≠ { ]</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">EscapeSequence</span></div>
+ <div class="rhs"><span class="nt">LineContinuation</span></div>
+ <div class="rhs"><span class="nt">LineTerminatorSequence</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">`</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">$</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <p>A conforming implementation must not use the extended definition of <span class="nt">EscapeSequence</span> described in
+ <a href="#sec-additional-syntax-string-literals">B.1.2</a> when parsing a <span class="nt">TemplateCharacter</span>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <i>TemplateSubstitutionTail</i> is used by the <i>InputElementTemplateTail</i>
+ alternative lexical goal.</p>
+ </div>
+ </div>
+
+ <section id="sec-static-semantics-tv-s-and-trv-s">
+ <h1><span class="secnum" id="sec-11.8.6.1"><a href="#sec-static-semantics-tv-s-and-trv-s"
+ title="link to this section">11.8.6.1</a></span> Static Semantics: <i>TV’s and TRV’s</i></h1>
+
+ <p>A template literal component is interpreted as a sequence of Unicode code points. The Template Value (TV) of a literal
+ component is described in terms of code unit values (SV, <a href="#sec-literals-string-literals">11.8.4</a>) contributed
+ by the various parts of the template literal component. As part of this process, some Unicode code points within the
+ template component are interpreted as having a mathematical value (MV, <a
+ href="#sec-literals-numeric-literals">11.8.3</a>). In determining a TV, escape sequences are replaced by the UTF-16 code
+ unit(s) of the Unicode code point represented by the escape sequence. The Template Raw Value (TRV) is similar to a
+ Template Value with the difference that in TRVs escape sequences are interpreted literally.</p>
+
+ <ul>
+ <li>
+ <p>The TV and TRV of <span class="prod"><span class="nt">NoSubstitutionTemplate</span> <span class="geq">::</span>
+ <code class="t">``</code></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The TV and TRV of <span class="prod"><span class="nt">TemplateHead</span> <span class="geq">::</span> <code
+ class="t">`${</code></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The TV and TRV of <span class="prod"><span class="nt">TemplateMiddle</span> <span class="geq">::</span> <code
+ class="t">}${</code></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The TV and TRV of <span class="prod"><span class="nt">TemplateTail</span> <span class="geq">::</span> <code
+ class="t">}`</code></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">NoSubstitutionTemplate</span> <span class="geq">::</span> <code
+ class="t">`</code> <span class="nt">TemplateCharacters</span> <code class="t">`</code></span> is the TV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateHead</span> <span class="geq">::</span> <code
+ class="t">`</code> <span class="nt">TemplateCharacters</span> <code class="t">${</code></span> is the TV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateMiddle</span> <span class="geq">::</span> <code
+ class="t">}</code> <span class="nt">TemplateCharacters</span> <code class="t">${</code></span> is the TV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateTail</span> <span class="geq">::</span> <code
+ class="t">}</code> <span class="nt">TemplateCharacters</span> <code class="t">`</code></span> is the TV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateCharacters</span> <span class="geq">::</span> <span
+ class="nt">TemplateCharacter</span></span> is the TV of <i>TemplateCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateCharacters</span> <span class="geq">::</span> <span
+ class="nt">TemplateCharacter</span> <span class="nt">TemplateCharacters</span></span> is a sequence consisting of the
+ code units in the TV of <i>TemplateCharacter</i> followed by all the code units in the TV of <i>TemplateCharacters</i>
+ in order.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">`</code> <span
+ class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">$</code> <span
+ class="grhsmod">or</span> <span class="nt">LineTerminator</span></span> is the <a
+ href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of the code point value of
+ <i>SourceCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <code
+ class="t">$</code></span> is the code unit value 0x0024.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">EscapeSequence</span></span> is the SV of <i>EscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <span
+ class="nt">LineContinuation</span></span> is the TV of <i>LineContinuation</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <span
+ class="nt">LineTerminatorSequence</span></span> is the TRV of <i>LineTerminatorSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TV of <span class="prod"><span class="nt">LineContinuation</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">LineTerminatorSequence</span></span> is the empty code unit sequence.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">NoSubstitutionTemplate</span> <span class="geq">::</span> <code
+ class="t">`</code> <span class="nt">TemplateCharacters</span> <code class="t">`</code></span> is the TRV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateHead</span> <span class="geq">::</span> <code
+ class="t">`</code> <span class="nt">TemplateCharacters</span> <code class="t">${</code></span> is the TRV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateMiddle</span> <span class="geq">::</span> <code
+ class="t">}</code> <span class="nt">TemplateCharacters</span> <code class="t">${</code></span> is the TRV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateTail</span> <span class="geq">::</span> <code
+ class="t">}</code> <span class="nt">TemplateCharacters</span> <code class="t">`</code></span> is the TRV of
+ <i>TemplateCharacters</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateCharacters</span> <span class="geq">::</span> <span
+ class="nt">TemplateCharacter</span></span> is the TRV of <i>TemplateCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateCharacters</span> <span class="geq">::</span> <span
+ class="nt">TemplateCharacter</span> <span class="nt">TemplateCharacters</span></span> is a sequence consisting of the
+ code units in the TRV of <i>TemplateCharacter</i> followed by all the code units in the TRV of
+ <i>TemplateCharacters,</i> in order.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">`</code> <span
+ class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">$</code> <span
+ class="grhsmod">or</span> <span class="nt">LineTerminator</span></span> is the <a
+ href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of the code point value of
+ <i>SourceCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <code
+ class="t">$</code></span> is the code unit value 0x0024.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">EscapeSequence</span></span> is the sequence consisting of the code unit value
+ 0x005C followed by the code units of TRV of <i>EscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <span
+ class="nt">LineContinuation</span></span> is the TRV of <i>LineContinuation</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> <span
+ class="nt">LineTerminatorSequence</span></span> is the TRV of <i>LineTerminatorSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">CharacterEscapeSequence</span></span> is the TRV of the <i>CharacterEscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <code
+ class="t">0</code></span> is the code unit value 0x0030.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">HexEscapeSequence</span></span> is the TRV of the <i>HexEscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">UnicodeEscapeSequence</span></span> is the TRV of the <i>UnicodeEscapeSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">CharacterEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">SingleEscapeCharacter</span></span> is the TRV of the <i>SingleEscapeCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">CharacterEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">NonEscapeCharacter</span></span> is the SV of the <i>NonEscapeCharacter</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">SingleEscapeCharacter</span> <span class="geq">::</span> <span
+ class="grhsmod">one of</span> <code class="t">'</code> <code class="t">"</code> <code class="t">\</code> <code
+ class="t">b</code> <code class="t">f</code> <code class="t">n</code> <code class="t">r</code> <code class="t">t</code>
+ <code class="t">v</code></span> is the SV of the <i>SourceCharacter</i> that is that single code point.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">HexEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">x</code> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></span> is the sequence
+ consisting of code unit value 0x0078 followed by TRV of the first <i>HexDigit</i> followed by the TRV of the second
+ <i>HexDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">UnicodeEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">u</code> <span class="nt">Hex4Digits</span></span> is the sequence consisting of code unit value 0x0075
+ followed by TRV of <span class="nt">Hex4Digits</span>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">UnicodeEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></span> is the sequence consisting of
+ code unit value 0x0075 followed by code unit value 0x007B followed by TRV of <i>HexDigits</i> followed by code unit
+ value 0x007D.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">Hex4Digits</span> <span class="geq">::</span> <span
+ class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span
+ class="nt">HexDigit</span></span> is the sequence consisting of the TRV of the first <i>HexDigit</i> followed by the
+ TRV of the second <i>HexDigit</i> followed by the TRV of the third <i>HexDigit</i> followed by the TRV of the fourth
+ <span class="nt">HexDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">HexDigits</span> <span class="geq">::</span> <span
+ class="nt">HexDigit</span></span> is the TRV of <i>HexDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">HexDigits</span> <span class="geq">::</span> <span
+ class="nt">HexDigits</span> <span class="nt">HexDigit</span></span> is the sequence consisting of TRV of
+ <i>HexDigits</i> followed by TRV of <i>HexDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of a <i>HexDigit</i> is the SV of the <i>SourceCharacter</i> that is that <i>HexDigit</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">LineContinuation</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">LineTerminatorSequence</span></span> is the sequence consisting of the code unit
+ value 0x005C followed by the code units of TRV of <i>LineTerminatorSequence</i>.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">LineTerminatorSequence</span> <span class="geq">::</span></span>
+ <LF> is the code unit value 0x000A.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">LineTerminatorSequence</span> <span class="geq">::</span></span>
+ <CR> is the code unit value 0x000A.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">LineTerminatorSequence</span> <span class="geq">::</span></span>
+ <LS> is the code unit value 0x2028.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">LineTerminatorSequence</span> <span class="geq">::</span></span>
+ <PS> is the code unit value 0x2029.</p>
+ </li>
+
+ <li>
+ <p>The TRV of <span class="prod"><span class="nt">LineTerminatorSequence</span> <span class="geq">::</span></span>
+ <CR><LF> is the sequence consisting of the code unit value 0x000A.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> TV excludes the code units of <i>LineContinuation</i> while TRV includes them.
+ <CR><LF> and <CR> <i>LineTerminatorSequences</i> are normalized to <LF> for both TV and TRV. An
+ explicit <i>EscapeSequence</i> is needed to include a <CR> or <CR><LF> sequence.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-automatic-semicolon-insertion">
+ <div class="front">
+ <h1><span class="secnum" id="sec-11.9"><a href="#sec-automatic-semicolon-insertion"
+ title="link to this section">11.9</a></span> Automatic Semicolon Insertion</h1>
+
+ <p>Certain ECMAScript statements (empty statement, <code>let</code>, <code>const</code>, <code>import</code>, and
+ <code>export</code> declarations, variable statement, expression statement, <code>debugger</code> statement,
+ <code>continue</code> statement, <code>break</code> statement, <code>return</code> statement, and <code>throw</code>
+ statement) must be terminated with semicolons. Such semicolons may always appear explicitly in the source text. For
+ convenience, however, such semicolons may be omitted from the source text in certain situations. These situations are
+ described by saying that semicolons are automatically inserted into the source code token stream in those situations.</p>
+ </div>
+
+ <section id="sec-rules-of-automatic-semicolon-insertion">
+ <h1><span class="secnum" id="sec-11.9.1"><a href="#sec-rules-of-automatic-semicolon-insertion"
+ title="link to this section">11.9.1</a></span> Rules of Automatic Semicolon Insertion</h1>
+
+ <p>In the following rules, “token” means the actual recognized lexical token determined using the current
+ lexical goal symbol is described in <a href="#sec-ecmascript-language-lexical-grammar">clause 11</a>.</p>
+
+ <p>There are three basic rules of semicolon insertion:</p>
+
+ <ol class="proc">
+ <li>When, as a <span style="font-family: Times New Roman"><i>Script</i> or <i>Module</i></span> is parsed from left to
+ right, a token (called the <i>offending token</i>) is encountered that is not allowed by any production of the
+ grammar, then a semicolon is automatically inserted before the offending token if one or more of the following
+ conditions is true:
+ <ul>
+ <li>The offending token is separated from the previous token by at least one <i>LineTerminator</i>.</li>
+ <li>The offending token is <code>}</code>.</li>
+ </ul>
+ </li>
+ <li>When, as the <span style="font-family: Times New Roman"><i>Script</i> or <i>Module</i></span> is parsed from left to
+ right, the end of the input stream of tokens is encountered and the parser is unable to parse the input token stream
+ as a single complete ECMAScript <span style="font-family: Times New Roman"><i>Script</i> or <i>Module</i></span>, then
+ a semicolon is automatically inserted at the end of the input stream.</li>
+ <li>When, as the <span style="font-family: Times New Roman"><i>Script</i> or <i>Module</i></span> is parsed from left to
+ right, a token is encountered that is allowed by some production of the grammar, but the production is a <i>restricted
+ production</i> and the token would be the first token for a terminal or nonterminal immediately following the
+ annotation <span style="font-family: Times New Roman">“</span>[no <span style="font-family: Times New
+ Roman"><i>LineTerminator</i></span> here]<span style="font-family: Times New Roman">”</span> within the
+ restricted production (and therefore such a token is called a restricted token), and the restricted token is separated
+ from the previous token by at least one <span class="nt">LineTerminator</span>, then a semicolon is automatically
+ inserted before the restricted token.</li>
+ </ol>
+
+ <p>However, there is an additional overriding condition on the preceding rules: a semicolon is never inserted automatically
+ if the semicolon would then be parsed as an empty statement or if that semicolon would become one of the two semicolons in
+ the header of a <code>for</code> statement (<a href="#sec-for-statement">see 13.6.3</a>).</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The following are the only restricted productions in the grammar:</p>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PostfixExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">++</code></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">--</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ContinueStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">continue;</code></div>
+ <div class="rhs"><code class="t">continue</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BreakStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">break</code> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">break</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ReturnStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">return</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">return</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ThrowStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">throw</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArrowFunction</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ArrowParameters</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">=></code> <span class="nt">ConciseBody</span><sub>[?In]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">YieldExpression</span><sub>[In]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">yield</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">*</code> <span class="nt">AssignmentExpression</span><sub>[?In, Yield]</sub></div>
+ <div class="rhs"><code class="t">yield</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">AssignmentExpression</span><sub>[?In, Yield]</sub></div>
+ </div>
+
+ <p>The practical effect of these restricted productions is as follows:</p>
+
+ <p>When a <code>++</code> or <code>--</code> token is encountered where the parser would treat it as a postfix operator, and
+ at least one <span class="nt">LineTerminator</span> occurred between the preceding token and the <code>++</code> or
+ <code>--</code> token, then a semicolon is automatically inserted before the <code>++</code> or <code>--</code> token.</p>
+
+ <p>When a <code>continue</code>, <code>break</code>, <code>return</code>, <code>throw</code>, or <code>yield</code> token is
+ encountered and a <span class="nt">LineTerminator</span> is encountered before the next token, a semicolon is automatically
+ inserted after the <code>continue</code>, <code>break</code>, <code>return</code>, <code>throw</code>, or <code>yield</code>
+ token.</p>
+
+ <p>The resulting practical advice to ECMAScript programmers is:</p>
+
+ <p>A postfix <code>++</code> or <code>--</code> operator should appear on the same line as its operand.</p>
+
+ <p>An <span class="nt">Expression</span> in a <code>return</code> or <code>throw</code> statement or an <span
+ class="nt">AssignmentExpression</span> in a <code>yield</code> expression should start on the same line as the
+ <code>return</code>, <code>throw</code>, or <code>yield</code> token.</p>
+
+ <p>An <span class="nt">IdentifierReference</span> in a <code>break</code> or <code>continue</code> statement should be on
+ the same line as the <code>break</code> or <code>continue</code> token.</p>
+ </section>
+
+ <section id="sec-examples-of-automatic-semicolon-insertion">
+ <h1><span class="secnum" id="sec-11.9.2"><a href="#sec-examples-of-automatic-semicolon-insertion"
+ title="link to this section">11.9.2</a></span> Examples of Automatic Semicolon Insertion</h1>
+
+ <p>The source</p>
+
+ <pre>{ 1 2 } 3</pre>
+
+ <p>is not a valid sentence in the ECMAScript grammar, even with the <a href="#sec-automatic-semicolon-insertion">automatic
+ semicolon insertion</a> rules. In contrast, the source</p>
+
+ <pre>{ 1<br>2 } 3</pre>
+
+ <p>is also not a valid ECMAScript sentence, but is transformed by <a href="#sec-automatic-semicolon-insertion">automatic
+ semicolon insertion</a> into the following:</p>
+
+ <pre>{ 1<br>;2 ;} 3;</pre>
+
+ <p>which is a valid ECMAScript sentence.</p>
+
+ <p>The source</p>
+
+ <pre>for (a; b<br>)</pre>
+
+ <p>is not a valid ECMAScript sentence and is not altered by <a href="#sec-automatic-semicolon-insertion">automatic semicolon
+ insertion</a> because the semicolon is needed for the header of a <code>for</code> statement. Automatic semicolon insertion
+ never inserts one of the two semicolons in the header of a <code>for</code> statement.</p>
+
+ <p>The source</p>
+
+ <pre>return<br>a + b</pre>
+
+ <p>is transformed by <a href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a> into the following:</p>
+
+ <pre>return;<br>a + b;</pre>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The expression <code>a + b</code> is not treated as a value to be returned by the
+ <code>return</code> statement, because a <i>LineTerminator</i> separates it from the token <code>return</code>.</p>
+ </div>
+
+ <p>The source</p>
+
+ <pre>a = b<br>++c</pre>
+
+ <p>is transformed by <a href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a> into the following:</p>
+
+ <pre>a = b;<br>++c;</pre>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The token <code>++</code> is not treated as a postfix operator applying to the variable
+ <code>b</code>, because a <i>LineTerminator</i> occurs between <code>b</code> and <code>++</code>.</p>
+ </div>
+
+ <p>The source</p>
+
+ <pre>if (a > b)<br>else c = d</pre>
+
+ <p>is not a valid ECMAScript sentence and is not altered by <a href="#sec-automatic-semicolon-insertion">automatic semicolon
+ insertion</a> before the <code>else</code> token, even though no production of the grammar applies at that point, because an
+ automatically inserted semicolon would then be parsed as an empty statement.</p>
+
+ <p>The source</p>
+
+ <pre>a = b + c<br>(d + e).print()</pre>
+
+ <p>is <i>not</i> transformed by <a href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a>, because the
+ parenthesized expression that begins the second line can be interpreted as an argument list for a function call:</p>
+
+ <pre>a = b + c(d + e).print()</pre>
+
+ <p>In the circumstance that an assignment statement must begin with a left parenthesis, it is a good idea for the programmer
+ to provide an explicit semicolon at the end of the preceding statement rather than to rely on <a
+ href="#sec-automatic-semicolon-insertion">automatic semicolon insertion</a>.</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-ecmascript-language-expressions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12"><a href="#sec-ecmascript-language-expressions" title="link to this section">12</a></span>
+ ECMAScript Language: Expressions</h1>
+ </div>
+
+ <section id="sec-identifiers">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.1"><a href="#sec-identifiers" title="link to this section">12.1</a></span>
+ Identifiers</h1>
+
+ <p><b>Syntax</b></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IdentifierReference</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Identifier</span></div>
+ <div class="rhs"><span class="grhsannot">[~Yield]</span> <code class="t">yield</code></div>
+ </div>
+
+ <p><i>BindingIdentifier</i><span style="font-family: sans-serif"><sub>[Yield]</sub></span> <b>:</b></p>
+
+ <p><span style="font-family: Times New Roman"><i>Identifier<br></i></span>[~Yield] <code>yield</code></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LabelIdentifier</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Identifier</span></div>
+ <div class="rhs"><span class="grhsannot">[~Yield]</span> <code class="t">yield</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Identifier</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <span class="grhsmod">but not</span> <span class="nt">ReservedWord</span></div>
+ </div>
+ </div>
+
+ <section id="sec-identifiers-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.1.1"><a href="#sec-identifiers-static-semantics-early-errors"
+ title="link to this section">12.1.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">BindingIdentifier</span> <span class="geq">:</span> <span class="nt">Identifier</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the code matched by this production is contained in <a href="#sec-strict-mode-code">strict
+ code</a> and the StringValue of <span class="nt">Identifier</span> is <code>"arguments"</code> or
+ <code>"eval"</code>.</p>
+ </li>
+ </ul>
+
+ <p><span class="nt">IdentifierReference</span><sub>[Yield]</sub> <b>:</b> <code>yield</code></p>
+
+ <p><span class="nt">BindingIdentifier</span><sub>[Yield]</sub> <b>:</b> <code>yield</code></p>
+
+ <p><span class="nt">LabelIdentifier</span><sub>[Yield]</sub> <b>:</b> <code>yield</code></p>
+
+ <ul>
+ <li>
+ <p>It is a Syntax Error if this production has a <sub>[Yield]</sub> parameter.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if the code match by this production is contained in <a href="#sec-strict-mode-code">strict
+ code</a><var>.</var></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if the code match by this production is within the <span class="nt">GeneratorBody</span> of a
+ <i><span style="font-family: Times New Roman">GeneratorMethod</span>, <span style="font-family: Times New
+ Roman">GeneratorDeclaration</span>,</i> or <span class="nt">GeneratorExpression</span>.</p>
+ </li>
+ </ul>
+
+ <p><i>IdentifierReference</i><span style="font-family: sans-serif"><sub>[Yield]</sub> <b>:</b></span> <i>Identifier</i></p>
+
+ <p><i>BindingIdentifier</i><span style="font-family: sans-serif"><sub>[Yield]</sub> <b>:</b></span> <i>Identifier</i></p>
+
+ <p><i>LabelIdentifier</i><span style="font-family: sans-serif"><sub>[Yield]</sub> <b>:</b></span> <i>Identifier</i></p>
+
+ <ul>
+ <li>
+ <p>It is a Syntax Error if this production has a <sub>[Yield]</sub> parameter and StringValue of <span
+ class="nt">Identifier</span> is <code>"yield"</code>.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">Identifier</span> <span class="geq">::</span> <span class="nt">IdentifierName</span> <span class="grhsmod">but not</span> <span class="nt">ReservedWord</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if this phrase is contained in <a href="#sec-strict-mode-code">strict code</a> and the
+ StringValue of <span class="nt">IdentifierName</span> is: <code>"implements"</code>, <code>"interface"</code>,
+ <code>"let"</code>, <code>"package"</code>, <code>"private"</code>, <code>"protected"</code>, <code>"public"</code>,
+ <code>"static"</code>, or <code>"yield"</code>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if StringValue of <span class="nt">IdentifierName</span> is the same string value as the
+ StringValue of any <span class="nt">ReservedWord</span> except for <code>yield</code>.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <span style="font-family: sans-serif">StringValue of</span> <i>IdentifierName</i>
+ normalizes any Unicode escape sequences in <i>IdentifierName</i> hence such escapes cannot be used to write an
+ <i>Identifier</i> whose code point sequence is the same as a <i>ReservedWord</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-identifiers-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-12.1.2"><a href="#sec-identifiers-static-semantics-boundnames"
+ title="link to this section">12.1.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">BindingIdentifier</span> <span class="geq">:</span> <span class="nt">Identifier</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing the StringValue of
+ <i>Identifier</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingIdentifier</span> <span class="geq">:</span> <code class="t">yield</code></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <code>"yield"</code>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.1.3"><a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.1.3</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isvalidsimpleassignmenttarget">12.2.0.4</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">IdentifierReference</span> <span class="geq">:</span> <span class="nt">Identifier</span></div>
+ <ol class="proc">
+ <li>If this <i>IdentifierReference</i> is contained in <a href="#sec-strict-mode-code">strict code</a> and StringValue of
+ <i>Identifier</i> is <code>"eval"</code> or <code>"arguments"</code>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IdentifierReference</span> <span class="geq">:</span> <code class="t">yield</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-identifiers-static-semantics-stringvalue">
+ <h1><span class="secnum" id="sec-12.1.4"><a href="#sec-identifiers-static-semantics-stringvalue"
+ title="link to this section">12.1.4</a></span> Static Semantics<span style="font-family: sans-serif">:</span>
+ <i>StringValue</i></h1>
+
+ <p>See also: <a href="#sec-identifier-names-static-semantics-stringvalue">11.6.1.2</a>, <a
+ href="#sec-string-literals-static-semantics-stringvalue">11.8.4.2</a>.</p>
+
+ <p><span class="prod"><span class="nt">IdentifierReference</span> <span class="geq">:</span> <code
+ class="t">yield</code></span></p>
+
+ <p><span class="prod"><span class="nt">BindingIdentifier</span> <span class="geq">:</span> <code
+ class="t">yield</code></span></p>
+
+ <div class="gp prod"><span class="nt">LabelIdentifier</span> <span class="geq">:</span> <code class="t">yield</code></div>
+ <ol class="proc">
+ <li>Return <code>"yield"</code>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Identifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span> <span class="grhsmod">but not</span> <span class="nt">ReservedWord</span></div>
+ <ol class="proc">
+ <li>Return the StringValue of <i>IdentifierName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-identifiers-runtime-semantics-bindinginitialization">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.1.5"><a href="#sec-identifiers-runtime-semantics-bindinginitialization"
+ title="link to this section">12.1.5</a></span> Runtime Semantics: BindingInitialization</h1>
+
+ <p>With arguments <var>value</var> and <var>environment</var>.</p>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-runtime-semantics-bindinginitialization">13.2.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-bindinginitialization">13.6.4.9</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <b>undefined</b> is passed for <var>environment</var> to indicate that a <a
+ href="#sec-putvalue">PutValue</a> operation should be used to assign the initialization value. This is the case for
+ <code>var</code> statements and formal parameter lists of some non-strict mode functions (See <a
+ href="#sec-functiondeclarationinstantiation">9.2.13</a>). In those cases a lexical binding is hoisted and preinitialized
+ prior to evaluation of its initializer.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">BindingIdentifier</span> <span class="geq">:</span> <span class="nt">Identifier</span></div>
+ <ol class="proc">
+ <li>Let <i>name</i> be StringValue of <i>Identifier</i>.</li>
+ <li>Return <a href="#sec-initializeboundname">InitializeBoundName</a>( <i>name</i>, <i>value</i>,
+ <i>environment</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingIdentifier</span> <span class="geq">:</span> <code class="t">yield</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-initializeboundname">InitializeBoundName</a>(<code>"yield"</code>, <i>value</i>,
+ <i>environment</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-initializeboundname">
+ <h1><span class="secnum" id="sec-12.1.5.1"><a href="#sec-initializeboundname"
+ title="link to this section">12.1.5.1</a></span> Runtime Semantics: InitializeBoundName(name, value, environment)</h1>
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>name</i>) is String.</li>
+ <li>If <i>environment</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>env</i> be the environment record component of <i>environment</i>.</li>
+ <li>Perform <i>env</i>.InitializeBinding(<i>name</i>, <i>value</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>lhs</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(<i>name</i>).</li>
+ <li>Return <a href="#sec-putvalue">PutValue</a>(<i>lhs</i>, <i>value</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-identifiers-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.1.6"><a href="#sec-identifiers-runtime-semantics-evaluation"
+ title="link to this section">12.1.6</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">IdentifierReference</span> <span class="geq">:</span> <span class="nt">Identifier</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-resolvebinding">ResolveBinding</a>(StringValue of <i>Identifier</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IdentifierReference</span> <span class="geq">:</span> <code class="t">yield</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-resolvebinding">ResolveBinding</a>(<code>"yield"</code>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1:</span> The result of evaluating an <i>IdentifierReference</i> is always a value of type <a
+ href="#sec-reference-specification-type">Reference</a>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2:</span> In non-<a href="#sec-strict-mode-code">strict code</a>, the keyword <code>yield</code>
+ may be used as an identifier. Evaluating the <i>IdentifierReference</i> production resolves the binding of
+ <code>yield</code> as if it was an <i>Identifier</i>. Early Error restriction ensures that such an evaluation only can
+ occur for non-<a href="#sec-strict-mode-code">strict code</a>. See <a href="#sec-let-and-const-declarations">13.2.1</a>
+ for the handling of <code>yield</code> in binding creation contexts.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-primary-expression">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2"><a href="#sec-primary-expression" title="link to this section">12.2</a></span>
+ Primary Expression</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PrimaryExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">this</code></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">Literal</span></div>
+ <div class="rhs"><span class="nt">ArrayLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ObjectLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">FunctionExpression</span></div>
+ <div class="rhs"><span class="nt">ClassExpression</span></div>
+ <div class="rhs"><span class="nt">GeneratorExpression</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">,</code> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">)</code></div>
+ </div>
+
+ <h2>Supplemental Syntax</h2>
+
+ <p>When processing the production</p>
+
+ <p><span class="nt">PrimaryExpression</span><sub>[Yield]</sub> <b>:</b> <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub><span style="font-family: Times New
+ Roman"><i><br></i></span>the interpretation of <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span> is
+ refined using the following grammar:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ParenthesizedExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code></div>
+ </div>
+ </div>
+
+ <section id="sec-primary-expression-semantics">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.0"><a href="#sec-primary-expression-semantics"
+ title="link to this section">12.2.0</a></span> Semantics</h1>
+ </div>
+
+ <section id="sec-static-semantics-coveredparenthesizedexpression">
+ <h1><span class="secnum" id="sec-12.2.0.1"><a href="#sec-static-semantics-coveredparenthesizedexpression"
+ title="link to this section">12.2.0.1</a></span> Static Semantics: CoveredParenthesizedExpression</h1>
+ <div class="gp prod"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[Yield]</sub> <span class="geq">:</span> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code></div>
+ <ol class="proc">
+ <li>Return the result of parsing the lexical token stream matched by
+ <i>CoverParenthesizedExpressionAndArrowParameterList</i><sub>[Yield]</sub> using either
+ <i>ParenthesizedExpression</i> or <i>ParenthesizedExpression</i><sub>[Yield]</sub> as the goal symbol depending upon
+ whether the <sub>[Yield]</sub> grammar parameter was present when
+ <i>CoverParenthesizedExpressionAndArrowParameterList was matched.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-semantics-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.2.0.2"><a href="#sec-semantics-static-semantics-isfunctiondefinition"
+ title="link to this section">12.2.0.2</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PrimaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">this</code></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span></div>
+ <div class="rhs"><span class="nt">Literal</span></div>
+ <div class="rhs"><span class="nt">ArrayLiteral</span></div>
+ <div class="rhs"><span class="nt">ObjectLiteral</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be CoveredParenthesizedExpression of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return IsFunctionDefinition of <i>expr</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-semantics-static-semantics-isidentifierref">
+ <h1><span class="secnum" id="sec-12.2.0.3"><a href="#sec-semantics-static-semantics-isidentifierref"
+ title="link to this section">12.2.0.3</a></span> Static Semantics: IsIdentifierRef</h1>
+
+ <p>See also: <a href="#sec-static-semantics-static-semantics-isidentifierref">12.3.1.4</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PrimaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PrimaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">this</code></div>
+ <div class="rhs"><span class="nt">Literal</span></div>
+ <div class="rhs"><span class="nt">ArrayLiteral</span></div>
+ <div class="rhs"><span class="nt">ObjectLiteral</span></div>
+ <div class="rhs"><span class="nt">FunctionExpression</span></div>
+ <div class="rhs"><span class="nt">ClassExpression</span></div>
+ <div class="rhs"><span class="nt">GeneratorExpression</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateLiteral</span></div>
+ <div class="rhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-semantics-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.2.0.4"><a href="#sec-semantics-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.2.0.4</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PrimaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">this</code></div>
+ <div class="rhs"><span class="nt">Literal</span></div>
+ <div class="rhs"><span class="nt">ArrayLiteral</span></div>
+ <div class="rhs"><span class="nt">ObjectLiteral</span></div>
+ <div class="rhs"><span class="nt">FunctionExpression</span></div>
+ <div class="rhs"><span class="nt">ClassExpression</span></div>
+ <div class="rhs"><span class="nt">GeneratorExpression</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be CoveredParenthesizedExpression of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return IsValidSimpleAssignmentTarget of <i>expr</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-this-keyword">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.1"><a href="#sec-this-keyword" title="link to this section">12.2.1</a></span> The
+ <code>this</code> Keyword</h1>
+ </div>
+
+ <section id="sec-this-keyword-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.2.1.1"><a href="#sec-this-keyword-runtime-semantics-evaluation"
+ title="link to this section">12.2.1.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <code class="t">this</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-resolvethisbinding">ResolveThisBinding</a>( ) .</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-identifier-reference">
+ <h1><span class="secnum" id="sec-12.2.2"><a href="#sec-identifier-reference" title="link to this section">12.2.2</a></span>
+ Identifier Reference</h1>
+
+ <p>See <a href="#sec-identifiers">12.1</a> for <span class="nt">IdentifierReference</span>.</p>
+ </section>
+
+ <section id="sec-primary-expression-literals">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.3"><a href="#sec-primary-expression-literals"
+ title="link to this section">12.2.3</a></span> Literals</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Literal</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">NullLiteral</span></div>
+ <div class="rhs"><span class="nt">BooleanLiteral</span></div>
+ <div class="rhs"><span class="nt">NumericLiteral</span></div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ </div>
+ </div>
+
+ <section id="sec-literals-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.2.3.1"><a href="#sec-literals-runtime-semantics-evaluation"
+ title="link to this section">12.2.3.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">Literal</span> <span class="geq">:</span> <span class="nt">NullLiteral</span></div>
+ <ol class="proc">
+ <li>Return <b>null</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Literal</span> <span class="geq">:</span> <span class="nt">BooleanLiteral</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b> if <i>BooleanLiteral</i> is the token <code>false</code>.</li>
+ <li>Return <b>true</b> if <i>BooleanLiteral</i> is the token <code>true</code>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Literal</span> <span class="geq">:</span> <span class="nt">NumericLiteral</span></div>
+ <ol class="proc">
+ <li>Return the number whose value is MV of <i>NumericLiteral</i> as defined in <a
+ href="#sec-literals-numeric-literals">11.8.3</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Literal</span> <span class="geq">:</span> <span class="nt">StringLiteral</span></div>
+ <ol class="proc">
+ <li>Return the StringValue of <i>StringLiteral</i> as defined in <a
+ href="#sec-string-literals-static-semantics-stringvalue">11.8.4.2</a>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-array-initializer">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.4"><a href="#sec-array-initializer" title="link to this section">12.2.4</a></span>
+ Array Initializer</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An <i>ArrayLiteral</i> is an expression describing the initialization of an Array
+ object, using a list, of zero or more expressions each of which represents an array element, enclosed in square
+ brackets. The elements need not be literals; they are evaluated each time the array initializer is evaluated.</p>
+ </div>
+
+ <p>Array elements may be elided at the beginning, middle or end of the element list. Whenever a comma in the element list
+ is not preceded by an <span class="nt">AssignmentExpression</span> (i.e., a comma at the beginning or after another
+ comma), the missing array element contributes to the length of the Array and increases the index of subsequent elements.
+ Elided array elements are not defined. If an element is elided at the end of an array, that element does not contribute to
+ the length of the Array.</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArrayLiteral</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ElementList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">Elision</span><sub>opt</sub> <span class="nt">SpreadElement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">SpreadElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Elision</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">,</code></div>
+ <div class="rhs"><span class="nt">Elision</span> <code class="t">,</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SpreadElement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">...</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-static-semantics-elisionwidth">
+ <h1><span class="secnum" id="sec-12.2.4.1"><a href="#sec-static-semantics-elisionwidth"
+ title="link to this section">12.2.4.1</a></span> Static Semantics: ElisionWidth</h1>
+ <div class="gp prod"><span class="nt">Elision</span> <span class="geq">:</span> <code class="t">,</code></div>
+ <ol class="proc">
+ <li>Return the numeric value 1.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Elision</span> <span class="geq">:</span> <span class="nt">Elision</span> <code class="t">,</code></div>
+ <ol class="proc">
+ <li>Let <i>preceding</i> be the ElisionWidth of <i>Elision</i>.</li>
+ <li>Return <i>preceding</i>+1.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-arrayaccumulation">
+ <h1><span class="secnum" id="sec-12.2.4.2"><a href="#sec-runtime-semantics-arrayaccumulation"
+ title="link to this section">12.2.4.2</a></span> Runtime Semantics: ArrayAccumulation</h1>
+
+ <p>With parameters <var>array</var> and <var>nextIndex</var>.</p>
+
+ <div class="gp prod"><span class="nt">ElementList</span> <span class="geq">:</span> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>padding</i> be the ElisionWidth of <i>Elision</i>; if <i>Elision</i> is not present, use the numeric value
+ zero.</li>
+ <li>Let <i>initResult</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>initValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>initResult</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>initValue</i>).</li>
+ <li>Let <i>created</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>array</i>, <a
+ href="#sec-tostring">ToString</a>(<a href="#sec-touint32">ToUint32</a>(<i>nextIndex+padding</i>)),
+ <i>initValue</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>created</i> is <b>true</b><i>.</i></li>
+ <li>Return <i>nextIndex+padding+</i>1.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ElementList</span> <span class="geq">:</span> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">SpreadElement</span></div>
+ <ol class="proc">
+ <li>Let <i>padding</i> be the ElisionWidth of <i>Elision</i>; if <i>Elision</i> is not present, use the numeric value
+ zero.</li>
+ <li>Return the result of performing ArrayAccumulation for <i>SpreadElement</i> with arguments <i>array</i> and
+ <i>nextIndex</i>+<i>padding</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ElementList</span> <span class="geq">:</span> <span class="nt">ElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>postIndex</i> be the result of performing ArrayAccumulation for <i>ElementList</i> with arguments
+ <i>array</i> and <i>nextIndex</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>postIndex</i>).</li>
+ <li>Let <i>padding</i> be the ElisionWidth of <i>Elision</i>; if <i>Elision</i> is not present, use the numeric value
+ zero.</li>
+ <li>Let <i>initResult</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>initValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>initResult</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>initValue</i>).</li>
+ <li>Let <i>created</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>array</i>, <a
+ href="#sec-tostring">ToString</a>(<a href="#sec-touint32">ToUint32</a>(<i>postIndex</i>+<i>padding</i>)),
+ <i>initValue</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>created</i> is <b>true</b>.</li>
+ <li>Return <i>postIndex</i>+<i>padding+</i>1.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ElementList</span> <span class="geq">:</span> <span class="nt">ElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">SpreadElement</span></div>
+ <ol class="proc">
+ <li>Let <i>postIndex</i> be the result of performing ArrayAccumulation for <i>ElementList</i> with arguments
+ <i>array</i> and <i>nextIndex</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>postIndex</i>).</li>
+ <li>Let <i>padding</i> be the ElisionWidth of <i>Elision</i>; if <i>Elision</i> is not present, use the numeric value
+ zero.</li>
+ <li>Return the result of performing ArrayAccumulation for <i>SpreadElement</i> with arguments <i>array</i> and
+ <i>postIndex</i>+<i>padding</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SpreadElement</span> <span class="geq">:</span> <code class="t">...</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>spreadRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>spreadObj</i> be <a href="#sec-getvalue">GetValue</a>(<i>spreadRef</i>).</li>
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>spreadObj</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, return <i>nextIndex</i>.</li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>array</i>, <a
+ href="#sec-tostring">ToString</a>(<i>nextIndex</i>), <i>nextValue</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is <b>true</b> .</li>
+ <li>Let <i>nextIndex</i> be <i>nextIndex</i> + 1.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <a href="#sec-createdataproperty">CreateDataProperty</a> is used to ensure that own
+ properties are defined for the array even if the standard built-in Array prototype object has been modified in a manner
+ that would preclude the creation of new own properties using [[Set]].</p>
+ </div>
+ </section>
+
+ <section id="sec-array-initializer-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.2.4.3"><a href="#sec-array-initializer-runtime-semantics-evaluation"
+ title="link to this section">12.2.4.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ArrayLiteral</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>array</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>pad</i> be the ElisionWidth of <i>Elision</i>; if <i>Elision</i> is not present, use the numeric value
+ zero.</li>
+ <li>Perform <a href="#sec-set-o-p-v-throw">Set</a>(<i>array</i>, <code>"length"</code>, <i>pad</i>, <b>false</b>).</li>
+ <li>NOTE: The above Set cannot fail because of the nature of the object returned by <a
+ href="#sec-arraycreate">ArrayCreate</a>.</li>
+ <li>Return <i>array</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayLiteral</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">ElementList</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>array</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>len</i> be the result of performing ArrayAccumulation for <i>ElementList</i> with arguments <i>array</i> and
+ 0.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Perform <a href="#sec-set-o-p-v-throw">Set</a>(<i>array</i>, <code>"length"</code>, <i>len</i>, <b>false</b>).</li>
+ <li>NOTE: The above Set cannot fail because of the nature of the object returned by <a
+ href="#sec-arraycreate">ArrayCreate</a>.</li>
+ <li>Return <i>array</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayLiteral</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">ElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>array</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>len</i> be the result of performing ArrayAccumulation for <i>ElementList</i> with arguments <i>array</i> and
+ 0.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>padding</i> be the ElisionWidth of <i>Elision</i>; if <i>Elision</i> is not present, use the numeric value
+ zero.</li>
+ <li>Perform <a href="#sec-set-o-p-v-throw">Set</a>(<i>array</i>, <code>"length"</code>, <a
+ href="#sec-touint32">ToUint32</a>(<i>padding</i>+<i>len</i>), <b>false</b>).</li>
+ <li>NOTE: The above Set cannot fail because of the nature of the object returned by <a
+ href="#sec-arraycreate">ArrayCreate</a>.</li>
+ <li>Return <i>array</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-object-initializer">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.5"><a href="#sec-object-initializer" title="link to this section">12.2.5</a></span>
+ Object Initializer</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> An object initializer is an expression describing the initialization of an Object,
+ written in a form resembling a literal. It is a list of zero or more pairs of property keys and associated values,
+ enclosed in curly brackets. The values need not be literals; they are evaluated each time the object initializer is
+ evaluated.</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ObjectLiteral</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">PropertyDefinitionList</span><sub>[?Yield]</sub> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">PropertyDefinitionList</span><sub>[?Yield]</sub> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PropertyDefinitionList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">PropertyDefinition</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">PropertyDefinitionList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">PropertyDefinition</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PropertyDefinition</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CoverInitializedName</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">:</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MethodDefinition</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PropertyName</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LiteralPropertyName</span></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">ComputedPropertyName</span></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">ComputedPropertyName</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ <div class="rhs"><span class="nt">NumericLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ComputedPropertyName</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CoverInitializedName</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Initializer</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">=</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> <i>MethodDefinition</i> is defined in <a href="#sec-method-definitions">14.3</a>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> In certain contexts, <i>ObjectLiteral</i> is used as a cover grammar for a more
+ restricted secondary grammar. The <i>CoverInitializedName</i> production is necessary to fully cover these secondary
+ grammars. However, use of this production results in an early Syntax Error in normal contexts where an actual
+ <i>ObjectLiteral</i> is expected.</p>
+ </div>
+ </div>
+
+ <section id="sec-object-initializer-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.2.5.1"><a href="#sec-object-initializer-static-semantics-early-errors"
+ title="link to this section">12.2.5.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">MethodDefinition</span></div>
+ <ul>
+ <li>It is a Syntax Error if HasDirectSuper of <span class="nt">MethodDefinition</span> is <span style="font-family:
+ Times New Roman"><b><i>true</i></b></span>.</li>
+ </ul>
+
+ <p>In addition to describing an actual object initializer the <span class="nt">ObjectLiteral</span> productions are also
+ used as a cover grammar for <span class="nt">ObjectAssignmentPattern</span> (<a
+ href="#sec-destructuring-assignment">12.14.5</a>). and may be recognized as part of a <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span>. When <span class="nt">ObjectLiteral</span> appears in
+ a context where <span class="nt">ObjectAssignmentPattern</span> is required the following Early Error rules are <b>not</b>
+ applied. In addition, they are not applied when initially parsing a
+ <var>CoverParenthesizedExpressionAndArrowParameterList.</var></p>
+
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">CoverInitializedName</span></div>
+ <ul>
+ <li>Always throw a Syntax Error if code matches <span style="font-family: Times New Roman">this production.</span></li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This production exists so that <i>ObjectLiteral</i> can serve as a cover grammar for
+ <i>ObjectAssignmentPattern</i> (<a href="#sec-destructuring-assignment">12.14.5</a>). It cannot occur in an actual
+ object initializer.</p>
+ </div>
+ </section>
+
+ <section id="sec-object-initializer-static-semantics-computedpropertycontains">
+ <h1><span class="secnum" id="sec-12.2.5.2"><a href="#sec-object-initializer-static-semantics-computedpropertycontains"
+ title="link to this section">12.2.5.2</a></span> Static Semantics: ComputedPropertyContains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-method-definitions-static-semantics-computedpropertycontains">14.3.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-computedpropertycontains">14.4.3</a>, <a
+ href="#sec-class-definitions-static-semantics-computedpropertycontains">14.5.5</a>.</p>
+
+ <div class="gp prod"><span class="nt">PropertyName</span> <span class="geq">:</span> <span class="nt">LiteralPropertyName</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyName</span> <span class="geq">:</span> <span class="nt">ComputedPropertyName</span></div>
+ <ol class="proc">
+ <li>Return the result of <i>ComputedPropertyName</i> Contains <i>symbol</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-initializer-static-semantics-contains">
+ <h1><span class="secnum" id="sec-12.2.5.3"><a href="#sec-object-initializer-static-semantics-contains"
+ title="link to this section">12.2.5.3</a></span> Static Semantics: Contains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-static-semantic-rules">5.3</a>, <a
+ href="#sec-static-semantics-static-semantics-contains">12.3.1.1</a>, <a
+ href="#sec-function-definitions-static-semantics-contains">14.1.4</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-contains">14.2.3</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-contains">14.4.4</a>, <a
+ href="#sec-class-definitions-static-semantics-contains">14.5.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">MethodDefinition</span></div>
+ <ol class="proc">
+ <li>If <i>symbol</i> is <i>MethodDefinition</i>, return <b>true</b>.</li>
+ <li>Return the result of ComputedPropertyContains for <i>MethodDefinition</i> with argument <i>symbol</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Static semantic rules that depend upon substructure generally do not look into function
+ definitions.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>If <i>symbol</i> is a <i>ReservedWord</i>, return <b>false</b>.</li>
+ <li>If <i>symbol</i> is an <i>Identifier</i> and StringValue of <i>symbol</i> is the same value as the StringValue of
+ <i>IdentifierName</i>, return <b>true</b>;</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-initializer-static-semantics-hascomputedpropertykey">
+ <h1><span class="secnum" id="sec-12.2.5.4"><a href="#sec-object-initializer-static-semantics-hascomputedpropertykey"
+ title="link to this section">12.2.5.4</a></span> Static Semantics: HasComputedPropertyKey</h1>
+
+ <p>See also: <a href="#sec-method-definitions-static-semantics-hascomputedpropertykey">14.3.4</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-hascomputedpropertykey">14.4.5</a></p>
+
+ <div class="gp prod"><span class="nt">PropertyDefinitionList</span> <span class="geq">:</span> <span class="nt">PropertyDefinitionList</span> <code class="t">,</code> <span class="nt">PropertyDefinition</span></div>
+ <ol class="proc">
+ <li>If HasComputedPropertyKey of <i>PropertyDefinitionList</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return HasComputedPropertyKey of <i>PropertyDefinition</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">IdentifierReference</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return IsComputedPropertyKey of <i>PropertyName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-iscomputedpropertykey">
+ <h1><span class="secnum" id="sec-12.2.5.5"><a href="#sec-static-semantics-iscomputedpropertykey"
+ title="link to this section">12.2.5.5</a></span> Static Semantics: IsComputedPropertyKey</h1>
+ <div class="gp prod"><span class="nt">PropertyName</span> <span class="geq">:</span> <span class="nt">LiteralPropertyName</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyName</span> <span class="geq">:</span> <span class="nt">ComputedPropertyName</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-initializer-static-semantics-propname">
+ <h1><span class="secnum" id="sec-12.2.5.6"><a href="#sec-object-initializer-static-semantics-propname"
+ title="link to this section">12.2.5.6</a></span> Static Semantics: <i>PropName</i></h1>
+
+ <p>See also: <a href="#sec-method-definitions-static-semantics-propname">14.3.6</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-propname">14.4.10</a>, <a
+ href="#sec-class-definitions-static-semantics-propname">14.5.12</a></p>
+
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">IdentifierReference</span></div>
+ <ol class="proc">
+ <li>Return StringValue of <i>IdentifierReference</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return PropName of <i>PropertyName</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return StringValue of <i>IdentifierName</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> <span class="nt">StringLiteral</span></div>
+ <ol class="proc">
+ <li>Return a String value whose code units are the SV of the <i>StringLiteral</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> <span class="nt">NumericLiteral</span></div>
+ <ol class="proc">
+ <li>Let <i>nbr</i> be the result of forming the value of the <i>NumericLiteral</i>.</li>
+ <li>Return <a href="#sec-tostring">ToString</a>(<i>nbr</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ComputedPropertyName</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">AssignmentExpression</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return <span style="font-family: sans-serif">empty</span>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-propertynamelist">
+ <h1><span class="secnum" id="sec-12.2.5.7"><a href="#sec-static-semantics-propertynamelist"
+ title="link to this section">12.2.5.7</a></span> Static Semantics: PropertyNameList</h1>
+ <div class="gp prod"><span class="nt">PropertyDefinitionList</span> <span class="geq">:</span> <span class="nt">PropertyDefinition</span></div>
+ <ol class="proc">
+ <li>If PropName of <i>PropertyDefinition</i> is <span style="font-family: sans-serif">empty</span>, return a new empty
+ <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing PropName of
+ <i>PropertyDefinition</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyDefinitionList</span> <span class="geq">:</span> <span class="nt">PropertyDefinitionList</span> <code class="t">,</code> <span class="nt">PropertyDefinition</span></div>
+ <ol class="proc">
+ <li>Let <i>list</i> be PropertyNameList of <i>PropertyDefinitionList.</i></li>
+ <li>If PropName of <i>PropertyDefinition</i> is <span style="font-family: sans-serif">empty</span>, return
+ <i>list</i>.</li>
+ <li>Append PropName of <i>PropertyDefinition</i> to the end of <i>list</i>.</li>
+ <li>Return <i>list</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-initializer-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.2.5.8"><a href="#sec-object-initializer-runtime-semantics-evaluation"
+ title="link to this section">12.2.5.8</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ObjectLiteral</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%ObjectPrototype%</span>).</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">ObjectLiteral</span> <span class="geq">:</span></span><br>	<code>{</code> <span
+ class="nt">PropertyDefinitionList</span> <code>}</code><span style="font-family: Times New
+ Roman"><i><br></i></span>	<code>{</code> <span class="nt">PropertyDefinitionList</span> <code>,</code>
+ <code>}</code></p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%ObjectPrototype%).</li>
+ <li>Let <i>status</i> be the result of performing PropertyDefinitionEvaluation of <i>PropertyDefinitionList</i> with
+ arguments <i>obj</i> and <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return StringValue of <i>IdentifierName</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> <span class="nt">StringLiteral</span></div>
+ <ol class="proc">
+ <li>Return a String value whose code units are the SV of the <i>StringLiteral</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> <span class="nt">NumericLiteral</span></div>
+ <ol class="proc">
+ <li>Let <i>nbr</i> be the result of forming the value of the <i>NumericLiteral</i>.</li>
+ <li>Return <a href="#sec-tostring">ToString</a>(<i>nbr</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ComputedPropertyName</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">AssignmentExpression</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>exprValue</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>propName</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propName</i>).</li>
+ <li>Return <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propName</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object-initializer-runtime-semantics-propertydefinitionevaluation">
+ <h1><span class="secnum" id="sec-12.2.5.9"><a
+ href="#sec-object-initializer-runtime-semantics-propertydefinitionevaluation"
+ title="link to this section">12.2.5.9</a></span> Runtime Semantics: PropertyDefinitionEvaluation</h1>
+
+ <p>With parameter <var>object</var> and <span style="font-family: Times New Roman"><i>enumerable</i>.</span></p>
+
+ <p>See also: <a href="#sec-method-definitions-runtime-semantics-propertydefinitionevaluation">14.3.10</a>, <a
+ href="#sec-generator-function-definitions-runtime-semantics-propertydefinitionevaluation">14.4.13</a>, B.3.1</p>
+
+ <div class="gp prod"><span class="nt">PropertyDefinitionList</span> <span class="geq">:</span> <span class="nt">PropertyDefinitionList</span> <code class="t">,</code> <span class="nt">PropertyDefinition</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing PropertyDefinitionEvaluation of <i>PropertyDefinitionList</i> with
+ arguments <i>object</i> and <i>enumerable</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing PropertyDefinitionEvaluation of <i>PropertyDefinition</i> with arguments
+ <i>object</i> and <i>enumerable</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">IdentifierReference</span></div>
+ <ol class="proc">
+ <li>Let <i>propName</i> be StringValue of <i>IdentifierReference</i>.</li>
+ <li>Let <i>exprValue</i> be the result of evaluating <i>IdentifierReference</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exprValue</i>).</li>
+ <li>Let <i>propValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propValue</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>enumerable</i> is <b>true</b>.</li>
+ <li>Return <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>object</i>, <i>propName</i>,
+ <i>propValue</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>propKey</i> be the result of evaluating <i>PropertyName</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propKey</i>).</li>
+ <li>Let <i>exprValueRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>propValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprValueRef</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propValue</i>).</li>
+ <li>If IsFunctionDefinition of <i>AssignmentExpression</i> is <b>true</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>AssignmentExpression)</i>
+ is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>propValue</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>propValue</i>, <i>propKey</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>enumerable</i> is <b>true</b>.</li>
+ <li>Return <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>object</i>, <i>propKey</i>,
+ <i>propValue</i>).</li>
+ </ol>
+
+ <p class="Note"><i>NOTE	An alternative semantics for this production is given in <a
+ href="#sec-__proto__-property-names-in-object-initializers">B.3.1</a>.</i></p>
+ </section>
+ </section>
+
+ <section id="sec-function-defining-expressions">
+ <h1><span class="secnum" id="sec-12.2.6"><a href="#sec-function-defining-expressions"
+ title="link to this section">12.2.6</a></span> Function Defining Expressions</h1>
+
+ <p>See <a href="#sec-function-definitions">14.1</a> for <span class="prod"><span class="nt">PrimaryExpression</span> <span
+ class="geq">:</span> <span class="nt">FunctionExpression</span></span> .</p>
+
+ <p>See <a href="#sec-generator-function-definitions">14.4</a> for <span class="prod"><span
+ class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">GeneratorExpression</span></span> .</p>
+
+ <p>See <a href="#sec-class-definitions">14.5</a> for <span class="prod"><span class="nt">PrimaryExpression</span> <span
+ class="geq">:</span> <span class="nt">ClassExpression</span></span> .</p>
+ </section>
+
+ <section id="sec-primary-expression-regular-expression-literals">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.7"><a href="#sec-primary-expression-regular-expression-literals"
+ title="link to this section">12.2.7</a></span> Regular Expression Literals</h1>
+ <h2>Syntax</h2>
+
+ <p>See <a href="#sec-literals-string-literals">11.8.4</a>.</p>
+ </div>
+
+ <section id="sec-primary-expression-regular-expression-literals-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.2.7.1"><a
+ href="#sec-primary-expression-regular-expression-literals-static-semantics-early-errors"
+ title="link to this section">12.2.7.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">RegularExpressionLiteral</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span style="font-family: Times New Roman">BodyText</span> of <span
+ class="nt">RegularExpressionLiteral</span> cannot be recognized using the goal symbol <span class="nt">Pattern</span>
+ of the ECMAScript RegExp grammar specified in <a href="#sec-patterns">21.2.1</a><var>.</var></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <span style="font-family: Times New Roman">FlagText</span> of <span
+ class="nt">RegularExpressionLiteral</span> contains any code points other than <code>"g"</code>, <code>"i"</code>,
+ <code>"m"</code>, <code>"u"</code>, or <code>"y"</code>, or if it contains the same code point more than once.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-regular-expression-literals-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.2.7.2"><a href="#sec-regular-expression-literals-runtime-semantics-evaluation"
+ title="link to this section">12.2.7.2</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">RegularExpressionLiteral</span></div>
+ <ol class="proc">
+ <li>Let <i>pattern</i> be the string value consisting of the <a href="#sec-utf16encoding">UTF16Encoding</a> of each code
+ point of BodyText of <i>RegularExpressionLiteral</i>.</li>
+ <li>Let <i>flags</i> be the string value consisting of the <a href="#sec-utf16encoding">UTF16Encoding</a> of each code
+ point of FlagText of <i>RegularExpressionLiteral</i>.</li>
+ <li>Return <a href="#sec-regexpcreate">RegExpCreate</a>(<i>pattern</i>, <i>flags</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-template-literals">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.8"><a href="#sec-template-literals" title="link to this section">12.2.8</a></span>
+ Template Literals</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateLiteral</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">NoSubstitutionTemplate</span></div>
+ <div class="rhs"><span class="nt">TemplateHead</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <span class="nt">TemplateSpans</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateSpans</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">TemplateTail</span></div>
+ <div class="rhs"><span class="nt">TemplateMiddleList</span><sub>[?Yield]</sub> <span class="nt">TemplateTail</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TemplateMiddleList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">TemplateMiddle</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">TemplateMiddleList</span><sub>[?Yield]</sub> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-static-semantics-templatestrings">
+ <h1><span class="secnum" id="sec-12.2.8.1"><a href="#sec-static-semantics-templatestrings"
+ title="link to this section">12.2.8.1</a></span> Static Semantics: TemplateStrings</h1>
+
+ <p>With parameter <var>raw</var>.</p>
+
+ <div class="gp prod"><span class="nt">TemplateLiteral</span> <span class="geq">:</span> <span class="nt">NoSubstitutionTemplate</span></div>
+ <ol class="proc">
+ <li>If <i>raw</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>string</i> be the TV of <i>NoSubstitutionTemplate</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>string</i> be the TRV of <i>NoSubstitutionTemplate</i>.</li>
+ </ol>
+ </li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the single element,
+ <i>string</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateLiteral</span> <span class="geq">:</span> <span class="nt">TemplateHead</span> <span class="nt">Expression</span> <span class="nt">TemplateSpans</span></div>
+ <ol class="proc">
+ <li>If <i>raw</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>head</i> be the TV of <i>TemplateHead</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>head</i> be the TRV of <i>TemplateHead</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>tail</i> be TemplateStrings of <i>TemplateSpans</i> with argument <i>raw</i>.</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing <i>head</i> followed by the element,
+ in order of <i>tail</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateSpans</span> <span class="geq">:</span> <span class="nt">TemplateTail</span></div>
+ <ol class="proc">
+ <li>If <i>raw</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>tail</i> be the TV of <i>TemplateTail</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>tail</i> be the TRV of <i>TemplateTail</i>.</li>
+ </ol>
+ </li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the single element, <i>tail</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateSpans</span> <span class="geq">:</span> <span class="nt">TemplateMiddleList</span> <span class="nt">TemplateTail</span></div>
+ <ol class="proc">
+ <li>Let <i>middle</i> be TemplateStrings of <i>TemplateMiddleList</i> with argument <i>raw</i>.</li>
+ <li>If <i>raw</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>tail</i> be the TV of <i>TemplateTail</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>tail</i> be the TRV of <i>TemplateTail</i>.</li>
+ </ol>
+ </li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the elements, in order, of
+ <i>middle</i> followed by <i>tail</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateMiddleList</span> <span class="geq">:</span> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span></div>
+ <ol class="proc">
+ <li>If <i>raw</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>string</i> be the TV of <i>TemplateMiddle</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>string</i> be the TRV of <i>TemplateMiddle</i>.</li>
+ </ol>
+ </li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the single element,
+ <i>string</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateMiddleList</span> <span class="geq">:</span> <span class="nt">TemplateMiddleList</span> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span></div>
+ <ol class="proc">
+ <li>Let <i>front</i> be TemplateStrings of <i>TemplateMiddleList</i> with argument <i>raw</i>.</li>
+ <li>If <i>raw</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>last</i> be the TV of <i>TemplateMiddle</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>last</i> be the TRV of <i>TemplateMiddle</i>.</li>
+ </ol>
+ </li>
+ <li>Append <i>last</i> as the last element of the <a href="#sec-list-and-record-specification-type">List</a>
+ <i>front</i>.</li>
+ <li>Return <i>front</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-template-literals-runtime-semantics-argumentlistevaluation">
+ <h1><span class="secnum" id="sec-12.2.8.2"><a href="#sec-template-literals-runtime-semantics-argumentlistevaluation"
+ title="link to this section">12.2.8.2</a></span> <span style="font-family: sans-serif">Runtime Semantics:</span>
+ ArgumentListEvaluation</h1>
+
+ <p>See also: <a href="#sec-argument-lists-runtime-semantics-argumentlistevaluation">12.3.6.1</a></p>
+
+ <div class="gp prod"><span class="nt">TemplateLiteral</span> <span class="geq">:</span> <span class="nt">NoSubstitutionTemplate</span></div>
+ <ol class="proc">
+ <li>Let <i>templateLiteral</i> be this <i>TemplateLiteral.</i></li>
+ <li>Let <i>siteObj</i> be <a href="#sec-gettemplateobject">GetTemplateObject</a>(<i>templateLiteral</i>).</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the one element which is
+ <i>siteObj</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateLiteral</span> <span class="geq">:</span> <span class="nt">TemplateHead</span> <span class="nt">Expression</span> <span class="nt">TemplateSpans</span></div>
+ <ol class="proc">
+ <li>Let <i>templateLiteral</i> be this <i>TemplateLiteral.</i></li>
+ <li>Let <i>siteObj</i> be <a href="#sec-gettemplateobject">GetTemplateObject</a>(<i>templateLiteral</i>).</li>
+ <li>Let <i>firstSub</i> be the result of evaluating <i>Expression</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>firstSub</i>).</li>
+ <li>Let <i>restSub</i> be SubstitutionEvaluation of <i>TemplateSpans</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>restSub</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>restSub</i> is a <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> whose first element is <i>siteObj</i>, whose
+ second elements is <i>firstSub</i>, and whose subsequent elements are the elements of <i>restSub</i>, in order.
+ <i>restSub</i> may contain no elements.</li>
+ </ol>
+ </section>
+
+ <section id="sec-gettemplateobject">
+ <h1><span class="secnum" id="sec-12.2.8.3"><a href="#sec-gettemplateobject"
+ title="link to this section">12.2.8.3</a></span> Runtime Semantics: GetTemplateObject ( templateLiteral )</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">GetTemplateObject</span> is called with a grammar
+ production, <var>templateLiteral</var>, as an argument. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>rawStrings</i> be TemplateStrings of <i>templateLiteral</i> with argument <b>true</b>.</li>
+ <li>Let <i>ctx</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>realm</i> be the <i>ctx</i>’s <a href="#sec-code-realms">Realm</a>.</li>
+ <li>Let <i>templateRegistry</i> be <i>realm</i>.[[templateMap]].</li>
+ <li>For each element <i>e</i> of <i>templateRegistry</i>, do
+ <ol class="block">
+ <li>If <i>e</i>.[[strings]] and <i>rawStrings</i> contain the same values in the same order, then
+ <ol class="block">
+ <li>Return <i>e.</i>[[array]].</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>cookedStrings</i> be TemplateStrings of <i>templateLiteral</i> with argument <b>false</b>.</li>
+ <li>Let <i>count</i> be the number of elements in the <a href="#sec-list-and-record-specification-type">List</a>
+ <i>cookedStrings</i>.</li>
+ <li>Let <i>template</i> be <a href="#sec-arraycreate">ArrayCreate</a>(<i>count</i>).</li>
+ <li>Let <i>rawObj</i> be <a href="#sec-arraycreate">ArrayCreate</a>(<i>count</i>).</li>
+ <li>Let <i>index</i> be 0.</li>
+ <li>Repeat while <i>index</i> < <i>count</i>
+ <ol class="block">
+ <li>Let <i>prop</i> be <a href="#sec-tostring">ToString</a>(<i>index</i>).</li>
+ <li>Let <i>cookedValue</i> be the string value <i>cookedStrings</i>[<i>index</i>].</li>
+ <li><a href="#sec-call">Call</a> the [[DefineOwnProperty]] internal method of <i>template</i> with arguments
+ <i>prop</i> and PropertyDescriptor{[[Value]]: <i>cookedValue</i>, [[Enumerable]]: <b>true</b>, [[Writable]]:
+ <b>false</b>, [[Configurable]]: <b>false</b>}<i>.</i></li>
+ <li>Let <i>rawValue</i> be the string value <i>rawStrings</i>[<i>index</i>].</li>
+ <li><a href="#sec-call">Call</a> the [[DefineOwnProperty]] internal method of <i>rawObj</i> with arguments
+ <i>prop</i> and PropertyDescriptor{[[Value]]: <i>rawValue</i>, [[Enumerable]]: <b>true</b>, [[Writable]]:
+ <b>false</b>, [[Configurable]]: <b>false</b>}<i>.</i></li>
+ <li>Let <i>index</i> be <i>index</i>+1.</li>
+ </ol>
+ </li>
+ <li>Perform <a href="#sec-setintegritylevel">SetIntegrityLevel</a>(<i>rawObj</i>, "<code>frozen</code>").</li>
+ <li><a href="#sec-call">Call</a> the [[DefineOwnProperty]] internal method of <i>template</i> with arguments
+ <b>"<code>raw</code>"</b> and PropertyDescriptor{[[Value]]: <i>rawObj</i>, [[Writable]]: <b>false</b>,
+ [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b>}<i>.</i></li>
+ <li>Perform <a href="#sec-setintegritylevel">SetIntegrityLevel</a>(<i>template</i>, "<code>frozen</code>").</li>
+ <li>Append the Record{[[strings]]: <i>rawStrings</i>, [[array]]: <i>template</i>} to <i>templateRegistry</i>.</li>
+ <li>Return <i>template</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The creation of a template object cannot result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Each <i>TemplateLiteral</i> in the program code of a <a
+ href="#sec-code-realms">Realm</a> is associated with a unique template object that is used in the evaluation of tagged
+ Templates (<a href="#sec-template-literals-runtime-semantics-evaluation">12.2.8.5</a>). The template objects are frozen
+ and the same template object is used each time a specific tagged Template is evaluated. Whether template objects are
+ created lazily upon first evaluation of the <i>TemplateLiteral</i> or eagerly prior to first evaluation is an
+ implementation choice that is not observable to ECMAScript code.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> Future editions of this specification may define additional non-enumerable properties
+ of template objects.</p>
+ </div>
+ </section>
+
+ <section id="sec-runtime-semantics-substitutionevaluation">
+ <h1><span class="secnum" id="sec-12.2.8.4"><a href="#sec-runtime-semantics-substitutionevaluation"
+ title="link to this section">12.2.8.4</a></span> Runtime Semantics: SubstitutionEvaluation</h1>
+ <div class="gp prod"><span class="nt">TemplateSpans</span> <span class="geq">:</span> <span class="nt">TemplateTail</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateSpans</span> <span class="geq">:</span> <span class="nt">TemplateMiddleList</span> <span class="nt">TemplateTail</span></div>
+ <ol class="proc">
+ <li>Return the result of SubstitutionEvaluation of <i>TemplateMiddleList</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateMiddleList</span> <span class="geq">:</span> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span></div>
+ <ol class="proc">
+ <li>Let <i>sub</i> be the result of evaluating <i>Expression</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>sub</i>).</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing only <i>sub</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateMiddleList</span> <span class="geq">:</span> <span class="nt">TemplateMiddleList</span> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span></div>
+ <ol class="proc">
+ <li>Let <i>preceding</i> be the result of SubstitutionEvaluation of <i>TemplateMiddleList</i> .</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>preceding</i>).</li>
+ <li>Let <i>next</i> be the result of evaluating <i>Expression</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>Append <i>next</i> as the last element of the <a href="#sec-list-and-record-specification-type">List</a>
+ <i>preceding</i>.</li>
+ <li>Return <i>preceding</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-template-literals-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.2.8.5"><a href="#sec-template-literals-runtime-semantics-evaluation"
+ title="link to this section">12.2.8.5</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">TemplateLiteral</span> <span class="geq">:</span> <span class="nt">NoSubstitutionTemplate</span></div>
+ <ol class="proc">
+ <li>Return the string value whose code units are the elements of the TV of <i>NoSubstitutionTemplate</i> as defined in
+ <a href="#sec-template-literal-lexical-components">11.8.6</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateLiteral</span> <span class="geq">:</span> <span class="nt">TemplateHead</span> <span class="nt">Expression</span> <span class="nt">TemplateSpans</span></div>
+ <ol class="proc">
+ <li>Let <i>head</i> be the TV of <i>TemplateHead</i> as defined in <a
+ href="#sec-template-literal-lexical-components">11.8.6</a>.</li>
+ <li>Let <i>sub</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>middle</i> be <a href="#sec-tostring">ToString</a>(<i>sub</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>middle</i>).</li>
+ <li>Let <i>tail</i> be the result of evaluating <i>TemplateSpans</i> .</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>tail</i>).</li>
+ <li>Return the string value whose code units are the elements of <i>head</i> followed by the elements of <i>middle</i>
+ followed by the elements of <i>tail</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The string conversion semantics applied to the <i>Expression</i> value are like <code><a
+ href="#sec-string.prototype.concat">String.prototype.concat</a></code> rather than the <code>+</code> operator.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">TemplateSpans</span> <span class="geq">:</span> <span class="nt">TemplateTail</span></div>
+ <ol class="proc">
+ <li>Let <i>tail</i> be the TV of <i>TemplateTail</i> as defined in <a
+ href="#sec-template-literal-lexical-components">11.8.6</a>.</li>
+ <li>Return the string consisting of the code units of <i>tail</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateSpans</span> <span class="geq">:</span> <span class="nt">TemplateMiddleList</span> <span class="nt">TemplateTail</span></div>
+ <ol class="proc">
+ <li>Let <i>head</i> be the result of evaluating <i>TemplateMiddleList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>head</i>).</li>
+ <li>Let <i>tail</i> be the TV of <i>TemplateTail</i> as defined in <a
+ href="#sec-template-literal-lexical-components">11.8.6</a>.</li>
+ <li>Return the string whose code units are the elements of <i>head</i> followed by the elements of <i>tail</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TemplateMiddleList</span> <span class="geq">:</span> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span></div>
+ <ol class="proc">
+ <li>Let <i>head</i> be the TV of <i>TemplateMiddle</i> as defined in <a
+ href="#sec-template-literal-lexical-components">11.8.6</a>.</li>
+ <li>Let <i>sub</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>middle</i> be <a href="#sec-tostring">ToString</a>(<i>sub</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>middle</i>).</li>
+ <li>Return the sequence of code units consisting of the code units of <i>head</i> followed by the elements of
+ <i>middle</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The string conversion semantics applied to the <i>Expression</i> value are like <code><a
+ href="#sec-string.prototype.concat">String.prototype.concat</a></code> rather than the <code>+</code> operator.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">TemplateMiddleList</span> <span class="geq">:</span> <span class="nt">TemplateMiddleList</span> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span></div>
+ <ol class="proc">
+ <li>Let <i>rest</i> be the result of evaluating <i>TemplateMiddleList</i> .</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rest</i>).</li>
+ <li>Let <i>middle</i> be the TV of <i>TemplateMiddle</i> as defined in <a
+ href="#sec-template-literal-lexical-components">11.8.6</a>.</li>
+ <li>Let <i>sub</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>last</i> be <a href="#sec-tostring">ToString</a>(<i>sub</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>last</i>).</li>
+ <li>Return the sequence of code units consisting of the elements of <i>rest</i> followed by the code units of
+ <i>middle</i> followed by the elements of <i>last</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The string conversion semantics applied to the <i>Expression</i> value are like <code><a
+ href="#sec-string.prototype.concat">String.prototype.concat</a></code> rather than the <code>+</code> operator.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-grouping-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.2.9"><a href="#sec-grouping-operator" title="link to this section">12.2.9</a></span>
+ The Grouping Operator</h1>
+ </div>
+
+ <section id="sec-grouping-operator-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.2.9.1"><a href="#sec-grouping-operator-static-semantics-early-errors"
+ title="link to this section">12.2.9.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the lexical token sequence matched by <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span> cannot be parsed with no tokens left over using
+ <span class="nt">ParenthesizedExpression</span> as the goal symbol.</p>
+ </li>
+
+ <li>
+ <p>All Early Errors rules for <span class="nt">ParenthesizedExpression</span> and its derived productions also apply
+ to <span style="font-family: Times New Roman">CoveredParenthesizedExpression</span> of <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-grouping-operator-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.2.9.2"><a href="#sec-grouping-operator-static-semantics-isfunctiondefinition"
+ title="link to this section">12.2.9.2</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">ParenthesizedExpression</span> <span class="geq">:</span> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code></div>
+ <ol class="proc">
+ <li>Return IsFunctionDefinition of <i>Expression</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.2.9.3"><a href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.2.9.3</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ParenthesizedExpression</span> <span class="geq">:</span> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code></div>
+ <ol class="proc">
+ <li>Return IsValidSimpleAssignmentTarget of <i>Expression</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-grouping-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.2.9.4"><a href="#sec-grouping-operator-runtime-semantics-evaluation"
+ title="link to this section">12.2.9.4</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be CoveredParenthesizedExpression of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return the result of evaluating <i>expr</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ParenthesizedExpression</span> <span class="geq">:</span> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>Expression</i>. This may be of type <a
+ href="#sec-reference-specification-type">Reference</a>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This algorithm does not apply <a href="#sec-getvalue">GetValue</a> to the result of
+ evaluating <i>Expression</i>. The principal motivation for this is so that operators such as <code>delete</code> and
+ <code>typeof</code> may be applied to parenthesized expressions.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-left-hand-side-expressions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3"><a href="#sec-left-hand-side-expressions"
+ title="link to this section">12.3</a></span> Left-Hand-Side Expressions</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">PrimaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <code class="t">[</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <span class="nt">TemplateLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">SuperProperty</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MetaProperty</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">MemberExpression</span><sub>[?Yield]</sub> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SuperProperty</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">super</code> <code class="t">[</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">super</code> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MetaProperty</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">NewTarget</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NewTarget</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">new</code> <code class="t">.</code> <code class="t">target</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NewExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">NewExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CallExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">SuperCall</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <code class="t">[</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <span class="nt">TemplateLiteral</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SuperCall</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">super</code> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Arguments</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">ArgumentList</span><sub>[?Yield]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArgumentList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><code class="t">...</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ArgumentList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ArgumentList</span><sub>[?Yield]</sub> <code class="t">,</code> <code class="t">...</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LeftHandSideExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">NewExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-static-semantics">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.1"><a href="#sec-static-semantics" title="link to this section">12.3.1</a></span>
+ Static Semantics</h1>
+ </div>
+
+ <section id="sec-static-semantics-static-semantics-contains">
+ <h1><span class="secnum" id="sec-12.3.1.1"><a href="#sec-static-semantics-static-semantics-contains"
+ title="link to this section">12.3.1.1</a></span> Static Semantics: Contains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-static-semantic-rules">5.3</a>, <a
+ href="#sec-object-initializer-static-semantics-contains">12.2.5.3</a>, <a
+ href="#sec-function-definitions-static-semantics-contains">14.1.4</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-contains">14.2.3</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-contains">14.4.4</a>, <a
+ href="#sec-class-definitions-static-semantics-contains">14.5.4</a></p>
+
+ <div class="gp prod"><span class="nt">MemberExpression</span> <span class="geq">:</span> <span class="nt">MemberExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>If <i>MemberExpression</i> Contains <i>symbol</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>If <i>symbol</i> is a <i>ReservedWord</i>, return <b>false</b>.</li>
+ <li>If <i>symbol</i> is an <i>Identifier</i> and StringValue of <i>symbol</i> is the same value as the StringValue of
+ <i>IdentifierName</i>, return <b>true</b>;</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SuperProperty</span> <span class="geq">:</span> <code class="t">super</code> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>If <i>symbol</i> is the <i>ReservedWord</i> <code>super</code>, return <b>true</b>.</li>
+ <li>If <i>symbol</i> is a <i>ReservedWord</i>, return <b>false</b>.</li>
+ <li>If <i>symbol</i> is an <i>Identifier</i> and StringValue of <i>symbol</i> is the same value as the StringValue of
+ <i>IdentifierName</i>, return <b>true</b>;</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CallExpression</span> <span class="geq">:</span> <span class="nt">CallExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>If <i>CallExpression</i> Contains <i>symbol</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>If <i>symbol</i> is a <i>ReservedWord</i>, return <b>false</b>.</li>
+ <li>If <i>symbol</i> is an <i>Identifier</i> and StringValue of <i>symbol</i> is the same value as the StringValue of
+ <i>IdentifierName</i>, return <b>true</b>;</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.3.1.2"><a href="#sec-static-semantics-static-semantics-isfunctiondefinition"
+ title="link to this section">12.3.1.2</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">TemplateLiteral</span></div>
+ <div class="rhs"><span class="nt">SuperProperty</span></div>
+ <div class="rhs"><span class="nt">MetaProperty</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NewExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">NewExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CallExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">SuperCall</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-static-semantics-isdestructuring">
+ <h1><span class="secnum" id="sec-12.3.1.3"><a href="#sec-static-semantics-static-semantics-isdestructuring"
+ title="link to this section">12.3.1.3</a></span> Static Semantics: IsDestructuring</h1>
+
+ <p>See also: <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>.</p>
+
+ <div class="gp prod"><span class="nt">MemberExpression</span> <span class="geq">:</span> <span class="nt">PrimaryExpression</span></div>
+ <ol class="proc">
+ <li>If <i>PrimaryExpression</i> is either an <i>ObjectLiteral</i> or an <i>ArrayLiteral</i>, return <b>true.</b></li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">TemplateLiteral</span></div>
+ <div class="rhs"><span class="nt">SuperProperty</span></div>
+ <div class="rhs"><span class="nt">MetaProperty</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NewExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">NewExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CallExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">SuperCall</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-static-semantics-isidentifierref">
+ <h1><span class="secnum" id="sec-12.3.1.4"><a href="#sec-static-semantics-static-semantics-isidentifierref"
+ title="link to this section">12.3.1.4</a></span> Static Semantics: IsIdentifierRef</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LeftHandSideExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">TemplateLiteral</span></div>
+ <div class="rhs"><span class="nt">SuperProperty</span></div>
+ <div class="rhs"><span class="nt">MetaProperty</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NewExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">NewExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.3.1.5"><a href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.3.1.5</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CallExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">SuperProperty</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CallExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">SuperCall</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NewExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">NewExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">TemplateLiteral</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NewTarget</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">new</code> <code class="t">.</code> <code class="t">target</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-property-accessors">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.2"><a href="#sec-property-accessors" title="link to this section">12.3.2</a></span>
+ Property Accessors</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Properties are accessed by name, using either the dot notation:</p>
+ </div>
+
+ <div class="lhs">MemberExpression <code>.</code> IdentifierName<br>CallExpression <code>.</code> IdentifierName</div>
+
+ <p>or the bracket notation:</p>
+
+ <div class="lhs">MemberExpression <code>[</code> Expression <code>]</code><br>CallExpression <code>[</code> Expression <code>]</code></div>
+
+ <p>The dot notation is explained by the following syntactic conversion:</p>
+
+ <div class="lhs">MemberExpression <code>.</code> IdentifierName</div>
+
+ <p>is identical in its behaviour to</p>
+
+ <div class="lhs">MemberExpression <code>[</code> <identifier-name-string> <code>]</code></div>
+
+ <p>and similarly</p>
+
+ <div class="lhs">CallExpression <code>.</code> IdentifierName</div>
+
+ <p>is identical in its behaviour to</p>
+
+ <div class="lhs">CallExpression <code>[</code> <identifier-name-string> <code>]</code></div>
+
+ <p>where <var><identifier-name-string></var> is the result of evaluating <span style="font-family: Times New
+ Roman">StringValue of</span> <span class="nt">IdentifierName</span>.</p>
+ </div>
+
+ <section id="sec-property-accessors-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.3.2.1"><a href="#sec-property-accessors-runtime-semantics-evaluation"
+ title="link to this section">12.3.2.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">MemberExpression</span> <span class="geq">:</span> <span class="nt">MemberExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>baseReference</i> be the result of evaluating <i>MemberExpression</i>.</li>
+ <li>Let <i>baseValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>baseReference</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>baseValue</i>).</li>
+ <li>Let <i>propertyNameReference</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>propertyNameValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>propertyNameReference</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propertyNameValue</i>).</li>
+ <li>Let <i>bv</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<i>baseValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>bv</i>).</li>
+ <li>Let <i>propertyKey</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyNameValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propertyKey</i>).</li>
+ <li>If the code matched by the syntactic production that is being evaluated is <a href="#sec-strict-mode-code">strict
+ mode code</a>, let <i>strict</i> be <b>true</b>, else let <i>strict</i> be <b>false</b>.</li>
+ <li>Return a value of type <a href="#sec-reference-specification-type">Reference</a> whose base value is <i>bv</i> and
+ whose referenced name is <i>propertyKey</i>, and whose strict reference flag is <i>strict</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MemberExpression</span> <span class="geq">:</span> <span class="nt">MemberExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Let <i>baseReference</i> be the result of evaluating <i>MemberExpression</i>.</li>
+ <li>Let <i>baseValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>baseReference</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>baseValue</i>).</li>
+ <li>Let <i>bv</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<i>baseValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>bv</i>).</li>
+ <li>Let <i>propertyNameString</i> be StringValue of <i>IdentifierName</i></li>
+ <li>If the code matched by the syntactic production that is being evaluated is <a href="#sec-strict-mode-code">strict
+ mode code</a>, let <i>strict</i> be <b>true</b>, else let <i>strict</i> be <b>false</b>.</li>
+ <li>Return a value of type <a href="#sec-reference-specification-type">Reference</a> whose base value is <i>bv</i> and
+ whose referenced name is <i>propertyNameString</i>, and whose strict reference flag is <i>strict</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CallExpression</span> <span class="geq">:</span> <span class="nt">CallExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+
+ <p>Is evaluated in exactly the same manner as <span class="prod"><span class="nt">MemberExpression</span> <span
+ class="geq">:</span> <span class="nt">MemberExpression</span> <code class="t">[</code> <span class="nt">Expression</span>
+ <code class="t">]</code></span> except that the contained <span class="nt">CallExpression</span> is evaluated in step
+ 1.</p>
+
+ <div class="gp prod"><span class="nt">CallExpression</span> <span class="geq">:</span> <span class="nt">CallExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+
+ <p>Is evaluated in exactly the same manner as <span class="prod"><span class="nt">MemberExpression</span> <span
+ class="geq">:</span> <span class="nt">MemberExpression</span> <code class="t">.</code> <span
+ class="nt">IdentifierName</span></span> except that the contained <span class="nt">CallExpression</span> is evaluated in
+ step 1.</p>
+ </section>
+ </section>
+
+ <section id="sec-new-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.3"><a href="#sec-new-operator" title="link to this section">12.3.3</a></span> The
+ <code>new</code> Operator</h1>
+ </div>
+
+ <section id="sec-new-operator-runtime-semantics-evaluation">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.3.1"><a href="#sec-new-operator-runtime-semantics-evaluation"
+ title="link to this section">12.3.3.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">NewExpression</span> <span class="geq">:</span> <code class="t">new</code> <span class="nt">NewExpression</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-evaluatenew">EvaluateNew</a>(<i>NewExpression</i>, <span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MemberExpression</span> <span class="geq">:</span> <code class="t">new</code> <span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-evaluatenew">EvaluateNew</a>(<i>MemberExpression</i>, <i>Arguments</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-evaluatenew">
+ <h1><span class="secnum" id="sec-12.3.3.1.1"><a href="#sec-evaluatenew"
+ title="link to this section">12.3.3.1.1</a></span> Runtime Semantics: EvaluateNew(constructProduction,
+ arguments)</h1>
+
+ <p>The abstract operation EvaluateNew with arguments <span style="font-family: Times New
+ Roman"><i>constructProduction</i>,</span> and <var>arguments</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>constructProduction</i> is either a <i>NewExpression</i> or a
+ <i>MemberExpression</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>arguments</i> is either <span style="font-family:
+ sans-serif">empty</span> or an <i>Arguments</i> production.</li>
+ <li>Let <i>ref</i> be the result of evaluating <i>constructProduction</i>.</li>
+ <li>Let <i>constructor</i> be <a href="#sec-getvalue">GetValue</a>(<i>ref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>constructor</i>).</li>
+ <li>If <i>arguments</i> is <span style="font-family: sans-serif">empty</span>, let <i>argList</i> be an empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>argList</i> be ArgumentListEvaluation of <i>arguments</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argList</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a> (<i>constructor</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <a href="#sec-construct">Construct</a>(<i>constructor</i>, <i>argList</i>).</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-function-calls">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.4"><a href="#sec-function-calls" title="link to this section">12.3.4</a></span>
+ Function Calls</h1>
+ </div>
+
+ <section id="sec-function-calls-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.3.4.1"><a href="#sec-function-calls-runtime-semantics-evaluation"
+ title="link to this section">12.3.4.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">CallExpression</span> <span class="geq">:</span> <span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ <ol class="proc">
+ <li>Let <i>ref</i> be the result of evaluating <i>MemberExpression</i>.</li>
+ <li>Let <i>func</i> be <a href="#sec-getvalue">GetValue</a>(<i>ref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>func</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>ref</i>) is <a
+ href="#sec-reference-specification-type">Reference</a> and <a
+ href="#sec-reference-specification-type">IsPropertyReference</a>(<i>ref</i>) is <b>false</b> and <a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>ref</i>) <i>is</i> <code>"eval"</code>, then
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>func</i>, %eval%) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>argList</i> be ArgumentListEvaluation(<i>Arguments</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argList</i>).</li>
+ <li>If <i>argList</i> has no elements, return <b>undefined.</b></li>
+ <li>Let <i>evalText</i> be the first element of <i>argList</i>.</li>
+ <li>If the source code matching this <i>CallExpression</i> is <a href="#sec-strict-mode-code">strict code</a>,
+ let <i>strictCaller</i> be <b>true.</b> Otherwise let <i>strictCaller</i> be <b>false.</b></li>
+ <li>Let <i>evalRealm</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-code-realms">Realm</a>.</li>
+ <li>Return <a href="#sec-performeval">PerformEval</a>(<i>evalText</i>, <i>evalRealm</i>, <i>strictCaller</i>,
+ <b>true</b>). .</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>ref</i>) is <a
+ href="#sec-reference-specification-type">Reference</a>, then
+ <ol class="block">
+ <li>If <a href="#sec-reference-specification-type">IsPropertyReference</a>(<i>ref</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>thisValue</i> be <a href="#sec-getthisvalue">GetThisValue</a>(<i>ref</i>).</li>
+ </ol>
+ </li>
+ <li>Else, the base of <i>ref</i> is an <a href="#sec-environment-records">Environment Record</a>
+ <ol class="block">
+ <li>Let <i>refEnv</i> be <a href="#sec-reference-specification-type">GetBase</a>(<i>ref</i>).</li>
+ <li>Let <i>thisValue</i> be <i>refEnv</i>.WithBaseObject().</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>ref</i>) is not <a
+ href="#sec-reference-specification-type">Reference</a>,
+ <ol class="block">
+ <li>Let <i>thisValue</i> be <b>undefined</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>thisCall</i> be this <i>CallExpression</i>.</li>
+ <li>Let <i>tailCall</i> be <a href="#sec-isintailposition">IsInTailPosition</a>(<i>thisCall</i>). (See <a
+ href="#sec-isintailposition">14.6.1</a>)</li>
+ <li>Return <a href="#sec-evaluatedirectcall">EvaluateDirectCall</a>(<i>func</i>, <i>thisValue</i>, <i>Arguments</i>,
+ <i>tailCall</i>).</li>
+ </ol>
+
+ <p>A <span class="nt">CallExpression</span> whose evaluation executes step 4.a.vii is a <i>direct eval</i>.</p>
+
+ <div class="gp prod"><span class="nt">CallExpression</span> <span class="geq">:</span> <span class="nt">CallExpression</span> <span class="nt">Arguments</span></div>
+ <ol class="proc">
+ <li>Let <i>ref</i> be the result of evaluating <i>CallExpression</i>.</li>
+ <li>Let <i>thisCall</i> be this <i>CallExpression</i></li>
+ <li>Let <i>tailCall</i> be <a href="#sec-isintailposition">IsInTailPosition</a>(<i>thisCall</i>). (See <a
+ href="#sec-isintailposition">14.6.1</a>)</li>
+ <li>Return <a href="#sec-evaluatecall">EvaluateCall</a>(<i>ref</i>, <i>Arguments</i>, <i>tailCall</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-evaluatecall">
+ <h1><span class="secnum" id="sec-12.3.4.2"><a href="#sec-evaluatecall" title="link to this section">12.3.4.2</a></span>
+ Runtime Semantics: EvaluateCall( ref, arguments, tailPosition )</h1>
+
+ <p>The abstract operation EvaluateCall takes as arguments a value <var>ref</var>, a syntactic grammar production
+ <var>arguments</var>, and a Boolean argument <var>tailPosition</var>. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>func</i> be <a href="#sec-getvalue">GetValue</a>(<i>ref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>func</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>ref</i>) is <a
+ href="#sec-reference-specification-type">Reference</a>, then
+ <ol class="block">
+ <li>If <a href="#sec-reference-specification-type">IsPropertyReference</a>(<i>ref</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>thisValue</i> be <a href="#sec-getthisvalue">GetThisValue</a>(<i>ref</i>).</li>
+ </ol>
+ </li>
+ <li>Else, the base of <i>ref</i> is an <a href="#sec-environment-records">Environment Record</a>
+ <ol class="block">
+ <li>Let <i>refEnv</i> be <a href="#sec-reference-specification-type">GetBase</a>(<i>ref</i>).</li>
+ <li>Let <i>thisValue</i> be <i>refEnv</i>.WithBaseObject().</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>ref</i>) is not <a
+ href="#sec-reference-specification-type">Reference</a>,
+ <ol class="block">
+ <li>Let <i>thisValue</i> be <b>undefined</b>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-evaluatedirectcall">EvaluateDirectCall</a>(<i>func</i>, <i>thisValue</i>, <i>arguments</i>,
+ <i>tailPosition</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-evaluatedirectcall">
+ <h1><span class="secnum" id="sec-12.3.4.3"><a href="#sec-evaluatedirectcall"
+ title="link to this section">12.3.4.3</a></span> Runtime Semantics: EvaluateDirectCall( func, thisValue, arguments,
+ tailPosition )</h1>
+
+ <p>The abstract operation EvaluateDirectCall takes as arguments a value <var>func</var>, a value <var>thisValue</var>, a
+ syntactic grammar production <var>arguments</var>, and a Boolean argument <var>tailPosition</var>. It performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>argList</i> be ArgumentListEvaluation(<i>arguments</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argList</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>func</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>func</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <i>tailPosition</i> is <b>true</b>, perform the <a href="#sec-preparefortailcall">PrepareForTailCall</a> abstract
+ operation.</li>
+ <li>Let <i>result</i> be <a href="#sec-call">Call</a>(<i>func</i>, <i>thisValue</i>, <i>argList</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If <i>tailPosition</i> is <b>true</b>, the above call will not
+ return here, but instead evaluation will continue as if the following return has already occurred.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If <i>result</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a> then <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>result</i>) is an <a
+ href="#sec-ecmascript-language-types">ECMAScript language type</a>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-super-keyword">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.5"><a href="#sec-super-keyword" title="link to this section">12.3.5</a></span> The
+ <code>super</code> Keyword</h1>
+ </div>
+
+ <section id="sec-super-keyword-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.3.5.1"><a href="#sec-super-keyword-runtime-semantics-evaluation"
+ title="link to this section">12.3.5.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">SuperProperty</span> <span class="geq">:</span> <code class="t">super</code> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>propertyNameReference</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>propertyNameValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>propertyNameReference</i>).</li>
+ <li>Let <i>propertyKey</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyNameValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propertyKey</i>).</li>
+ <li>If the code matched by the syntactic production that is being evaluated is <a href="#sec-strict-mode-code">strict
+ mode code</a>, let <i>strict</i> be <b>true</b>, else let <i>strict</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-makesuperpropertyreference">MakeSuperPropertyReference</a>(<i>propertyKey</i>,
+ <i>strict</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SuperProperty</span> <span class="geq">:</span> <code class="t">super</code> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Let <i>propertyKey</i> be StringValue of <i>IdentifierName</i>.</li>
+ <li>If the code matched by the syntactic production that is being evaluated is <a href="#sec-strict-mode-code">strict
+ mode code</a>, let <i>strict</i> be <b>true</b>, else let <i>strict</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-makesuperpropertyreference">MakeSuperPropertyReference</a>(<i>propertyKey</i>,
+ <i>strict</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SuperCall</span> <span class="geq">:</span> <code class="t">super</code> <span class="nt">Arguments</span></div>
+ <ol class="proc">
+ <li>Let <i>newTarget</i> be <a href="#sec-getnewtarget">GetNewTarget</a>().</li>
+ <li>If <i>newTarget</i> is <b>undefined</b>, throw a <b>ReferenceError</b> exception.</li>
+ <li>Let <i>func</i> be <a href="#sec-getsuperconstructor">GetSuperConstructor</a>().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>func</i>).</li>
+ <li>Let <i>argList</i> be ArgumentListEvaluation of <i>Arguments</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argList</i>).</li>
+ <li>Let <i>result</i> be <a href="#sec-construct">Construct</a>(<i>func</i>, <i>argList</i>, <i>newTarget</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>Let <i>thisER</i> be <a href="#sec-getthisenvironment">GetThisEnvironment</a>( ).</li>
+ <li>Return <i>thisER</i>.<a href="#sec-bindthisvalue">BindThisValue</a>(<i>result</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-getsuperconstructor">
+ <h1><span class="secnum" id="sec-12.3.5.2"><a href="#sec-getsuperconstructor"
+ title="link to this section">12.3.5.2</a></span> Runtime Semantics: GetSuperConstructor ( )</h1>
+
+ <p>The abstract operation GetSuperConstructor performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <a href="#sec-getthisenvironment">GetThisEnvironment</a>( ).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> is a <a
+ href="#sec-function-environment-records">Function environment record</a>.</li>
+ <li>Let <i>activeFunction</i> be <i>envRec</i>.[[FunctionObject]].</li>
+ <li>Let <i>superConstructor</i> be <i>activeFunction</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>superConstructor</i>).</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>superConstructor</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>superConstructor</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-makesuperpropertyreference">
+ <h1><span class="secnum" id="sec-12.3.5.3"><a href="#sec-makesuperpropertyreference"
+ title="link to this section">12.3.5.3</a></span> Runtime Semantics: MakeSuperPropertyReference(propertyKey,
+ strict)</h1>
+
+ <p>The abstract operation MakeSuperPropertyReference with arguments <var>propertyKey</var> and <var>strict</var> performs
+ the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>env</i> be <a href="#sec-getthisenvironment">GetThisEnvironment</a>( ).</li>
+ <li>If <i>env</i>.HasSuperBinding() is <b>false</b>, throw a <b>ReferenceError</b> exception.</li>
+ <li>Let <i>actualThis</i> be <i>env</i>.GetThisBinding().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>actualThis</i>).</li>
+ <li>Let <i>baseValue</i> be <i>env</i>.<a href="#sec-getsuperbase">GetSuperBase</a>().</li>
+ <li>Let <i>bv</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<i>baseValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>bv</i>).</li>
+ <li>Return a value of type <a href="#sec-reference-specification-type">Reference</a> that is a Super <a
+ href="#sec-reference-specification-type">Reference</a> whose base value is <i>bv</i>, whose referenced name is
+ <i>propertyKey</i>, whose thisValue is <i>actualThis</i>, and whose strict reference flag is <i>strict</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-argument-lists">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.6"><a href="#sec-argument-lists" title="link to this section">12.3.6</a></span>
+ Argument Lists</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The evaluation of an argument list produces a <a
+ href="#sec-list-and-record-specification-type">List</a> of values (<a href="#sec-list-and-record-specification-type">see
+ 6.2.1</a>).</p>
+ </div>
+ </div>
+
+ <section id="sec-argument-lists-runtime-semantics-argumentlistevaluation">
+ <h1><span class="secnum" id="sec-12.3.6.1"><a href="#sec-argument-lists-runtime-semantics-argumentlistevaluation"
+ title="link to this section">12.3.6.1</a></span> <span style="font-family: sans-serif">Runtime Semantics:</span>
+ ArgumentListEvaluation</h1>
+
+ <p>See also: <a href="#sec-template-literals-runtime-semantics-argumentlistevaluation">12.2.8.2</a></p>
+
+ <div class="gp prod"><span class="nt">Arguments</span> <span class="geq">:</span> <code class="t">(</code> <code class="t">)</code></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArgumentList</span> <span class="geq">:</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>ref</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>arg</i> be <a href="#sec-getvalue">GetValue</a>(<i>ref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>arg</i>).</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> whose sole item is <i>arg</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArgumentList</span> <span class="geq">:</span> <code class="t">...</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>list</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>spreadRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>spreadObj</i> be <a href="#sec-getvalue">GetValue</a>(<i>spreadRef</i>).</li>
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>spreadObj</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, return <i>list</i>.</li>
+ <li>Let <i>nextArg</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextArg</i>).</li>
+ <li>Append <i>nextArg</i> as the last element of <i>list</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArgumentList</span> <span class="geq">:</span> <span class="nt">ArgumentList</span> <code class="t">,</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>precedingArgs</i> be the result of evaluating <i>ArgumentList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>precedingArgs</i>).</li>
+ <li>Let <i>ref</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>arg</i> be <a href="#sec-getvalue">GetValue</a>(<i>ref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>arg</i>).</li>
+ <li>Append <i>arg</i> to the end of <i>precedingArgs</i>.</li>
+ <li>Return <i>precedingArgs</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArgumentList</span> <span class="geq">:</span> <span class="nt">ArgumentList</span> <code class="t">,</code> <code class="t">...</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>precedingArgs</i> be the result of evaluating <i>ArgumentList</i>.</li>
+ <li>Let <i>spreadRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<a
+ href="#sec-getvalue">GetValue</a>(<i>spreadRef</i>) ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, return <i>precedingArgs</i>.</li>
+ <li>Let <i>nextArg</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextArg</i>).</li>
+ <li>Append <i>nextArg</i> as the last element of <i>precedingArgs</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-tagged-templates">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.7"><a href="#sec-tagged-templates" title="link to this section">12.3.7</a></span>
+ Tagged Templates</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A tagged template is a function call where the arguments of the call are derived from a
+ <i>TemplateLiteral</i> (<a href="#sec-template-literals">12.2.8</a>). The actual arguments include a template object (<a
+ href="#sec-gettemplateobject">12.2.8.3</a>) and the values produced by evaluating the expressions embedded within the
+ <i>TemplateLiteral</i>.</p>
+ </div>
+ </div>
+
+ <section id="sec-tagged-templates-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.3.7.1"><a href="#sec-tagged-templates-runtime-semantics-evaluation"
+ title="link to this section">12.3.7.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">MemberExpression</span> <span class="geq">:</span> <span class="nt">MemberExpression</span> <span class="nt">TemplateLiteral</span></div>
+ <ol class="proc">
+ <li>Let <i>tagRef</i> be the result of evaluating <i>MemberExpression</i>.</li>
+ <li>Let <i>thisCall</i> be this <i>MemberExpression</i>.</li>
+ <li>Let <i>tailCall</i> be <a href="#sec-isintailposition">IsInTailPosition</a>(<i>thisCall</i>). (See <a
+ href="#sec-isintailposition">14.6.1</a>)</li>
+ <li>Return <a href="#sec-evaluatecall">EvaluateCall</a>(<i>tagRef</i>, <i>TemplateLiteral</i>, <i>tailCall</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CallExpression</span> <span class="geq">:</span> <span class="nt">CallExpression</span> <span class="nt">TemplateLiteral</span></div>
+ <ol class="proc">
+ <li>Let <i>tagRef</i> be the result of evaluating <i>CallExpression</i>.</li>
+ <li>Let <i>thisCall</i> be this <i>CallExpression</i>.</li>
+ <li>Let <i>tailCall</i> be <a href="#sec-isintailposition">IsInTailPosition</a>(<i>thisCall</i>). (See <a
+ href="#sec-isintailposition">14.6.1</a>)</li>
+ <li>Return <a href="#sec-evaluatecall">EvaluateCall</a>(<i>tagRef</i>, <i>TemplateLiteral</i>, <i>tailCall</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-meta-properties">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.3.8"><a href="#sec-meta-properties" title="link to this section">12.3.8</a></span>
+ Meta Properties</h1>
+ </div>
+
+ <section id="sec-meta-properties-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.3.8.1"><a href="#sec-meta-properties-runtime-semantics-evaluation"
+ title="link to this section">12.3.8.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">NewTarget</span> <span class="geq">:</span> <code class="t">new</code> <code class="t">.</code> <code class="t">target</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-getnewtarget">GetNewTarget</a>().</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-postfix-expressions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.4"><a href="#sec-postfix-expressions" title="link to this section">12.4</a></span>
+ Postfix Expressions</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PostfixExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">++</code></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">--</code></div>
+ </div>
+ </div>
+
+ <section id="sec-postfix-expressions-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.4.1"><a href="#sec-postfix-expressions-static-semantics-early-errors"
+ title="link to this section">12.4.1</a></span> Static Semantics: Early Errors</h1>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PostfixExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">++</code></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">--</code></div>
+ </div>
+
+ <ul>
+ <li>
+ <p>It is an early <a href="#sec-reference-specification-type">Reference</a> Error if <span style="font-family: Times New
+ Roman">IsValidSimpleAssignmentTarget</span> of <span class="nt">LeftHandSideExpression</span> is <span
+ class="value">false</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-postfix-expressions-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.4.2"><a href="#sec-postfix-expressions-static-semantics-isfunctiondefinition"
+ title="link to this section">12.4.2</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PostfixExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">++</code></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">--</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.4.3"><a href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.4.3</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PostfixExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">++</code></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">--</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-postfix-increment-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.4.4"><a href="#sec-postfix-increment-operator"
+ title="link to this section">12.4.4</a></span> Postfix Increment Operator</h1>
+ </div>
+
+ <section id="sec-postfix-increment-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.4.4.1"><a href="#sec-postfix-increment-operator-runtime-semantics-evaluation"
+ title="link to this section">12.4.4.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">PostfixExpression</span> <span class="geq">:</span> <span class="nt">LeftHandSideExpression</span> <code class="t">++</code></div>
+ <ol class="proc">
+ <li>Let <i>lhs</i> be the result of evaluating <i>LeftHandSideExpression</i>.</li>
+ <li>Let <i>oldValue</i> be <a href="#sec-tonumber">ToNumber</a>(<a href="#sec-getvalue">GetValue</a>(<i>lhs</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>oldValue</i>).</li>
+ <li>Let <i>newValue</i> be the result of adding the value <code>1</code> to <i>oldValue</i>, using the same rules as for
+ the <code>+</code> operator (<a href="#sec-applying-the-additive-operators-to-numbers">see 12.7.5</a>).</li>
+ <li>Let <i>status</i> be <a href="#sec-putvalue">PutValue</a>(<i>lhs</i>, <i>newValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>oldValue</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-postfix-decrement-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.4.5"><a href="#sec-postfix-decrement-operator"
+ title="link to this section">12.4.5</a></span> Postfix Decrement Operator</h1>
+ </div>
+
+ <section id="sec-postfix-decrement-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.4.5.1"><a href="#sec-postfix-decrement-operator-runtime-semantics-evaluation"
+ title="link to this section">12.4.5.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">PostfixExpression</span> <span class="geq">:</span> <span class="nt">LeftHandSideExpression</span> <code class="t">--</code></div>
+ <ol class="proc">
+ <li>Let <i>lhs</i> be the result of evaluating <i>LeftHandSideExpression</i>.</li>
+ <li>Let <i>oldValue</i> be <a href="#sec-tonumber">ToNumber</a>(<a href="#sec-getvalue">GetValue</a>(<i>lhs</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>oldValue</i>).</li>
+ <li>Let <i>newValue</i> be the result of subtracting the value <code>1</code> from <i>oldValue</i>, using the same rules
+ as for the <code>-</code> operator (<a href="#sec-applying-the-additive-operators-to-numbers">12.7.5</a>).</li>
+ <li>Let <i>status</i> be <a href="#sec-putvalue">PutValue</a>(<i>lhs</i>, <i>newValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>oldValue</i>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-unary-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5"><a href="#sec-unary-operators" title="link to this section">12.5</a></span> Unary
+ Operators</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnaryExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">PostfixExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">delete</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">void</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">typeof</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">++</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">--</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">~</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">!</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-unary-operators-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.5.1"><a href="#sec-unary-operators-static-semantics-early-errors"
+ title="link to this section">12.5.1</a></span> Static Semantics: Early Errors</h1>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">++</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">--</code> <span class="nt">UnaryExpression</span></div>
+ </div>
+
+ <ul>
+ <li>
+ <p>It is an early <a href="#sec-reference-specification-type">Reference</a> Error if <span style="font-family: Times New
+ Roman">IsValidSimpleAssignmentTarget</span> of <span class="nt">UnaryExpression</span> is <span
+ class="value">false</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-unary-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.5.2"><a href="#sec-unary-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.5.2</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">delete</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">void</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">typeof</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">++</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">--</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">~</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">!</code> <span class="nt">UnaryExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.5.3"><a href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.5.3</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">delete</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">void</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">typeof</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">++</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">--</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">~</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">!</code> <span class="nt">UnaryExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-delete-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.4"><a href="#sec-delete-operator" title="link to this section">12.5.4</a></span> The
+ <code>delete</code> Operator</h1>
+ </div>
+
+ <section id="sec-delete-operator-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.5.4.1"><a href="#sec-delete-operator-static-semantics-early-errors"
+ title="link to this section">12.5.4.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">delete</code> <span class="nt">UnaryExpression</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the <span class="nt">UnaryExpression</span> is contained in <a
+ href="#sec-strict-mode-code">strict code</a> and the derived <span class="nt">UnaryExpression</span> is <span
+ class="prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span></span>
+ <var>IdentifierReference.</var></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if the derived <span class="nt">UnaryExpression</span> is<br> <span style="font-family:
+ Times New Roman"><i>PrimaryExpression : CoverParenthesizedExpressionAndArrowParameterList<br></i></span>and <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span> ultimately derives a phrase that, if used in place
+ of <var>UnaryExpression,</var> would produce a Syntax Error according to these rules. This rule is recursively
+ applied.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The last rule means that expressions such as<br>		<code>delete
+ (((foo)))</code><br>produce early errors because of recursive application of the first rule.</p>
+ </div>
+ </section>
+
+ <section id="sec-delete-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.4.2"><a href="#sec-delete-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.4.2</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">delete</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>ref</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ref</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>ref</i>) is not <a
+ href="#sec-reference-specification-type">Reference</a>, return <b>true</b>.</li>
+ <li>If <a href="#sec-reference-specification-type">IsUnresolvableReference</a>(<i>ref</i>) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-reference-specification-type">IsStrictReference</a>(<i>ref</i>) is <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-reference-specification-type">IsPropertyReference</a>(<i>ref</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-reference-specification-type">IsSuperReference</a>(<i>ref</i>), throw a <b>ReferenceError</b>
+ exception.</li>
+ <li>Let <i>baseObj</i> be <a href="#sec-toobject">ToObject</a>(<a
+ href="#sec-reference-specification-type">GetBase</a>(<i>ref</i>)).</li>
+ <li>Let <i>deleteStatus</i> be <i>baseObj</i>.[[Delete]](<a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>ref</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ <li>If <i>deleteStatus</i> is <b>false</b> and <a
+ href="#sec-reference-specification-type">IsStrictReference</a>(<i>ref</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Return <i>deleteStatus</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>ref</i> is a <a href="#sec-reference-specification-type">Reference</a> to an <a
+ href="#sec-environment-records">Environment Record</a> binding,
+ <ol class="block">
+ <li>Let <i>bindings</i> be <a href="#sec-reference-specification-type">GetBase</a>(<i>ref</i>).</li>
+ <li>Return <i>bindings</i>.DeleteBinding(<a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>ref</i>)).</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When a <code>delete</code> operator occurs within <a href="#sec-strict-mode-code">strict
+ mode code</a>, a <b>SyntaxError</b> exception is thrown if its <i>UnaryExpression</i> is a direct reference to a
+ variable, function argument, or function name. In addition, if a <code>delete</code> operator occurs within <a
+ href="#sec-strict-mode-code">strict mode code</a> and the property to be deleted has the attribute { [[Configurable]]:
+ <b>false</b> }, a <b>TypeError</b> exception is thrown.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-void-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.5"><a href="#sec-void-operator" title="link to this section">12.5.5</a></span> The
+ <code>void</code> Operator</h1>
+ </div>
+
+ <section id="sec-void-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.5.1"><a href="#sec-void-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.5.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">void</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Let <i>status</i> be <a href="#sec-getvalue">GetValue</a>(<i>expr</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <a href="#sec-getvalue">GetValue</a> must be called even though its value is not used
+ because it may have observable side-effects.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-typeof-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.6"><a href="#sec-typeof-operator" title="link to this section">12.5.6</a></span> The
+ <code>typeof</code> Operator</h1>
+ </div>
+
+ <section id="sec-typeof-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.6.1"><a href="#sec-typeof-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.6.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">typeof</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>val</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>val</i>) is <a
+ href="#sec-reference-specification-type">Reference</a>, then
+ <ol class="block">
+ <li>If <a href="#sec-reference-specification-type">IsUnresolvableReference</a>(<i>val</i>) is <b>true</b>, return
+ <code>"undefined"</code>.</li>
+ </ol>
+ </li>
+ <li>Let <i>val</i> be <a href="#sec-getvalue">GetValue</a>(<i>val</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>val</i>).</li>
+ <li>Return a String according to <a href="#table-35">Table 35</a>.</li>
+ </ol>
+
+ <figure>
+ <figcaption><span id="table-35">Table 35</span> — typeof Operator Results</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000"><b>Type of</b> <span style="font-family: Times New Roman">val</span></th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Result</th>
+ </tr>
+ <tr>
+ <td>Undefined</td>
+ <td><code>"undefined"</code></td>
+ </tr>
+ <tr>
+ <td>Null</td>
+ <td><code>"object"</code></td>
+ </tr>
+ <tr>
+ <td>Boolean</td>
+ <td><code>"boolean"</code></td>
+ </tr>
+ <tr>
+ <td>Number</td>
+ <td><code>"number"</code></td>
+ </tr>
+ <tr>
+ <td>String</td>
+ <td><code>"string"</code></td>
+ </tr>
+ <tr>
+ <td>Symbol</td>
+ <td><code>"symbol"</code></td>
+ </tr>
+ <tr>
+ <td>Object (ordinary and does not implement [[Call]])</td>
+ <td><code>"object"</code></td>
+ </tr>
+ <tr>
+ <td>Object (standard exotic and does not implement [[Call]])</td>
+ <td><code>"object"</code></td>
+ </tr>
+ <tr>
+ <td>Object (implements [[Call]])</td>
+ <td><code>"function"</code></td>
+ </tr>
+ <tr>
+ <td>Object (non-standard exotic and does not implement [[Call]])</td>
+ <td>Implementation-defined. Must not be <code>"undefined"</code>, <code>"boolean"</code>, <code>"function"</code>, <code>"number</code>", <code>"symbol"</code>, or <code>"string".</code></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Implementations are discouraged from defining new <code>typeof</code> result values for
+ non-standard exotic objects. If possible <code>"object"</code>should be used for such objects.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-prefix-increment-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.7"><a href="#sec-prefix-increment-operator"
+ title="link to this section">12.5.7</a></span> Prefix Increment Operator</h1>
+ </div>
+
+ <section id="sec-prefix-increment-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.7.1"><a href="#sec-prefix-increment-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.7.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">++</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Let <i>oldValue</i> be <a href="#sec-tonumber">ToNumber</a>(<a href="#sec-getvalue">GetValue</a>(<i>expr</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>oldValue</i>).</li>
+ <li>Let <i>newValue</i> be the result of adding the value <code>1</code> to <i>oldValue</i>, using the same rules as for
+ the <code>+</code> operator (<a href="#sec-applying-the-additive-operators-to-numbers">see 12.7.5</a>).</li>
+ <li>Let <i>status</i> be <a href="#sec-putvalue">PutValue</a>(<i>expr</i>, <i>newValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>newValue</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-prefix-decrement-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.8"><a href="#sec-prefix-decrement-operator"
+ title="link to this section">12.5.8</a></span> Prefix Decrement Operator</h1>
+ </div>
+
+ <section id="sec-prefix-decrement-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.8.1"><a href="#sec-prefix-decrement-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.8.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">--</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Let <i>oldValue</i> be <a href="#sec-tonumber">ToNumber</a>(<a href="#sec-getvalue">GetValue</a>(<i>expr</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>oldValue</i>).</li>
+ <li>Let <i>newValue</i> be the result of subtracting the value <code>1</code> from <i>oldValue</i>, using the same
+ rules as for the <code>-</code> operator (<a href="#sec-applying-the-additive-operators-to-numbers">see
+ 12.7.5</a>).</li>
+ <li>Let <i>status</i> be <a href="#sec-putvalue">PutValue</a>(<i>expr</i>, <i>newValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>newValue</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-unary-plus-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.9"><a href="#sec-unary-plus-operator" title="link to this section">12.5.9</a></span>
+ Unary <code>+</code> Operator</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The unary + operator converts its operand to Number type.</p>
+ </div>
+ </div>
+
+ <section id="sec-unary-plus-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.9.1"><a href="#sec-unary-plus-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.9.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">+</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Return <a href="#sec-tonumber">ToNumber</a>(<a href="#sec-getvalue">GetValue</a>(<i>expr</i>)).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-unary-minus-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.10"><a href="#sec-unary-minus-operator"
+ title="link to this section">12.5.10</a></span> Unary <code>-</code> Operator</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The unary <code>-</code> operator converts its operand to Number type and then negates
+ it. Negating <b>+0</b> produces <b>−0</b>, and negating <b>−0</b> produces <b>+0</b>.</p>
+ </div>
+ </div>
+
+ <section id="sec-unary-minus-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.10.1"><a href="#sec-unary-minus-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.10.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">-</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Let <i>oldValue</i> be <a href="#sec-tonumber">ToNumber</a>(<a href="#sec-getvalue">GetValue</a>(<i>expr</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>oldValue</i>).</li>
+ <li>If <i>oldValue</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return the result of negating <i>oldValue</i>; that is, compute a Number with the same magnitude but opposite
+ sign.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-bitwise-not-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.11"><a href="#sec-bitwise-not-operator"
+ title="link to this section">12.5.11</a></span> Bitwise NOT Operator ( <code>~</code> )</h1>
+ </div>
+
+ <section id="sec-bitwise-not-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.11.1"><a href="#sec-bitwise-not-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.11.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">~</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Let <i>oldValue</i> be <a href="#sec-toint32">ToInt32</a>(<a href="#sec-getvalue">GetValue</a>(<i>expr</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>oldValue</i>).</li>
+ <li>Return the result of applying bitwise complement to <i>oldValue</i>. The result is a signed 32-bit integer.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-logical-not-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.5.12"><a href="#sec-logical-not-operator"
+ title="link to this section">12.5.12</a></span> Logical NOT Operator ( <code>!</code> )</h1>
+ </div>
+
+ <section id="sec-logical-not-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.5.12.1"><a href="#sec-logical-not-operator-runtime-semantics-evaluation"
+ title="link to this section">12.5.12.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">UnaryExpression</span> <span class="geq">:</span> <code class="t">!</code> <span class="nt">UnaryExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Let <i>oldValue</i> be <a href="#sec-toboolean">ToBoolean</a>(<a
+ href="#sec-getvalue">GetValue</a>(<i>expr</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>oldValue</i>).</li>
+ <li>If <i>oldValue</i> is <b>true</b>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-multiplicative-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.6"><a href="#sec-multiplicative-operators" title="link to this section">12.6</a></span>
+ Multiplicative Operators</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiplicativeExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub> <span class="nt">MultiplicativeOperator</span> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiplicativeOperator</span> <span class="geq">:</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">*</code> <code class="t">/</code> <code class="t">%</code></div>
+ </div>
+ </div>
+
+ <section id="sec-multiplicative-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.6.1"><a href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.6.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <p><i>MultiplicativeExpression <b>:</b></i> <i>MultiplicativeExpression</i> <i>MultiplicativeOperator</i>
+ <i>UnaryExpression</i></p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.6.2"><a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.6.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <p><i>MultiplicativeExpression <b>:</b></i> <i>MultiplicativeExpression</i> <i>MultiplicativeOperator</i>
+ <i>UnaryExpression</i></p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-multiplicative-operators-runtime-semantics-evaluation">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.6.3"><a href="#sec-multiplicative-operators-runtime-semantics-evaluation"
+ title="link to this section">12.6.3</a></span> Runtime Semantics: Evaluation</h1>
+
+ <p><i>MultiplicativeExpression <b>:</b></i> <i>MultiplicativeExpression</i> <i>MultiplicativeOperator</i>
+ <i>UnaryExpression</i></p>
+
+ <ol class="proc">
+ <li>Let <i>left</i> be the result of evaluating <i>MultiplicativeExpression</i>.</li>
+ <li>Let <i>leftValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>left</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>leftValue</i>).</li>
+ <li>Let <i>right</i> be the result of evaluating <i>UnaryExpression</i>.</li>
+ <li>Let <i>rightValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>right</i>).</li>
+ <li>Let <i>lnum</i> be <a href="#sec-tonumber">ToNumber</a>(<i>leftValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lnum</i>).</li>
+ <li>Let <i>rnum</i> be <a href="#sec-tonumber">ToNumber</a>(<i>rightValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rnum</i>).</li>
+ <li>Return the result of applying the <i>MultiplicativeOperator</i> (*, /, or %) to <i>lnum</i> and <i>rnum</i> as
+ specified in <a href="#sec-applying-the-mul-operator">12.6.3.1</a>, <a
+ href="#sec-applying-the-div-operator">12.6.3.2</a>, or <a href="#sec-applying-the-mod-operator">12.6.3.3</a>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-applying-the-mul-operator">
+ <h1><span class="secnum" id="sec-12.6.3.1"><a href="#sec-applying-the-mul-operator"
+ title="link to this section">12.6.3.1</a></span> Applying the <code>*</code> Operator</h1>
+
+ <p>The <code>*</code> <span class="nt">MultiplicativeOperator</span> performs multiplication, producing the product of its
+ operands. Multiplication is commutative. Multiplication is not always associative in ECMAScript, because of finite
+ precision.</p>
+
+ <p>The result of a floating-point multiplication is governed by the rules of IEEE 754 binary double-precision
+ arithmetic:</p>
+
+ <ul>
+ <li>
+ <p>If either operand is <b>NaN</b>, the result is <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>The sign of the result is positive if both operands have the same sign, negative if the operands have different
+ signs.</p>
+ </li>
+
+ <li>
+ <p>Multiplication of an infinity by a zero results in <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>Multiplication of an infinity by an infinity results in an infinity. The sign is determined by the rule already
+ stated above.</p>
+ </li>
+
+ <li>
+ <p>Multiplication of an infinity by a finite nonzero value results in a signed infinity. The sign is determined by the
+ rule already stated above.</p>
+ </li>
+
+ <li>
+ <p>In the remaining cases, where neither an infinity nor NaN is involved, the product is computed and rounded to the
+ nearest representable value using IEEE 754 round-to-nearest mode. If the magnitude is too large to represent, the
+ result is then an infinity of appropriate sign. If the magnitude is too small to represent, the result is then a zero
+ of appropriate sign. The ECMAScript language requires support of gradual underflow as defined by IEEE 754.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-applying-the-div-operator">
+ <h1><span class="secnum" id="sec-12.6.3.2"><a href="#sec-applying-the-div-operator"
+ title="link to this section">12.6.3.2</a></span> Applying the <code>/</code> Operator</h1>
+
+ <p>The <code>/</code> <span class="nt">MultiplicativeOperator</span> performs division, producing the quotient of its
+ operands. The left operand is the dividend and the right operand is the divisor. ECMAScript does not perform integer
+ division. The operands and result of all division operations are double-precision floating-point numbers. The result of
+ division is determined by the specification of IEEE 754 arithmetic:</p>
+
+ <ul>
+ <li>
+ <p>If either operand is <b>NaN</b>, the result is <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>The sign of the result is positive if both operands have the same sign, negative if the operands have different
+ signs.</p>
+ </li>
+
+ <li>
+ <p>Division of an infinity by an infinity results in <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>Division of an infinity by a zero results in an infinity. The sign is determined by the rule already stated
+ above.</p>
+ </li>
+
+ <li>
+ <p>Division of an infinity by a nonzero finite value results in a signed infinity. The sign is determined by the rule
+ already stated above.</p>
+ </li>
+
+ <li>
+ <p>Division of a finite value by an infinity results in zero. The sign is determined by the rule already stated
+ above.</p>
+ </li>
+
+ <li>
+ <p>Division of a zero by a zero results in <b>NaN</b>; division of zero by any other finite value results in zero,
+ with the sign determined by the rule already stated above.</p>
+ </li>
+
+ <li>
+ <p>Division of a nonzero finite value by a zero results in a signed infinity. The sign is determined by the rule
+ already stated above.</p>
+ </li>
+
+ <li>
+ <p>In the remaining cases, where neither an infinity, nor a zero, nor <b>NaN</b> is involved, the quotient is computed
+ and rounded to the nearest representable value using IEEE 754 round-to-nearest mode. If the magnitude is too large to
+ represent, the operation overflows; the result is then an infinity of appropriate sign. If the magnitude is too small
+ to represent, the operation underflows and the result is a zero of the appropriate sign. The ECMAScript language
+ requires support of gradual underflow as defined by IEEE 754.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-applying-the-mod-operator">
+ <h1><span class="secnum" id="sec-12.6.3.3"><a href="#sec-applying-the-mod-operator"
+ title="link to this section">12.6.3.3</a></span> Applying the <code>%</code> Operator</h1>
+
+ <p>The <code>%</code> <span class="nt">MultiplicativeOperator</span> yields the remainder of its operands from an implied
+ division; the left operand is the dividend and the right operand is the divisor.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In C and C++, the remainder operator accepts only integral operands; in ECMAScript, it
+ also accepts floating-point operands.</p>
+ </div>
+
+ <p>The result of a floating-point remainder operation as computed by the <code>%</code> operator is not the same as the
+ “remainder” operation defined by IEEE 754. The IEEE 754 “remainder” operation computes the
+ remainder from a rounding division, not a truncating division, and so its behaviour is not analogous to that of the usual
+ integer remainder operator. Instead the ECMAScript language defines <code>%</code> on floating-point operations to behave
+ in a manner analogous to that of the Java integer remainder operator; this may be compared with the C library function
+ fmod.</p>
+
+ <p>The result of an ECMAScript floating-point remainder operation is determined by the rules of IEEE arithmetic:</p>
+
+ <ul>
+ <li>
+ <p>If either operand is <b>NaN</b>, the result is <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>The sign of the result equals the sign of the dividend.</p>
+ </li>
+
+ <li>
+ <p>If the dividend is an infinity, or the divisor is a zero, or both, the result is <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>If the dividend is finite and the divisor is an infinity, the result equals the dividend.</p>
+ </li>
+
+ <li>
+ <p>If the dividend is a zero and the divisor is nonzero and finite, the result is the same as the dividend.</p>
+ </li>
+
+ <li>
+ <p>In the remaining cases, where neither an infinity, nor a zero, nor <b>NaN</b> is involved, the floating-point
+ remainder r from a dividend n and a divisor d is defined by the mathematical relation r = n − (d × q)
+ where q is an integer that is negative only if n/d is negative and positive only if n/d is positive, and whose
+ magnitude is as large as possible without exceeding the magnitude of the true mathematical quotient of n and d. r is
+ computed and rounded to the nearest representable value using IEEE 754 round-to-nearest mode.</p>
+ </li>
+ </ul>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-additive-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.7"><a href="#sec-additive-operators" title="link to this section">12.7</a></span>
+ Additive Operators</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AdditiveExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span><sub>[?Yield]</sub> <code class="t">+</code> <span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span><sub>[?Yield]</sub> <code class="t">-</code> <span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-additive-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.7.1"><a href="#sec-additive-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.7.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AdditiveExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span> <code class="t">+</code> <span class="nt">MultiplicativeExpression</span></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span> <code class="t">-</code> <span class="nt">MultiplicativeExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.7.2"><a href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.7.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AdditiveExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span> <code class="t">+</code> <span class="nt">MultiplicativeExpression</span></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span> <code class="t">-</code> <span class="nt">MultiplicativeExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-addition-operator-plus">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.7.3"><a href="#sec-addition-operator-plus"
+ title="link to this section">12.7.3</a></span> The Addition operator ( <code>+</code> )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The addition operator either performs string concatenation or numeric addition.</p>
+ </div>
+ </div>
+
+ <section id="sec-addition-operator-plus-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.7.3.1"><a href="#sec-addition-operator-plus-runtime-semantics-evaluation"
+ title="link to this section">12.7.3.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">AdditiveExpression</span> <span class="geq">:</span> <span class="nt">AdditiveExpression</span> <code class="t">+</code> <span class="nt">MultiplicativeExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>AdditiveExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>MultiplicativeExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>lprim</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lprim</i>).</li>
+ <li>Let <i>rprim</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>rval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rprim</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>lprim</i>) is String or <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>rprim</i>) is String, then
+ <ol class="block">
+ <li>Let <i>lstr</i> be <a href="#sec-tostring">ToString</a>(<i>lprim</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lstr</i>).</li>
+ <li>Let <i>rstr</i> be <a href="#sec-tostring">ToString</a>(<i>rprim</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rstr</i>).</li>
+ <li>Return the String that is the result of concatenating <i>lstr</i> and <i>rstr.</i></li>
+ </ol>
+ </li>
+ <li>Let <i>lnum</i> be <a href="#sec-tonumber">ToNumber</a>(<i>lprim</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lnum</i>).</li>
+ <li>Let <i>rnum</i> be <a href="#sec-tonumber">ToNumber</a>(<i>rprim</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rnum</i>).</li>
+ <li>Return the result of applying the addition operation to <i>lnum</i> and <i>rnum</i>. See the Note below <a
+ href="#sec-applying-the-additive-operators-to-numbers">12.7.5</a>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> No hint is provided in the calls to <a href="#sec-toprimitive">ToPrimitive</a> in
+ steps 7 and 9. All standard objects except Date objects handle the absence of a hint as if the hint Number were given;
+ Date objects handle the absence of a hint as if the hint String were given. Exotic objects may handle the absence of a
+ hint in some other manner.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Step 11 differs from step 5 of the Abstract Relational Comparison algorithm (<a
+ href="#sec-ispropertykey">7.2.7</a>), by using the logical-or operation instead of the logical-and operation.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-subtraction-operator-minus">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.7.4"><a href="#sec-subtraction-operator-minus"
+ title="link to this section">12.7.4</a></span> The Subtraction Operator ( <code>-</code> )</h1>
+ </div>
+
+ <section id="sec-subtraction-operator-minus-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.7.4.1"><a href="#sec-subtraction-operator-minus-runtime-semantics-evaluation"
+ title="link to this section">12.7.4.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">AdditiveExpression</span> <span class="geq">:</span> <span class="nt">AdditiveExpression</span> <code class="t">-</code> <span class="nt">MultiplicativeExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>AdditiveExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>MultiplicativeExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>lnum</i> be <a href="#sec-tonumber">ToNumber</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lnum</i>).</li>
+ <li>Let <i>rnum</i> be <a href="#sec-tonumber">ToNumber</a>(<i>rval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rnum</i>).</li>
+ <li>Return the result of applying the subtraction operation to <i>lnum</i> and <i>rnum</i>. See the note below <a
+ href="#sec-applying-the-additive-operators-to-numbers">12.7.5</a>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-applying-the-additive-operators-to-numbers">
+ <h1><span class="secnum" id="sec-12.7.5"><a href="#sec-applying-the-additive-operators-to-numbers"
+ title="link to this section">12.7.5</a></span> Applying the Additive Operators to Numbers</h1>
+
+ <p>The <code>+</code> operator performs addition when applied to two operands of numeric type, producing the sum of the
+ operands. The <code>-</code> operator performs subtraction, producing the difference of two numeric operands.</p>
+
+ <p>Addition is a commutative operation, but not always associative.</p>
+
+ <p>The result of an addition is determined using the rules of IEEE 754 binary double-precision arithmetic:</p>
+
+ <ul>
+ <li>
+ <p>If either operand is <b>NaN</b>, the result is <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>The sum of two infinities of opposite sign is <b>NaN</b>.</p>
+ </li>
+
+ <li>
+ <p>The sum of two infinities of the same sign is the infinity of that sign.</p>
+ </li>
+
+ <li>
+ <p>The sum of an infinity and a finite value is equal to the infinite operand.</p>
+ </li>
+
+ <li>
+ <p>The sum of two negative zeroes is <b>−0</b>. The sum of two positive zeroes, or of two zeroes of opposite sign,
+ is <b>+0</b>.</p>
+ </li>
+
+ <li>
+ <p>The sum of a zero and a nonzero finite value is equal to the nonzero operand.</p>
+ </li>
+
+ <li>
+ <p>The sum of two nonzero finite values of the same magnitude and opposite sign is <b>+0</b>.</p>
+ </li>
+
+ <li>
+ <p>In the remaining cases, where neither an infinity, nor a zero, nor NaN is involved, and the operands have the same
+ sign or have different magnitudes, the sum is computed and rounded to the nearest representable value using IEEE 754
+ round-to-nearest mode. If the magnitude is too large to represent, the operation overflows and the result is then an
+ infinity of appropriate sign. The ECMAScript language requires support of gradual underflow as defined by IEEE 754.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>-</code> operator performs subtraction when applied to two operands of numeric
+ type, producing the difference of its operands; the left operand is the minuend and the right operand is the subtrahend.
+ Given numeric operands <i>a</i> and <i>b</i>, it is always the case that <i>a<code>–</code>b</i> produces the same
+ result as <i>a <code>+(–</code>b<code>)</code></i>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-bitwise-shift-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.8"><a href="#sec-bitwise-shift-operators" title="link to this section">12.8</a></span>
+ Bitwise Shift Operators</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ShiftExpression</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub> <code class="t"><<</code> <span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub> <code class="t">>></code> <span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub> <code class="t">>>></code> <span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.8.1"><a href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.8.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ShiftExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t"><<</code> <span class="nt">AdditiveExpression</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t">>></code> <span class="nt">AdditiveExpression</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t">>>></code> <span class="nt">AdditiveExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.8.2"><a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.8.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ShiftExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t"><<</code> <span class="nt">AdditiveExpression</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t">>></code> <span class="nt">AdditiveExpression</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t">>>></code> <span class="nt">AdditiveExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-left-shift-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.8.3"><a href="#sec-left-shift-operator" title="link to this section">12.8.3</a></span>
+ The Left Shift Operator ( <code><<</code> )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Performs a bitwise left shift operation on the left operand by the amount specified by
+ the right operand.</p>
+ </div>
+ </div>
+
+ <section id="sec-left-shift-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.8.3.1"><a href="#sec-left-shift-operator-runtime-semantics-evaluation"
+ title="link to this section">12.8.3.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ShiftExpression</span> <span class="geq">:</span> <span class="nt">ShiftExpression</span> <code class="t"><<</code> <span class="nt">AdditiveExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>AdditiveExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>lnum</i> be <a href="#sec-toint32">ToInt32</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lnum</i>).</li>
+ <li>Let <i>rnum</i> be <a href="#sec-touint32">ToUint32</a>(<i>rval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rnum</i>).</li>
+ <li>Let <i>shiftCount</i> be the result of masking out all but the least significant 5 bits of <i>rnum</i>, that is,
+ compute <i>rnum</i> & 0x1F.</li>
+ <li>Return the result of left shifting <i>lnum</i> by <i>shiftCount</i> bits. The result is a signed 32-bit
+ integer.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-signed-right-shift-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.8.4"><a href="#sec-signed-right-shift-operator"
+ title="link to this section">12.8.4</a></span> The Signed Right Shift Operator ( <code>>></code> )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Performs a sign-filling bitwise right shift operation on the left operand by the amount
+ specified by the right operand.</p>
+ </div>
+ </div>
+
+ <section id="sec-signed-right-shift-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.8.4.1"><a href="#sec-signed-right-shift-operator-runtime-semantics-evaluation"
+ title="link to this section">12.8.4.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ShiftExpression</span> <span class="geq">:</span> <span class="nt">ShiftExpression</span> <code class="t">>></code> <span class="nt">AdditiveExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>AdditiveExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>lnum</i> be <a href="#sec-toint32">ToInt32</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lnum</i>).</li>
+ <li>Let <i>rnum</i> be <a href="#sec-touint32">ToUint32</a>(<i>rval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rnum</i>).</li>
+ <li>Let <i>shiftCount</i> be the result of masking out all but the least significant 5 bits of <i>rnum</i>, that is,
+ compute <i>rnum</i> & 0x1F.</li>
+ <li>Return the result of performing a sign-extending right shift of <i>lnum</i> by <i>shiftCount</i> bits. The most
+ significant bit is propagated. The result is a signed 32-bit integer.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-unsigned-right-shift-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.8.5"><a href="#sec-unsigned-right-shift-operator"
+ title="link to this section">12.8.5</a></span> The Unsigned Right Shift Operator ( <code>>>></code> )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Performs a zero-filling bitwise right shift operation on the left operand by the amount
+ specified by the right operand.</p>
+ </div>
+ </div>
+
+ <section id="sec-unsigned-right-shift-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.8.5.1"><a href="#sec-unsigned-right-shift-operator-runtime-semantics-evaluation"
+ title="link to this section">12.8.5.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ShiftExpression</span> <span class="geq">:</span> <span class="nt">ShiftExpression</span> <code class="t">>>></code> <span class="nt">AdditiveExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>AdditiveExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>lnum</i> be <a href="#sec-touint32">ToUint32</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lnum</i>).</li>
+ <li>Let <i>rnum</i> be <a href="#sec-touint32">ToUint32</a>(<i>rval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rnum</i>).</li>
+ <li>Let <i>shiftCount</i> be the result of masking out all but the least significant 5 bits of <i>rnum</i>, that is,
+ compute <i>rnum</i> & 0x1F.</li>
+ <li>Return the result of performing a zero-filling right shift of <i>lnum</i> by <i>shiftCount</i> bits. Vacated bits
+ are filled with zero. The result is an unsigned 32-bit integer.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-relational-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.9"><a href="#sec-relational-operators" title="link to this section">12.9</a></span>
+ Relational Operators</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The result of evaluating a relational operator is always of type Boolean, reflecting
+ whether the relationship named by the operator holds between its two operands.</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RelationalExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t"><</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t">></code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t"><=</code> <span class="nt">ShiftExpression</span><sub>[? Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t">>=</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t">instanceof</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+In]</span> <span class="nt">RelationalExpression</span><sub>[In, ?Yield]</sub> <code class="t">in</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The [In] grammar parameter is needed to avoid confusing the <code>in</code> operator in a
+ relational expression with the <code>in</code> operator in a <code>for</code> statement.</p>
+ </div>
+ </div>
+
+ <section id="sec-relational-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.9.1"><a href="#sec-relational-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.9.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RelationalExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t"><</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">></code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t"><=</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">>=</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">instanceof</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">in</code> <span class="nt">ShiftExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.9.2"><a href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.9.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RelationalExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t"><</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">></code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t"><=</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">>=</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">instanceof</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">in</code> <span class="nt">ShiftExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-relational-operators-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.9.3"><a href="#sec-relational-operators-runtime-semantics-evaluation"
+ title="link to this section">12.9.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">RelationalExpression</span> <span class="geq">:</span> <span class="nt">RelationalExpression</span> <code class="t"><</code> <span class="nt">ShiftExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li>Let <i>r</i> be the result of performing Abstract Relational Comparison <i>lval</i> < <i>rval</i>. (<a
+ href="#sec-ispropertykey">see 7.2.7</a>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>r</i>).</li>
+ <li>If <i>r</i> is <b>undefined</b>, return <b>false</b>. Otherwise, return <i>r</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">RelationalExpression</span> <span class="geq">:</span> <span class="nt">RelationalExpression</span> <code class="t">></code> <span class="nt">ShiftExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li>Let <i>r</i> be the result of performing Abstract Relational Comparison <i>rval</i> < <i>lval</i> with
+ <i>LeftFirst</i> equal to <b>false</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>r</i>).</li>
+ <li>If <i>r</i> is <b>undefined</b>, return <b>false</b>. Otherwise, return <i>r</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">RelationalExpression</span> <span class="geq">:</span> <span class="nt">RelationalExpression</span> <code class="t"><=</code> <span class="nt">ShiftExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li>Let <i>r</i> be the result of performing Abstract Relational Comparison <i>rval</i> < <i>lval</i> with
+ <i>LeftFirst</i> equal to <b>false</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>r</i>).</li>
+ <li>If <i>r</i> is <b>true</b> or <b>undefined</b>, return <b>false</b>. Otherwise, return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">RelationalExpression</span> <span class="geq">:</span> <span class="nt">RelationalExpression</span> <code class="t">>=</code> <span class="nt">ShiftExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li>Let <i>r</i> be the result of performing Abstract Relational Comparison <i>lval</i> < <i>rval</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>r</i>).</li>
+ <li>If <i>r</i> is <b>true</b> or <b>undefined</b>, return <b>false</b>. Otherwise, return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">RelationalExpression</span> <span class="geq">:</span> <span class="nt">RelationalExpression</span> <code class="t">instanceof</code> <span class="nt">ShiftExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Return <a href="#sec-instanceofoperator">InstanceofOperator</a>(<i>lval</i>, <i>rval</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">RelationalExpression</span> <span class="geq">:</span> <span class="nt">RelationalExpression</span> <code class="t">in</code> <span class="nt">ShiftExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>ShiftExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>rval</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <a href="#sec-hasproperty">HasProperty</a>(<i>rval</i>, <a
+ href="#sec-topropertykey">ToPropertyKey</a>(<i>lval</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-instanceofoperator">
+ <h1><span class="secnum" id="sec-12.9.4"><a href="#sec-instanceofoperator" title="link to this section">12.9.4</a></span>
+ Runtime Semantics: InstanceofOperator(O, C)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">InstanceofOperator(<i>O</i>, <i>C</i>)</span>
+ implements the generic algorithm for determining if an object <var>O</var> inherits from the inheritance path defined by
+ constructor <var>C</var>. This abstract operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>C</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>instOfHandler</i> be <a href="#sec-getmethod">GetMethod</a>(<i>C</i>,@@hasInstance).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>instOfHandler</i>).</li>
+ <li>If <i>instOfHandler</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>instOfHandler</i>, <i>C</i>,
+ «<i>O</i>»)).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>C</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <a href="#sec-ordinaryhasinstance">OrdinaryHasInstance</a>(<i>C</i>, <i>O</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Steps 5 and 6 provide compatibility with previous editions of ECMAScript that did not use
+ a @@hasInstance method to define the <code>instanceof</code> operator semantics. If a function object does not define or
+ inherit @@hasInstance it uses the default <code>instanceof</code> semantics.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-equality-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.10"><a href="#sec-equality-operators" title="link to this section">12.10</a></span>
+ Equality Operators</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The result of evaluating an equality operator is always of type Boolean, reflecting
+ whether the relationship named by the operator holds between its two operands.</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EqualityExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">==</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">!=</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">===</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">!==</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-equality-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.10.1"><a href="#sec-equality-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.10.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EqualityExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">==</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">!=</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">===</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">!==</code> <span class="nt">RelationalExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.10.2"><a href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.10.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EqualityExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">==</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">!=</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">===</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">!==</code> <span class="nt">RelationalExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-equality-operators-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.10.3"><a href="#sec-equality-operators-runtime-semantics-evaluation"
+ title="link to this section">12.10.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">EqualityExpression</span> <span class="geq">:</span> <span class="nt">EqualityExpression</span> <code class="t">==</code> <span class="nt">RelationalExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>EqualityExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Return the result of performing Abstract Equality Comparison <i>rval</i> == <i>lval</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">EqualityExpression</span> <span class="geq">:</span> <span class="nt">EqualityExpression</span> <code class="t">!=</code> <span class="nt">RelationalExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>EqualityExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>r</i> be the result of performing Abstract Equality Comparison <i>rval</i> == <i>lval</i>.</li>
+ <li>If <i>r</i> is <b>true</b>, return <b>false</b>. Otherwise, return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">EqualityExpression</span> <span class="geq">:</span> <span class="nt">EqualityExpression</span> <code class="t">===</code> <span class="nt">RelationalExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>EqualityExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>)</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Return the result of performing Strict Equality Comparison <i>rval</i> === <i>lval</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">EqualityExpression</span> <span class="geq">:</span> <span class="nt">EqualityExpression</span> <code class="t">!==</code> <span class="nt">RelationalExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>EqualityExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>RelationalExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>r</i> be the result of performing Strict Equality Comparison <i>rval</i> === <i>lval</i>.</li>
+ <li>If <i>r</i> is <b>true</b>, return <b>false</b>. Otherwise, return <b>true</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> Given the above definition of equality:</p>
+
+ <ul>
+ <li>String comparison can be forced by: <code>"" + a == "" + b</code>.</li>
+ <li>Numeric comparison can be forced by: <code>+a == +b</code>.</li>
+ <li>Boolean comparison can be forced by: <code>!a == !b</code>.</li>
+ </ul>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The equality operators maintain the following invariants:</p>
+
+ <ul>
+ <li><code>A</code> <code>!=</code> <code>B</code> is equivalent to <code>!(A</code> <code>==</code>
+ <code>B)</code>.</li>
+ <li><code>A</code> <code>==</code> <code>B</code> is equivalent to <code>B</code> <code>==</code> <code>A</code>, except
+ in the order of evaluation of <code>A</code> and <code>B</code>.</li>
+ </ul>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> The equality operator is not always transitive. For example, there might be two distinct
+ String objects, each representing the same String value; each String object would be considered equal to the String value
+ by the <code>==</code> operator, but the two String objects would not be equal to each other. For Example:</p>
+
+ <ul>
+ <li><code>new String("a")</code> <code>==</code> <code>"a"</code> and <code>"a"</code> <code>==</code> <code>new
+ String("a")</code>are both <b>true</b>.</li>
+ <li><code>new String("a")</code> <code>==</code> <code>new String("a")</code> is <b>false</b>.</li>
+ </ul>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 4</span> Comparison of Strings uses a simple equality test on sequences of code unit values.
+ There is no attempt to use the more complex, semantically oriented definitions of character or string equality and
+ collating order defined in the Unicode specification. Therefore Strings values that are canonically equal according to the
+ Unicode standard could test as unequal. In effect this algorithm assumes that both Strings are already in normalized
+ form.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-binary-bitwise-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.11"><a href="#sec-binary-bitwise-operators"
+ title="link to this section">12.11</a></span> Binary Bitwise Operators</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BitwiseANDExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BitwiseANDExpression</span><sub>[?In, ?Yield]</sub> <code class="t">&</code> <span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BitwiseXORExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BitwiseANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BitwiseXORExpression</span><sub>[?In, ?Yield]</sub> <code class="t">^</code> <span class="nt">BitwiseANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BitwiseORExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BitwiseXORExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BitwiseORExpression</span><sub>[?In, ?Yield]</sub> <code class="t">|</code> <span class="nt">BitwiseXORExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.11.1"><a href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.11.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <p><span class="prod"><span class="nt">BitwiseANDExpression</span> <span class="geq">:</span> <span
+ class="nt">BitwiseANDExpression</span> <code class="t">&</code> <span class="nt">EqualityExpression</span></span></p>
+
+ <p><span class="prod"><span class="nt">BitwiseXORExpression</span> <span class="geq">:</span> <span
+ class="nt">BitwiseXORExpression</span> <code class="t">^</code> <span class="nt">BitwiseANDExpression</span></span></p>
+
+ <div class="gp prod"><span class="nt">BitwiseORExpression</span> <span class="geq">:</span> <span class="nt">BitwiseORExpression</span> <code class="t">|</code> <span class="nt">BitwiseXORExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.11.2"><a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.11.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <p><span class="prod"><span class="nt">BitwiseANDExpression</span> <span class="geq">:</span> <span
+ class="nt">BitwiseANDExpression</span> <code class="t">&</code> <span class="nt">EqualityExpression</span></span></p>
+
+ <p><span class="prod"><span class="nt">BitwiseXORExpression</span> <span class="geq">:</span> <span
+ class="nt">BitwiseXORExpression</span> <code class="t">^</code> <span class="nt">BitwiseANDExpression</span></span></p>
+
+ <div class="gp prod"><span class="nt">BitwiseORExpression</span> <span class="geq">:</span> <span class="nt">BitwiseORExpression</span> <code class="t">|</code> <span class="nt">BitwiseXORExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-binary-bitwise-operators-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.11.3"><a href="#sec-binary-bitwise-operators-runtime-semantics-evaluation"
+ title="link to this section">12.11.3</a></span> Runtime Semantics: Evaluation</h1>
+
+ <p>The production <var>A</var> <b>:</b> <i><span style="font-family: Times New Roman">A</span> @ <span style="font-family:
+ Times New Roman">B</span></i>, where @ is one of the bitwise operators in the productions above, is evaluated as
+ follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>A</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>B</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>lnum</i> be <a href="#sec-toint32">ToInt32</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lnum</i>).</li>
+ <li>Let <i>rnum</i> be <a href="#sec-toint32">ToInt32</a>(<i>rval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rnum</i>).</li>
+ <li>Return the result of applying the bitwise operator @ to <i>lnum</i> and <i>rnum</i>. The result is a signed 32 bit
+ integer.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-binary-logical-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.12"><a href="#sec-binary-logical-operators"
+ title="link to this section">12.12</a></span> Binary Logical Operators</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LogicalANDExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BitwiseORExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LogicalANDExpression</span><sub>[?In, ?Yield]</sub> <code class="t">&&</code> <span class="nt">BitwiseORExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LogicalORExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LogicalANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LogicalORExpression</span><sub>[?In, ?Yield]</sub> <code class="t">||</code> <span class="nt">LogicalANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value produced by a <code>&&</code> or <code>||</code> operator is not
+ necessarily of type Boolean. The value produced will always be the value of one of the two operand expressions.</p>
+ </div>
+ </div>
+
+ <section id="sec-binary-logical-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.12.1"><a href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.12.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <p><span class="prod"><span class="nt">LogicalANDExpression</span> <span class="geq">:</span> <span
+ class="nt">LogicalANDExpression</span> <code class="t">&&</code> <span
+ class="nt">BitwiseORExpression</span></span></p>
+
+ <div class="gp prod"><span class="nt">LogicalORExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">||</code> <span class="nt">LogicalANDExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.12.2"><a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.12.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <p><span class="prod"><span class="nt">LogicalANDExpression</span> <span class="geq">:</span> <span
+ class="nt">LogicalANDExpression</span> <code class="t">&&</code> <span
+ class="nt">BitwiseORExpression</span></span></p>
+
+ <div class="gp prod"><span class="nt">LogicalORExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">||</code> <span class="nt">LogicalANDExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-binary-logical-operators-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.12.3"><a href="#sec-binary-logical-operators-runtime-semantics-evaluation"
+ title="link to this section">12.12.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">LogicalANDExpression</span> <span class="geq">:</span> <span class="nt">LogicalANDExpression</span> <code class="t">&&</code> <span class="nt">BitwiseORExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>LogicalANDExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li>Let <i>lbool</i> be <a href="#sec-toboolean">ToBoolean</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lbool</i>).</li>
+ <li>If <i>lbool</i> is <b>false</b>, return <i>lval</i>.</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>BitwiseORExpression</i>.</li>
+ <li>Return <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LogicalORExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">||</code> <span class="nt">LogicalANDExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>LogicalORExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li>Let <i>lbool</i> be <a href="#sec-toboolean">ToBoolean</a>(<i>lval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lbool</i>).</li>
+ <li>If <i>lbool</i> is <b>true</b>, return <i>lval</i>.</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>LogicalANDExpression</i>.</li>
+ <li>Return <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-conditional-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.13"><a href="#sec-conditional-operator" title="link to this section">12.13</a></span>
+ Conditional Operator ( <code>? : )</code></h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ConditionalExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LogicalORExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LogicalORExpression</span><sub>[?In,?Yield]</sub> <code class="t">?</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">:</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The grammar for a <i>ConditionalExpression</i> in ECMAScript is slightly different from
+ that in C and Java, which each allow the second subexpression to be an <i>Expression</i> but restrict the third expression
+ to be a <i>ConditionalExpression</i>. The motivation for this difference in ECMAScript is to allow an assignment
+ expression to be governed by either arm of a conditional and to eliminate the confusing and fairly useless case of a comma
+ expression as the centre expression.</p>
+ </div>
+ </div>
+
+ <section id="sec-conditional-operator-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.13.1"><a href="#sec-conditional-operator-static-semantics-isfunctiondefinition"
+ title="link to this section">12.13.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">ConditionalExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">?</code> <span class="nt">AssignmentExpression</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.13.2"><a href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.13.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ConditionalExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">?</code> <span class="nt">AssignmentExpression</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-conditional-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.13.3"><a href="#sec-conditional-operator-runtime-semantics-evaluation"
+ title="link to this section">12.13.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ConditionalExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">?</code> <span class="nt">AssignmentExpression</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>LogicalORExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-getvalue">GetValue</a>(<i>lref</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>If <i>lval</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>trueRef</i> be the result of evaluating the first <i>AssignmentExpression</i>.</li>
+ <li>Return <a href="#sec-getvalue">GetValue</a>(<i>trueRef</i>).</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>falseRef</i> be the result of evaluating the second <i>AssignmentExpression</i>.</li>
+ <li>Return <a href="#sec-getvalue">GetValue</a>(<i>falseRef</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-assignment-operators">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.14"><a href="#sec-assignment-operators" title="link to this section">12.14</a></span>
+ Assignment Operators</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ConditionalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+Yield]</span> <span class="nt">YieldExpression</span><sub>[?In]</sub></div>
+ <div class="rhs"><span class="nt">ArrowFunction</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <code class="t">=</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="nt">AssignmentOperator</span> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp prod"><span class="nt">AssignmentOperator</span> <span class="geq">:</span> <span class="grhsmod">one of</span></div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>*=</code></td>
+ <td><code>/=</code></td>
+ <td><code>%=</code></td>
+ <td><code>+=</code></td>
+ <td><code>-=</code></td>
+ <td><code><<=</code></td>
+ <td><code>>>=</code></td>
+ <td><code>>>>=</code></td>
+ <td><code>&=</code></td>
+ <td><code>^=</code></td>
+ <td><code>|=</code></td>
+ </tr>
+ </table>
+ </figure>
+ </div>
+
+ <section id="sec-assignment-operators-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.14.1"><a href="#sec-assignment-operators-static-semantics-early-errors"
+ title="link to this section">12.14.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">AssignmentExpression</span> <span class="geq">:</span> <span class="nt">LeftHandSideExpression</span> <code class="t">=</code> <span class="nt">AssignmentExpression</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span class="nt">LeftHandSideExpression</span> is either an <span
+ class="nt">ObjectLiteral</span> or an <span class="nt">ArrayLiteral</span> and the lexical token sequence matched by
+ <span class="nt">LeftHandSideExpression</span> cannot be parsed with no tokens left over using <span
+ class="nt">AssignmentPattern</span> as the goal symbol.</p>
+ </li>
+
+ <li>
+ <p>It is an early <a href="#sec-reference-specification-type">Reference</a> Error if <span
+ class="nt">LeftHandSideExpression</span> is neither an <span class="nt">ObjectLiteral</span> nor an <span
+ class="nt">ArrayLiteral</span> and IsValidSimpleAssignmentTarget of <span class="nt">LeftHandSideExpression</span> is
+ <span class="value">false</span>.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">AssignmentExpression</span> <span class="geq">:</span> <span class="nt">LeftHandSideExpression</span> <span class="nt">AssignmentOperator</span> <span class="nt">AssignmentExpression</span></div>
+ <ul>
+ <li>
+ <p>It is an early <a href="#sec-reference-specification-type">Reference</a> Error if IsValidSimpleAssignmentTarget of
+ <span class="nt">LeftHandSideExpression</span> is <span class="value">false</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-assignment-operators-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.14.2"><a href="#sec-assignment-operators-static-semantics-isfunctiondefinition"
+ title="link to this section">12.14.2</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">AssignmentExpression</span> <span class="geq">:</span> <span class="nt">ArrowFunction</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">YieldExpression</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">=</code> <span class="nt">AssignmentExpression</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <span class="nt">AssignmentOperator</span> <span class="nt">AssignmentExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.14.3"><a href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.14.3</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">12.15.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">YieldExpression</span></div>
+ <div class="rhs"><span class="nt">ArrowFunction</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">=</code> <span class="nt">AssignmentExpression</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <span class="nt">AssignmentOperator</span> <span class="nt">AssignmentExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-assignment-operators-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.14.4"><a href="#sec-assignment-operators-runtime-semantics-evaluation"
+ title="link to this section">12.14.4</a></span> Runtime Semantics: Evaluation</h1>
+
+ <p><span class="nt">AssignmentExpression</span><sub>[In, Yield]</sub> <b>:</b> <span
+ class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <code>=</code> <span
+ class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></p>
+
+ <ol class="proc">
+ <li>If <i>LeftHandSideExpression</i> is neither an <i>ObjectLiteral</i> nor an <i>ArrayLiteral</i>, then
+ <ol class="block">
+ <li>Let <i>lref</i> be the result of evaluating <i>LeftHandSideExpression</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lref</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>AssignmentExpression)</i> and
+ IsIdentifierRef of <i>LeftHandSideExpression</i> are both <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>rval</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>rval</i>, <a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>lref</i>)).</li>
+ </ol>
+ </li>
+ <li>Let <i>status</i> be <a href="#sec-putvalue">PutValue</a>(<i>lref</i>, <i>rval</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>rval</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>assignmentPattern</i> be the parse of the source text corresponding to <i>LeftHandSideExpression</i> using
+ <i>AssignmentPattern</i><sub>[?Yield]</sub> as the goal symbol.</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>status</i> be the result of performing DestructuringAssignmentEvaluation of <i>assignmentPattern</i> using
+ <i>rval</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>rval</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">AssignmentExpression</span> <span class="geq">:</span> <span class="nt">LeftHandSideExpression</span> <span class="nt">AssignmentOperator</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>LeftHandSideExpression</i>.</li>
+ <li>Let <i>lval</i> be <a href="#sec-getvalue">GetValue</a>(<i>lref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lval</i>).</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Let <i>op</i> be the <code>@</code> where <i>AssignmentOperator</i> is <code>@=</code></li>
+ <li>Let <i>r</i> be the result of applying <i>op</i> to <i>lval</i> and <i>rval</i> as if evaluating the expression
+ <i>lval</i> <i>op</i> <i>rval</i>.</li>
+ <li>Let <i>status</i> be <a href="#sec-putvalue">PutValue</a>(<i>lref</i>, <i>r</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>r</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When an assignment occurs within <a href="#sec-strict-mode-code">strict mode code</a>, it
+ is an runtime error if <i>lref</i> in step 1.f.of the first algorithm or step 9 of the second algorithm it is an
+ unresolvable reference. If it is, a <b>ReferenceError</b> exception is thrown. The <i>LeftHandSide</i> also may not be a
+ reference to a data property with the attribute value {[[Writable]]:<b>false</b>}, to an accessor property with the
+ attribute value {[[Set]]:<b>undefined</b>}, nor to a non-existent property of an object for which the <a
+ href="#sec-isextensible-o">IsExtensible</a> predicate returns the value <b>false</b>. In these cases a <b>TypeError</b>
+ exception is thrown.</p>
+ </div>
+ </section>
+
+ <section id="sec-destructuring-assignment">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.14.5"><a href="#sec-destructuring-assignment"
+ title="link to this section">12.14.5</a></span> Destructuring Assignment</h1>
+ <h2>Supplemental Syntax</h2>
+
+ <p>In certain circumstances when processing the production <span class="prod"><span class="nt">AssignmentExpression</span>
+ <span class="geq">:</span> <span class="nt">LeftHandSideExpression</span> <code class="t">=</code> <span
+ class="nt">AssignmentExpression</span></span> the following grammar is used to refine the interpretation of <span
+ class="nt">LeftHandSideExpression</span>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentPattern</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ObjectAssignmentPattern</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ArrayAssignmentPattern</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ObjectAssignmentPattern</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">AssignmentPropertyList</span><sub>[?Yield]</sub> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">AssignmentPropertyList</span><sub>[?Yield]</sub> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArrayAssignmentPattern</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentRestElement</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">AssignmentElementList</span><sub>[?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">AssignmentElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentRestElement</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentPropertyList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AssignmentProperty</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">AssignmentPropertyList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">AssignmentProperty</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentElementList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AssignmentElisionElement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">AssignmentElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">AssignmentElisionElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentElisionElement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentProperty</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In,?Yield]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">AssignmentElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentElement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">DestructuringAssignmentTarget</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In,?Yield]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentRestElement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">...</code> <span class="nt">DestructuringAssignmentTarget</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DestructuringAssignmentTarget</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-destructuring-assignment-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-12.14.5.1"><a href="#sec-destructuring-assignment-static-semantics-early-errors"
+ title="link to this section">12.14.5.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">AssignmentProperty</span> <span class="geq">:</span> <span class="nt">IdentifierReference</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if IsValidSimpleAssignmentTarget of <span class="nt">IdentifierReference</span> is <span
+ class="value">false</span>.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">DestructuringAssignmentTarget</span> <span class="geq">:</span> <span class="nt">LeftHandSideExpression</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span class="nt">LeftHandSideExpression</span> is either an <span
+ class="nt">ObjectLiteral</span> or an <span class="nt">ArrayLiteral</span> and if the lexical token sequence matched
+ by <span class="nt">LeftHandSideExpression</span> cannot be parsed with no tokens left over using <span
+ class="nt">AssignmentPattern</span> as the goal symbol.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <span class="nt">LeftHandSideExpression</span> is neither an <span
+ class="nt">ObjectLiteral</span> nor an <span class="nt">ArrayLiteral</span> and <span style="font-family: Times New
+ Roman">IsValidSimpleAssignmentTarget</span>(<span class="nt">LeftHandSideExpression</span>) is <span
+ class="value">false</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-runtime-semantics-destructuringassignmentevaluation">
+ <h1><span class="secnum" id="sec-12.14.5.2"><a href="#sec-runtime-semantics-destructuringassignmentevaluation"
+ title="link to this section">12.14.5.2</a></span> Runtime Semantics: DestructuringAssignmentEvaluation</h1>
+
+ <p>with parameter <var>value</var></p>
+
+ <div class="gp prod"><span class="nt">ObjectAssignmentPattern</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>valid</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayAssignmentPattern</span> <span class="geq">:</span> <code class="t">[</code> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Return <a href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>)).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayAssignmentPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <i>iterator</i>, [[done]]: <b>false</b>}.</li>
+ <li>Let <i>result</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>result</i>).</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayAssignmentPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentRestElement</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <i>iterator</i>, [[done]]: <b>false</b>}.</li>
+ <li>If <i>Elision</i> is present, then
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>status</i>).</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>result</i> be the result of performing IteratorDestructuringAssignmentEvaluation of
+ <i>AssignmentRestElement</i> with <i>iteratorRecord</i> as the argument.</li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>result</i>).</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayAssignmentPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">AssignmentElementList</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <i>iterator</i>, [[done]]: <b>false</b>}.</li>
+ <li>Let <i>result</i> be the result of performing IteratorDestructuringAssignmentEvaluation of
+ <i>AssignmentElementList</i> using <i>iteratorRecord</i> as the argument.</li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>result</i>).</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayAssignmentPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">AssignmentElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentRestElement</span><sub>opt</sub> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <i>iterator</i>, [[done]]: <b>false</b>}.</li>
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of
+ <i>AssignmentElementList</i> using <i>iteratorRecord</i> as the argument.</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>status</i>).</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>Elision</i> is present, then
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>status</i>).</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>AssignmentRestElement</i> is present, then
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of
+ <i>AssignmentRestElement</i> with <i>iteratorRecord</i> as the argument.</li>
+ </ol>
+ </li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>status</i>).</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">AssignmentPropertyList</span> <span class="geq">:</span> <span class="nt">AssignmentPropertyList</span> <code class="t">,</code> <span class="nt">AssignmentProperty</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing DestructuringAssignmentEvaluation for <i>AssignmentPropertyList</i>
+ using <i>value</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing DestructuringAssignmentEvaluation for <i>AssignmentProperty</i> using <i>value</i>
+ as the argument.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">AssignmentProperty</span> <span class="geq">:</span> <span class="nt">IdentifierReference</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Let <i>P</i> be StringValue of <i>IdentifierReference</i>.</li>
+ <li>Let <i>lref</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(<i>P)</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>Let <i>v</i> be <a href="#sec-getv">GetV</a>(<i>value</i>, <i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <i>Initializer</i><sub>opt</sub> is present and <i>v</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>defaultValue</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>v</i> be <a href="#sec-getvalue">GetValue</a>(<i>defaultValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>Initializer</i>) is
+ <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>v</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>v</i>, <i>P</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-putvalue">PutValue</a>(<i>lref</i>,<i>v</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">AssignmentProperty</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">AssignmentElement</span></div>
+ <ol class="proc">
+ <li>Let <i>name</i> be the result of evaluating <i>PropertyName</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>name</i>).</li>
+ <li>Return the result of performing KeyedDestructuringAssignmentEvaluation of <i>AssignmentElement</i> with <i>value</i>
+ and <i>name</i> as the arguments.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-iteratordestructuringassignmentevaluation">
+ <h1><span class="secnum" id="sec-12.14.5.3"><a href="#sec-runtime-semantics-iteratordestructuringassignmentevaluation"
+ title="link to this section">12.14.5.3</a></span> Runtime Semantics: IteratorDestructuringAssignmentEvaluation</h1>
+
+ <p>with parameters <var>iteratorRecord</var></p>
+
+ <div class="gp prod"><span class="nt">AssignmentElementList</span> <span class="geq">:</span> <span class="nt">AssignmentElisionElement</span></div>
+ <ol class="proc">
+ <li>Return the result of performing IteratorDestructuringAssignmentEvaluation of <i>AssignmentElisionElement</i> using
+ <i>iteratorRecord</i> as the <i>argument</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">AssignmentElementList</span> <span class="geq">:</span> <span class="nt">AssignmentElementList</span> <code class="t">,</code> <span class="nt">AssignmentElisionElement</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of
+ <i>AssignmentElementList</i> using <i>iteratorRecord</i> as the <i>argument.</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing IteratorDestructuringAssignmentEvaluation of <i>AssignmentElisionElement</i> using
+ <i>iteratorRecord</i> as the <i>argument</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">AssignmentElisionElement</span> <span class="geq">:</span> <span class="nt">AssignmentElement</span></div>
+ <ol class="proc">
+ <li><i>R</i>eturn the result of performing IteratorDestructuringAssignmentEvaluation of <i>AssignmentElement</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">AssignmentElisionElement</span> <span class="geq">:</span> <span class="nt">Elision</span> <span class="nt">AssignmentElement</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing IteratorDestructuringAssignmentEvaluation of <i>AssignmentElement</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Elision</span> <span class="geq">:</span> <code class="t">,</code></div>
+ <ol class="proc">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Elision</span> <span class="geq">:</span> <span class="nt">Elision</span> <code class="t">,</code></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+
+ <p><span class="nt">AssignmentElement</span><sub>[Yield]</sub> <b>:</b> <span
+ class="nt">DestructuringAssignmentTarget</span> <span class="nt">Initializer</span><sub>opt</sub></p>
+
+ <ol class="proc">
+ <li>If <i>DestructuringAssignmentTarget</i> is neither an <i>ObjectLiteral</i> nor an <i>ArrayLiteral</i>, then
+ <ol class="block">
+ <li>Let <i>lref</i> be the result of evaluating <i>DestructuringAssignmentTarget</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lref</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>value</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>true</b>, let <i>value</i> be <b>undefined</b>.</li>
+ <li>If <i>Initializer</i> is present and <i>value</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>defaultValue</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>v</i> be <a href="#sec-getvalue">GetValue</a>(<i>defaultValue</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ </ol>
+ </li>
+ <li>Else, let <i>v</i> be <i>value</i>.</li>
+ <li>If <i>DestructuringAssignmentTarget</i> is an <i>ObjectLiteral or an ArrayLiteral</i>, then
+ <ol class="block">
+ <li>Let <i>nestedAssignmentPattern</i> be the parse of the source text corresponding to
+ <i>DestructuringAssignmentTarget</i> using either <i>AssignmentPattern</i> or
+ <i>AssignmentPattern</i><sub>[Yield]</sub> as the goal symbol depending upon whether this
+ <i>AssignmentElement</i> has the <span style="font-family: sans-serif"><sub>Yield</sub></span> parameter.</li>
+ <li>Return the result of performing DestructuringAssignmentEvaluation of <i>nestedAssignmentPattern</i> with
+ <i>v</i> as the argument.</li>
+ </ol>
+ </li>
+ <li>If <i>Initializer</i> is present and <i>value</i> is <b>undefined</b> and <a
+ href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>Initializer)</i> and IsIdentifierRef
+ of <i>DestructuringAssignmentTarget</i> are both <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>v</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>v</i>,
+ <a href="#sec-reference-specification-type">GetReferencedName</a>(<i>lref</i>)).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-putvalue">PutValue</a>(<i>lref</i>, <i>v</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Left to right evaluation order is maintained by evaluating a
+ <i>DestructuringAssignmentTarget</i> that is not a destructuring pattern prior to accessing the iterator or evaluating
+ the <i>Initializer</i>.</p>
+ </div>
+
+ <p><i>AssignmentRestElement</i><span style="font-family: sans-serif"><sub>[Yield]</sub> <b>:</b></span> <code>...</code>
+ <i>DestructuringAssignmentTarget</i></p>
+
+ <ol class="proc">
+ <li>If <i>DestructuringAssignmentTarget</i> is neither an <i>ObjectLiteral</i> nor an <i>ArrayLiteral</i>, then
+ <ol class="block">
+ <li>Let <i>lref</i> be the result of evaluating <i>DestructuringAssignmentTarget</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lref</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>n</i>=0;</li>
+ <li>Repeat while <i>iteratorRecord</i>.[[done]] is <b>false,</b>
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li>else,
+ <ol class="block">
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>nextValue</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>), <i>nextValue</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is <b>true</b>.</li>
+ <li>Increment <i>n</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>DestructuringAssignmentTarget</i> is neither an <i>ObjectLiteral</i> nor an <i>ArrayLiteral</i>, then
+ <ol class="block">
+ <li>Return <a href="#sec-putvalue">PutValue</a>(<i>lref</i>, <i>A</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>nestedAssignmentPattern</i> be the parse of the source text corresponding to
+ <i>DestructuringAssignmentTarget</i> using either <i>AssignmentPattern</i> or
+ <i>AssignmentPattern</i><sub>[Yield]</sub> as the goal symbol depending upon whether this <i>AssignmentElement</i>
+ has the <span style="font-family: sans-serif"><sub>Yield</sub></span> parameter.</li>
+ <li>Return the result of performing DestructuringAssignmentEvaluation of <i>nestedAssignmentPattern</i> with <i>A</i> as
+ the argument.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-keyeddestructuringassignmentevaluation">
+ <h1><span class="secnum" id="sec-12.14.5.4"><a href="#sec-runtime-semantics-keyeddestructuringassignmentevaluation"
+ title="link to this section">12.14.5.4</a></span> Runtime Semantics: KeyedDestructuringAssignmentEvaluation</h1>
+
+ <p>with parameters <var>value</var> and <var>propertyName</var></p>
+
+ <p><span style="font-family: Times New Roman"><i>AssignmentElement<sub>[Yield]</sub></i></span> <b>:</b> <span
+ class="nt">DestructuringAssignmentTarget</span> <span class="nt">Initializer</span><sub>opt</sub></p>
+
+ <ol class="proc">
+ <li>If <i>DestructuringAssignmentTarget</i> is neither an <i>ObjectLiteral</i> nor an <i>ArrayLiteral</i>, then
+ <ol class="block">
+ <li>Let <i>lref</i> be the result of evaluating <i>DestructuringAssignmentTarget</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lref</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>v</i> be <a href="#sec-getv">GetV</a>(<i>value</i>, <i>propertyName</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <i>Initializer</i> is present and <i>v</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>defaultValue</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>rhsValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>defaultValue</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rhsValue</i>).</li>
+ </ol>
+ </li>
+ <li>Else, let <i>rhsValue</i> be <i>v</i>.</li>
+ <li>If <i>DestructuringAssignmentTarget</i> is an <i>ObjectLiteral or an ArrayLiteral</i>, then
+ <ol class="block">
+ <li>Let <i>assignmentPattern</i> be the parse of the source text corresponding to
+ <i>DestructuringAssignmentTarget</i> using either <i>AssignmentPattern</i> or
+ <i>AssignmentPattern</i><sub>[Yield]</sub> as the goal symbol depending upon whether this
+ <i>AssignmentElement</i> has the <span style="font-family: sans-serif"><sub>Yield</sub></span> parameter.</li>
+ <li>Return the result of performing DestructuringAssignmentEvaluation of <i>assignmentPattern</i> with
+ <i>rhsValue</i> as the argument.</li>
+ </ol>
+ </li>
+ <li>If <i>Initializer</i> is present and <i>v</i> is <b>undefined</b> and <a
+ href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>Initializer)</i> and IsIdentifierRef
+ of <i>DestructuringAssignmentTarget</i> are both <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>rhsValue</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>rhsValue</i>, <a
+ href="#sec-reference-specification-type">GetReferencedName</a>(<i>lref</i>)).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-putvalue">PutValue</a>(<i>lref</i>, <i>rhsValue</i>).</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-comma-operator">
+ <div class="front">
+ <h1><span class="secnum" id="sec-12.15"><a href="#sec-comma-operator" title="link to this section">12.15</a></span> Comma
+ Operator ( <code>, )</code></h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Expression</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">Expression</span><sub>[?In, ?Yield]</sub> <code class="t">,</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-comma-operator-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-12.15.1"><a href="#sec-comma-operator-static-semantics-isfunctiondefinition"
+ title="link to this section">12.15.1</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">Expression</span> <span class="geq">:</span> <span class="nt">Expression</span> <code class="t">,</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget">
+ <h1><span class="secnum" id="sec-12.15.2"><a href="#sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget"
+ title="link to this section">12.15.2</a></span> Static Semantics: IsValidSimpleAssignmentTarget</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-isvalidsimpleassignmenttarget">12.1.3</a>, <a
+ href="#sec-semantics-static-semantics-isidentifierref">12.2.0.3</a>, <a
+ href="#sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget">12.2.9.3</a>, <a
+ href="#sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget">12.3.1.5</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isvalidsimpleassignmenttarget">12.4.3</a>, <a
+ href="#sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget">12.5.3</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget">12.6.2</a>, <a
+ href="#sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget">12.7.2</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget">12.8.2</a>, <a
+ href="#sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget">12.9.2</a>, <a
+ href="#sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget">12.10.2</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget">12.11.2</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget">12.12.2</a>, <a
+ href="#sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget">12.13.2</a>, <a
+ href="#sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget">12.14.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">Expression</span> <span class="geq">:</span> <span class="nt">Expression</span> <code class="t">,</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-comma-operator-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-12.15.3"><a href="#sec-comma-operator-runtime-semantics-evaluation"
+ title="link to this section">12.15.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">Expression</span> <span class="geq">:</span> <span class="nt">Expression</span> <code class="t">,</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>lref</i> be the result of evaluating <i>Expression</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<a href="#sec-getvalue">GetValue</a>(<i>lref</i>))</li>
+ <li>Let <i>rref</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Return <a href="#sec-getvalue">GetValue</a>(<i>rref</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <a href="#sec-getvalue">GetValue</a> must be called even though its value is not used
+ because it may have observable side-effects.</p>
+ </div>
+ </section>
+ </section>
+</section>
+
+<section id="sec-ecmascript-language-statements-and-declarations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13"><a href="#sec-ecmascript-language-statements-and-declarations"
+ title="link to this section">13</a></span> ECMAScript Language: Statements and Declarations</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Statement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BlockStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">VariableStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">IfStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">BreakableStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">ContinueStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BreakStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+Return]</span> <span class="nt">ReturnStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">WithStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">LabelledStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">TryStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Declaration</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">HoistableDeclaration</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ClassDeclaration</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LexicalDeclaration</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">HoistableDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FunctionDeclaration</span><sub>[?Yield,?Default]</sub></div>
+ <div class="rhs"><span class="nt">GeneratorDeclaration</span><sub>[?Yield, ?Default]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BreakableStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IterationStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">SwitchStatement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-statement-semantics">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.0"><a href="#sec-statement-semantics" title="link to this section">13.0</a></span>
+ Statement Semantics</h1>
+ </div>
+
+ <section id="sec-statement-semantics-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.0.1"><a href="#sec-statement-semantics-static-semantics-containsduplicatelabels"
+ title="link to this section">13.0.1</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Statement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">VariableStatement</span></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ <div class="rhs"><span class="nt">ContinueStatement</span></div>
+ <div class="rhs"><span class="nt">BreakStatement</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-statement-semantics-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.0.2"><a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.0.2</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Statement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">VariableStatement</span></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ <div class="rhs"><span class="nt">ContinueStatement</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.0.3"><a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.0.3</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Statement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">VariableStatement</span></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ <div class="rhs"><span class="nt">BreakStatement</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BreakableStatement</span> <span class="geq">:</span> <span class="nt">IterationStatement</span></div>
+ <ol class="proc">
+ <li>Let <i>newIterationSet</i> be a copy of <i>iterationSet</i> with all the elements of <i>labelSet</i> appended.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>IterationStatement</i> with arguments <i>newIterationSet</i> and «
+ ».</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-declarationpart">
+ <h1><span class="secnum" id="sec-13.0.4"><a href="#sec-static-semantics-declarationpart"
+ title="link to this section">13.0.4</a></span> Static Semantics: DeclarationPart</h1>
+ <div class="gp prod"><span class="nt">HoistableDeclaration</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <i>FunctionDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">HoistableDeclaration</span> <span class="geq">:</span> <span class="nt">GeneratorDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <i>GeneratorDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span class="nt">ClassDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <i>ClassDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span class="nt">LexicalDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <i>LexicalDeclaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-statement-semantics-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.0.5"><a href="#sec-statement-semantics-static-semantics-vardeclarednames"
+ title="link to this section">13.0.5</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Statement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ <div class="rhs"><span class="nt">ContinueStatement</span></div>
+ <div class="rhs"><span class="nt">BreakStatement</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-statement-semantics-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.0.6"><a href="#sec-statement-semantics-static-semantics-varscopeddeclarations"
+ title="link to this section">13.0.6</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Statement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ <div class="rhs"><span class="nt">ContinueStatement</span></div>
+ <div class="rhs"><span class="nt">BreakStatement</span></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-statement-semantics-runtime-semantics-labelledevaluation">
+ <h1><span class="secnum" id="sec-13.0.7"><a href="#sec-statement-semantics-runtime-semantics-labelledevaluation"
+ title="link to this section">13.0.7</a></span> Runtime Semantics: LabelledEvaluation</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-do-while-statement-runtime-semantics-labelledevaluation">13.6.1.6</a>, <a
+ href="#sec-while-statement-runtime-semantics-labelledevaluation">13.6.2.6</a>, <a
+ href="#sec-for-statement-runtime-semantics-labelledevaluation">13.6.3.7</a>, <a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-labelledevaluation">13.6.4.11</a>, <a
+ href="#sec-labelled-statements-runtime-semantics-labelledevaluation">13.12.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">BreakableStatement</span> <span class="geq">:</span> <span class="nt">IterationStatement</span></div>
+ <ol class="proc">
+ <li>Let <i>stmtResult</i> be the result of performing LabelledEvaluation of <i>IterationStatement</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>stmtResult</i>.[[type]] is <span style="font-family: sans-serif">break</span>, then
+ <ol class="block">
+ <li>If <i>stmtResult</i>.[[target]] is <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>If <i>stmtResult</i>.[[value]] is <span style="font-family: sans-serif">empty</span>, let <i>stmtResult</i> be
+ <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>Else, let <i>stmtResult</i> be <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>stmtResult</i>.[[value]]).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>stmtResult</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BreakableStatement</span> <span class="geq">:</span> <span class="nt">SwitchStatement</span></div>
+ <ol class="proc">
+ <li>Let <i>stmtResult</i> be the result of evaluating <i>SwitchStatement</i>.</li>
+ <li>If <i>stmtResult</i>.[[type]] is <span style="font-family: sans-serif">break</span>, then
+ <ol class="block">
+ <li>If <i>stmtResult</i>.[[target]] is <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>If <i>stmtResult</i>.[[value]] is <span style="font-family: sans-serif">empty</span>, let <i>stmtResult</i> be
+ <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>Else, let <i>stmtResult</i> be <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>stmtResult</i>.[[value]]).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>stmtResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A <i>BreakableStatement</i> is one that can be exited via an unlabelled
+ <i>BreakStatement.</i></p>
+ </div>
+ </section>
+
+ <section id="sec-statement-semantics-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.0.8"><a href="#sec-statement-semantics-runtime-semantics-evaluation"
+ title="link to this section">13.0.8</a></span> Runtime Semantics: Evaluation</h1>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">HoistableDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FunctionDeclaration</span></div>
+ <div class="rhs"><span class="nt">GeneratorDeclaration</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BreakableStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IterationStatement</span></div>
+ <div class="rhs"><span class="nt">SwitchStatement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Let <i>newLabelSet</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return the result of performing LabelledEvaluation of this <i>BreakableStatement</i> with argument
+ <i>newLabelSet</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-block">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.1"><a href="#sec-block" title="link to this section">13.1</a></span> Block</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BlockStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Block</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Block</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementList</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">StatementListItem</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub> <span class="nt">StatementListItem</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StatementListItem</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">Declaration</span><sub>[?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-block-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.1.1"><a href="#sec-block-static-semantics-early-errors"
+ title="link to this section">13.1.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">StatementList</span> <code class="t">}</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the LexicallyDeclaredNames of <span class="nt">StatementList</span> contains any duplicate
+ entries.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the LexicallyDeclaredNames of <span class="nt">StatementList</span> also
+ occurs in the VarDeclaredNames of <span class="nt">StatementList</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-block-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.1.2"><a href="#sec-block-static-semantics-containsduplicatelabels"
+ title="link to this section">13.1.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>StatementList</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsDuplicateLabels of <i>StatementListItem</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.1.3"><a href="#sec-block-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.1.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>StatementList</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>StatementListItem</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.1.4"><a href="#sec-block-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.1.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>StatementList</i> with arguments
+ <i>iterationSet</i> and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>StatementListItem</i> with arguments <i>iterationSet</i> and
+ « ».</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-lexicallydeclarednames">
+ <h1><span class="secnum" id="sec-13.1.5"><a href="#sec-block-static-semantics-lexicallydeclarednames"
+ title="link to this section">13.1.5</a></span> Static Semantics: LexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-switch-statement-static-semantics-lexicallydeclarednames">13.11.5</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallydeclarednames">13.12.6</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallydeclarednames">14.1.14</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">14.2.10</a>, <a
+ href="#sec-scripts-static-semantics-lexicallydeclarednames">15.1.3</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallydeclarednames">15.2.1.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be LexicallyDeclaredNames of <i>StatementList</i>.</li>
+ <li>Append to <i>names</i> the elements of the LexicallyDeclaredNames of <i>StatementListItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If <i>Statement</i> is <span class="prod"><span class="nt">Statement</span> <span class="geq">:</span> <span
+ class="nt">LabelledStatement</span></span> , return LexicallyDeclaredNames of <i>Statement</i>.</li>
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>Declaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-lexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.1.6"><a href="#sec-block-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">13.1.6</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a>, <a
+ href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations">15.2.1.12</a>, <a
+ href="#sec-exports-static-semantics-lexicallyscopeddeclarations">15.2.3.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be LexicallyScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the LexicallyScopedDeclarations of <i>StatementListItem.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If <i>Statement</i> is <span class="prod"><span class="nt">Statement</span> <span class="geq">:</span> <span
+ class="nt">LabelledStatement</span></span> , return LexicallyScopedDeclarations of <i>Statement</i>.</li>
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing DeclarationPart of
+ <i>Declaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-toplevellexicallydeclarednames">
+ <h1><span class="secnum" id="sec-13.1.7"><a href="#sec-block-static-semantics-toplevellexicallydeclarednames"
+ title="link to this section">13.1.7</a></span> Static Semantics: TopLevelLexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-labelled-statements-static-semantics-toplevellexicallydeclarednames">13.12.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be TopLevelLexicallyDeclaredNames of <i>StatementList</i>.</li>
+ <li>Append to <i>names</i> the elements of the TopLevelLexicallyDeclaredNames of <i>StatementListItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">FunctionDeclaration</span></span> , return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">GeneratorDeclaration</span></span> , return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return the BoundNames of <i>Declaration</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> At the top level of a function, or script, function declarations are treated like var
+ declarations rather than like lexical declarations.</p>
+ </div>
+ </section>
+
+ <section id="sec-block-static-semantics-toplevellexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.1.8"><a href="#sec-block-static-semantics-toplevellexicallyscopeddeclarations"
+ title="link to this section">13.1.8</a></span> Static Semantics: TopLevelLexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-labelled-statements-static-semantics-toplevellexicallyscopeddeclarations">13.12.9</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be TopLevelLexicallyScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the TopLevelLexicallyScopedDeclarations of
+ <i>StatementListItem.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">FunctionDeclaration</span></span> , return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">GeneratorDeclaration</span></span> , return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>Declaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-toplevelvardeclarednames">
+ <h1><span class="secnum" id="sec-13.1.9"><a href="#sec-block-static-semantics-toplevelvardeclarednames"
+ title="link to this section">13.1.9</a></span> Static Semantics: TopLevelVarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-labelled-statements-static-semantics-toplevelvardeclarednames">13.12.10</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be TopLevelVarDeclaredNames of <i>StatementList</i>.</li>
+ <li>Append to <i>names</i> the elements of the TopLevelVarDeclaredNames of <i>StatementListItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">FunctionDeclaration</span></span> , return the BoundNames of <i>Declaration</i>.</li>
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">GeneratorDeclaration</span></span> , return the BoundNames of <i>Declaration</i>.</li>
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If <i>Statement</i> is <span class="prod"><span class="nt">Statement</span> <span class="geq">:</span> <span
+ class="nt">LabelledStatement</span></span> , return TopLevelVarDeclaredNames of <i>Statement</i>.</li>
+ <li>Return VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> At the top level of a function or script, inner function declarations are treated like var
+ declarations.</p>
+ </div>
+ </section>
+
+ <section id="sec-block-static-semantics-toplevelvarscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.1.10"><a href="#sec-block-static-semantics-toplevelvarscopeddeclarations"
+ title="link to this section">13.1.10</a></span> Static Semantics: TopLevelVarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-labelled-statements-static-semantics-toplevelvarscopeddeclarations">13.12.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be TopLevelVarScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the TopLevelVarScopedDeclarations of <i>StatementListItem.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If <i>Statement</i> is <span class="prod"><span class="nt">Statement</span> <span class="geq">:</span> <span
+ class="nt">LabelledStatement</span></span> , return TopLevelVarScopedDeclarations of <i>Statement</i>.</li>
+ <li>Return VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">FunctionDeclaration</span></span> , return a new <a href="#sec-list-and-record-specification-type">List</a>
+ containing <i>FunctionDeclaration</i>.</li>
+ <li>If <i>Declaration</i> is <span class="prod"><span class="nt">Declaration</span> <span class="geq">:</span> <span
+ class="nt">GeneratorDeclaration</span></span> , return a new <a
+ href="#sec-list-and-record-specification-type">List</a> containing <i>GeneratorDeclaration</i>.</li>
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.1.11"><a href="#sec-block-static-semantics-vardeclarednames"
+ title="link to this section">13.1.11</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be VarDeclaredNames of <i>StatementList</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>StatementListItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.1.12"><a href="#sec-block-static-semantics-varscopeddeclarations"
+ title="link to this section">13.1.12</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>StatementListItem.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-block-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.1.13"><a href="#sec-block-runtime-semantics-evaluation"
+ title="link to this section">13.1.13</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Block</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">StatementList</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>oldEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>blockEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>oldEnv</i>).</li>
+ <li>Perform <a href="#sec-blockdeclarationinstantiation">BlockDeclarationInstantiation</a>(<i>StatementList,</i>
+ <i>blockEnv</i>).</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>blockEnv</i>.</li>
+ <li>Let <i>blockValue</i> be the result of evaluating <i>StatementList</i>.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <i>blockValue</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> No matter how control leaves the <i>Block</i> the <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> is always restored to its former state.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>sl</i> be the result of evaluating <i>StatementList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>sl</i>).</li>
+ <li>Let <i>s</i> be the result of evaluating <i>StatementListItem</i>.</li>
+ <li>If <i>s</i>.[[type]] is <span style="font-family: sans-serif">throw</span>, return <i>s</i>.</li>
+ <li>If <i>s</i>.[[value]] is <span style="font-family: sans-serif">empty</span>, let <i>V</i> = <i>sl</i>.[[value]],
+ otherwise let <i>V</i> = <i>s</i>.[[value]].</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>s</i>.[[type]], [[value]]:
+ <i>V</i>, [[target]]: <i>s</i>.[[target]]}.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Steps 5 and 6 of the above algorithm ensure that the value of a <i>StatementList</i> is
+ the value of the last value producing item in the <i>StatementList</i>. For example, the following calls to the
+ <code>eval</code> function all return the value 1:</p>
+
+ <pre>eval("1;;;;;")</pre>
+ <pre>eval("1;{}")</pre>
+ <pre>eval("1;var a;")</pre>
+ </div>
+ </section>
+
+ <section id="sec-blockdeclarationinstantiation">
+ <h1><span class="secnum" id="sec-13.1.14"><a href="#sec-blockdeclarationinstantiation"
+ title="link to this section">13.1.14</a></span> Runtime Semantics: BlockDeclarationInstantiation( code, env )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When a <span class="nt">Block</span> or <span class="nt">CaseBlock</span> production is
+ evaluated a new <a href="#sec-declarative-environment-records">Declarative Environment Record</a> is created and bindings
+ for each block scoped variable, constant, function, generator function, or class declared in the block are instantiated in
+ the environment record.</p>
+ </div>
+
+ <p>BlockDeclarationInstantiation is performed as follows using arguments <var>code</var> and <var>env</var>. <var>code</var>
+ is the grammar production corresponding to the body of the block. <var>env</var> is the <a
+ href="#sec-declarative-environment-records">declarative environment record</a> in which bindings are to be created.</p>
+
+ <ol class="proc">
+ <li>Let <i>declarations</i> be the LexicallyScopedDeclarations of <i>code</i>.</li>
+ <li>For each element <i>d</i> in <i>declarations</i> do
+ <ol class="block">
+ <li>For each element <i>dn</i> of the BoundNames of <i>d</i> do
+ <ol class="block">
+ <li>If IsConstantDeclaration of <i>d</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>env</i>.CreateImmutableBinding(<i>dn</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>env</i>.CreateMutableBinding(<i>dn</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>If <i>d</i> is a <i>GeneratorDeclaration</i> production or a <i>FunctionDeclaration</i> production, then
+ <ol class="block">
+ <li>Let <i>fn</i> be the sole element of the BoundNames of <i>d</i></li>
+ <li>Let <i>fo</i> be the result of performing InstantiateFunctionObject for <i>d</i> with argument
+ <i>env</i>.</li>
+ <li>Perform <i>env</i>.InitializeBinding(<i>fn</i>, <i>fo</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-declarations-and-the-variable-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.2"><a href="#sec-declarations-and-the-variable-statement"
+ title="link to this section">13.2</a></span> Declarations and the Variable Statement</h1>
+ </div>
+
+ <section id="sec-let-and-const-declarations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.2.1"><a href="#sec-let-and-const-declarations"
+ title="link to this section">13.2.1</a></span> Let and Const Declarations</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <code>let</code> and <code>const</code> declarations define variables that are scoped to
+ <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>. The variables are created when their containing <a
+ href="#sec-lexical-environments">Lexical Environment</a> is instantiated but may not be accessed in any way until the
+ variable’s <span class="nt">LexicalBinding</span> is evaluated. A variable defined by a <span
+ class="nt">LexicalBinding</span> with an <span class="nt">Initializer</span> is assigned the value of its <span
+ style="font-family: Times New Roman"><i>Initializer</i>’s</span> <span class="nt">AssignmentExpression</span> when
+ the <span class="nt">LexicalBinding</span> is evaluated, not when the variable is created. If a <span
+ class="nt">LexicalBinding</span> in a <code>let</code> declaration does not have an <span class="nt">Initializer</span>
+ the variable is assigned the value <b>undefined</b> when the <span class="nt">LexicalBinding</span> is evaluated.</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LexicalDeclaration</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LetOrConst</span> <span class="nt">BindingList</span><sub>[?In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LetOrConst</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">let</code></div>
+ <div class="rhs"><code class="t">const</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingList</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LexicalBinding</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BindingList</span><sub>[?In, ?Yield]</sub> <code class="t">,</code> <span class="nt">LexicalBinding</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LexicalBinding</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-let-and-const-declarations-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.2.1.1"><a href="#sec-let-and-const-declarations-static-semantics-early-errors"
+ title="link to this section">13.2.1.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">LexicalDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">BindingList</span> <code class="t">;</code></div>
+ <ul>
+ <li>It is a Syntax Error if the BoundNames of <span class="nt">BindingList</span> contains <code>"let"</code>.</li>
+ <li>It is a Syntax Error if the BoundNames of <span class="nt">BindingList</span> contains any duplicate entries.</li>
+ </ul>
+ <div class="gp prod"><span class="nt">LexicalBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span class="nt">Initializer</span> is not present and IsConstantDeclaration of the <span
+ class="nt">LexicalDeclaration</span> containing this production is <span class="value">true</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-let-and-const-declarations-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-13.2.1.2"><a href="#sec-let-and-const-declarations-static-semantics-boundnames"
+ title="link to this section">13.2.1.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">LexicalDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">BindingList</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingList</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingList</span> <span class="geq">:</span> <span class="nt">BindingList</span> <code class="t">,</code> <span class="nt">LexicalBinding</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the BoundNames of <i>BindingList</i>.</li>
+ <li>Append to <i>names</i> the elements of the BoundNames of <i>LexicalBinding.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LexicalBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingIdentifier</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LexicalBinding</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingPattern</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-let-and-const-declarations-static-semantics-isconstantdeclaration">
+ <h1><span class="secnum" id="sec-13.2.1.3"><a
+ href="#sec-let-and-const-declarations-static-semantics-isconstantdeclaration"
+ title="link to this section">13.2.1.3</a></span> Static Semantics: IsConstantDeclaration</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-isconstantdeclaration">14.1.10</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isconstantdeclaration">14.4.8</a>, <a
+ href="#sec-class-definitions-static-semantics-isconstantdeclaration">14.5.7</a>, <a
+ href="#sec-exports-static-semantics-isconstantdeclaration">15.2.3.7</a>.</p>
+
+ <div class="gp prod"><span class="nt">LexicalDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">BindingList</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return IsConstantDeclaration of <i>LetOrConst</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LetOrConst</span> <span class="geq">:</span> <code class="t">let</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LetOrConst</span> <span class="geq">:</span> <code class="t">const</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-let-and-const-declarations-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.2.1.4"><a href="#sec-let-and-const-declarations-runtime-semantics-evaluation"
+ title="link to this section">13.2.1.4</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">LexicalDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">BindingList</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>next</i> be the result of evaluating <i>BindingList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingList</span> <span class="geq">:</span> <span class="nt">BindingList</span> <code class="t">,</code> <span class="nt">LexicalBinding</span></div>
+ <ol class="proc">
+ <li>Let <i>next</i> be the result of evaluating <i>BindingList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>Return the result of evaluating <i>LexicalBinding</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LexicalBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Let <i>lhs</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(StringValue of <i>BindingIdentifier</i>).</li>
+ <li>Return <a href="#sec-initializereferencedbinding">InitializeReferencedBinding</a>(<i>lhs</i>,
+ <b>undefined</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A static semantics rule ensures that this form of <span class="nt">LexicalBinding</span>
+ never occurs in a <code>const</code> declaration.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">LexicalBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Let <i>bindingId</i> be StringValue of <i>BindingIdentifier.</i></li>
+ <li>Let <i>lhs</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(<i>bindingId</i>).</li>
+ <li>Let <i>rhs</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>value</i> be <a href="#sec-getvalue">GetValue</a>(<i>rhs</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>Initializer)</i> is
+ <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>value</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>value</i>, <i>bindingId</i>).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-initializereferencedbinding">InitializeReferencedBinding</a>(<i>lhs</i>, <i>value</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LexicalBinding</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Let <i>rhs</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>value</i> be <a href="#sec-getvalue">GetValue</a>(<i>rhs</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>Let <i>env</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Return the result of performing BindingInitialization for <i>BindingPattern</i> using <i>value</i> and <i>env</i> as
+ the <i>arguments</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-variable-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.2.2"><a href="#sec-variable-statement" title="link to this section">13.2.2</a></span>
+ Variable Statement</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A <code>var</code> statement declares variables that are scoped to <a
+ href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">VariableEnvironment</a>. Var variables are created when their containing <a
+ href="#sec-lexical-environments">Lexical Environment</a> is instantiated and are initialized to <b>undefined</b> when
+ created. Within the scope of any <a href="#sec-execution-contexts">VariableEnvironment</a> a common <span
+ class="nt">BindingIdentifier</span> may appear in more than one <span class="nt">VariableDeclaration</span> but those
+ declarations collective define only one variable. A variable defined by a <span class="nt">VariableDeclaration</span>
+ with an <span class="nt">Initializer</span> is assigned the value of its <span style="font-family: Times New
+ Roman"><i>Initializer</i>’s</span> <span class="nt">AssignmentExpression</span> when the <span
+ class="nt">VariableDeclaration</span> is executed, not when the variable is created.</p>
+ </div>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">var</code> <span class="nt">VariableDeclarationList</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclarationList</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">VariableDeclaration</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">VariableDeclarationList</span><sub>[?In, ?Yield]</sub> <code class="t">,</code> <span class="nt">VariableDeclaration</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">VariableDeclaration</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-variable-statement-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-13.2.2.1"><a href="#sec-variable-statement-static-semantics-boundnames"
+ title="link to this section">13.2.2.1</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">VariableDeclarationList</span> <span class="geq">:</span> <span class="nt">VariableDeclarationList</span> <code class="t">,</code> <span class="nt">VariableDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>VariableDeclarationList</i>.</li>
+ <li>Append to <i>names</i> the elements of BoundNames of <i>VariableDeclaration.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">VariableDeclaration</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingIdentifier</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">VariableDeclaration</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingPattern</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-variable-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.2.2.2"><a href="#sec-variable-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.2.2.2</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">VariableStatement</span> <span class="geq">:</span> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return BoundNames of <i>VariableDeclarationList.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-variable-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.2.2.3"><a href="#sec-variable-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.2.2.3</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">VariableDeclarationList</span> <span class="geq">:</span> <span class="nt">VariableDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>VariableDeclaration.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">VariableDeclarationList</span> <span class="geq">:</span> <span class="nt">VariableDeclarationList</span> <code class="t">,</code> <span class="nt">VariableDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>VariableDeclarationList</i>.</li>
+ <li>Append <i>VariableDeclaration</i> to <i>declarations.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-variable-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.2.2.4"><a href="#sec-variable-statement-runtime-semantics-evaluation"
+ title="link to this section">13.2.2.4</a></span> <span style="font-family: sans-serif">Runtime</span> Semantics:
+ Evaluation</h1>
+ <div class="gp prod"><span class="nt">VariableStatement</span> <span class="geq">:</span> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>next</i> be the result of evaluating <i>VariableDeclarationList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>( <span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">VariableDeclarationList</span> <span class="geq">:</span> <span class="nt">VariableDeclarationList</span> <code class="t">,</code> <span class="nt">VariableDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>next</i> be the result of evaluating <i>VariableDeclarationList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>Return the result of evaluating <i>VariableDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">VariableDeclaration</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">VariableDeclaration</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Let <i>bindingId</i> be StringValue of <i>BindingIdentifier.</i></li>
+ <li>Let <i>lhs</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(<i>bindingId</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lhs</i>).</li>
+ <li>Let <i>rhs</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>value</i> be <a href="#sec-getvalue">GetValue</a>(<i>rhs</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>Initializer)</i> is
+ <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>value</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>value</i>, <i>bindingId</i>).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-putvalue">PutValue</a>(<i>lhs</i>, <i>value</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE </span> If a <i>VariableDeclaration</i> is nested within a with statement and the
+ <i>BindingIdentifier</i> in the <i>VariableDeclaration</i> is the same as a property name of the binding object of the
+ with statement’s <a href="#sec-object-environment-records">object environment record</a>, then step 7 will assign
+ <i>value</i> to the property instead of assigning to the <a href="#sec-execution-contexts">VariableEnvironment</a>
+ binding of the <i>Identifier</i>.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">VariableDeclaration</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Let <i>rhs</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>rval</i> be <a href="#sec-getvalue">GetValue</a>(<i>rhs</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rval</i>).</li>
+ <li>Return the result of performing BindingInitialization for <i>BindingPattern</i> passing <i>rval</i> and
+ <b>undefined</b> as arguments.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-destructuring-binding-patterns">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.2.3"><a href="#sec-destructuring-binding-patterns"
+ title="link to this section">13.2.3</a></span> Destructuring Binding Patterns</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingPattern</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ObjectBindingPattern</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">ArrayBindingPattern</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ObjectBindingPattern</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">BindingPropertyList</span><sub>[?Yield,?GeneratorParameter]</sub> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">BindingPropertyList</span><sub>[?Yield,?GeneratorParameter]</sub> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArrayBindingPattern</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span><sub>[?Yield, ?GeneratorParameter]</sub><sub>opt</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">BindingElementList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">BindingElementList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span><sub>[?Yield, ?GeneratorParameter]</sub><sub>opt</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingPropertyList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingProperty</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">BindingPropertyList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">BindingProperty</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingElementList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingElisionElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">BindingElementList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">BindingElisionElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingElisionElement</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingProperty</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">SingleNameBinding</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">PropertyName</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">:</code> <span class="nt">BindingElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingElement</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">SingleNameBinding</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">BindingPattern</span><sub>[?Yield,GeneratorParameter]</sub> <span class="nt">Initializer</span><sub>[In]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">BindingPattern</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In, ?Yield]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleNameBinding</span> <span class="grhsannot">[Yield, <span class="nt">GeneratorParameter</span>]</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">BindingIdentifier</span><sub>[Yield]</sub> <span class="nt">Initializer</span><sub>[In]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In, ?Yield]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BindingRestElement</span><sub>[Yield, GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-destructuring-binding-patterns-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-13.2.3.1"><a href="#sec-destructuring-binding-patterns-static-semantics-boundnames"
+ title="link to this section">13.2.3.1</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ObjectBindingPattern</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingRestElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingElementList</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>BindingElementList</i>.</li>
+ <li>Append to <i>names</i> the elements of BoundNames of <i>BindingRestElement.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingPropertyList</span> <span class="geq">:</span> <span class="nt">BindingPropertyList</span> <code class="t">,</code> <span class="nt">BindingProperty</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>BindingPropertyList</i>.</li>
+ <li>Append to <i>names</i> the elements of BoundNames of <i>BindingProperty.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElementList</span> <span class="geq">:</span> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">BindingElisionElement</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>BindingElementList</i>.</li>
+ <li>Append to <i>names</i> the elements of BoundNames of <i>BindingElisionElement.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElisionElement</span> <span class="geq">:</span> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Return BoundNames of <i>BindingElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingProperty</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingIdentifier</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingPattern</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-destructuring-binding-patterns-static-semantics-containsexpression">
+ <h1><span class="secnum" id="sec-13.2.3.2"><a
+ href="#sec-destructuring-binding-patterns-static-semantics-containsexpression"
+ title="link to this section">13.2.3.2</a></span> Static Semantics: ContainsExpression</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-containsexpression">14.1.5</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-containsexpression">14.2.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">ObjectBindingPattern</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return ContainsExpression of <i>BindingElementList</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return ContainsExpression of <i>BindingElementList</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingPropertyList</span> <span class="geq">:</span> <span class="nt">BindingPropertyList</span> <code class="t">,</code> <span class="nt">BindingProperty</span></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be ContainsExpression of <i>BindingPropertyList</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b><i>.</i></li>
+ <li>Return ContainsExpression of <i>BindingProperty</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElementList</span> <span class="geq">:</span> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">BindingElisionElement</span></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be ContainsExpression of <i>BindingElementList</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b><i>.</i></li>
+ <li>Return ContainsExpression of <i>BindingElisionElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElisionElement</span> <span class="geq">:</span> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Return ContainsExpression of <i>BindingElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingProperty</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be IsComputedPropertyKey of <i>PropertyName</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b><i>.</i></li>
+ <li>Return the ContainsExpression of <i>BindingElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-destructuring-binding-patterns-static-semantics-hasinitializer">
+ <h1><span class="secnum" id="sec-13.2.3.3"><a href="#sec-destructuring-binding-patterns-static-semantics-hasinitializer"
+ title="link to this section">13.2.3.3</a></span> Static Semantics: HasInitializer</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-hasinitializer">14.1.7</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-hasinitializer">14.2.7</a>.</p>
+
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-destructuring-binding-patterns-static-semantics-issimpleparameterlist">
+ <h1><span class="secnum" id="sec-13.2.3.4"><a
+ href="#sec-destructuring-binding-patterns-static-semantics-issimpleparameterlist"
+ title="link to this section">13.2.3.4</a></span> Static Semantics: IsSimpleParameterList</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-issimpleparameterlist">14.1.12</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-hasname">14.2.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-destructuring-binding-patterns-runtime-semantics-bindinginitialization">
+ <h1><span class="secnum" id="sec-13.2.3.5"><a
+ href="#sec-destructuring-binding-patterns-runtime-semantics-bindinginitialization"
+ title="link to this section">13.2.3.5</a></span> Runtime Semantics: BindingInitialization</h1>
+
+ <p>With parameters <var>value</var> and <var>environment</var>.</p>
+
+ <p>See also: <a href="#sec-identifiers-runtime-semantics-bindinginitialization">12.1.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-bindinginitialization">13.6.4.9</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When <b>undefined</b> is passed for <var>environment</var> it indicates that a <a
+ href="#sec-putvalue">PutValue</a> operation should be used to assign the initialization value. This is the case for
+ formal parameter lists of non-strict mode functions. In that case the formal parameter bindings are preinitialized in
+ order to deal with the possibility of multiple parameters with the same name.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">BindingPattern</span> <span class="geq">:</span> <span class="nt">ObjectBindingPattern</span></div>
+ <ol class="proc">
+ <li>Let <i>valid</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Return the result of performing BindingInitialization for <i>ObjectBindingPattern</i> using <i>value</i> and
+ <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingPattern</span> <span class="geq">:</span> <span class="nt">ArrayBindingPattern</span></div>
+ <ol class="proc">
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <i>iterator</i>, [[done]]: <b>false</b>}.</li>
+ <li>Let <i>result</i> be IteratorBindingInitialization for <i>ArrayBindingPattern</i> using <i>iteratorRecord</i>, and
+ <i>environment</i> as arguments.</li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>result</i>).</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ObjectBindingPattern</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingPropertyList</span> <span class="geq">:</span> <span class="nt">BindingPropertyList</span> <code class="t">,</code> <span class="nt">BindingProperty</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing BindingInitialization for <i>BindingPropertyList</i> using
+ <i>value</i> and <i>environment</i> as arguments.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing BindingInitialization for <i>BindingProperty</i> using <i>value</i> and
+ <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingProperty</span> <span class="geq">:</span> <span class="nt">SingleNameBinding</span></div>
+ <ol class="proc">
+ <li>Let <i>name</i> be the string that is the only element of BoundNames of <i>SingleNameBinding</i>.</li>
+ <li>Return the result of performing KeyedBindingInitialization for <i>SingleNameBinding</i> using <i>value</i>,
+ <i>environment</i>, and <i>name</i> as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingProperty</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Let <i>P</i> be the result of evaluating <i>PropertyName</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>Return the result of performing KeyedBindingInitialization for <i>BindingElement</i> using <i>value</i>,
+ <i>environment</i>, and <i>P</i> as arguments.</li>
+ </ol>
+ </section>
+
+ <section id="sec-destructuring-binding-patterns-runtime-semantics-iteratorbindinginitialization">
+ <h1><span class="secnum" id="sec-13.2.3.6"><a
+ href="#sec-destructuring-binding-patterns-runtime-semantics-iteratorbindinginitialization"
+ title="link to this section">13.2.3.6</a></span> Runtime Semantics: IteratorBindingInitialization</h1>
+
+ <p>With parameters <var>iteratorRecord,</var> and <var>environment</var>.</p>
+
+ <p>See also: <a href="#sec-function-definitions-runtime-semantics-iteratorbindinginitialization">14.1.19</a>, <a
+ href="#sec-arrow-function-definitions-runtime-semantics-iteratorbindinginitialization">14.2.13</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When <b>undefined</b> is passed for <var>environment</var> it indicates that a <a
+ href="#sec-putvalue">PutValue</a> operation should be used to assign the initialization value. This is the case for
+ formal parameter lists of non-strict mode functions. In that case the formal parameter bindings are preinitialized in
+ order to deal with the possibility of multiple parameters with the same name.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>If <i>Elision</i> is present, then
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return the result of performing IteratorBindingInitialization for <i>BindingRestElement</i> with
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return the result of performing IteratorBindingInitialization for <i>BindingElementList</i> with
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">,</code> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Return the result of performing IteratorBindingInitialization for <i>BindingElementList</i> with
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">Elision</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorBindingInitialization for <i>BindingElementList</i> with
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrayBindingPattern</span> <span class="geq">:</span> <code class="t">[</code> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span> <code class="t">]</code></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorBindingInitialization for <i>BindingElementList</i> with
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>Elision</i> is present, then
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return the result of performing IteratorBindingInitialization for <i>BindingRestElement</i> with
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElementList</span> <span class="geq">:</span> <span class="nt">BindingElisionElement</span></div>
+ <ol class="proc">
+ <li>Return the result of performing IteratorBindingInitialization for <i>BindingElisionElement</i> with
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElementList</span> <span class="geq">:</span> <span class="nt">BindingElementList</span> <code class="t">,</code> <span class="nt">BindingElisionElement</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorBindingInitialization for <i>BindingElementList</i>
+ <i>with</i> <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing IteratorBindingInitialization for <i>BindingElisionElement</i> using
+ <i>iteratorRecord</i> and <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElisionElement</span> <span class="geq">:</span> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Return the result of performing IteratorBindingInitialization of <i>BindingElement</i> with <i>iteratorRecord</i>
+ and <i>environment</i> as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElisionElement</span> <span class="geq">:</span> <span class="nt">Elision</span> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorDestructuringAssignmentEvaluation of <i>Elision</i> with
+ <i>iteratorRecord</i> as the argument.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing IteratorBindingInitialization of <i>BindingElement</i> with <i>iteratorRecord</i>
+ and <i>environment</i> as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">SingleNameBinding</span></div>
+ <ol class="proc">
+ <li>Return the result of performing IteratorBindingInitialization for <i>SingleNameBinding</i> with
+ <i>iteratorRecord</i> <i>and</i> <i>environment</i> as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Let <i>bindingId</i> be StringValue of <i>BindingIdentifier.</i></li>
+ <li>Let <i>lhs</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(<i>bindingId</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lhs</i>).</li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>v</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>true</b>, let <i>v</i> be <b>undefined</b>.</li>
+ <li>If <i>Initializer</i> is present and <i>v</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>defaultValue</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>v</i> be <a href="#sec-getvalue">GetValue</a>(<i>defaultValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>Initializer)</i> is
+ <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>v</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>v</i>, <i>bindingId</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>environment</i> is <b>undefined</b>, return <a href="#sec-putvalue">PutValue</a>(<i>lhs</i>, <i>v</i>).</li>
+ <li>Return <a href="#sec-initializereferencedbinding">InitializeReferencedBinding</a>(<i>lhs</i>, <i>v</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>v</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>true</b>, let <i>v</i> be <b>undefined</b>.</li>
+ <li>If <i>Initializer</i> is present and <i>v</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>defaultValue</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>v</i> be <a href="#sec-getvalue">GetValue</a>(<i>defaultValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ </ol>
+ </li>
+ <li>Return the result of performing BindingInitialization of <i>BindingPattern</i> with <i>v</i> and <i>environment</i>
+ as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BindingRestElement</span> <span class="geq">:</span> <code class="t">...</code> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Let <i>lhs</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(StringValue of <i>BindingIdentifier</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lhs</i>).</li>
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>n</i>=0.</li>
+ <li>Repeat<b>,</b>
+ <ol class="block">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>,
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>true</b>, then
+ <ol class="block">
+ <li>If <i>environment</i> is <b>undefined</b>, return <a href="#sec-putvalue">PutValue</a>(<i>lhs</i>,
+ <i>A</i>).</li>
+ <li>Return <a href="#sec-initializereferencedbinding">InitializeReferencedBinding</a>(<i>lhs</i>,
+ <i>A</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>nextValue</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a> (<i>n</i>), <i>nextValue</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is <b>true</b>.</li>
+ <li>Increment <i>n</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-keyedbindinginitialization">
+ <h1><span class="secnum" id="sec-13.2.3.7"><a href="#sec-runtime-semantics-keyedbindinginitialization"
+ title="link to this section">13.2.3.7</a></span> Runtime Semantics: KeyedBindingInitialization</h1>
+
+ <p>With parameters <var>value</var>, <var>environment,</var> and <var>propertyName</var>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When <b>undefined</b> is passed for <var>environment</var> it indicates that a <a
+ href="#sec-putvalue">PutValue</a> operation should be used to assign the initialization value. This is the case for
+ formal parameter lists of non-strict mode functions. In that case the formal parameter bindings are preinitialized in
+ order to deal with the possibility of multiple parameters with the same name.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">BindingElement</span> <span class="geq">:</span> <span class="nt">BindingPattern</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Let <i>v</i> be <a href="#sec-getv">GetV</a>(<i>value</i>, <i>propertyName</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <i>Initializer</i> is present and <i>v</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>defaultValue</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>v</i> be <a href="#sec-getvalue">GetValue</a>(<i>defaultValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ </ol>
+ </li>
+ <li>Return the result of performing BindingInitialization for <i>BindingPattern</i> passing <i>v</i> and
+ <i>environment</i> as arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SingleNameBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span> <span class="nt">Initializer</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Let <i>bindingId</i> be StringValue of <i>BindingIdentifier.</i></li>
+ <li>Let <i>lhs</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(<i>bindingId</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lhs</i>).</li>
+ <li>Let <i>v</i> be <a href="#sec-getv">GetV</a>(<i>value</i>, <i>propertyName</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <i>Initializer</i> is present and <i>v</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>defaultValue</i> be the result of evaluating <i>Initializer</i>.</li>
+ <li>Let <i>v</i> be <a href="#sec-getvalue">GetValue</a>(<i>defaultValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>Initializer</i>) is
+ <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>v</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>v</i>, <i>bindingId</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>environment</i> is <b>undefined</b>, return <a href="#sec-putvalue">PutValue</a>(<i>lhs</i>, <i>v</i>).</li>
+ <li>Return <a href="#sec-initializereferencedbinding">InitializeReferencedBinding</a>(<i>lhs</i>, <i>v</i>).</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-empty-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.3"><a href="#sec-empty-statement" title="link to this section">13.3</a></span> Empty
+ Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EmptyStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">;</code></div>
+ </div>
+ </div>
+
+ <section id="sec-empty-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.3.1"><a href="#sec-empty-statement-runtime-semantics-evaluation"
+ title="link to this section">13.3.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">EmptyStatement</span> <span class="geq">:</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>)<span
+ style="font-family: sans-serif">.</span></li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-expression-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.4"><a href="#sec-expression-statement" title="link to this section">13.4</a></span>
+ Expression Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExpressionStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[lookahead ∉ {<code class="t">{</code>, <code class="t">function</code>, <code class="t">class</code>, <code class="t">let [</code>}]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An <i>ExpressionStatement</i> cannot start with a left curly bracket because that might
+ make it ambiguous with a <i>Block</i>. Also, an <i>ExpressionStatement</i> cannot start with the <code>function</code> or
+ <code>class</code> keywords because that would make it ambiguous with a <i>FunctionDeclaration</i>, a
+ <i>GeneratorDeclaration</i>, or a <i>ClassDeclaration</i>. An <i>ExpressionStatement</i> cannot start with the two token
+ sequence <code>let [</code> because that would make it ambiguous with a <code>let</code> <i>LexicalDeclaration</i> whose
+ first <i>LexicalBinding</i> was an <i>ArrayBindingPattern</i>.</p>
+ </div>
+ </div>
+
+ <section id="sec-expression-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.4.1"><a href="#sec-expression-statement-runtime-semantics-evaluation"
+ title="link to this section">13.4.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ExpressionStatement</span> <span class="geq">:</span> <span class="nt">Expression</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Return <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-if-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.5"><a href="#sec-if-statement" title="link to this section">13.5</a></span> The
+ <code>if</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IfStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub> <code class="t">else</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <p>Each <code>else</code> for which the choice of associated <code>if</code> is ambiguous shall be associated with the
+ nearest possible <b>if</b> that would otherwise have no corresponding <code>else</code>.</p>
+ </div>
+
+ <section id="sec-if-statement-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.5.1"><a href="#sec-if-statement-static-semantics-early-errors"
+ title="link to this section">13.5.1</a></span> Static Semantics: Early Errors</h1>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IfStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <a href="#sec-islabelledfunction">IsLabelledFunction</a>(<span class="nt">Statement</span>)
+ is <span class="value">true</span> for any occurrence of <span class="nt">Statement</span> in these rules.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> It is only necessary to apply this rule if the extension specified in <a
+ href="#sec-labelled-function-declarations">B.3.2</a> is implemented.</p>
+ </div>
+ </section>
+
+ <section id="sec-if-statement-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.5.2"><a href="#sec-if-statement-static-semantics-containsduplicatelabels"
+ title="link to this section">13.5.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsDuplicateLabels of <i>the first Statement</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsDuplicateLabels of <i>the second Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-if-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.5.3"><a href="#sec-if-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.5.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>the first Statement</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>the second Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-if-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.5.4"><a href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.5.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>the first Statement</i> with arguments
+ <i>iterationSet</i> and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>the second Statement</i> with arguments <i>iterationSet</i> and «
+ »<i>.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>Statement</i> with arguments <i>iterationSet</i> and «
+ »<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-if-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.5.5"><a href="#sec-if-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.5.5</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be VarDeclaredNames of the first <i>Statement</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of the second <i>Statement.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-if-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.5.6"><a href="#sec-if-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.5.6</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of the first <i>Statement</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of the second <i>Statement.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-if-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.5.7"><a href="#sec-if-statement-runtime-semantics-evaluation"
+ title="link to this section">13.5.7</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-toboolean">ToBoolean</a>(<a
+ href="#sec-getvalue">GetValue</a>(<i>exprRef</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exprValue</i>).</li>
+ <li>If <i>exprValue</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>stmtCompletion</i> be the result of evaluating the first <i>Statement</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>stmtCompletion</i> be the result of evaluating the second <i>Statement</i>.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>stmtCompletion</i>).</li>
+ <li>If <i>stmtCompletion</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, return
+ <i>stmtCompletion</i>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-toboolean">ToBoolean</a>(<a
+ href="#sec-getvalue">GetValue</a>(<i>exprRef</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exprValue</i>).</li>
+ <li>If <i>exprValue</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>stmtCompletion</i> be the result of evaluating <i>Statement</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>stmtCompletion</i>).</li>
+ <li>If <i>stmtCompletion</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, return
+ <i>stmtCompletion</i>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-iteration-statements">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.6"><a href="#sec-iteration-statements" title="link to this section">13.6</a></span>
+ Iteration Statements</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">do</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <div class="rhs"><code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="grhsannot">[lookahead ∉ {<code class="t">let [</code>}]</span> <span class="nt">Expression</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span><sub>[?Yield]</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span><sub>[?Yield]</sub> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <code class="t">in</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span><sub>[?Yield]</sub> <code class="t">in</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span><sub>[?Yield]</sub> <code class="t">in</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="grhsannot">[lookahead ≠ let ]</span> <span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <code class="t">of</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span> <span class="grhsannot">[?Yield, ?Return]</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span><sub>[?Yield]</sub> <code class="t">of</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span><sub>[?Yield]</sub> <code class="t">of</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ForDeclaration</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LetOrConst</span> <span class="nt">ForBinding</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ForBinding</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> A semicolon is not required after a <code>do-while</code> statement.</p>
+ </div>
+ </div>
+
+ <section id="sec-iteration-statements-semantics">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.6.0"><a href="#sec-iteration-statements-semantics"
+ title="link to this section">13.6.0</a></span> Semantics</h1>
+ </div>
+
+ <section id="sec-semantics-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.6.0.1"><a href="#sec-semantics-static-semantics-early-errors"
+ title="link to this section">13.6.0.1</a></span> Static Semantics: Early Errors</h1>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <div class="rhs"><code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="grhsannot">[lookahead ∉ {<code class="t">let [</code>}]</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="grhsannot">[lookahead ∉ {<code class="t">let [</code>}]</span> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <a href="#sec-islabelledfunction">IsLabelledFunction</a>(<span class="nt">Statement</span>)
+ is <span class="value">true</span> for any occurrence of <span class="nt">Statement</span> in these rules.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> It is only necessary to apply this rule if the extension specified in <a
+ href="#sec-labelled-function-declarations">B.3.2</a> is implemented.</p>
+ </div>
+ </section>
+
+ <section id="sec-loopcontinues">
+ <h1><span class="secnum" id="sec-13.6.0.2"><a href="#sec-loopcontinues" title="link to this section">13.6.0.2</a></span>
+ Runtime Semantics: LoopContinues(completion, labelSet)</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">LoopContinues</span> with arguments
+ <var>completion</var> and <var>labelSet</var> is defined by the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>completion</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, return <b>true</b>.</li>
+ <li>If <i>completion</i>.[[type]] is not <span style="font-family: sans-serif">continue</span>, return
+ <b>false</b>.</li>
+ <li>If <i>completion</i>.[[target]] is <span style="font-family: sans-serif">empty</span>, return <b>true</b>.</li>
+ <li>If <i>completion</i>.[[target]] is an element of <i>labelSet</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Within the <i>Statement</i> part of an <i>IterationStatement</i> a
+ <i>ContinueStatement</i> may be used to begin a new iteration.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-do-while-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.6.1"><a href="#sec-do-while-statement" title="link to this section">13.6.1</a></span>
+ The <code>do</code>-<code>while</code> Statement</h1>
+ </div>
+
+ <section id="sec-do-while-statement-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.6.1.1"><a href="#sec-do-while-statement-static-semantics-containsduplicatelabels"
+ title="link to this section">13.6.1.1</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-do-while-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.6.1.2"><a href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.6.1.2</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.6.1.3"><a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.6.1.3</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>Statement</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-do-while-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.6.1.4"><a href="#sec-do-while-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.6.1.4</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-do-while-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.6.1.5"><a href="#sec-do-while-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.6.1.5</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-do-while-statement-runtime-semantics-labelledevaluation">
+ <h1><span class="secnum" id="sec-13.6.1.6"><a href="#sec-do-while-statement-runtime-semantics-labelledevaluation"
+ title="link to this section">13.6.1.6</a></span> Runtime Semantics: LabelledEvaluation</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-labelledevaluation">13.6.4.11</a>, <a
+ href="#sec-labelled-statements-runtime-semantics-labelledevaluation">13.12.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Let <i>V</i> = <b>undefined</b>.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>stmt</i> be the result of evaluating <i>Statement</i>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a> (<i>stmt</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>stmt</i>.</li>
+ <li>If <i>stmt</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>stmt</i>.[[value]]<i>.</i></li>
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li>If <i>exprValue</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, then
+ <ol class="block">
+ <li>If <a href="#sec-toboolean">ToBoolean</a>(<i>exprValue</i>) is <b>false</b>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>V</i>).</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>exprValue</i> is an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a> (<i>exprValue</i>,<i>labelSet</i>) is <b>false</b>,
+ return <i>exprValue.</i></li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-while-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.6.2"><a href="#sec-while-statement" title="link to this section">13.6.2</a></span> The
+ <code>while</code> Statement</h1>
+ </div>
+
+ <section id="sec-while-statement-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.6.2.1"><a href="#sec-while-statement-static-semantics-containsduplicatelabels"
+ title="link to this section">13.6.2.1</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-while-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.6.2.2"><a href="#sec-while-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.6.2.2</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-while-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.6.2.3"><a href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.6.2.3</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>Statement</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-while-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.6.2.4"><a href="#sec-while-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.6.2.4</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-while-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.6.2.5"><a href="#sec-while-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.6.2.5</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-while-statement-runtime-semantics-labelledevaluation">
+ <h1><span class="secnum" id="sec-13.6.2.6"><a href="#sec-while-statement-runtime-semantics-labelledevaluation"
+ title="link to this section">13.6.2.6</a></span> Runtime Semantics: LabelledEvaluation</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-runtime-semantics-labelledevaluation">13.0.7</a>, <a
+ href="#sec-do-while-statement-runtime-semantics-labelledevaluation">13.6.1.6</a>, <a
+ href="#sec-for-statement-runtime-semantics-labelledevaluation">13.6.3.7</a>, <a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-labelledevaluation">13.6.4.11</a>, <a
+ href="#sec-labelled-statements-runtime-semantics-labelledevaluation">13.12.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>V</i> = <b>undefined</b>.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li>If <i>exprValue</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, then
+ <ol class="block">
+ <li>If <a href="#sec-toboolean">ToBoolean</a>(<i>exprValue</i>) is <b>false</b>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>V</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>exprValue</i> is an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a> (<i>exprValue</i>,<i>labelSet</i>) is <b>false</b>,
+ return <i>exprValue.</i></li>
+ </ol>
+ </li>
+ <li>Let <i>stmt</i> be the result of evaluating <i>Statement</i>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a> (<i>stmt</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>stmt</i>.</li>
+ <li>If <i>stmt</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>stmt</i>.[[value]].</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-for-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.6.3"><a href="#sec-for-statement" title="link to this section">13.6.3</a></span> The
+ <code>for</code> Statement</h1>
+ </div>
+
+ <section id="sec-for-statement-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.6.3.1"><a href="#sec-for-statement-static-semantics-early-errors"
+ title="link to this section">13.6.3.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <span class="nt">LexicalDeclaration</span> also occurs in
+ the VarDeclaredNames of <span class="nt">Statement</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-for-statement-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.6.3.2"><a href="#sec-for-statement-static-semantics-containsduplicatelabels"
+ title="link to this section">13.6.3.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-for-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.6.3.3"><a href="#sec-for-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.6.3.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-for-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.6.3.4"><a href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.6.3.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>Statement</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-for-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.6.3.5"><a href="#sec-for-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.6.3.5</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>VariableDeclarationList</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>Statement.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-for-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.6.3.6"><a href="#sec-for-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.6.3.6</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>VariableDeclarationList</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>Statement.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-for-statement-runtime-semantics-labelledevaluation">
+ <h1><span class="secnum" id="sec-13.6.3.7"><a href="#sec-for-statement-runtime-semantics-labelledevaluation"
+ title="link to this section">13.6.3.7</a></span> Runtime Semantics: LabelledEvaluation</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-runtime-semantics-labelledevaluation">13.0.7</a>, <a
+ href="#sec-do-while-statement-runtime-semantics-labelledevaluation">13.6.1.6</a>,, <a
+ href="#sec-while-statement-runtime-semantics-labelledevaluation">13.6.2.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-labelledevaluation">13.6.4.11</a>, <a
+ href="#sec-labelled-statements-runtime-semantics-labelledevaluation">13.12.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If the first <i>Expression</i> is present, then
+ <ol class="block">
+ <li>Let <i>exprRef</i> be the result of evaluating the first <i>Expression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a>(<i>exprValue</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>exprValue.</i></li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-forbodyevaluation">ForBodyEvaluation</a>(the second <i>Expression</i>, the third
+ <i>Expression</i>, <i>Statement</i>, « », <i>labelSet</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>varDcl</i> be the result of evaluating <i>VariableDeclarationList</i>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a>(<i>varDcl</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>varDcl</i>.</li>
+ <li>Return <a href="#sec-forbodyevaluation">ForBodyEvaluation</a>(the first <i>Expression</i>, the second
+ <i>Expression</i>, <i>Statement</i>, « », <i>labelSet</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>oldEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>loopEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>oldEnv</i>).</li>
+ <li>Let <i>isConst</i> be the result of performing IsConstantDeclaration of <i>LexicalDeclaration</i>.</li>
+ <li>Let <i>boundNames</i> be the BoundNames of <i>LexicalDeclaration</i>.</li>
+ <li>For each element <i>dn</i> of <i>boundNames</i> do
+ <ol class="block">
+ <li>If <i>isConst</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Perform <i>loopEnv</i>.CreateImmutableBinding(<i>dn</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Perform <i>loopEnv</i>.CreateMutableBinding(<i>dn,</i> <b>false</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above call to CreateMutableBinding will never return an
+ <a href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>loopEnv</i>.</li>
+ <li>Let <i>forDcl</i> be the result of evaluating <i>LexicalDeclaration</i>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a>(<i>forDcl</i>,<i>labelSet</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <i>forDcl</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>isConst</i> is <b>false</b>, let <i>perIterationLets</i> be <i>boundNames</i> otherwise let
+ <i>perIterationLets</i> be « ».</li>
+ <li>Let <i>bodyResult</i> be <a href="#sec-forbodyevaluation">ForBodyEvaluation</a>(the first <i>Expression</i>, the
+ second <i>Expression</i>, <i>Statement</i>, <i>perIterationLets</i>, <i>labelSet</i>).</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <i>bodyResult</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-forbodyevaluation">
+ <h1><span class="secnum" id="sec-13.6.3.8"><a href="#sec-forbodyevaluation"
+ title="link to this section">13.6.3.8</a></span> Runtime Semantics: ForBodyEvaluation( test, increment, stmt,
+ perIterationBindings, labelSet )</h1>
+
+ <p>The abstract operation ForBodyEvaluation with arguments <var>test</var>, <var>increment</var>, <var>stmt</var>,
+ <var>perIterationBindings</var>, and <var>labelSet</var> is performed as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>V</i> = <b>undefined</b>.</li>
+ <li>Let <i>status</i> be <a
+ href="#sec-createperiterationenvironment">CreatePerIterationEnvironment</a>(<i>perIterationBindings</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Repeat
+ <ol class="block">
+ <li>If <i>test</i> is not <span style="font-family: sans-serif">[empty]</span>, then
+ <ol class="block">
+ <li>Let <i>testRef</i> be the result of evaluating <i>test</i>.</li>
+ <li>Let <i>testValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>testRef</i>).</li>
+ <li>If <i>testValue</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, then
+ <ol class="block">
+ <li>If <a href="#sec-toboolean">ToBoolean</a>(<i>testValue</i>) is <b>false</b>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>V</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>testValue</i> is an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a> (<i>testValue</i>,<i>labelSet</i>) is <b>false</b>,
+ return <i>testValue.</i></li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>result</i> be the result of evaluating <i>stmt</i>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a> (<i>result</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>result</i></li>
+ <li>If <i>result</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>result</i>.[[value]].</li>
+ <li>Let <i>status</i> be <a
+ href="#sec-createperiterationenvironment">CreatePerIterationEnvironment</a>(<i>perIterationBindings</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>increment</i> is not <span style="font-family: sans-serif">[empty]</span>, then
+ <ol class="block">
+ <li>Let <i>incRef</i> be the result of evaluating <i>increment</i>.</li>
+ <li>Let <i>incValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>incRef</i>).</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a>(<i>incValue</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>incValue.</i></li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-createperiterationenvironment">
+ <h1><span class="secnum" id="sec-13.6.3.9"><a href="#sec-createperiterationenvironment"
+ title="link to this section">13.6.3.9</a></span> Runtime Semantics: CreatePerIterationEnvironment(
+ perIterationBindings )</h1>
+
+ <p>The abstract operation CreatePerIterationEnvironment with argument <var>perIterationBindings</var> is performed as
+ follows:</p>
+
+ <ol class="proc">
+ <li>If <i>perIterationBindings</i> has any elements, then
+ <ol class="block">
+ <li>Let <i>lastIterationEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>outer</i> be <i>lastIterationEnv</i>’s <a href="#sec-lexical-environments">outer environment
+ reference</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>outer</i> is not <b>null</b>.</li>
+ <li>Let <i>thisIterationEnv</i> be <a
+ href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>outer</i>).</li>
+ <li>For each element <i>bn</i> of <i>perIterationBindings</i> do,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>thisIterationEnv</i>.CreateMutableBinding(<i>bn</i>, <b>false</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Let <i>lastValue</i> be <i>lastIterationEnv</i>.GetBindingValue(<i>bn</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lastValue</i>).</li>
+ <li>Perform <i>thisIterationEnv</i>.InitializeBinding(<i>bn</i>, <i>lastValue</i>).</li>
+ </ol>
+ </li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>thisIterationEnv.</i></li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b></li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.6.4"><a href="#sec-for-in-and-for-of-statements"
+ title="link to this section">13.6.4</a></span> The <code>for</code>-<code>in</code> and
+ <code>for</code>-<code>of</code> Statements</h1>
+ </div>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.6.4.1"><a href="#sec-for-in-and-for-of-statements-static-semantics-early-errors"
+ title="link to this section">13.6.4.1</a></span> Static Semantics: Early Errors</h1>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span class="nt">LeftHandSideExpression</span> is either an <span
+ class="nt">ObjectLiteral</span> or an <span class="nt">ArrayLiteral</span> and if the lexical token sequence matched
+ by <span class="nt">LeftHandSideExpression</span> cannot be parsed with no tokens left over using <span
+ class="nt">AssignmentPattern</span> as the goal symbol.</p>
+ </li>
+ </ul>
+
+ <p>If <span class="nt">LeftHandSideExpression</span> is either an <span class="nt">ObjectLiteral</span> or an <span
+ class="nt">ArrayLiteral</span> and if the lexical token sequence matched by <span class="nt">LeftHandSideExpression</span>
+ can be parsed with no tokens left over using <span class="nt">AssignmentPattern</span> as the goal symbol then the
+ following rules are not applied. Instead, the Early Error rules for <span class="nt">AssignmentPattern</span> are
+ used.</p>
+
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span style="font-family: Times New Roman">IsValidSimpleAssignmentTarget</span> of <span
+ class="nt">LeftHandSideExpression</span> is <span class="value">false</span>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if the <span class="nt">LeftHandSideExpression</span> is <span
+ class="prod"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span> <span class="geq">:</span>
+ <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code></span> and <span
+ class="nt">Expression</span> derives a production that would produce a Syntax Error according to these rules if that
+ production is substituted for <span class="nt">LeftHandSideExpression</span>. This rule is recursively applied.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The last rule means that the other rules are applied even if parentheses surround
+ <i>Expression</i>.</p>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the BoundNames of <span class="nt">ForDeclaration</span> contains <code>"let"</code>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <span class="nt">ForDeclaration</span> also occurs in the
+ VarDeclaredNames of <span class="nt">Statement</span>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if the BoundNames of <span class="nt">ForDeclaration</span> contains any duplicate
+ entries.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-13.6.4.2"><a href="#sec-for-in-and-for-of-statements-static-semantics-boundnames"
+ title="link to this section">13.6.4.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ForDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">ForBinding</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>ForBinding</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.6.4.3"><a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels"
+ title="link to this section">13.6.4.3</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.6.4.4"><a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.6.4.4</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.6.4.5"><a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.6.4.5</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>Statement</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-isdestructuring">
+ <h1><span class="secnum" id="sec-13.6.4.6"><a href="#sec-for-in-and-for-of-statements-static-semantics-isdestructuring"
+ title="link to this section">13.6.4.6</a></span> Static Semantics: IsDestructuring</h1>
+
+ <p>See also: <a href="#sec-static-semantics-static-semantics-isdestructuring">12.3.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">ForDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">ForBinding</span></div>
+ <ol class="proc">
+ <li>Return IsDestructuring of <i>ForBinding</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ForBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ForBinding</span> <span class="geq">:</span> <span class="nt">BindingPattern</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.6.4.7"><a href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames"
+ title="link to this section">13.6.4.7</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the BoundNames of <i>ForBinding</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>Statement.</i></li>
+ <li>Return <i>names.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the BoundNames of <i>ForBinding</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>Statement.</i></li>
+ <li>Return <i>names.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.6.4.8"><a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations"
+ title="link to this section">13.6.4.8</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be a <a href="#sec-list-and-record-specification-type">List</a> containing
+ <i>ForBinding</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>Statement.</i></li>
+ <li>Return <i>declarations.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be a <a href="#sec-list-and-record-specification-type">List</a> containing
+ <i>ForBinding</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>Statement.</i></li>
+ <li>Return <i>declarations.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-runtime-semantics-bindinginitialization">
+ <h1><span class="secnum" id="sec-13.6.4.9"><a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-bindinginitialization"
+ title="link to this section">13.6.4.9</a></span> Runtime Semantics: BindingInitialization</h1>
+
+ <p>With arguments <var>value</var> and <var>environment</var>.</p>
+
+ <p>See also: <a href="#sec-identifiers-runtime-semantics-bindinginitialization">12.1.5</a>, <a
+ href="#sec-destructuring-binding-patterns-runtime-semantics-bindinginitialization">13.2.3.5</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <b>undefined</b> is passed for <i>environment</i> to indicate that a <a
+ href="#sec-putvalue">PutValue</a> operation should be used to assign the initialization value. This is the case for
+ <code>var</code> statements and the formal parameter lists of some non-strict mode functions (<a
+ href="#sec-functiondeclarationinstantiation">see 9.2.13</a>). In those cases a lexical binding is hoisted and
+ preinitialized prior to evaluation of its initializer.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ForDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">ForBinding</span></div>
+ <ol class="proc">
+ <li>Return the result of performing BindingInitialization for <i>ForBinding</i> passing <i>value</i> and
+ <i>environment</i> as the arguments.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-bindinginstantiation">
+ <h1><span class="secnum" id="sec-13.6.4.10"><a href="#sec-runtime-semantics-bindinginstantiation"
+ title="link to this section">13.6.4.10</a></span> Runtime Semantics: BindingInstantiation</h1>
+
+ <p>With argument <var>environment</var>.</p>
+
+ <div class="gp prod"><span class="nt">ForDeclaration</span> <span class="geq">:</span> <span class="nt">LetOrConst</span> <span class="nt">ForBinding</span></div>
+ <ol class="proc">
+ <li>For each element <i>name</i> of the BoundNames of <i>ForBinding</i> do
+ <ol class="block">
+ <li>If IsConstantDeclaration of <i>LetOrConst</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Perform <i>environment</i>.CreateImmutableBinding(<i>name</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Perform <i>environment</i>.CreateMutableBinding(<i>name</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above call to CreateMutableBinding will never return an
+ <a href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-runtime-semantics-labelledevaluation">
+ <h1><span class="secnum" id="sec-13.6.4.11"><a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-labelledevaluation"
+ title="link to this section">13.6.4.11</a></span> Runtime Semantics: LabelledEvaluation</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-runtime-semantics-labelledevaluation">13.0.7</a>, <a
+ href="#sec-do-while-statement-runtime-semantics-labelledevaluation">13.6.1.6</a>,, <a
+ href="#sec-while-statement-runtime-semantics-labelledevaluation">13.6.2.6</a>, <a
+ href="#sec-for-statement-runtime-semantics-labelledevaluation">13.6.3.7</a>, <a
+ href="#sec-labelled-statements-runtime-semantics-labelledevaluation">13.12.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>keyResult</i> be ForIn/OfHeadEvaluation( « », <i>Expression</i>, <span style="font-family:
+ sans-serif">enumerate</span>, <i>labelSet</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keyResult</i>).</li>
+ <li>Return ForIn/OfBodyEvaluation(<i>LeftHandSideExpression</i>, <i>Statement</i>, <i>keyResult</i>, <span
+ style="font-family: sans-serif">assignment</span>, <i>labelSet</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>keyResult</i> be ForIn/OfHeadEvaluation( « », <i>Expression</i>, <span style="font-family:
+ sans-serif">enumerate</span>, <i>labelSet</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keyResult</i>).</li>
+ <li>Return ForIn/OfBodyEvaluation(<i>ForBinding</i>, <i>Statement</i>, <i>keyResult</i>, <span style="font-family:
+ sans-serif">varBinding</span>, <i>labelSet</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>keyResult</i> be the result of performing ForIn/OfHeadEvaluation(BoundNames of <i>ForDeclaration,</i>
+ <i>Expression</i>, <span style="font-family: sans-serif">enumerate</span>, <i>labelSet</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keyResult</i>).</li>
+ <li>Return ForIn/OfBodyEvaluation(<i>ForDeclaration</i>, <i>Statement</i>, <i>keyResult</i>, <span style="font-family:
+ sans-serif">lexicalBinding</span>, <i>labelSet</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>keyResult</i> be the result of performing ForIn/OfHeadEvaluation( « »,
+ <i>AssignmentExpression</i>, <span style="font-family: sans-serif">iterate</span>, <i>labelSet</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keyResult</i>).</li>
+ <li>Return ForIn/OfBodyEvaluation(<i>LeftHandSideExpression</i>, <i>Statement</i>, <i>keyResult</i>, <span
+ style="font-family: sans-serif">assignment</span>, <i>labelSet</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>keyResult</i> be the result of performing ForIn/OfHeadEvaluation( « »,
+ <i>AssignmentExpression</i>, <span style="font-family: sans-serif">iterate</span>, <i>labelSet</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keyResult</i>).</li>
+ <li>Return ForIn/OfBodyEvaluation(<i>ForBinding</i>, <i>Statement</i>, <i>keyResult</i>, <span style="font-family:
+ sans-serif">varBinding</span>, <i>labelSet</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IterationStatement</span> <span class="geq">:</span> <code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>keyResult</i> be the result of performing ForIn/OfHeadEvaluation( BoundNames of <i>ForDeclaration</i>,
+ <i>AssignmentExpression</i>, <span style="font-family: sans-serif">iterate</span>, <i>labelSet</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keyResult</i>).</li>
+ <li>Return ForIn/OfBodyEvaluation(<i>ForDeclaration</i>, <i>Statement</i>, <i>keyResult</i>, <span style="font-family:
+ sans-serif">lexicalBinding</span>, <i>labelSet</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-forin-div-ofheadevaluation-tdznames-expr-iterationkind-labelset">
+ <h1><span class="secnum" id="sec-13.6.4.12"><a
+ href="#sec-runtime-semantics-forin-div-ofheadevaluation-tdznames-expr-iterationkind-labelset"
+ title="link to this section">13.6.4.12</a></span> Runtime Semantics: ForIn/OfHeadEvaluation ( TDZnames, expr,
+ iterationKind, labelSet)</h1>
+
+ <p>The abstract operation ForIn/OfHeadEvaluation is called with arguments <span class="nt">TDZnames</span>,
+ <var>expr</var>, <var>iterationKind</var>, and <span style="font-family: Times New Roman"><i>labelSet</i>.</span> The
+ value of <var>iterationKind</var> is either <b>enumerate</b> or <b>iterate</b>.</p>
+
+ <ol class="proc">
+ <li>Let <i>oldEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>If <i>TDZnames</i> is not an empty <a href="#sec-list-and-record-specification-type">List</a>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>TDZnames</i> has no duplicate entries.</li>
+ <li>Let <i>TDZ</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>oldEnv</i>).</li>
+ <li>For each string <i>name</i> in <i>TDZnames</i>, do
+ <ol class="block">
+ <li>Let <i>status</i> be <i>TDZ</i>.CreateMutableBinding(<i>name</i>, <b>false</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>TDZ</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>exprRef</i> be the result of evaluating the production that is <i>expr</i>.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li>If <i>exprValue</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ <ol class="block">
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a>(<i>exprValue</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>exprValue</i>.</li>
+ <li>Else, return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">break</span>, [[value]]: <span style="font-family: sans-serif">empty,</span>
+ [[target]]: <span style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+ </li>
+ <li>If <i>iterationKind</i> is <span style="font-family: sans-serif">enumerate</span>, then
+ <ol class="block">
+ <li>If <i>exprValue</i>.[[value]] is <b>null</b> or <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">break</span>, [[value]]: <span style="font-family: sans-serif">empty,</span>
+ [[target]]: <span style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+ </li>
+ <li>Let <i>obj</i> be <a href="#sec-toobject">ToObject</a>(<i>exprValue</i>).</li>
+ <li>Let <i>keys</i> be <i>obj</i>.[[Enumerate]]().</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>iterationKind</i> is <span style="font-family:
+ sans-serif">iterate</span>.</li>
+ <li>Let <i>keys</i> be <a href="#sec-getiterator">GetIterator</a>(<i>exprValue</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>keys</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a>(<i>keys</i>,<i>labelSet</i>) is <b>false</b>, return
+ <i>keys</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>keys</i>.[[type]] is <span style="font-family:
+ sans-serif">continue</span></li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">break</span>, [[value]]: <span style="font-family: sans-serif">empty</span>, [[target]]: <span
+ style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+ </li>
+ <li>Return <i>keys</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-forin-div-ofbodyevaluation-lhs-stmt-iterator-lhskind-labelset">
+ <h1><span class="secnum" id="sec-13.6.4.13"><a
+ href="#sec-runtime-semantics-forin-div-ofbodyevaluation-lhs-stmt-iterator-lhskind-labelset"
+ title="link to this section">13.6.4.13</a></span> Runtime Semantics: ForIn/OfBodyEvaluation ( lhs, stmt, iterator,
+ lhsKind, labelSet )</h1>
+
+ <p>The abstract operation ForIn/OfBodyEvaluation is called with arguments <var>lhs</var>, <var>stmt, iterator,</var>
+ <var>lhsKind</var>, and <var>labelSet.</var> The value of <var>lhsKind</var> is either <b>assignment</b>,
+ <b>varBinding</b> or <b>lexicalBinding</b>.</p>
+
+ <ol class="proc">
+ <li>Let <i>oldEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>V</i> = <b>undefined</b> .</li>
+ <li>Let <i>destructuring</i> be IsDestructuring of <i>lhs</i>.</li>
+ <li>If <i>destructuring</i> is <b>true</b> and if <i>lhsKind</i> is <span style="font-family:
+ sans-serif">assignment</span>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhs</i> is a <i>LeftHandSideExpression</i>.</li>
+ <li>Let <i>assignmentPattern</i> be the parse of the source text corresponding to <i>lhs</i> using
+ <i>AssignmentPattern</i> as the goal symbol.</li>
+ </ol>
+ </li>
+ <li>Repeat
+ <ol class="block">
+ <li>If <i>lhsKind</i> is either <span style="font-family: sans-serif">assignment</span> or <span style="font-family:
+ sans-serif">varBinding</span>, then
+ <ol class="block">
+ <li>If <i>destructuring</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>lhsRef</i> be the result of evaluating <i>lhs</i> ( it may be evaluated repeatedly).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lhsRef</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhsKind</i> is <span style="font-family:
+ sans-serif">lexicalBinding</span>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhs</i> is a <i>ForDeclaration</i>.</li>
+ <li>Let <i>iterationEnv</i> be <a
+ href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>oldEnv</i>).</li>
+ <li>Perform BindingInstantiation for <i>lhs</i> passing <i>iterationEnv</i> as the argument.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>iterationEnv</i>.</li>
+ <li>If <i>destructuring</i> is <b>false</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhs</i> binds a single name.</li>
+ <li>Let <i>lhsName</i> be the sole element of BoundNames of <i>lhs.</i></li>
+ <li>Let <i>lhsRef</i> be <a href="#sec-resolvebinding">ResolveBinding</a>(the sole element of
+ <i>lhs</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhsRef</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>nextResult</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iterator</i>).</li>
+ <li>If <i>nextResult</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <i>nextResult</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>nextResult</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>V</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>nextResult</i>).</li>
+ <li>If <i>nextValue</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <i>nextValue</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>destructuring</i> is <b>false</b>, then
+ <ol class="block">
+ <li>If <i>lhsKind</i> is <span style="font-family: sans-serif">lexicalBinding</span>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <a
+ href="#sec-initializereferencedbinding">InitializeReferencedBinding</a>(<i>lhsRef</i>,
+ <i>nextValue</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-putvalue">PutValue</a>(<i>lhsRef</i>, <i>nextValue</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>If <i>lhsKind</i> is <span style="font-family: sans-serif">assignment</span>, then
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing DestructuringAssignmentEvaluation of
+ <i>assignmentPattern</i> using <i>nextValue</i> as the argument.</li>
+ </ol>
+ </li>
+ <li>Else if <i>lhsKind</i> is <span style="font-family: sans-serif">varBinding</span>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhs</i> is a <i>ForBinding</i>.</li>
+ <li>Let <i>status</i> be the result of performing BindingInitialization for <i>lhs</i> passing
+ <i>nextValue</i> and <b>undefined</b> as the arguments.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhsKind</i> is <span style="font-family:
+ sans-serif">lexicalBinding</span>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>lhs</i> is a <i>ForDeclaration</i>.</li>
+ <li>Let <i>status</i> be the result of performing BindingInitialization for <i>lhs</i> passing
+ <i>nextValue</i> and <i>iterationEnv</i> as arguments.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <a href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>status</i> be the result of evaluating <i>stmt</i>.</li>
+ <li>If <i>status</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>status</i>.[[value]] is
+ not <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>Let <i>V</i> = <i>status</i>.[[value]].</li>
+ </ol>
+ </li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>If <a href="#sec-loopcontinues">LoopContinues</a>(<i>status</i>,<i>labelSet</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-for-in-and-for-of-statements-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.6.4.14"><a href="#sec-for-in-and-for-of-statements-runtime-semantics-evaluation"
+ title="link to this section">13.6.4.14</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ForBinding</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Let <i>bindingId</i> be StringValue of <i>BindingIdentifier.</i></li>
+ <li>Return <a href="#sec-resolvebinding">ResolveBinding</a>(<i>bindingId</i>)</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-continue-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.7"><a href="#sec-continue-statement" title="link to this section">13.7</a></span> The
+ <code>continue</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ContinueStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">continue</code> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">continue</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">;</code></div>
+ </div>
+ </div>
+
+ <section id="sec-continue-statement-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.7.1"><a href="#sec-continue-statement-static-semantics-early-errors"
+ title="link to this section">13.7.1</a></span> Static Semantics: Early Errors</h1>
+
+ <p><span class="prod"><span class="nt">ContinueStatement</span> <span class="geq">:</span> <code class="t">continue</code>
+ <code class="t">;</code></span></p>
+
+ <div class="gp prod"><span class="nt">ContinueStatement</span> <span class="geq">:</span> <code class="t">continue</code> <span class="nt">LabelIdentifier</span> <code class="t">;</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if this production is not nested, directly or indirectly (but not crossing function boundaries),
+ within an <span class="nt">IterationStatement</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-continue-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.7.2"><a href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.7.2</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">ContinueStatement</span> <span class="geq">:</span> <code class="t">continue</code> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ContinueStatement</span> <span class="geq">:</span> <code class="t">continue</code> <span class="nt">LabelIdentifier</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>If the StringValue of <i>LabelIdentifier</i> is not an element of <i>iterationSet</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-continue-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.7.3"><a href="#sec-continue-statement-runtime-semantics-evaluation"
+ title="link to this section">13.7.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ContinueStatement</span> <span class="geq">:</span> <code class="t">continue</code> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">continue</span>, [[value]]: <span style="font-family: sans-serif">empty</span>, [[target]]: <span
+ style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ContinueStatement</span> <span class="geq">:</span> <code class="t">continue</code> <span class="nt">LabelIdentifier</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>label</i> be the StringValue of <i>LabelIdentifier</i>.</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">continue</span>, [[value]]: <span style="font-family: sans-serif">empty</span>, [[target]]: <i>label</i>
+ }.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-break-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.8"><a href="#sec-break-statement" title="link to this section">13.8</a></span> The
+ <code>break</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">BreakStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">break</code> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">break</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">;</code></div>
+ </div>
+ </div>
+
+ <section id="sec-break-statement-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.8.1"><a href="#sec-break-statement-static-semantics-early-errors"
+ title="link to this section">13.8.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">BreakStatement</span> <span class="geq">:</span> <code class="t">break</code> <code class="t">;</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if this production is not nested, directly or indirectly (but not crossing function boundaries),
+ within an <span class="nt">IterationStatement</span> or a <span class="nt">SwitchStatement</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-break-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.8.2"><a href="#sec-break-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.8.2</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">BreakStatement</span> <span class="geq">:</span> <code class="t">break</code> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BreakStatement</span> <span class="geq">:</span> <code class="t">break</code> <span class="nt">LabelIdentifier</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>If the StringValue of <i>LabelIdentifier</i> is not an element of <i>labelSet</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-break-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.8.3"><a href="#sec-break-statement-runtime-semantics-evaluation"
+ title="link to this section">13.8.3</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">BreakStatement</span> <span class="geq">:</span> <code class="t">break</code> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">break</span>, [[value]]: <span style="font-family: sans-serif">empty</span>, [[target]]: <span
+ style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">BreakStatement</span> <span class="geq">:</span> <code class="t">break</code> <span class="nt">LabelIdentifier</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>label</i> be the StringValue of <i>LabelIdentifier</i>.</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">break</span>, [[value]]: <span style="font-family: sans-serif">empty</span>, [[target]]: <i>label</i>
+ }.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-return-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.9"><a href="#sec-return-statement" title="link to this section">13.9</a></span> The
+ <code>return</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ReturnStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">return</code> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">return</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A <code>return</code> statement causes a function to cease execution and return a value to
+ the caller. If <span class="nt">Expression</span> is omitted, the return value is <b>undefined</b>. Otherwise, the return
+ value is the value of <span class="nt">Expression</span>.</p>
+ </div>
+ </div>
+
+ <section id="sec-return-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.9.1"><a href="#sec-return-statement-runtime-semantics-evaluation"
+ title="link to this section">13.9.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ReturnStatement</span> <span class="geq">:</span> <code class="t">return</code> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">return</span>, [[value]]: <b>undefined</b>, [[target]]: <span style="font-family:
+ sans-serif">empty</span>}.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ReturnStatement</span> <span class="geq">:</span> <code class="t">return</code> <span class="nt">Expression</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exprValue</i>).</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">return</span>, [[value]]: <i>exprValue</i>, [[target]]: <span style="font-family:
+ sans-serif">empty</span>}.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-with-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.10"><a href="#sec-with-statement" title="link to this section">13.10</a></span> The
+ <code>with</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">WithStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>with</code> statement adds an <a href="#sec-object-environment-records">object
+ environment record</a> for a computed object to the <a href="#sec-lexical-environments">lexical environment</a> of <a
+ href="#sec-execution-contexts">the running execution context</a>. It then executes a statement using this augmented <a
+ href="#sec-lexical-environments">lexical environment</a>. Finally, it restores the original <a
+ href="#sec-lexical-environments">lexical environment</a>.</p>
+ </div>
+ </div>
+
+ <section id="sec-with-statement-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.10.1"><a href="#sec-with-statement-static-semantics-early-errors"
+ title="link to this section">13.10.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">WithStatement</span> <span class="geq">:</span> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ul>
+ <li>It is a Syntax Error if the code that matches this production is contained in <a href="#sec-strict-mode-code">strict
+ code</a>.</li>
+ <li>It is a Syntax Error if <a href="#sec-islabelledfunction">IsLabelledFunction</a>(<span class="nt">Statement</span>) is
+ <span class="value">true</span>.</li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> It is only necessary to apply the second rule if the extension specified in <a
+ href="#sec-labelled-function-declarations">B.3.2</a> is implemented.</p>
+ </div>
+ </section>
+
+ <section id="sec-with-statement-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.10.2"><a href="#sec-with-statement-static-semantics-containsduplicatelabels"
+ title="link to this section">13.10.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">WithStatement</span> <span class="geq">:</span> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-with-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.10.3"><a href="#sec-with-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.10.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">WithStatement</span> <span class="geq">:</span> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>Statement</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-with-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.10.4"><a href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.10.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">WithStatement</span> <span class="geq">:</span> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>Statement</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-with-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.10.5"><a href="#sec-with-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.10.5</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">WithStatement</span> <span class="geq">:</span> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-with-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.10.6"><a href="#sec-with-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.10.6</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">WithStatement</span> <span class="geq">:</span> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-with-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.10.7"><a href="#sec-with-statement-runtime-semantics-evaluation"
+ title="link to this section">13.10.7</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">WithStatement</span> <span class="geq">:</span> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>val</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>obj</i> be <a href="#sec-toobject">ToObject</a>(<a href="#sec-getvalue">GetValue</a>(<i>val</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>Let <i>oldEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>newEnv</i> be <a href="#sec-newobjectenvironment">NewObjectEnvironment</a>(<i>obj</i>, <i>oldEnv</i>).</li>
+ <li>Set the <i>withEnvironment</i> flag of <i>newEnv’s</i> environment record to <b>true</b>.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>newEnv</i>.</li>
+ <li>Let <i>C</i> be the result of evaluating <i>Statement</i>.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-lexical-environments">Lexical Environment</a> to <i>oldEnv</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>If <i>C</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>C</i>.[[value]] is <span
+ style="font-family: sans-serif">empty</span>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>Return <i>C</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> No matter how control leaves the embedded <i>Statement</i>, whether normally or by some
+ form of <a href="#sec-completion-record-specification-type">abrupt completion</a> or exception, the <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> is always restored to its former state.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-switch-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.11"><a href="#sec-switch-statement" title="link to this section">13.11</a></span> The
+ <code>switch</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SwitchStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">CaseBlock</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CaseBlock</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <span class="nt">DefaultClause</span><sub>[?Yield, ?Return]</sub> <span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CaseClauses</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">CaseClause</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub> <span class="nt">CaseClause</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CaseClause</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">case</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">:</code> <span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DefaultClause</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub><sub>opt</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-switch-statement-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.11.1"><a href="#sec-switch-statement-static-semantics-early-errors"
+ title="link to this section">13.11.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span> <code class="t">}</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the LexicallyDeclaredNames of <span class="nt">CaseClauses</span> contains any duplicate
+ entries.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the LexicallyDeclaredNames of <span class="nt">CaseClauses</span> also occurs
+ in the VarDeclaredNames of <span class="nt">CaseClauses</span>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-switch-statement-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.11.2"><a href="#sec-switch-statement-static-semantics-containsduplicatelabels"
+ title="link to this section">13.11.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">SwitchStatement</span> <span class="geq">:</span> <code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">CaseBlock</span></div>
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>CaseBlock</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the first <i>CaseClauses</i> is present, then
+ <ol class="block">
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of the first <i>CaseClauses</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>DefaultClause</i> with argument <i>labelSet.</i></li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>If the second <i>CaseClauses</i> is not present, return <b>false</b>.</li>
+ <li>Return ContainsDuplicateLabels of the second <i>CaseClauses</i> with argument <i>labelSet</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>CaseClauses</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsDuplicateLabels of <i>CaseClause</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return ContainsDuplicateLabels of <i>StatementList</i> with argument
+ <i>labelSet</i>.</li>
+ <li>Else return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return ContainsDuplicateLabels of <i>StatementList</i> with argument
+ <i>labelSet</i>.</li>
+ <li>Else return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-switch-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.11.3"><a href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.11.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">SwitchStatement</span> <span class="geq">:</span> <code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">CaseBlock</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>CaseBlock</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the first <i>CaseClauses</i> is present, then
+ <ol class="block">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of the first <i>CaseClauses</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>DefaultClause</i> with argument
+ <i>labelSet.</i></li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>If the second <i>CaseClauses</i> is not present, return <b>false</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of the second <i>CaseClauses</i> with argument <i>labelSet</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>CaseClauses</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>CaseClause</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return ContainsUndefinedBreakTarget of <i>StatementList</i> with argument
+ <i>labelSet</i>.</li>
+ <li>Else return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return ContainsUndefinedBreakTarget of <i>StatementList</i> with argument
+ <i>labelSet</i>.</li>
+ <li>Else return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-switch-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.11.4"><a href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.11.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>,<a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">SwitchStatement</span> <span class="geq">:</span> <code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">CaseBlock</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>CaseBlock</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the first <i>CaseClauses</i> is present, then
+ <ol class="block">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of the first <i>CaseClauses</i> with arguments
+ <i>iterationSet</i> and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>DefaultClause</i> with arguments
+ <i>iterationSet</i> and « »<i>.</i></li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>If the second <i>CaseClauses</i> is not present, return <b>false</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of the second <i>CaseClauses</i> with arguments <i>iterationSet</i> and
+ « ».</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>CaseClauses</i> with arguments
+ <i>iterationSet</i> and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>CaseClause</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return ContainsUndefinedContinueTarget of <i>StatementList</i> with arguments
+ <i>iterationSet</i> and « ».</li>
+ <li>Else return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return ContainsUndefinedContinueTarget of <i>StatementList</i> with arguments
+ <i>iterationSet</i> and « ».</li>
+ <li>Else return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-switch-statement-static-semantics-lexicallydeclarednames">
+ <h1><span class="secnum" id="sec-13.11.5"><a href="#sec-switch-statement-static-semantics-lexicallydeclarednames"
+ title="link to this section">13.11.5</a></span> Static Semantics: LexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallydeclarednames">13.12.6</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallydeclarednames">14.1.14</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">14.2.10</a>, <a
+ href="#sec-scripts-static-semantics-lexicallydeclarednames">15.1.3</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallydeclarednames">15.2.1.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the first <i>CaseClauses</i> is present, let <i>names</i> be the LexicallyDeclaredNames of the first
+ <i>CaseClauses</i>.</li>
+ <li>Else let <i>names</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Append to <i>names</i> the elements of the LexicallyDeclaredNames of the <i>DefaultClause.</i></li>
+ <li>If the second <i>CaseClauses</i> is not present, return <i>names</i>.</li>
+ <li>Else return the result of appending to <i>names</i> the elements of the LexicallyDeclaredNames of the second
+ <i>CaseClauses</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be LexicallyDeclaredNames of <i>CaseClauses</i>.</li>
+ <li>Append to <i>names</i> the elements of the LexicallyDeclaredNames of <i>CaseClause.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the LexicallyDeclaredNames of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the LexicallyDeclaredNames of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-switch-statement-static-semantics-lexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.11.6"><a href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">13.11.6</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a>, <a
+ href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations">15.2.1.12</a>, <a
+ href="#sec-exports-static-semantics-lexicallyscopeddeclarations">15.2.3.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the first <i>CaseClauses</i> is present, let <i>declarations</i> be the LexicallyScopedDeclarations of the first
+ <i>CaseClauses</i>.</li>
+ <li>Else let <i>declarations</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Append to <i>declarations</i> the elements of the LexicallyScopedDeclarations of the <i>DefaultClause.</i></li>
+ <li>If the second <i>CaseClauses</i> is not present, return <i>declarations</i>.</li>
+ <li>Else return the result of appending to <i>declarations</i> the elements of the LexicallyScopedDeclarations of the
+ second <i>CaseClauses</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be LexicallyScopedDeclarations of <i>CaseClauses</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the LexicallyScopedDeclarations of <i>CaseClause.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the LexicallyScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the LexicallyScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-switch-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.11.7"><a href="#sec-switch-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.11.7</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">SwitchStatement</span> <span class="geq">:</span> <code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">CaseBlock</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>CaseBlock</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the first <i>CaseClauses</i> is present, let <i>names</i> be the VarDeclaredNames of the first
+ <i>CaseClauses</i>.</li>
+ <li>Else let <i>names</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of the <i>DefaultClause.</i></li>
+ <li>If the second <i>CaseClauses</i> is not present, return <i>names</i>.</li>
+ <li>Else return the result of appending to <i>names</i> the elements of the VarDeclaredNames of the second
+ <i>CaseClauses</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be VarDeclaredNames of <i>CaseClauses</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>CaseClause.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the VarDeclaredNames of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the VarDeclaredNames of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-switch-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.11.8"><a href="#sec-switch-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.11.8</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">SwitchStatement</span> <span class="geq">:</span> <code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">CaseBlock</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>CaseBlock</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the first <i>CaseClauses</i> is present, let <i>declarations</i> be the VarScopedDeclarations of the first
+ <i>CaseClauses</i>.</li>
+ <li>Else let <i>declarations</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of the <i>DefaultClause.</i></li>
+ <li>If the second <i>CaseClauses</i> is not present, return <i>declarations</i>.</li>
+ <li>Else return the result of appending to <i>declarations</i> the elements of the VarScopedDeclarations of the second
+ <i>CaseClauses</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>CaseClauses</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>CaseClause.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the VarScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If the <i>StatementList</i> is present, return the VarScopedDeclarations of <i>StatementList</i>.</li>
+ <li>Else return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-caseblockevaluation">
+ <h1><span class="secnum" id="sec-13.11.9"><a href="#sec-runtime-semantics-caseblockevaluation"
+ title="link to this section">13.11.9</a></span> Runtime Semantics: CaseBlockEvaluation</h1>
+
+ <p>With argument <var>input</var>.</p>
+
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>V</i> = <b>undefined</b>.</li>
+ <li>Let <i>A</i> be the <a href="#sec-list-and-record-specification-type">List</a> of <i>CaseClause</i> items in
+ <i>CaseClauses</i>, in source text order.</li>
+ <li>Let <i>searching</i> be <b>true</b>.</li>
+ <li>Repeat, for each <i>CaseClause</i>, <i>C</i>, in <i>A</i>
+ <ol class="block">
+ <li>If <i>searching</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>clauseSelector</i> be the result of CaseSelectorEvaluation of <i>C</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>clauseSelector</i>).</li>
+ <li>Let <i>matched</i> be the result of performing Strict Equality Comparison <i>input</i> ===
+ <i>clauseSelector</i>.</li>
+ <li>If <i>matched</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>searching</i> to <b>false</b>.</li>
+ <li>If <i>C</i> has a <i>StatementList</i>, then
+ <ol class="block">
+ <li>Let <i>V</i> be the result of evaluating <i>C</i>’s <i>StatementList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>V</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else <i>searching</i> is <b>false</b>,
+ <ol class="block">
+ <li>If <i>C</i> has a <i>StatementList</i>, then
+ <ol class="block">
+ <li>Let <i>R</i> be the result of evaluating <i>C</i>’s <i>StatementList</i>.</li>
+ <li>If <i>R</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>R</i>.[[value]].</li>
+ <li>If <i>R</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>R</i>.[[type]], [[value]]:
+ <i>V</i>, [[target]]: <i>R</i>.[[target]]}.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>V</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>V</i> = <b>undefined</b>.</li>
+ <li>Let <i>A</i> be the list of <i>CaseClause</i> items in the first <i>CaseClauses</i>, in source text order. If the
+ first <i>CaseClauses</i> is not present <i>A</i> is « ».</li>
+ <li>Let <i>found</i> be <b>false</b>.</li>
+ <li>Repeat letting <i>C</i> be in order each <i>CaseClause</i> in <i>A</i>
+ <ol class="block">
+ <li>If <i>found</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>clauseSelector</i> be the result of CaseSelectorEvaluation of <i>C</i>.</li>
+ <li>If <i>clauseSelector</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>If <i>clauseSelector</i>.[[value]] is <span style="font-family: sans-serif">empty</span>, return <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>clauseSelector</i>.[[type]],
+ [[value]]: <b>undefined</b>, [[target]]: <i>clauseSelector</i>.[[target]]}.</li>
+ <li>Else, return <i>clauseSelector</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>found</i> be the result of performing Strict Equality Comparison <i>input</i> ===
+ <i>clauseSelector</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>found</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>R</i> be the result of evaluating <i>CaseClause</i> <i>C</i>.</li>
+ <li>If <i>R</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>R</i>.[[value]].</li>
+ <li>If <i>R</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>R</i>.[[type]], [[value]]:
+ <i>V</i>, [[target]]: <i>R</i>.[[target]]}.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>foundInB</i> be <b>false</b>.</li>
+ <li>Let <i>B</i> be a new <a href="#sec-list-and-record-specification-type">List</a> containing the <i>CaseClause</i>
+ items in the second <i>CaseClauses</i>, in source text order. If the second <i>CaseClauses</i> is not present <i>B</i>
+ is « ».</li>
+ <li>If <i>found</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Repeat, letting <i>C</i> be in order each <i>CaseClause</i> in <i>B</i>
+ <ol class="block">
+ <li>If <i>foundInB</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>clauseSelector</i> be the result of CaseSelectorEvaluation of <i>C</i>.</li>
+ <li>If <i>clauseSelector</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ then
+ <ol class="block">
+ <li>If <i>clauseSelector</i>.[[value]] is <span style="font-family: sans-serif">empty</span>, return <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]:
+ <i>clauseSelector</i>.[[type]], [[value]]: <b>undefined</b>, [[target]]:
+ <i>clauseSelector</i>.[[target]]}.</li>
+ <li>Else, return <i>clauseSelector</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>foundInB</i> be the result of performing Strict Equality Comparison <i>input</i> ===
+ <i>clauseSelector</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>foundInB</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>R</i> be the result of evaluating <i>CaseClause C</i>.</li>
+ <li>If <i>R</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>R</i>.[[value]].</li>
+ <li>If <i>R</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>R</i>.[[type]], [[value]]:
+ <i>V</i>, [[target]]: <i>R</i>.[[target]]}.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>foundInB</i> is <b>true</b>, return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>V</i>).</li>
+ <li>Let <i>R</i> be the result of evaluating <i>DefaultClause</i>.</li>
+ <li>If <i>R</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>R</i>.[[value]].</li>
+ <li>If <i>R</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>R</i>.[[type]], [[value]]: <i>V</i>,
+ [[target]]: <i>R</i>.[[target]]}.</li>
+ <li>Repeat, letting <i>C</i> be in order each <i>CaseClause</i> in <i>B</i> (NOTE this is another complete iteration of
+ the second <i>CaseClauses</i>)
+ <ol class="block">
+ <li>Let <i>R</i> be the result of evaluating <i>CaseClause</i> <i>C</i>.</li>
+ <li>If <i>R</i>.[[value]] is not <span style="font-family: sans-serif">empty</span>, let <i>V</i> =
+ <i>R</i>.[[value]].</li>
+ <li>If <i>R</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>R</i>.[[type]], [[value]]: <i>V</i>,
+ [[target]]: <i>R</i>.[[target]]}.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>V</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-caseselectorevaluation">
+ <h1><span class="secnum" id="sec-13.11.10"><a href="#sec-runtime-semantics-caseselectorevaluation"
+ title="link to this section">13.11.10</a></span> Runtime Semantics: CaseSelectorEvaluation</h1>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Return <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> CaseSelectorEvaluation does not execute the associated <i>StatementList</i>. It simply
+ evaluates the <i>Expression</i> and returns the value, which the <i>CaseBlock</i> algorithm uses to determine which
+ <i>StatementList</i> to start executing.</p>
+ </div>
+ </section>
+
+ <section id="sec-switch-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.11.11"><a href="#sec-switch-statement-runtime-semantics-evaluation"
+ title="link to this section">13.11.11</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">SwitchStatement</span> <span class="geq">:</span> <code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">CaseBlock</span></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>switchValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>switchValue</i>).</li>
+ <li>Let <i>oldEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>blockEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>oldEnv</i>).</li>
+ <li>Perform <a href="#sec-blockdeclarationinstantiation">BlockDeclarationInstantiation</a>(<i>CaseBlock,</i>
+ <i>blockEnv</i>).</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>blockEnv</i>.</li>
+ <li>Let <i>R</i> be the result of performing CaseBlockEvaluation of <i>CaseBlock</i> with argument
+ <i>switchValue</i>.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <i>R</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> No matter how control leaves the <i>SwitchStatement</i> the <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> is always restored to its former state.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>StatementList</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>StatementList</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-labelled-statements">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.12"><a href="#sec-labelled-statements" title="link to this section">13.12</a></span>
+ Labelled Statements</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LabelledStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">:</code> <span class="nt">LabelledItem</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LabelledItem</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A <span class="nt">Statement</span> may be prefixed by a label. Labelled statements are
+ only used in conjunction with labelled <code>break</code> and <code>continue</code> statements. ECMAScript has no
+ <code>goto</code> statement. A <span class="nt">Statement</span> can be part of a <span
+ class="nt">LabelledStatement</span>, which itself can be part of a <span class="nt">LabelledStatement</span>, and so on.
+ The labels introduced this way are collectively referred to as the “current label set” when describing the
+ semantics of individual statements. A <span class="nt">LabelledStatement</span> has no semantic meaning other than the
+ introduction of a label to a <i>label set</i>.</p>
+ </div>
+ </div>
+
+ <section id="sec-labelled-statements-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.12.1"><a href="#sec-labelled-statements-static-semantics-early-errors"
+ title="link to this section">13.12.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ul>
+ <li>It is a Syntax Error if any source text matches this rule.</li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An alternative definition for this rule is provided in <a
+ href="#sec-labelled-function-declarations">B.3.2</a>.</p>
+ </div>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.12.2"><a href="#sec-labelled-statements-static-semantics-containsduplicatelabels"
+ title="link to this section">13.12.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Let <i>label</i> be the StringValue of <i>LabelIdentifier</i>.</li>
+ <li>If <i>label</i> is an element of <i>labelSet</i>, return <b>true</b>.</li>
+ <li>Let <i>newLabelSet</i> be a copy of <i>labelSet</i> with <i>label</i> appended.</li>
+ <li>Return ContainsDuplicateLabels of <i>LabelledItem</i> with argument <i>newLabelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.12.3"><a href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.12.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Let <i>label</i> be the StringValue of <i>LabelIdentifier</i>.</li>
+ <li>Let <i>newLabelSet</i> be a copy of <i>labelSet</i> with <i>label</i> appended.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>LabelledItem</i> with argument <i>newLabelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.12.4"><a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.12.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Let <i>label</i> be the StringValue of <i>LabelIdentifier</i>.</li>
+ <li>Let <i>newLabelSet</i> be a copy of <i>labelSet</i> with <i>label</i> appended.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>LabelledItem</i> with arguments <i>iterationSet</i> and
+ <i>newLabelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-islabelledfunction">
+ <h1><span class="secnum" id="sec-13.12.5"><a href="#sec-islabelledfunction" title="link to this section">13.12.5</a></span>
+ Static Semantics: IsLabelledFunction ( stmt )</h1>
+
+ <p>The abstract operation IsLabelledFunction with argument <var>stmt</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>stmt</i> is not a <i>LabelledStatement</i>, return <b>false</b>.</li>
+ <li>Let <i>item</i> be the <i>LabelledItem</i> component of <i>stmt</i>.</li>
+ <li>If <i>item</i> is <span class="prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span
+ class="nt">FunctionDeclaration</span></span> , return <b>true</b>.</li>
+ <li>Let <i>subStmt</i> be the <i>Statement</i> component of <i>item</i>.</li>
+ <li>Return IsLabelledFunction(<i>subStmt</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-lexicallydeclarednames">
+ <h1><span class="secnum" id="sec-13.12.6"><a href="#sec-labelled-statements-static-semantics-lexicallydeclarednames"
+ title="link to this section">13.12.6</a></span> Static Semantics: LexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallydeclarednames">13.11.5</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallydeclarednames">14.1.14</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">14.2.10</a>, <a
+ href="#sec-scripts-static-semantics-lexicallydeclarednames">15.1.3</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallydeclarednames">15.2.1.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return the LexicallyDeclaredNames of <i>LabelledItem</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return BoundNames of <i>FunctionDeclaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.12.7"><a href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">13.12.7</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a>, <a
+ href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations">15.2.1.12</a>, <a
+ href="#sec-exports-static-semantics-lexicallyscopeddeclarations">15.2.3.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return the LexicallyScopedDeclarations of <i>LabelledItem</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>FunctionDeclaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-toplevellexicallydeclarednames">
+ <h1><span class="secnum" id="sec-13.12.8"><a href="#sec-labelled-statements-static-semantics-toplevellexicallydeclarednames"
+ title="link to this section">13.12.8</a></span> Static Semantics: TopLevelLexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-toplevellexicallydeclarednames">13.1.7</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-toplevellexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.12.9"><a
+ href="#sec-labelled-statements-static-semantics-toplevellexicallyscopeddeclarations"
+ title="link to this section">13.12.9</a></span> Static Semantics: TopLevelLexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-toplevellexicallyscopeddeclarations">13.1.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-toplevelvardeclarednames">
+ <h1><span class="secnum" id="sec-13.12.10"><a href="#sec-labelled-statements-static-semantics-toplevelvardeclarednames"
+ title="link to this section">13.12.10</a></span> Static Semantics: TopLevelVarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-toplevelvardeclarednames">13.1.9</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return the TopLevelVarDeclaredNames of <i>LabelledItem</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If <i>Statement</i> is <span class="prod"><span class="nt">Statement</span> <span class="geq">:</span> <span
+ class="nt">LabelledStatement</span></span> , return TopLevelVarDeclaredNames of <i>Statement</i>.</li>
+ <li>Return VarDeclaredNames of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return BoundNames of <i>FunctionDeclaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-toplevelvarscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.12.11"><a href="#sec-labelled-statements-static-semantics-toplevelvarscopeddeclarations"
+ title="link to this section">13.12.11</a></span> Static Semantics: TopLevelVarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-toplevelvarscopeddeclarations">13.1.10</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return the TopLevelVarScopedDeclarations of <i>LabelledItem</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If <i>Statement</i> is <span class="prod"><span class="nt">Statement</span> <span class="geq">:</span> <span
+ class="nt">LabelledStatement</span></span> , return TopLevelVarScopedDeclarations of <i>Statement</i>.</li>
+ <li>Return VarScopedDeclarations of <i>Statement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>FunctionDeclaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.12.12"><a href="#sec-labelled-statements-static-semantics-vardeclarednames"
+ title="link to this section">13.12.12</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>LabelledItem</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.12.13"><a href="#sec-labelled-statements-static-semantics-varscopeddeclarations"
+ title="link to this section">13.12.13</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>LabelledItem</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-runtime-semantics-labelledevaluation">
+ <h1><span class="secnum" id="sec-13.12.14"><a href="#sec-labelled-statements-runtime-semantics-labelledevaluation"
+ title="link to this section">13.12.14</a></span> Runtime Semantics: LabelledEvaluation</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-runtime-semantics-labelledevaluation">13.0.7</a>, <a
+ href="#sec-do-while-statement-runtime-semantics-labelledevaluation">13.6.1.6</a>,, <a
+ href="#sec-while-statement-runtime-semantics-labelledevaluation">13.6.2.6</a>, <a
+ href="#sec-for-statement-runtime-semantics-labelledevaluation">13.6.3.7</a>, <a
+ href="#sec-for-in-and-for-of-statements-runtime-semantics-labelledevaluation">13.6.4.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Let <i>label</i> be the StringValue of <i>LabelIdentifier</i>.</li>
+ <li>Append <i>label</i> as an element of <i>labelSet</i>.</li>
+ <li>Let <i>stmtResult</i> be the result of performing LabelledEvaluation of <i>LabelledItem</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>stmtResult</i>.[[type]] is <span style="font-family: sans-serif">break</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>stmtResult</i>.[[target]], <i>label</i>), then
+ <ol class="block">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>stmtResult</i>.[[value]]).</li>
+ </ol>
+ </li>
+ <li>Return <i>stmtResult</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>If <i>Statement</i> is either a <i>LabelledStatement</i> or a <i>BreakableStatement</i>, then
+ <ol class="block">
+ <li>Return the result of performing LabelledEvaluation of <i>Statement</i> with argument <i>labelSet</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Return the result of evaluating <i>Statement</i>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span
+ class="nt">FunctionDeclaration</span></span></p>
+
+ <ol class="proc">
+ <li>Return the result of evaluating <i>FunctionDeclaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-statements-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.12.15"><a href="#sec-labelled-statements-runtime-semantics-evaluation"
+ title="link to this section">13.12.15</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">LabelledStatement</span> <span class="geq">:</span> <span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ <ol class="proc">
+ <li>Let <i>newLabelSet</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return the result of performing LabelledEvaluation of <i>LabelledItem</i> with argument <i>newLabelSet</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-throw-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.13"><a href="#sec-throw-statement" title="link to this section">13.13</a></span> The
+ <code>throw</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ThrowStatement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">throw</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+ </div>
+
+ <section id="sec-throw-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.13.1"><a href="#sec-throw-statement-runtime-semantics-evaluation"
+ title="link to this section">13.13.1</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ThrowStatement</span> <span class="geq">:</span> <code class="t">throw</code> <span class="nt">Expression</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>Expression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exprValue</i>).</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">throw</span>, [[value]]: <i>exprValue</i>, [[target]]: <span style="font-family:
+ sans-serif">empty</span>}.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-try-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.14"><a href="#sec-try-statement" title="link to this section">13.14</a></span> The
+ <code>try</code> Statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TryStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">try</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub> <span class="nt">Catch</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">try</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub> <span class="nt">Finally</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">try</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub> <span class="nt">Catch</span><sub>[?Yield, ?Return]</sub> <span class="nt">Finally</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Catch</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span><sub>[?Yield]</sub> <code class="t">)</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Finally</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">finally</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CatchParameter</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>try</code> statement encloses a block of code in which an exceptional condition
+ can occur, such as a runtime error or a <code>throw</code> statement. The <code>catch</code> clause provides the
+ exception-handling code. When a catch clause catches an exception, its <i>CatchParameter</i> is bound to that
+ exception.</p>
+ </div>
+ </div>
+
+ <section id="sec-try-statement-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-13.14.1"><a href="#sec-try-statement-static-semantics-early-errors"
+ title="link to this section">13.14.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <span class="nt">CatchParameter</span> also occurs in the
+ LexicallyDeclaredNames of <span class="nt">Block</span>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <span class="nt">CatchParameter</span> also occurs in the
+ VarDeclaredNames of <span class="nt">Block</span>.</p>
+ </li>
+ </ul>
+
+ <p class="Note"><i>NOTE	An alternative static semantics for this production is given in <a
+ href="#sec-variablestatements-in-catch-blocks">B.3.5</a>.</i></p>
+ </section>
+
+ <section id="sec-try-statement-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-13.14.2"><a href="#sec-try-statement-static-semantics-containsduplicatelabels"
+ title="link to this section">13.14.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-module-semantics-static-semantics-containsduplicatelabels">15.2.1.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span></div>
+ <ol class="proc">
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>Block</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsDuplicateLabels of <i>Catch</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>Block</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsDuplicateLabels of <i>Finally</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>Block</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>Catch</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsDuplicateLabels of <i>Finally</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ol class="proc">
+ <li>Return ContainsDuplicateLabels of <i>Block</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-try-statement-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-13.14.3"><a href="#sec-try-statement-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">13.14.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget">15.2.1.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>Block</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>Catch</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>Block</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>Finally</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>Block</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>Catch</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>Finally</i> with argument <i>labelSet.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedBreakTarget of <i>Block</i> with argument <i>labelSet.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-try-statement-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-13.14.4"><a href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">13.14.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>, <a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget">15.2.1.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>Block</i> with arguments <i>iterationSet</i>
+ and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>Catch</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>Block</i> with arguments <i>iterationSet</i>
+ and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>Finally</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>Block</i> with arguments <i>iterationSet</i>
+ and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>Catch</i> with arguments <i>iterationSet</i>
+ and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>Finally</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ol class="proc">
+ <li>Return ContainsUndefinedContinueTarget of <i>Block</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-try-statement-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-13.14.5"><a href="#sec-try-statement-static-semantics-vardeclarednames"
+ title="link to this section">13.14.5</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be VarDeclaredNames of <i>Block</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>Catch.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be VarDeclaredNames of <i>Block</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>Finally.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be VarDeclaredNames of <i>Block</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>Catch.</i></li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>Finally.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ol class="proc">
+ <li>Return the VarDeclaredNames of <i>Block</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-try-statement-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-13.14.6"><a href="#sec-try-statement-static-semantics-varscopeddeclarations"
+ title="link to this section">13.14.6</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>Block</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>Catch.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>Block</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>Finally.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>Block</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>Catch.</i></li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>Finally.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ol class="proc">
+ <li>Return the VarScopedDeclarations of <i>Block</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-catchclauseevaluation">
+ <h1><span class="secnum" id="sec-13.14.7"><a href="#sec-runtime-semantics-catchclauseevaluation"
+ title="link to this section">13.14.7</a></span> Runtime Semantics: CatchClauseEvaluation</h1>
+
+ <p>with parameter <var>thrownValue</var></p>
+
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ol class="proc">
+ <li>Let <i>oldEnv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>catchEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>oldEnv</i>).</li>
+ <li>For each element <i>argName</i> of the BoundNames of <i>CatchParameter</i>, do
+ <ol class="block">
+ <li>Perform <i>catchEnv</i>.CreateMutableBinding(<i>argName</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above call to CreateMutableBinding will never return an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>catchEnv</i>.</li>
+ <li>Let <i>status</i> be the result of performing BindingInitialization for <i>CatchParameter</i> passing
+ <i>thrownValue</i> and <i>catchEnv</i> as arguments.</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>B</i> be the result of evaluating <i>Block</i>.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>oldEnv</i>.</li>
+ <li>If <i>B</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>B</i>.[[value]] is <span
+ style="font-family: sans-serif">empty</span>, let <i>B</i> be <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>Return <i>B</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> No matter how control leaves the <i>Block</i> the <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> is always restored to its former state.</p>
+ </div>
+ </section>
+
+ <section id="sec-try-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.14.8"><a href="#sec-try-statement-runtime-semantics-evaluation"
+ title="link to this section">13.14.8</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span></div>
+ <ol class="proc">
+ <li>Let <i>B</i> be the result of evaluating <i>Block</i>.</li>
+ <li>If <i>B</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>B</i>.[[value]] is <span
+ style="font-family: sans-serif">empty</span>, let <i>B</i> be <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>If <i>B</i>.[[type]] is not <span style="font-family: sans-serif">throw</span>, return <i>B</i>.</li>
+ <li>Return the result of performing CatchClauseEvaluation of <i>Catch</i> with parameter <i>B</i>.[[value]].</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>B</i> be the result of evaluating <i>Block</i>.</li>
+ <li>If <i>B</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>B</i>.[[value]] is <span
+ style="font-family: sans-serif">empty</span>, let <i>B</i> be <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>Let <i>F</i> be the result of evaluating <i>Finally</i>.</li>
+ <li>If <i>F</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, return <i>B</i>.</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Let <i>B</i> be the result of evaluating <i>Block</i>.</li>
+ <li>If <i>B</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>B</i>.[[value]] is <span
+ style="font-family: sans-serif">empty</span>, let <i>B</i> be <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>If <i>B</i>.[[type]] is <span style="font-family: sans-serif">throw</span>, then
+ <ol class="block">
+ <li>Let <i>C</i> be the result of performing CatchClauseEvaluation of <i>Catch</i> with parameter
+ <i>B</i>.[[value]].</li>
+ </ol>
+ </li>
+ <li>Else <i>B</i>.[[type]] is not <span style="font-family: sans-serif">throw</span><b>,</b>
+ <ol class="block">
+ <li>Let <i>C</i> be <i>B</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>F</i> be the result of evaluating <i>Finally</i>.</li>
+ <li>If <i>F</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, return <i>C</i>.</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-debugger-statement">
+ <div class="front">
+ <h1><span class="secnum" id="sec-13.15"><a href="#sec-debugger-statement" title="link to this section">13.15</a></span> The
+ <code>debugger</code> statement</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DebuggerStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">debugger</code> <code class="t">;</code></div>
+ </div>
+ </div>
+
+ <section id="sec-debugger-statement-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-13.15.1"><a href="#sec-debugger-statement-runtime-semantics-evaluation"
+ title="link to this section">13.15.1</a></span> Runtime Semantics: Evaluation</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Evaluating the <span class="nt">DebuggerStatement</span> production may allow an
+ implementation to cause a breakpoint when run under a debugger. If a debugger is not present or active this statement has
+ no observable effect.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">DebuggerStatement</span> <span class="geq">:</span> <code class="t">debugger</code> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>If an implementation defined debugging facility is available and enabled, then
+ <ol class="block">
+ <li>Perform an implementation defined debugging action.</li>
+ <li>Let <i>result</i> be an implementation defined <a href="#sec-completion-record-specification-type">Completion</a>
+ value.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </li>
+ <li>Return <i>result.</i></li>
+ </ol>
+ </section>
+ </section>
+</section>
+
+<section id="sec-ecmascript-language-functions-and-classes">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14"><a href="#sec-ecmascript-language-functions-and-classes"
+ title="link to this section">14</a></span> ECMAScript Language: Functions and Classes</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Various ECMAScript language elements cause the creation of ECMAScript function objects (<a
+ href="#sec-ordinarycreatefromconstructor">9.1.14</a>). Evaluation of such functions starts with the execution of their
+ [[Call]] internal method (<a href="#sec-ecmascript-function-objects-call-thisargument-argumentslist">9.2.2</a>).</p>
+ </div>
+ </div>
+
+ <section id="sec-function-definitions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.1"><a href="#sec-function-definitions" title="link to this section">14.1</a></span>
+ Function Definitions</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FunctionDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">function</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><span class="grhsannot">[+Default]</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FunctionExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">function</code> <span class="nt">BindingIdentifier</span><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">StrictFormalParameters</span><sub>[Yield, GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FormalParameters</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">FormalParameterList</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FormalParameterList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FunctionRestParameter</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">FormalsList</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">FormalsList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">FunctionRestParameter</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FormalsList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FormalParameter</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">FormalsList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">FormalParameter</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FunctionRestParameter</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingRestElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FormalParameter</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FunctionBody</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FunctionStatementList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FunctionStatementList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">StatementList</span><sub>[?Yield, Return]</sub><sub>opt</sub></div>
+ </div>
+ </div>
+
+ <section id="sec-directive-prologues-and-the-use-strict-directive">
+ <h1><span class="secnum" id="sec-14.1.1"><a href="#sec-directive-prologues-and-the-use-strict-directive"
+ title="link to this section">14.1.1</a></span> Directive Prologues and the Use Strict Directive</h1>
+
+ <p>A Directive Prologue is the longest sequence of <span class="nt">ExpressionStatement</span> productions occurring as the
+ initial <span class="nt">StatementListItem</span> productions of a <span class="nt">FunctionBody</span> or a <span
+ class="nt">ScriptBody</span> and where each <span class="nt">ExpressionStatement</span> in the sequence consists entirely of
+ a <span class="nt">StringLiteral</span> token followed by a semicolon<span style="font-family: Times New Roman">.</span> The
+ semicolon may appear explicitly or may be inserted by <a href="#sec-automatic-semicolon-insertion">automatic semicolon
+ insertion</a>. A Directive Prologue may be an empty sequence.</p>
+
+ <p>A Use Strict Directive is an <span class="nt">ExpressionStatement</span> in a Directive Prologue whose <span
+ class="nt">StringLiteral</span> is either the exact code unit sequences <code>"use</code> <code>strict"</code> or
+ <code>'use</code> <code>strict'</code>. A Use Strict Directive may not contain an <span
+ class="nt">EscapeSequence</span> or <span class="nt">LineContinuation</span>.</p>
+
+ <p>A Directive Prologue may contain more than one Use Strict Directive. However, an implementation may issue a warning if
+ this occurs.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <i>ExpressionStatement</i> productions of a Directive Prologue are evaluated normally
+ during evaluation of the containing production. Implementations may define implementation specific meanings for
+ <i>ExpressionStatement</i> productions which are not a Use Strict Directive and which occur in a Directive Prologue. If an
+ appropriate notification mechanism exists, an implementation should issue a warning if it encounters in a Directive
+ Prologue an <i>ExpressionStatement</i> that is not a Use Strict Directive and which does not have a meaning defined by the
+ implementation.</p>
+ </div>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-14.1.2"><a href="#sec-function-definitions-static-semantics-early-errors"
+ title="link to this section">14.1.2</a></span> Static Semantics: Early Errors</h1>
+
+ <p><span class="prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code>
+ <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code
+ class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></span><br><span
+ class="prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code
+ class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span
+ class="nt">FunctionBody</span> <code class="t">}</code></span><br><span class="prod"><span
+ class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <span
+ class="nt">BindingIdentifier</span><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code
+ class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></span></p>
+
+ <ul>
+ <li>
+ <p>If the source code matching this production is <a href="#sec-strict-mode-code">strict code</a>, the Early Error rules
+ for <span class="prod"><span class="nt">StrictFormalParameters</span> <span class="geq">:</span> <span
+ class="nt">FormalParameters</span></span> are applied.</p>
+ </li>
+
+ <li>
+ <p>If the source code matching this production is <a href="#sec-strict-mode-code">strict code</a>, it is a Syntax Error
+ if <i>BindingIdentifier</i> is the <i>IdentifierName</i> <code>eval</code> or the <i>IdentifierName</i>
+ <code>arguments</code>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the <span style="font-family: sans-serif">BoundNames</span> of
+ <i>FormalParameters</i> also occurs in the <span style="font-family: sans-serif">LexicallyDeclaredNames</span> of
+ <i>FunctionBody</i>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <i>FormalParameters</i> Contains <i>SuperProperty</i> is <b><i>true</i></b>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <i>FunctionBody</i> Contains <i>SuperProperty</i> is <b><i>true</i></b>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <i>FormalParameters</i> Contains <i>SuperCall</i> is <b><i>true</i></b>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <i>FunctionBody</i> Contains <i>SuperCall</i> is <b><i>true</i></b>.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The LexicallyDeclaredNames of a <i>FunctionBody</i> does not include identifiers bound
+ using var or function declarations.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">StrictFormalParameters</span> <span class="geq">:</span> <span class="nt">FormalParameters</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if BoundNames of <i>FormalParameters</i> contains any duplicate elements.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">FormalParameters</span> <span class="geq">:</span> <span class="nt">FormalParameterList</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if IsSimpleParameterList of <i>FormalParameterList</i> is <b>false</b> and BoundNames of
+ <i>FormalParameterList</i> contains any duplicate elements.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Multiple occurrences of the same <i>BindingIdentifier</i> in a <i>FormalParameterList</i>
+ is only allowed for non-strict mode functions and generator functions that have simple parameter lists.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">FunctionBody</span> <span class="geq">:</span> <span class="nt">FunctionStatementList</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the LexicallyDeclaredNames of <i>FunctionStatementList</i> contains any duplicate
+ entries.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the LexicallyDeclaredNames of <i>FunctionStatementList</i> also occurs in the
+ VarDeclaredNames of <i>FunctionStatementList</i>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsDuplicateLabels of <i>FunctionStatementList</i> with argument « » is
+ <b>true</b>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsUndefinedBreakTarget of <i>FunctionStatementList</i> with argument « » is
+ <b>true</b>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsUndefinedContinueTarget of <i>FunctionStatementList</i> with arguments «
+ » and « » is <b>true</b>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-14.1.3"><a href="#sec-function-definitions-static-semantics-boundnames"
+ title="link to this section">14.1.3</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingIdentifier</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return «<code>"*default*"</code>».</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <code>"*default*"</code> is used within this specification as a synthetic name for
+ hoistable anonymous functions that are defined using export declarations.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">FormalParameters</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>FormalsList</i>.</li>
+ <li>Append to <i>names</i> the BoundNames of <i>FunctionRestParameter.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalsList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>FormalsList</i>.</li>
+ <li>Append to <i>names</i> the elements of BoundNames of <i>FormalParameter.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-contains">
+ <h1><span class="secnum" id="sec-14.1.4"><a href="#sec-function-definitions-static-semantics-contains"
+ title="link to this section">14.1.4</a></span> Static Semantics: Contains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-static-semantic-rules">5.3</a>, <a
+ href="#sec-object-initializer-static-semantics-contains">12.2.5.3</a>, <a
+ href="#sec-static-semantics-static-semantics-contains">12.3.1.1</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-contains">14.2.3</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-contains">14.4.4</a>, <a
+ href="#sec-class-definitions-static-semantics-contains">14.5.4</a></p>
+
+ <div class="gp prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+
+ <p><span class="prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code>
+ <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span
+ class="nt">FunctionBody</span> <code class="t">}</code></span><br><span class="prod"><span
+ class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <span
+ class="nt">BindingIdentifier</span><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code
+ class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></span></p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Static semantic rules that depend upon substructure generally do not look into function
+ definitions.</p>
+ </div>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-containsexpression">
+ <h1><span class="secnum" id="sec-14.1.5"><a href="#sec-function-definitions-static-semantics-containsexpression"
+ title="link to this section">14.1.5</a></span> Static Semantics: ContainsExpression</h1>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-static-semantics-containsexpression">13.2.3.2</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-containsexpression">14.2.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">FormalParameters</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Return ContainsExpression of <i>FormalsList</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalsList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>If ContainsExpression of <i>FormalsList</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsExpression of <i>FormalParameter</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-expectedargumentcount">
+ <h1><span class="secnum" id="sec-14.1.6"><a href="#sec-function-definitions-static-semantics-expectedargumentcount"
+ title="link to this section">14.1.6</a></span> Static Semantics: ExpectedArgumentCount</h1>
+
+ <p>See also: <a href="#sec-arrow-function-definitions-static-semantics-expectedargumentcount">14.2.6</a>, <a
+ href="#sec-method-definitions-static-semantics-expectedargumentcount">14.3.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">FormalParameters</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return 0.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Return 0.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Return the ExpectedArgumentCount of <i>FormalsList</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The ExpectedArgumentCount of a <i>FormalParameterList</i> is the number of
+ <i>FormalParameters</i> to the left of either the rest parameter or the first <i>FormalParameter</i> with an Initializer.
+ A <i>FormalParameter</i> without an initializer is allowed after the first parameter with an initializer but such
+ parameters are considered to be optional with <b>undefined</b> as their default value.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">FormalsList</span> <span class="geq">:</span> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>If HasInitializer of <i>FormalParameter</i> is <b>true</b> return 0</li>
+ <li>Return 1.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalsList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>Let <i>count</i> be the ExpectedArgumentCount of <i>FormalsList.</i></li>
+ <li>If HasInitializer of <i>FormalsList</i> is <b>true</b> or HasInitializer of <i>FormalParameter</i> is <b>true</b>,
+ return <i>count</i>.</li>
+ <li>Return <i>count</i>+1.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-hasinitializer">
+ <h1><span class="secnum" id="sec-14.1.7"><a href="#sec-function-definitions-static-semantics-hasinitializer"
+ title="link to this section">14.1.7</a></span> Static Semantics: HasInitializer</h1>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-static-semantics-hasinitializer">13.2.3.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-hasinitializer">14.2.7</a>.</p>
+
+ <div class="gp prod"><span class="nt">FormalParameters</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>If HasInitializer of <i>FormalsList</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalsList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>If HasInitializer of <i>FormalsList</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return HasInitializer of <i>FormalParameter</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-hasname">
+ <h1><span class="secnum" id="sec-14.1.8"><a href="#sec-function-definitions-static-semantics-hasname"
+ title="link to this section">14.1.8</a></span> Static Semantics: HasName</h1>
+
+ <p>See also: <a href="#sec-arrow-function-definitions-static-semantics-hasname">14.2.8</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-hasname">14.4.7</a>, <a
+ href="#sec-class-definitions-static-semantics-hasname">14.5.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isanonymousfunctiondefinition">
+ <h1><span class="secnum" id="sec-14.1.9"><a href="#sec-isanonymousfunctiondefinition"
+ title="link to this section">14.1.9</a></span> Static Semantics: IsAnonymousFunctionDefinition ( production )</h1>
+
+ <p>The abstract operation IsAnonymousFunctionDefinition determines if its argument is a function definition that does not
+ bind a name. The argument <var>production</var> is the result of parsing an <span class="nt">AssignmentExpression</span> or
+ <span class="nt">Initializer</span>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If IsFunctionDefinition of <i>production</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>Let <i>hasName</i> be the result of HasName of <i>production</i>.</li>
+ <li>If <i>hasName</i> is <b>true</b>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-isconstantdeclaration">
+ <h1><span class="secnum" id="sec-14.1.10"><a href="#sec-function-definitions-static-semantics-isconstantdeclaration"
+ title="link to this section">14.1.10</a></span> Static Semantics: IsConstantDeclaration</h1>
+
+ <p>See also: <a href="#sec-let-and-const-declarations-static-semantics-isconstantdeclaration">13.2.1.3</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isconstantdeclaration">14.4.8</a>, <a
+ href="#sec-class-definitions-static-semantics-isconstantdeclaration">14.5.7</a>, <a
+ href="#sec-exports-static-semantics-isconstantdeclaration">15.2.3.7</a>.</p>
+
+ <p><span class="prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code>
+ <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code
+ class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></span><br><span
+ class="prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code
+ class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span
+ class="nt">FunctionBody</span> <code class="t">}</code></span></p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-14.1.11"><a href="#sec-function-definitions-static-semantics-isfunctiondefinition"
+ title="link to this section">14.1.11</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-issimpleparameterlist">
+ <h1><span class="secnum" id="sec-14.1.12"><a href="#sec-function-definitions-static-semantics-issimpleparameterlist"
+ title="link to this section">14.1.12</a></span> Static Semantics: IsSimpleParameterList</h1>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-static-semantics-issimpleparameterlist">13.2.3.4</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-hasname">14.2.8</a></p>
+
+ <div class="gp prod"><span class="nt">FormalParameters</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalsList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>If IsSimpleParameterList of <i>FormalsList</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>Return IsSimpleParameterList of <i>FormalParameter</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameter</span> <span class="geq">:</span> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>Return IsSimpleParameterList of <i>BindingElement</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-isstrict">
+ <h1><span class="secnum" id="sec-14.1.13"><a href="#sec-function-definitions-static-semantics-isstrict"
+ title="link to this section">14.1.13</a></span> Static Semantics: IsStrict</h1>
+
+ <p>See also: <a href="#sec-scripts-static-semantics-isstrict">15.1.2</a>, <a
+ href="#sec-module-semantics-static-semantics-isstrict">15.2.1.9</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If this <i>FunctionStatementList</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if
+ <i>StatementList</i> is <a href="#sec-strict-mode-code">strict code</a>, return <b>true</b>. Otherwise, return
+ <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-lexicallydeclarednames">
+ <h1><span class="secnum" id="sec-14.1.14"><a href="#sec-function-definitions-static-semantics-lexicallydeclarednames"
+ title="link to this section">14.1.14</a></span> Static Semantics: LexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallydeclarednames">13.11.5</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallydeclarednames">13.12.6</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">14.2.10</a>, <a
+ href="#sec-scripts-static-semantics-lexicallydeclarednames">15.1.3</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallydeclarednames">15.2.1.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return TopLevelLexicallyDeclaredNames of <i>StatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-lexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-14.1.15"><a href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">14.1.15</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a>, <a
+ href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations">15.2.1.12</a>, <a
+ href="#sec-exports-static-semantics-lexicallyscopeddeclarations">15.2.3.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return the TopLevelLexicallyScopedDeclarations of <i>StatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-14.1.16"><a href="#sec-function-definitions-static-semantics-vardeclarednames"
+ title="link to this section">14.1.16</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return TopLevelVarDeclaredNames of <i>StatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-14.1.17"><a href="#sec-function-definitions-static-semantics-varscopeddeclarations"
+ title="link to this section">14.1.17</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return the TopLevelVarScopedDeclarations of <i>StatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-runtime-semantics-evaluatebody">
+ <h1><span class="secnum" id="sec-14.1.18"><a href="#sec-function-definitions-runtime-semantics-evaluatebody"
+ title="link to this section">14.1.18</a></span> Runtime Semantics: EvaluateBody</h1>
+
+ <p>With parameter <var>functionObject</var>.</p>
+
+ <p>See also: <a href="#sec-arrow-function-definitions-runtime-semantics-evaluatebody">14.2.14</a>, <a
+ href="#sec-generator-function-definitions-runtime-semantics-evaluatebody">14.4.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionBody</span> <span class="geq">:</span> <span class="nt">FunctionStatementList</span></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>FunctionStatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-function-definitions-runtime-semantics-iteratorbindinginitialization">
+ <h1><span class="secnum" id="sec-14.1.19"><a
+ href="#sec-function-definitions-runtime-semantics-iteratorbindinginitialization"
+ title="link to this section">14.1.19</a></span> Runtime Semantics: IteratorBindingInitialization</h1>
+
+ <p>With parameters <var>iteratorRecord</var> and <var>environment</var>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When <b>undefined</b> is passed for <var>environment</var> it indicates that a <a
+ href="#sec-putvalue">PutValue</a> operation should be used to assign the initialization value. This is the case for formal
+ parameter lists of non-strict mode functions. In that case the formal parameter bindings are preinitialized in order to
+ deal with the possibility of multiple parameters with the same name.</p>
+ </div>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-runtime-semantics-iteratorbindinginitialization">13.2.3.6</a>, <a
+ href="#sec-arrow-function-definitions-runtime-semantics-iteratorbindinginitialization">14.2.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">FormalParameters</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameterList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FunctionRestParameter</span></div>
+ <ol class="proc">
+ <li>Let <i>restIndex</i> be the result of performing IteratorBindingInitialization for <i>FormalsList</i> using
+ <i>iteratorRecord</i>, and <i>environment</i> as the arguments.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>restIndex</i>).</li>
+ <li>Return the result of performing IteratorBindingInitialization for <i>FunctionRestParameter</i> using
+ <i>iteratorRecord</i> and <i>environment</i> as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalsList</span> <span class="geq">:</span> <span class="nt">FormalsList</span> <code class="t">,</code> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of performing IteratorBindingInitialization for <i>FormalsList</i> using
+ <i>iteratorRecord</i> and <i>environment</i> as the arguments.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return the result of performing IteratorBindingInitialization for <i>FormalParameter</i> using <i>iteratorRecord</i>
+ and <i>environment</i> as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FormalParameter</span> <span class="geq">:</span> <span class="nt">BindingElement</span></div>
+ <ol class="proc">
+ <li>If HasInitializer of <i>BindingElement</i> is <b>false</b>, return the result of performing
+ IteratorBindingInitialization for <i>BindingElement</i> using <i>iteratorRecord</i> and <i>environment</i> as the
+ arguments.</li>
+ <li>Let <i>currentContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>originalEnv</i> be the <a href="#sec-execution-contexts">VariableEnvironment</a> of <i>currentContext</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The <a href="#sec-execution-contexts">VariableEnvironment</a> and <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> of <i>currentContext</i> are the same.</li>
+ <li>Let <i>paramVarEnv</i> be <a
+ href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>originalEnv</i>).</li>
+ <li>Set the <a href="#sec-execution-contexts">VariableEnvironment</a> of <i>currentContext</i> to <i>paramVarEnv</i>.</li>
+ <li>Set the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>currentContext</i> to <i>paramVarEnv</i>.</li>
+ <li>Let <i>result</i> be the result of performing IteratorBindingInitialization for <i>BindingElement</i> using
+ <i>iteratorRecord</i> and <i>environment</i> as the arguments.</li>
+ <li>Set the <a href="#sec-execution-contexts">VariableEnvironment</a> of <i>currentContext</i> to <i>originalEnv</i>.</li>
+ <li>Set the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>currentContext</i> to <i>originalEnv</i>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+
+ <p>The new environment record created in step 5 is only used if the <i><span style="font-family: Times New
+ Roman">BindElement</span>’</i>s <span class="nt">Initializer</span> contains a direct eval.</p>
+ </section>
+
+ <section id="sec-function-definitions-runtime-semantics-instantiatefunctionobject">
+ <h1><span class="secnum" id="sec-14.1.20"><a href="#sec-function-definitions-runtime-semantics-instantiatefunctionobject"
+ title="link to this section">14.1.20</a></span> Runtime Semantics: InstantiateFunctionObject</h1>
+
+ <p>With parameter <var>scope</var>.</p>
+
+ <p>See also: <a href="#sec-generator-function-definitions-runtime-semantics-instantiatefunctionobject">14.4.12</a>.</p>
+
+ <div class="gp prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the <i>FunctionDeclaration</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if its
+ <i>FunctionBody</i> is <a href="#sec-strict-mode-code">strict code</a>, let <i>strict</i> be <b>true</b>. Otherwise
+ let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>name</i> be StringValue of <i>BindingIdentifier.</i></li>
+ <li>Let <i>F</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<span style="font-family: sans-serif">Normal</span>,
+ <i>FormalParameters</i>, <i>FunctionBody, scope</i>, <i>strict</i>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>F</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>F</i>, <i>name</i>).</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the <i>FunctionDeclaration</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if its
+ <i>FunctionBody</i> is <a href="#sec-strict-mode-code">strict code</a>, let <i>strict</i> be <b>true</b>. Otherwise
+ let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>F</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<span style="font-family: sans-serif">Normal</span>,
+ <i>FormalParameters</i>, <i>FunctionBody, scope</i>, <i>strict</i>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>F</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>F</i>, <code>"default"</code>).</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An anonymous <i>FunctionDeclaration</i> can only occur as part of an <code>export
+ default</code> declaration.</p>
+ </div>
+ </section>
+
+ <section id="sec-function-definitions-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-14.1.21"><a href="#sec-function-definitions-runtime-semantics-evaluation"
+ title="link to this section">14.1.21</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+ <pre class="Note">NOTE	An alternative semantics is provided in <a href="#sec-block-level-function-declarations-web-legacy-compatibility-semantics">B.3.3</a>.</pre>
+ <div class="gp prod"><span class="nt">FunctionDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the <i>FunctionExpression</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if its
+ <i>FunctionBody</i> is <a href="#sec-strict-mode-code">strict code</a>, let <i>strict</i> be <b>true</b>. Otherwise
+ let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>scope</i> be the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <a
+ href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>closure</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<span style="font-family:
+ sans-serif">Normal</span>, <i>FormalParameters</i>, <i>FunctionBody, scope</i>, <i>strict</i>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>closure</i>).</li>
+ <li>Return <i>closure</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">FunctionExpression</span> <span class="geq">:</span> <code class="t">function</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the <i>FunctionExpression</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if its
+ <i>FunctionBody</i> is <a href="#sec-strict-mode-code">strict code</a>, let <i>strict</i> be <b>true</b>. Otherwise
+ let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>runningContext</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-lexical-environments">Lexical Environment</a>.</li>
+ <li>Let <i>funcEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>runningContext</i>
+ ).</li>
+ <li>Let <i>envRec</i> be <i>funcEnv’s</i> environment record.</li>
+ <li>Let <i>name</i> be StringValue of <i>BindingIdentifier</i>.</li>
+ <li>Perfrom <i>envRec.</i>CreateImmutableBinding(<i>name</i>).</li>
+ <li>Let <i>closure</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<span style="font-family:
+ sans-serif">Normal</span>, <i>FormalParameters</i>, <i>FunctionBody, funcEnv</i>, <i>strict</i>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>closure</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>closure</i>, <i>name</i>).</li>
+ <li>Perform <i>envRec</i> InitializeBinding(<i>name,</i> <i>closure</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>closure</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The <i>BindingIdentifier</i> in a <i>FunctionExpression</i> can be referenced from
+ inside the <i>FunctionExpression's</i> <i>FunctionBody</i> to allow the function to call itself recursively. However,
+ unlike in a <i>FunctionDeclaration</i>, the <i>BindingIdentifier</i> in a <i>FunctionExpression</i> cannot be referenced
+ from and does not affect the scope enclosing the <i>FunctionExpression</i>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> A <code>prototype</code> property is automatically created for every function defined
+ using a <i>FunctionDeclaration</i> or <i>FunctionExpression</i>, to allow for the possibility that the function will be
+ used as a constructor.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-arrow-function-definitions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.2"><a href="#sec-arrow-function-definitions"
+ title="link to this section">14.2</a></span> Arrow Function Definitions</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArrowFunction</span><sub>[In, Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ArrowParameters</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">=></code> <span class="nt">ConciseBody</span><sub>[?In]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArrowParameters</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ConciseBody</span><sub>[In]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[lookahead ≠ { ]</span> <span class="nt">AssignmentExpression</span><sub>[?In]</sub></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <h2>Supplemental Syntax</h2>
+
+ <p>When the production</p>
+
+ <p><span class="nt">ArrowParameters</span><sub>[Yield]</sub> <b>:</b> <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub></p>
+
+ <p>is recognized the following grammar is used to refine the interpretation of <span class="prod"><span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span> <span class="geq">:</span></span></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ArrowFormalParameters</span><sub>[Yield, GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">StrictFormalParameters</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">)</code></div>
+ </div>
+ </div>
+
+ <section id="sec-arrow-function-definitions-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-14.2.1"><a href="#sec-arrow-function-definitions-static-semantics-early-errors"
+ title="link to this section">14.2.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">ArrowFunction</span> <span class="geq">:</span> <span class="nt">ArrowParameters</span> <code class="t">=></code> <span class="nt">ConciseBody</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <i>ArrowParameters</i> also occurs in the
+ LexicallyDeclaredNames of <i>ConciseBody</i>.</p>
+ </li>
+ </ul>
+
+ <p><span class="nt">ArrowParameters</span><sub>[Yield]</sub> <b>:</b> <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub></p>
+
+ <ul>
+ <li>
+ <p>If the <sub>[Yield]</sub> grammar parameter is present on <i>ArrowParameters</i>, it is a Syntax Error if the
+ lexical token sequence matched by <i>CoverParenthesizedExpressionAndArrowParameterList</i><sub>[?Yield]</sub> cannot be
+ parsed with no tokens left over using <i>ArrowFormalParameters</i><sub>[Yield, GeneratorParameter]</sub> as the goal
+ symbol.</p>
+ </li>
+
+ <li>
+ <p>If the <sub>[Yield]</sub> grammar parameter is not present on <i>ArrowParameters</i>, it is a Syntax Error if the
+ lexical token sequence matched by <i>CoverParenthesizedExpressionAndArrowParameterList</i><sub>[?Yield]</sub> cannot be
+ parsed with no tokens left over using <i>ArrowFormalParameters</i> as the goal symbol.</p>
+ </li>
+
+ <li>
+ <p>All early errors rules for <i>ArrowFormalParameters</i> and its derived productions also apply to CoveredFormalsList
+ of <i>CoverParenthesizedExpressionAndArrowParameterList</i><sub>[?Yield]</sub>.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>yield</code> operator cannot be used within expressions that are part of an
+ <i>ArrowFormalParameters</i><span style="font-family: sans-serif">.</span></p>
+ </div>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-14.2.2"><a href="#sec-arrow-function-definitions-static-semantics-boundnames"
+ title="link to this section">14.2.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>formals</i> be CoveredFormalsList of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return the BoundNames of <i>formals</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-contains">
+ <h1><span class="secnum" id="sec-14.2.3"><a href="#sec-arrow-function-definitions-static-semantics-contains"
+ title="link to this section">14.2.3</a></span> Static Semantics: Contains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-static-semantic-rules">5.3</a>, <a
+ href="#sec-object-initializer-static-semantics-contains">12.2.5.3</a>, <a
+ href="#sec-static-semantics-static-semantics-contains">12.3.1.1</a>, <a
+ href="#sec-function-definitions-static-semantics-contains">14.1.4</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-contains">14.4.4</a>, <a
+ href="#sec-class-definitions-static-semantics-contains">14.5.4</a></p>
+
+ <div class="gp prod"><span class="nt">ArrowFunction</span> <span class="geq">:</span> <span class="nt">ArrowParameters</span> <code class="t">=></code> <span class="nt">ConciseBody</span></div>
+ <ol class="proc">
+ <li>If <i>symbol</i> is not one of <i>NewTarget</i>, <i>SuperProperty, SuperCall,</i> <code>super</code> or
+ <code>this</code>, return <b>false</b>.</li>
+ <li>If <i>ArrowParameters</i> Contains <i>symbol</i> is <b>true</b>, return <b>true</b>;</li>
+ <li>Return <i>ConciseBody</i> Contains <i>symbol</i> .</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <span style="font-family: sans-serif">Normally,</span> Contains <span style="font-family:
+ sans-serif">does not look inside most function forms However,</span> Contains is used to detect <code>new.target</code>,
+ <code>this</code>, and <code>super</code> usage within an <i>ArrowFunction</i>.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>formals</i> be CoveredFormalsList of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return <i>formals</i> Contains <i>symbol</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-containsexpression">
+ <h1><span class="secnum" id="sec-14.2.4"><a href="#sec-arrow-function-definitions-static-semantics-containsexpression"
+ title="link to this section">14.2.4</a></span> Static Semantics: ContainsExpression</h1>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-static-semantics-containsexpression">13.2.3.2</a>, <a
+ href="#sec-function-definitions-static-semantics-containsexpression">14.1.5</a>.</p>
+
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></span></p>
+
+ <ol class="proc">
+ <li>Let <i>formals</i> be CoveredFormalsList of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return the ContainsExpression of <i>formals</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-coveredformalslist">
+ <h1><span class="secnum" id="sec-14.2.5"><a href="#sec-static-semantics-coveredformalslist"
+ title="link to this section">14.2.5</a></span> Static Semantics: CoveredFormalsList</h1>
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <i>BindingIdentifier</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">...</code> <span class="nt">BindingIdentifier</span> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span> <code class="t">,</code> <code class="t">...</code> <span class="nt">BindingIdentifier</span> <code class="t">)</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>If the <sub>[Yield]</sub> grammar parameter is present for
+ <i>CoverParenthesizedExpressionAndArrowParameterList</i><sub>[Yield]</sub> return the result of parsing the lexical
+ token stream matched by <i>CoverParenthesizedExpressionAndArrowParameterList</i><sub>[Yield]</sub> using
+ <i>ArrowFormalParameters</i><sub>[Yield, GeneratorParameter]</sub> as the goal symbol.</li>
+ <li>If the <sub>[Yield]</sub> grammar parameter is not present for
+ <i>CoverParenthesizedExpressionAndArrowParameterList</i><sub>[Yield]</sub> return the result of parsing the lexical
+ token stream matched by <i>CoverParenthesizedExpressionAndArrowParameterList</i> using <i>ArrowFormalParameters</i> as
+ the goal symbol.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-expectedargumentcount">
+ <h1><span class="secnum" id="sec-14.2.6"><a href="#sec-arrow-function-definitions-static-semantics-expectedargumentcount"
+ title="link to this section">14.2.6</a></span> Static Semantics: ExpectedArgumentCount</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-containsexpression">14.1.5</a>,<a
+ href="#sec-method-definitions-static-semantics-expectedargumentcount">14.3.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return 1.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>formals</i> be CoveredFormalsList of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return the ExpectedArgumentCount of <i>formals</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-hasinitializer">
+ <h1><span class="secnum" id="sec-14.2.7"><a href="#sec-arrow-function-definitions-static-semantics-hasinitializer"
+ title="link to this section">14.2.7</a></span> Static Semantics: HasInitializer</h1>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-static-semantics-hasinitializer">13.2.3.3</a>, <a
+ href="#sec-function-definitions-static-semantics-hasinitializer">14.1.7</a>.</p>
+
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>formals</i> be CoveredFormalsList of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return the HasInitializer of <i>formals</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-hasname">
+ <h1><span class="secnum" id="sec-14.2.8"><a href="#sec-arrow-function-definitions-static-semantics-hasname"
+ title="link to this section">14.2.8</a></span> Static Semantics: HasName</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-hasname">14.1.8</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-hasname">14.4.7</a>, <a
+ href="#sec-class-definitions-static-semantics-hasname">14.5.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">ArrowFunction</span> <span class="geq">:</span> <span class="nt">ArrowParameters</span> <code class="t">=></code> <span class="nt">ConciseBody</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-issimpleparameterlist">
+ <h1><span class="secnum" id="sec-14.2.9"><a href="#sec-arrow-function-definitions-static-semantics-issimpleparameterlist"
+ title="link to this section">14.2.9</a></span> Static Semantics: IsSimpleParameterList</h1>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-static-semantics-issimpleparameterlist">13.2.3.4</a>, <a
+ href="#sec-function-definitions-static-semantics-issimpleparameterlist">14.1.12</a>.</p>
+
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>formals</i> be CoveredFormalsList of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return the IsSimpleParameterList of <i>formals</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">
+ <h1><span class="secnum" id="sec-14.2.10"><a href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames"
+ title="link to this section">14.2.10</a></span> Static Semantics: LexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallydeclarednames">13.11.5</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallydeclarednames">13.12.6</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallydeclarednames">14.1.14</a>, <a
+ href="#sec-scripts-static-semantics-lexicallydeclarednames">15.1.3</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallydeclarednames">15.2.1.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">ConciseBody</span> <span class="geq">:</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.2.11"><a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">14.2.11</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a>, <a
+ href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations">15.2.1.12</a>, <a
+ href="#sec-exports-static-semantics-lexicallyscopeddeclarations">15.2.3.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">ConciseBody</span> <span class="geq">:</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </div>
+
+ <section>
+ <h1>Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">ConciseBody</span> <span class="geq">:</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-arrow-function-definitions-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-14.2.12"><a href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations"
+ title="link to this section">14.2.12</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">ConciseBody</span> <span class="geq">:</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-runtime-semantics-iteratorbindinginitialization">
+ <h1><span class="secnum" id="sec-14.2.13"><a
+ href="#sec-arrow-function-definitions-runtime-semantics-iteratorbindinginitialization"
+ title="link to this section">14.2.13</a></span> Runtime Semantics: IteratorBindingInitialization</h1>
+
+ <p>With parameters <var>iteratorRecord</var> and <var>environment</var>.</p>
+
+ <p>See also: <a href="#sec-destructuring-binding-patterns-runtime-semantics-iteratorbindinginitialization">13.2.3.6</a>, <a
+ href="#sec-function-definitions-runtime-semantics-iteratorbindinginitialization">14.1.19</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When <b>undefined</b> is passed for <var>environment</var> it indicates that a <a
+ href="#sec-putvalue">PutValue</a> operation should be used to assign the initialization value. This is the case for formal
+ parameter lists of non-strict mode functions. In that case the formal parameter bindings are preinitialized in order to
+ deal with the possibility of multiple parameters with the same name.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">BindingIdentifier</span></div>
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>iteratorRecord</i>.[[done]] is <b>false.</b></li>
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, set <i>iteratorRecord</i>.[[done]] to <b>true</b></li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>v</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>true</b>, let <i>v</i> be <b>undefined</b>.</li>
+ <li>Return the result of performing BindingInitialization for <i>BindingIdentifier</i> using <i>v</i> and
+ <i>environment</i> as the arguments.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ArrowParameters</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>formals</i> be CoveredFormalsList of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return the result of performing IteratorBindingInitialization of <i>formals</i> with arguments <i>iteratorRecord</i>
+ and <i>environment</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-runtime-semantics-evaluatebody">
+ <h1><span class="secnum" id="sec-14.2.14"><a href="#sec-arrow-function-definitions-runtime-semantics-evaluatebody"
+ title="link to this section">14.2.14</a></span> Runtime Semantics: EvaluateBody</h1>
+
+ <p>With parameter <var>functionObject</var>.</p>
+
+ <p>See also: <a href="#sec-function-definitions-runtime-semantics-evaluatebody">14.1.18</a>, <a
+ href="#sec-generator-function-definitions-runtime-semantics-evaluatebody">14.4.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">ConciseBody</span> <span class="geq">:</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>exprValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exprValue</i>).</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">return</span>, [[value]]: <i>exprValue</i>, [[target]]: <span style="font-family:
+ sans-serif">empty</span>}.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arrow-function-definitions-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-14.2.15"><a href="#sec-arrow-function-definitions-runtime-semantics-evaluation"
+ title="link to this section">14.2.15</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ArrowFunction</span> <span class="geq">:</span> <span class="nt">ArrowParameters</span> <code class="t">=></code> <span class="nt">ConciseBody</span></div>
+ <ol class="proc">
+ <li>If the code of this <i>ArrowFunction</i> is contained in <a href="#sec-strict-mode-code">strict mode code</a> or if
+ any of the conditions in <a href="#sec-strict-mode-code">10.2.1</a> apply, let <i>strict</i> be <b>true</b>.
+ Otherwise let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>scope</i> be the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <a
+ href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>parameters</i> be CoveredFormalsList of <i>ArrowParameters</i>.</li>
+ <li>Let <i>closure</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<span style="font-family:
+ sans-serif">Arrow</span>, <i>parameters</i>, <i>ConciseBody, scope</i>, <i>strict</i>).</li>
+ <li>Return <i>closure</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An <i>ArrowFunction</i> does not define local bindings for <code>arguments</code>,
+ <code>super</code>, <code>this</code>, or <code>new.target</code>. Any reference to <code>arguments</code>,
+ <code>super</code>, or <code>this</code> within an <i>ArrowFunction</i> must resolve to a binding in a lexically enclosing
+ environment. Typically this will be the Function Environment of an immediately enclosing function. Even though an
+ <i>ArrowFunction</i> may contain references to <code>super</code>, the function object created in step 4 is not made into
+ a method by performing <a href="#sec-makemethod">MakeMethod</a>. An <i>ArrowFunction</i> that references
+ <code>super</code> is always contained within a non-<i>ArrowFunction</i> and the necessary state to implement
+ <code>super</code> is accessible via the <i>scope</i> that is captured by the function object of the
+ <i>ArrowFunction</i>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-method-definitions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.3"><a href="#sec-method-definitions" title="link to this section">14.3</a></span> Method
+ Definitions</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MethodDefinition</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><span class="nt">GeneratorMethod</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">get</code> <span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">set</code> <span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PropertySetParameterList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FormalParameter</span></div>
+ </div>
+ </div>
+
+ <section id="sec-method-definitions-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-14.3.1"><a href="#sec-method-definitions-static-semantics-early-errors"
+ title="link to this section">14.3.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <i>StrictFormalParameters</i> also occurs in the
+ LexicallyDeclaredNames of <i>FunctionBody</i>.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if BoundNames of <i>PropertySetParameterList</i> contains any duplicate elements.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <i>PropertySetParameterList</i> also occurs in the
+ LexicallyDeclaredNames of <i>FunctionBody</i>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-method-definitions-static-semantics-computedpropertycontains">
+ <h1><span class="secnum" id="sec-14.3.2"><a href="#sec-method-definitions-static-semantics-computedpropertycontains"
+ title="link to this section">14.3.2</a></span> Static Semantics: ComputedPropertyContains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-computedpropertycontains">12.2.5.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-computedpropertycontains">14.4.3</a>, <a
+ href="#sec-class-definitions-static-semantics-computedpropertycontains">14.5.5</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MethodDefinition</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">get</code> <span class="nt">PropertyName</span> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return the result of ComputedPropertyContains for <i>PropertyName</i> with argument <i>symbol</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-method-definitions-static-semantics-expectedargumentcount">
+ <h1><span class="secnum" id="sec-14.3.3"><a href="#sec-method-definitions-static-semantics-expectedargumentcount"
+ title="link to this section">14.3.3</a></span> Static Semantics: ExpectedArgumentCount</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-containsexpression">14.1.5</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-expectedargumentcount">14.2.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">PropertySetParameterList</span> <span class="geq">:</span> <span class="nt">FormalParameter</span></div>
+ <ol class="proc">
+ <li>If HasInitializer of <i>FormalParameter</i> is <b>true</b> return 0</li>
+ <li>Return 1.</li>
+ </ol>
+ </section>
+
+ <section id="sec-method-definitions-static-semantics-hascomputedpropertykey">
+ <h1><span class="secnum" id="sec-14.3.4"><a href="#sec-method-definitions-static-semantics-hascomputedpropertykey"
+ title="link to this section">14.3.4</a></span> Static Semantics: HasComputedPropertyKey</h1>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-hascomputedpropertykey">12.2.5.4</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-hascomputedpropertykey">14.4.5</a></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MethodDefinition</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">get</code> <span class="nt">PropertyName</span> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return HasComputedPropertyKey of <i>PropertyName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-method-definitions-static-semantics-hasdirectsuper">
+ <h1><span class="secnum" id="sec-14.3.5"><a href="#sec-method-definitions-static-semantics-hasdirectsuper"
+ title="link to this section">14.3.5</a></span> Static Semantics: HasDirectSuper</h1>
+
+ <p>See also: <a href="#sec-generator-function-definitions-static-semantics-hasdirectsuper">14.4.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If <i>StrictFormalParameters</i> Contains <i>SuperCall</i> is <b>true</b>, return <b>true.</b></li>
+ <li>Return <i>FunctionBody</i> Contains <i>SuperCall</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <code class="t">get</code> <span class="nt">PropertyName</span> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <i>FunctionBody</i> Contains <i>SuperCall</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If <i>PropertySetParameterList</i> Contains <i>SuperCall</i> is <b>true</b>, return <b>true.</b></li>
+ <li>Return <i>FunctionBody</i> Contains <i>SuperCall</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-method-definitions-static-semantics-propname">
+ <h1><span class="secnum" id="sec-14.3.6"><a href="#sec-method-definitions-static-semantics-propname"
+ title="link to this section">14.3.6</a></span> Static Semantics: PropName</h1>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-propname">12.2.5.6</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-propname">14.4.10</a>, <a
+ href="#sec-class-definitions-static-semantics-propname">14.5.12</a></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MethodDefinition</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">get</code> <span class="nt">PropertyName</span> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return PropName of <i>PropertyName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-needssuperbinding">
+ <h1><span class="secnum" id="sec-14.3.7"><a href="#sec-static-semantics-needssuperbinding"
+ title="link to this section">14.3.7</a></span> Static Semantics: NeedsSuperBinding</h1>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If <i>StrictFormalParameters</i> Contains <i>SuperProperty</i> is <b>true</b>, return <b>true.</b></li>
+ <li>Return <i>FunctionBody</i> Contains <i>SuperProperty</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <code class="t">get</code> <span class="nt">PropertyName</span> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <i>FunctionBody</i> Contains <i>SuperProperty</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If <i>PropertySetParameterList</i> Contains <i>SuperProperty</i> is <b>true</b>, return <b>true.</b></li>
+ <li>Return <i>FunctionBody</i> Contains <i>SuperProperty</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-specialmethod">
+ <h1><span class="secnum" id="sec-14.3.8"><a href="#sec-static-semantics-specialmethod"
+ title="link to this section">14.3.8</a></span> Static Semantics: SpecialMethod</h1>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MethodDefinition</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">GeneratorMethod</span></div>
+ <div class="rhs"><code class="t">get</code> <span class="nt">PropertyName</span> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-definemethod">
+ <h1><span class="secnum" id="sec-14.3.9"><a href="#sec-runtime-semantics-definemethod"
+ title="link to this section">14.3.9</a></span> Runtime Semantics: DefineMethod</h1>
+
+ <p>With parameters <var>object</var> and optional parameter <span style="font-family: Times New
+ Roman"><i>functionPrototype</i>.</span></p>
+
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>propKey</i> be the result of evaluating <i>PropertyName</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propKey</i>).</li>
+ <li>Let <i>strict</i> be IsStrict of <i>FunctionBody</i>.</li>
+ <li>Let <i>scope</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>If <i>functionPrototype</i> was passed as a parameter, let <i>kind</i> be <span style="font-family:
+ sans-serif">Normal</span>; otherwise let <i>kind</i> be <span style="font-family: sans-serif">Method</span>.</li>
+ <li>Let <i>closure</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<i>kind</i>, <i>StrictFormalParameters</i>,
+ <i>FunctionBody, scope</i>, <i>strict</i>). If <i>functionPrototype</i> was passed as a parameter then pass its value
+ as the <i>functionPrototype</i> optional argument of <a href="#sec-functioncreate">FunctionCreate</a>.</li>
+ <li>If NeedsSuperBinding of <i>MethodDefinition</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Perform <a href="#sec-makemethod">MakeMethod</a>(<i>closure</i>, <i>object</i>).</li>
+ </ol>
+ </li>
+ <li>Return the Record{[[key]]: <i>propKey</i>, [[closure]]: <i>closure</i>}.</li>
+ </ol>
+ </section>
+
+ <section id="sec-method-definitions-runtime-semantics-propertydefinitionevaluation">
+ <h1><span class="secnum" id="sec-14.3.10"><a href="#sec-method-definitions-runtime-semantics-propertydefinitionevaluation"
+ title="link to this section">14.3.10</a></span> Runtime Semantics: PropertyDefinitionEvaluation</h1>
+
+ <p>With parameters <var>object</var> and <span style="font-family: Times New Roman"><i>enumerable</i>.</span></p>
+
+ <p>See also: <a href="#sec-object-initializer-runtime-semantics-propertydefinitionevaluation">12.2.5.9</a>, <a
+ href="#sec-generator-function-definitions-runtime-semantics-propertydefinitionevaluation">14.4.13</a>, B.3.1</p>
+
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>methodDef</i> be DefineMethod of <i>MethodDefinition</i> with argument <i>object</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>methodDef</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>methodDef</i>.[[closure]],
+ <i>methodDef</i>.[[key]]).</li>
+ <li>Let <i>desc</i> be the <a href="#sec-property-descriptor-specification-type">Property Descriptor</a>{[[Value]]:
+ <i>methodDef</i>.[[closure]], [[Writable]]: <b>true</b>, [[Enumerable]]: <i>enumerable</i>, [[Configurable]]:
+ <b>true</b>}.</li>
+ <li>Return <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>object</i>, <i>methodDef</i>.[[key]],
+ <i>desc</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <span class="nt">GeneratorMethod</span></div>
+
+ <p>See <a href="#sec-generator-function-definitions">14.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <code class="t">get</code> <span class="nt">PropertyName</span> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>propKey</i> be the result of evaluating <i>PropertyName</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propKey</i>).</li>
+ <li>Let <i>strict</i> be IsStrict of <i>FunctionBody</i>.</li>
+ <li>Let <i>scope</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>formalParameterList</i> be the production <span class="prod"><span class="nt">FormalParameters</span> <span
+ class="geq">:</span> <span class="grhsannot">[empty]</span></span></li>
+ <li>Let <i>closure</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<span style="font-family:
+ sans-serif">Method</span>, <i>formalParameterList</i>, <i>FunctionBody, scope</i>, <i>strict</i>).</li>
+ <li>If NeedsSuperBinding of <i>MethodDefinition</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Perform <a href="#sec-makemethod">MakeMethod</a>(<i>closure</i>, <i>object</i>).</li>
+ </ol>
+ </li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>closure</i>, <i>propKey</i>,
+ <code>"<b>get</b>"</code>).</li>
+ <li>Let <i>desc</i> be the PropertyDescriptor{[[Get]]: <i>closure</i>, [[Enumerable]]: <i>enumerable</i>,
+ [[Configurable]]: <b>true</b>}</li>
+ <li>Return <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>object</i>, <i>propKey</i>,
+ <i>desc</i>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">MethodDefinition</span> <span class="geq">:</span> <code class="t">set</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>propKey</i> be the result of evaluating <i>PropertyName</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propKey</i>).</li>
+ <li>Let <i>strict</i> be IsStrict of <i>FunctionBody</i>.</li>
+ <li>Let <i>scope</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>closure</i> be <a href="#sec-functioncreate">FunctionCreate</a>(<span style="font-family:
+ sans-serif">Method</span>, <i>PropertySetParameterList</i>, <i>FunctionBody, scope</i>, <i>strict</i>).</li>
+ <li>If NeedsSuperBinding of <i>MethodDefinition</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Perform <a href="#sec-makemethod">MakeMethod</a>(<i>closure</i>, <i>object</i>).</li>
+ </ol>
+ </li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>closure</i>, <i>propKey</i>,
+ <code>"<b>set</b>"</code>).</li>
+ <li>Let <i>desc</i> be the PropertyDescriptor{[[Set]]: <i>closure</i>, [[Enumerable]]: <i>enumerable</i>,
+ [[Configurable]]: <b>true</b>}</li>
+ <li>Return <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>object</i>, <i>propKey</i>,
+ <i>desc</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-generator-function-definitions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.4"><a href="#sec-generator-function-definitions"
+ title="link to this section">14.4</a></span> Generator Function Definitions</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">GeneratorMethod</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">StrictFormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">GeneratorDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ <div class="rhs"><span class="grhsannot">[+Default]</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">GeneratorExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span><sub>[Yield]</sub><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">GeneratorBody</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">FunctionBody</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">YieldExpression</span><sub>[In]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">yield</code></div>
+ <div class="rhs"><code class="t">yield</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">AssignmentExpression</span><sub>[?In, Yield]</sub></div>
+ <div class="rhs"><code class="t">yield</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">*</code> <span class="nt">AssignmentExpression</span><sub>[?In, Yield]</sub></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The syntactic context immediately following <code>yield</code> requires use of the
+ <i>InputElementRegExpOrTemplateTail</i> lexical goal.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> <i>YieldExpression</i> cannot be used within the <i>FormalParameters</i> of a generator
+ function because any expressions that are part of <i>FormalParameters</i> are evaluated before the resulting generator
+ object is in a resumable state.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> Abstract operations relating to generator objects are defined in <a
+ href="#sec-generator-abstract-operations">25.3.3</a>.</p>
+ </div>
+ </div>
+
+ <section id="sec-generator-function-definitions-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-14.4.1"><a href="#sec-generator-function-definitions-static-semantics-early-errors"
+ title="link to this section">14.4.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">GeneratorMethod</span> <span class="geq">:</span> <code class="t">*</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if HasDirectSuper of <i>GeneratorMethod</i> is <b><i>true</i></b> .</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <i>StrictFormalParameters</i> also occurs in the
+ LexicallyDeclaredNames of <i>GeneratorBody</i>.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ul>
+ <li>It is a Syntax Error if HasDirectSuper of <i>GeneratorDeclaration</i> is <b><i>true</i></b> .</li>
+ </ul>
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ul>
+ <li>It is a Syntax Error if HasDirectSuper of <i>GeneratorExpression</i> is <b><i>true</i></b> .</li>
+ </ul>
+
+ <p><span class="prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code
+ class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span
+ class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span>
+ <code class="t">}</code></span><br><span class="prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span>
+ <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span><sub>opt</sub> <code
+ class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span
+ class="nt">GeneratorBody</span> <code class="t">}</code></span></p>
+
+ <ul>
+ <li>
+ <p>If the source code matching this production is <a href="#sec-strict-mode-code">strict code</a>, the Early Error rules
+ for <span class="prod"><span class="nt">StrictFormalParameters</span> <span class="geq">:</span> <span
+ class="nt">FormalParameters</span></span> are applied.</p>
+ </li>
+
+ <li>
+ <p>If the source code matching this production is <a href="#sec-strict-mode-code">strict code</a>, it is a Syntax Error
+ if <i>BindingIdentifier</i> is the <i>IdentifierName</i> <code>eval</code> or the <i>IdentifierName</i>
+ <code>arguments</code>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <i>FormalParameters</i> also occurs in the
+ LexicallyDeclaredNames of <i>GeneratorBody</i>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <i>FormalParameters</i> Contains <i>SuperProperty</i> is <b><i>true</i></b>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <i>GeneratorBody</i> Contains <i>SuperProperty</i> is <b><i>true</i></b>.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-14.4.2"><a href="#sec-generator-function-definitions-static-semantics-boundnames"
+ title="link to this section">14.4.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingIdentifier</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return «<code>"*default*"</code>».</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <code>"*default*"</code> is used within this specification as a synthetic name for
+ hoistable anonymous functions that are defined using export declarations.</p>
+ </div>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-computedpropertycontains">
+ <h1><span class="secnum" id="sec-14.4.3"><a
+ href="#sec-generator-function-definitions-static-semantics-computedpropertycontains"
+ title="link to this section">14.4.3</a></span> Static Semantics: ComputedPropertyContains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-computedpropertycontains">12.2.5.2</a>, <a
+ href="#sec-method-definitions-static-semantics-computedpropertycontains">14.3.2</a>, <a
+ href="#sec-class-definitions-static-semantics-computedpropertycontains">14.5.5</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorMethod</span> <span class="geq">:</span> <code class="t">*</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return the result of ComputedPropertyContains for <i>PropertyName</i> with argument <i>symbol</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-contains">
+ <h1><span class="secnum" id="sec-14.4.4"><a href="#sec-generator-function-definitions-static-semantics-contains"
+ title="link to this section">14.4.4</a></span> Static Semantics: Contains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-static-semantic-rules">5.3</a>, <a
+ href="#sec-object-initializer-static-semantics-contains">12.2.5.3</a>, <a
+ href="#sec-static-semantics-static-semantics-contains">12.3.1.1</a>, <a
+ href="#sec-function-definitions-static-semantics-contains">14.1.4</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-contains">14.2.3</a>, <a
+ href="#sec-class-definitions-static-semantics-contains">14.5.4</a></p>
+
+ <p><span class="prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code
+ class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span
+ class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span>
+ <code class="t">}</code></span></p>
+
+ <div class="gp prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Static semantic rules that depend upon substructure generally do not look into function
+ definitions.</p>
+ </div>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-hascomputedpropertykey">
+ <h1><span class="secnum" id="sec-14.4.5"><a
+ href="#sec-generator-function-definitions-static-semantics-hascomputedpropertykey"
+ title="link to this section">14.4.5</a></span> Static Semantics: HasComputedPropertyKey</h1>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-hascomputedpropertykey">12.2.5.4</a>, <a
+ href="#sec-method-definitions-static-semantics-hascomputedpropertykey">14.3.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorMethod</span> <span class="geq">:</span> <code class="t">*</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return IsComputedPropertyKey of <i>PropertyName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-hasdirectsuper">
+ <h1><span class="secnum" id="sec-14.4.6"><a href="#sec-generator-function-definitions-static-semantics-hasdirectsuper"
+ title="link to this section">14.4.6</a></span> Static Semantics: HasDirectSuper</h1>
+
+ <p>See also: <a href="#sec-method-definitions-static-semantics-hasdirectsuper">14.3.5</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorMethod</span> <span class="geq">:</span> <code class="t">*</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If <i>StrictFormalParameters</i> Contains <i>SuperCall</i> is <b>true</b>, return <b>true.</b></li>
+ <li>Return <i>GeneratorBody</i> Contains <i>SuperCall</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code
+ class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span
+ class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span>
+ <code class="t">}GeneratorDeclaration</code> <code class="t">:</code> <code class="t">function</code> <code
+ class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code
+ class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></span></p>
+
+ <p><span class="prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code>
+ <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code
+ class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></span></p>
+
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If <i>FormalParameters</i> Contains <i>SuperCall</i> is <b>true</b>, return <b>true.</b></li>
+ <li>Return <i>GeneratorBody</i> Contains <i>SuperCall</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-hasname">
+ <h1><span class="secnum" id="sec-14.4.7"><a href="#sec-generator-function-definitions-static-semantics-hasname"
+ title="link to this section">14.4.7</a></span> Static Semantics: HasName</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-hasname">14.1.8</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-hasname">14.2.8</a>, <a
+ href="#sec-class-definitions-static-semantics-hasname">14.5.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-isconstantdeclaration">
+ <h1><span class="secnum" id="sec-14.4.8"><a
+ href="#sec-generator-function-definitions-static-semantics-isconstantdeclaration"
+ title="link to this section">14.4.8</a></span> Static Semantics: IsConstantDeclaration</h1>
+
+ <p>See also: <a href="#sec-let-and-const-declarations-static-semantics-isconstantdeclaration">13.2.1.3</a>, <a
+ href="#sec-function-definitions-static-semantics-isconstantdeclaration">14.1.10</a>, <a
+ href="#sec-class-definitions-static-semantics-isconstantdeclaration">14.5.7</a>, <a
+ href="#sec-exports-static-semantics-isconstantdeclaration">15.2.3.7</a>.</p>
+
+ <p><span class="prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code
+ class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span
+ class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span>
+ <code class="t">}GeneratorDeclaration</code> <code class="t">:</code> <code class="t">function</code> <code
+ class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code
+ class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></span></p>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-14.4.9"><a href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition"
+ title="link to this section">14.4.9</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-class-definitions-static-semantics-isfunctiondefinition">14.5.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-static-semantics-propname">
+ <h1><span class="secnum" id="sec-14.4.10"><a href="#sec-generator-function-definitions-static-semantics-propname"
+ title="link to this section">14.4.10</a></span> Static Semantics: PropName</h1>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-propname">12.2.5.6</a>, <a
+ href="#sec-method-definitions-static-semantics-propname">14.3.6</a>, <a
+ href="#sec-class-definitions-static-semantics-propname">14.5.12</a></p>
+
+ <div class="gp prod"><span class="nt">GeneratorMethod</span> <span class="geq">:</span> <code class="t">*</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return PropName of <i>PropertyName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-runtime-semantics-evaluatebody">
+ <h1><span class="secnum" id="sec-14.4.11"><a href="#sec-generator-function-definitions-runtime-semantics-evaluatebody"
+ title="link to this section">14.4.11</a></span> Runtime Semantics: EvaluateBody</h1>
+
+ <p>With parameter <var>functionObject</var>.</p>
+
+ <p>See also: <a href="#sec-function-definitions-runtime-semantics-evaluatebody">14.1.18</a>, <a
+ href="#sec-arrow-function-definitions-runtime-semantics-evaluatebody">14.2.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorBody</span> <span class="geq">:</span> <span class="nt">FunctionBody</span></div>
+ <ol class="proc">
+ <li>Let <i>G</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(<i>functionObject</i>,
+ <code>"%GeneratorPrototype%"</code>, «‍[[GeneratorState]], [[GeneratorContext]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>G</i>).</li>
+ <li>Perform <a href="#sec-generatorstart">GeneratorStart</a>(<i>G</i>, <i>FunctionBody</i>).</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">return</span>, [[value]]: <i>G</i>, [[target]]: <span style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If the generator was invoked using [[Call]], the <code>this</code> binding will have
+ already been initialized in the normal manner. If the generator was invoked using [[Construct]], the <code>this</code>
+ bind is not initialized and any references to <code>this</code> within the <i>FunctionBody</i> will produce a
+ <b>ReferenceError</b> exception.</p>
+ </div>
+ </section>
+
+ <section id="sec-generator-function-definitions-runtime-semantics-instantiatefunctionobject">
+ <h1><span class="secnum" id="sec-14.4.12"><a
+ href="#sec-generator-function-definitions-runtime-semantics-instantiatefunctionobject"
+ title="link to this section">14.4.12</a></span> Runtime Semantics: InstantiateFunctionObject</h1>
+
+ <p>With parameter <var>scope</var>.</p>
+
+ <p>See also: <a href="#sec-function-definitions-runtime-semantics-instantiatefunctionobject">14.1.20</a>.</p>
+
+ <div class="gp prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the <i>GeneratorDeclaration</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if its
+ <i>GeneratorBody</i> is <a href="#sec-strict-mode-code">strict code</a>, let <i>strict</i> be <b>true</b>. Otherwise
+ let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>name</i> be StringValue of <i>BindingIdentifier.</i></li>
+ <li>Let <i>F</i> be <a href="#sec-generatorfunctioncreate">GeneratorFunctionCreate</a>(<span style="font-family:
+ sans-serif">Normal</span>, <i>FormalParameters</i>, <i>GeneratorBody</i>, <i>scope</i>, <i>strict</i>).</li>
+ <li>Let <i>prototype</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%GeneratorPrototype%</span>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>F</i>, <b>true</b>, <i>prototype</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>F</i>, <i>name</i>).</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">GeneratorDeclaration</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If the <i>GeneratorDeclaration</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if its
+ <i>GeneratorBody</i> is <a href="#sec-strict-mode-code">strict code</a>, let <i>strict</i> be <b>true</b>. Otherwise
+ let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>F</i> be <a href="#sec-generatorfunctioncreate">GeneratorFunctionCreate</a>(<span style="font-family:
+ sans-serif">Normal</span>, <i>FormalParameters</i>, <i>GeneratorBody</i>, <i>scope</i>, <i>strict</i>).</li>
+ <li>Let <i>prototype</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%GeneratorPrototype%</span>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>F</i>, <b>true</b>, <i>prototype</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>F</i>, <code>"default"</code>).</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An anonymous <i>GeneratorDeclaration</i> can only occur as part of an <code>export
+ default</code> declaration.</p>
+ </div>
+ </section>
+
+ <section id="sec-generator-function-definitions-runtime-semantics-propertydefinitionevaluation">
+ <h1><span class="secnum" id="sec-14.4.13"><a
+ href="#sec-generator-function-definitions-runtime-semantics-propertydefinitionevaluation"
+ title="link to this section">14.4.13</a></span> Runtime Semantics: PropertyDefinitionEvaluation</h1>
+
+ <p>With parameter <var>object</var> and <span style="font-family: Times New Roman"><i>enumerable</i>.</span></p>
+
+ <p>See also: <a href="#sec-object-initializer-runtime-semantics-propertydefinitionevaluation">12.2.5.9</a>, <a
+ href="#sec-method-definitions-runtime-semantics-propertydefinitionevaluation">14.3.10</a>, B.3.1</p>
+
+ <div class="gp prod"><span class="nt">GeneratorMethod</span> <span class="geq">:</span> <code class="t">*</code> <span class="nt">PropertyName</span> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>propKey</i> be the result of evaluating <i>PropertyName</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propKey</i>).</li>
+ <li>Let <i>strict</i> be IsStrict of <i>GeneratorBody</i>.</li>
+ <li>Let <i>scope</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>closure</i> be <a href="#sec-generatorfunctioncreate">GeneratorFunctionCreate</a>(<span style="font-family:
+ sans-serif">Method</span>, <i>StrictFormalParameters</i>, <i>GeneratorBody, scope</i>, <i>strict</i>).</li>
+ <li>If NeedsSuperBinding of <i>GeneratorMethod</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Perform <a href="#sec-makemethod">MakeMethod</a>(<i>closure</i>, <i>object</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>prototype</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%GeneratorPrototype</span>%).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>closure</i>, <b>true</b>, <i>prototype</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>closure</i>, <i>propKey</i>).</li>
+ <li>Let <i>desc</i> be the <a href="#sec-property-descriptor-specification-type">Property Descriptor</a>{[[Value]]:
+ <i>closure</i>, [[Writable]]: <b>true</b>, [[Enumerable]]: <i>enumerable</i>, [[Configurable]]: <b>true</b>}.</li>
+ <li>Return <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>object</i>, <i>propKey</i>,
+ <i>desc</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator-function-definitions-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-14.4.14"><a href="#sec-generator-function-definitions-runtime-semantics-evaluation"
+ title="link to this section">14.4.14</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>strict</i> be IsStrict of <i>GeneratorBody</i>.</li>
+ <li>Let <i>scope</i> be the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <a
+ href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>closure</i> be <a href="#sec-generatorfunctioncreate">GeneratorFunctionCreate</a>(<span style="font-family:
+ sans-serif">Normal</span>, <i>FormalParameters</i>, <i>GeneratorBody, scope</i>, <i>strict</i>).</li>
+ <li>Let <i>prototype</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%GeneratorPrototype%</span>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>closure</i>, <b>true</b>, <i>prototype</i>).</li>
+ <li>Return <i>closure</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> <code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>strict</i> be IsStrict of <i>GeneratorBody</i>.</li>
+ <li>Let <i>runningContext</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-lexical-environments">Lexical Environment</a>.</li>
+ <li>Let <i>funcEnv</i> be <a
+ href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>runningContext</i>).</li>
+ <li>Let <i>envRec</i> be <i>funcEnv’s</i> environment record.</li>
+ <li>Let <i>name</i> be StringValue of <i>BindingIdentifier</i>.</li>
+ <li>Perfrom <i>envRec.</i>CreateImmutableBinding(<i>name</i>).</li>
+ <li>Let <i>closure</i> be <a href="#sec-generatorfunctioncreate">GeneratorFunctionCreate</a>(<span style="font-family:
+ sans-serif">Normal</span>, <i>FormalParameters</i>, <i>GeneratorBody, funcEnv</i>, <i>strict</i>).</li>
+ <li>Let <i>prototype</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%GeneratorPrototype%</span>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a> (<i>closure</i>, <b>true</b>, <i>prototype</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>closure</i>, <i>name</i>).</li>
+ <li>Perform <i>envRec.</i>InitializeBinding(<i>name,</i> <i>closure</i>).</li>
+ <li>Return <i>closure</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The <i>BindingIdentifier</i> in a <i>GeneratorExpression</i> can be referenced from
+ inside the <i>GeneratorExpression's</i> <i>FunctionBody</i> to allow the generator code to call itself recursively.
+ However, unlike in a <i>GeneratorDeclaration</i>, the <i>BindingIdentifier</i> in a <i>GeneratorExpression</i> cannot be
+ referenced from and does not affect the scope enclosing the <i>GeneratorExpression</i>.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">YieldExpression</span> <span class="geq">:</span> <code class="t">yield</code></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-generatoryield">GeneratorYield</a>(<a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>false</b>)).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">YieldExpression</span> <span class="geq">:</span> <code class="t">yield</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>value</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>Return <a href="#sec-generatoryield">GeneratorYield</a>(<a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>value</i>, <b>false</b>)).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">YieldExpression</span> <span class="geq">:</span> <code class="t">yield</code> <code class="t">*</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>exprRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>value</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprRef</i>).</li>
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>)<i>.</i></li>
+ <li>Let <i>received</i> be <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ <li>Repeat
+ <ol class="block">
+ <li>If <i>received</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, then
+ <ol class="block">
+ <li>Let <i>innerResult</i> be <a href="#sec-iteratornext">IteratorNext</a>(<i>iterator</i>,
+ <i>received</i>.[[value]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>innerResult</i>).</li>
+ <li>Let <i>done</i> be <a href="#sec-iteratorcomplete">IteratorComplete</a>(<i>innerResult</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>done</i>).</li>
+ <li>If <i>done</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-iteratorvalue">IteratorValue</a> (<i>innerResult</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>received</i> be <a href="#sec-generatoryield">GeneratorYield</a>(<i>innerResult</i>).</li>
+ </ol>
+ </li>
+ <li>Else if <i>received</i>.[[type]] is <span style="font-family: sans-serif">throw</span>, then
+ <ol class="block">
+ <li>Let <i>throw</i> be <a href="#sec-getmethod">GetMethod</a>(<i>iterator</i>, <code>"throw"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>throw</i>)<span style="font-family:
+ sans-serif">.</span></li>
+ <li>If <i>throw</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>innerResult</i> be <a href="#sec-call">Call</a>(<i>throw</i>, <i>iterator</i>,
+ «‍<i>received</i>.[[value]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>innerResult</i>)<span style="font-family:
+ sans-serif">.</span></li>
+ <li>NOTE: Exceptions from the inner iterator <code>throw</code> method are propagated. Normal completions
+ from an inner <code>throw</code> method are processed similarly to an inner <code>next</code>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>innerResult</i>) is not Object, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Let <i>done</i> be <a href="#sec-iteratorcomplete">IteratorComplete</a>(<i>innerResult</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>done</i>).</li>
+ <li>If <i>done</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>innerResult</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">return</span> , [[value]]:<i>value</i>, [[target]]:<span
+ style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+ </li>
+ <li>Let <i>received</i> be <a href="#sec-generatoryield">GeneratorYield</a>(<i>innerResult</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>NOTE: If <var>iterator</var> does not have a <code>throw</code> method, this throw is going to terminate
+ the <code>yield*</code> loop. But first we need to give <var>iterator</var> a chance to clean up.</li>
+ <li>Let <i>closeResult</i> be <a href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>,
+ <i>received</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>closeResult</i>).</li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>received</i>.[[type]] is <span style="font-family:
+ sans-serif">return</span>.</li>
+ <li>Let <i>return</i> be <a href="#sec-getmethod">GetMethod</a>(<i>iterator</i>, <code>"return"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>return</i>)<span style="font-family:
+ sans-serif">.</span></li>
+ <li>If <i>return</i> is <b>undefined</b>, return <i>received</i>.</li>
+ <li>Let <i>innerReturnResult</i> be <a href="#sec-call">Call</a>(<i>return</i>, <i>iterator</i>,
+ «‍<i>received</i>.[[value]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>innerReturnResult</i>)<span style="font-family:
+ sans-serif">.</span></li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>innerReturnResult</i>) is not Object, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Let <i>done</i> be <a href="#sec-iteratorcomplete">IteratorComplete</a>(<i>innerReturnResult</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>done</i>).</li>
+ <li>If <i>done</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>innerReturnResult</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">return</span> , [[value]]: <i>value</i>, [[target]]:<span
+ style="font-family: sans-serif">empty</span>}.</li>
+ </ol>
+ </li>
+ <li>Let <i>received</i> be <a href="#sec-generatoryield">GeneratorYield</a>(<i>innerReturnResult</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-class-definitions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.5"><a href="#sec-class-definitions" title="link to this section">14.5</a></span> Class
+ Definitions</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">class</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">ClassTail</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+Default]</span> <code class="t">class</code> <span class="nt">ClassTail</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassExpression</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">class</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub><sub>opt</sub> <span class="nt">ClassTail</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassTail</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">ClassHeritage</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">{</code> <span class="nt">ClassBody</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">}</code></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">ClassHeritage</span><sub>opt</sub> <code class="t">{</code> <span class="nt">ClassBody</span><sub>opt</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassHeritage</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">extends</code> <span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassBody</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ClassElementList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassElementList</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ClassElement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ClassElementList</span><sub>[?Yield]</sub> <span class="nt">ClassElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassElement</span><sub>[Yield]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MethodDefinition</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">static</code> <span class="nt">MethodDefinition</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">;</code></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A <i>ClassBody</i> is always <a href="#sec-strict-mode-code">strict code</a>.</p>
+ </div>
+ </div>
+
+ <section id="sec-class-definitions-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-14.5.1"><a href="#sec-class-definitions-static-semantics-early-errors"
+ title="link to this section">14.5.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">ClassTail</span> <span class="geq">:</span> <span class="nt">ClassHeritage</span><sub>opt</sub> <code class="t">{</code> <span class="nt">ClassBody</span> <code class="t">}</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <i>ClassHeritage</i> <span style="font-family: sans-serif">is not present</span> <i>and the
+ following algorithm evaluates to <b>true</b>:</i></p>
+
+ <ol class="proc">
+ <li>Let <i>constructor</i> be ConstructorMethod of <i>ClassBody</i>.</li>
+ <li>If <i>constructor</i> is <span style="font-family: sans-serif">empty</span>, return <b>false</b>.</li>
+ <li>Return HasDirectSuper of <i>constructor</i>.</li>
+ </ol>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">ClassBody</span> <span class="geq">:</span> <span class="nt">ClassElementList</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if PrototypePropertyNameList of <i>ClassElementList</i> <i>contains more than one occurrence
+ of</i> <code>"constructor"</code>.</p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <span class="nt">MethodDefinition</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if PropName of <i>MethodDefinition</i> is not <code>"constructor"</code> <i>and</i>
+ HasDirectSuper of <i>MethodDefinition</i> is <b><i>true</i></b>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if PropName of <i>MethodDefinition</i> is <code>"constructor"</code> <i>and SpecialMethod of</i>
+ <i>MethodDefinition</i> <i>is</i> <i><b>true</b>.</i></p>
+ </li>
+ </ul>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <code class="t">static</code> <span class="nt">MethodDefinition</span></div>
+ <ul>
+ <li>It is a Syntax Error if HasDirectSuper of <i>MethodDefinition</i> is <b><i>true</i></b>.</li>
+ <li>It is a Syntax Error if PropName of <i>MethodDefinition</i> <i>is</i> <code>"prototype"</code><i>.</i></li>
+ </ul>
+ </section>
+
+ <section id="sec-class-definitions-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-14.5.2"><a href="#sec-class-definitions-static-semantics-boundnames"
+ title="link to this section">14.5.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">BindingIdentifier</span> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>BindingIdentifier</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return «<code>"*default*"</code>».</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-constructormethod">
+ <h1><span class="secnum" id="sec-14.5.3"><a href="#sec-static-semantics-constructormethod"
+ title="link to this section">14.5.3</a></span> Static Semantics: ConstructorMethod</h1>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>If <i>ClassElement</i> is the production <span class="prod"><span class="nt">ClassElement</span> <span
+ class="geq">:</span> <code class="t">;</code></span> , return <span style="font-family: sans-serif">empty</span>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>true</b>, return <span style="font-family: sans-serif">empty</span>.</li>
+ <li>If PropName of <i>ClassElement</i> is not <code>"constructor"</code>, return <span style="font-family:
+ sans-serif">empty</span>.</li>
+ <li>Return <i>ClassElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElementList</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>Let <i>head</i> be ConstructorMethod of <i>ClassElementList.</i></li>
+ <li>If <i>head</i> is not <span style="font-family: sans-serif">empty</span>, return <i>head</i>.</li>
+ <li>If <i>ClassElement</i> is the production <span class="prod"><span class="nt">ClassElement</span> <span
+ class="geq">:</span> <code class="t">;</code></span> , return <span style="font-family: sans-serif">empty</span>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>true</b>, return <span style="font-family: sans-serif">empty</span>.</li>
+ <li>If PropName of <i>ClassElement</i> is not <code>"constructor"</code>, return <span style="font-family:
+ sans-serif">empty</span>.</li>
+ <li>Return <i>ClassElement</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Early Error rules ensure that there is only one method definition named
+ <code>"constructor"</code> and that it is not an accessor property or generator definition.</p>
+ </div>
+ </section>
+
+ <section id="sec-class-definitions-static-semantics-contains">
+ <h1><span class="secnum" id="sec-14.5.4"><a href="#sec-class-definitions-static-semantics-contains"
+ title="link to this section">14.5.4</a></span> Static Semantics: Contains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-static-semantic-rules">5.3</a>, <a
+ href="#sec-object-initializer-static-semantics-contains">12.2.5.3</a>, <a
+ href="#sec-static-semantics-static-semantics-contains">12.3.1.1</a>, <a
+ href="#sec-function-definitions-static-semantics-contains">14.1.4</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-contains">14.2.3</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-contains">14.4.4</a></p>
+
+ <div class="gp prod"><span class="nt">ClassTail</span> <span class="geq">:</span> <span class="nt">ClassHeritage</span><sub>opt</sub> <code class="t">{</code> <span class="nt">ClassBody</span> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>If <i>symbol</i> is <i>ClassBody</i>, return <b>true</b>.</li>
+ <li>If <i>symbol</i> is <i>ClassHeritage</i>, then
+ <ol class="block">
+ <li>If <i>ClassHeritage</i> is present, return <b>true</b> otherwise return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>inHeritage</i> be <i>ClassHeritage</i> Contains <i>symbol</i>.</li>
+ <li>If <i>inHeritage</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return the result of ComputedPropertyContains for <i>ClassBody</i> with argument <i>symbol</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Static semantic rules that depend upon substructure generally do not look into class
+ bodies except for <i>PropertyName</i> productions.</p>
+ </div>
+ </section>
+
+ <section id="sec-class-definitions-static-semantics-computedpropertycontains">
+ <h1><span class="secnum" id="sec-14.5.5"><a href="#sec-class-definitions-static-semantics-computedpropertycontains"
+ title="link to this section">14.5.5</a></span> Static Semantics: ComputedPropertyContains</h1>
+
+ <p>With parameter <var>symbol</var>.</p>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-computedpropertycontains">12.2.5.2</a>, <a
+ href="#sec-method-definitions-static-semantics-computedpropertycontains">14.3.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-computedpropertycontains">14.4.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElementList</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>Let <i>inList</i> be the result of ComputedPropertyContains for <i>ClassElementList</i> with argument
+ <i>symbol.</i></li>
+ <li>If <i>inList</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return the result of ComputedPropertyContains for <i>ClassElement</i> with argument <i>symbol</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <span class="nt">MethodDefinition</span></div>
+ <ol class="proc">
+ <li>Return the result of ComputedPropertyContains for <i>MethodDefinition</i> with argument <i>symbol</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <code class="t">static</code> <span class="nt">MethodDefinition</span></div>
+ <ol class="proc">
+ <li>Return the result of ComputedPropertyContains for <i>MethodDefinition</i> with argument <i>symbol</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-class-definitions-static-semantics-hasname">
+ <h1><span class="secnum" id="sec-14.5.6"><a href="#sec-class-definitions-static-semantics-hasname"
+ title="link to this section">14.5.6</a></span> Static Semantics: HasName</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-hasname">14.1.8</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-hasname">14.2.8</a>,<a
+ href="#sec-class-definitions-static-semantics-hasname">14.5.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">ClassExpression</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassExpression</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">BindingIdentifier</span> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-class-definitions-static-semantics-isconstantdeclaration">
+ <h1><span class="secnum" id="sec-14.5.7"><a href="#sec-class-definitions-static-semantics-isconstantdeclaration"
+ title="link to this section">14.5.7</a></span> Static Semantics: IsConstantDeclaration</h1>
+
+ <p>See also: <a href="#sec-let-and-const-declarations-static-semantics-isconstantdeclaration">13.2.1.3</a>, <a
+ href="#sec-function-definitions-static-semantics-isconstantdeclaration">14.1.10</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isconstantdeclaration">14.4.8</a>, <a
+ href="#sec-exports-static-semantics-isconstantdeclaration">15.2.3.7</a>.</p>
+
+ <p><span class="prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span> <code class="t">class</code> <span
+ class="nt">BindingIdentifier</span> <span class="nt">ClassTail</span></span></p>
+
+ <div class="gp prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-class-definitions-static-semantics-isfunctiondefinition">
+ <h1><span class="secnum" id="sec-14.5.8"><a href="#sec-class-definitions-static-semantics-isfunctiondefinition"
+ title="link to this section">14.5.8</a></span> Static Semantics: IsFunctionDefinition</h1>
+
+ <p>See also: <a href="#sec-semantics-static-semantics-isfunctiondefinition">12.2.0.2</a>, <a
+ href="#sec-grouping-operator-static-semantics-isfunctiondefinition">12.2.9.2</a>, <a
+ href="#sec-static-semantics-static-semantics-isfunctiondefinition">12.3.1.2</a>, <a
+ href="#sec-postfix-expressions-static-semantics-isfunctiondefinition">12.4.2</a>, <a
+ href="#sec-unary-operators-static-semantics-isfunctiondefinition">12.5.2</a>, <a
+ href="#sec-multiplicative-operators-static-semantics-isfunctiondefinition">12.6.1</a>, <a
+ href="#sec-additive-operators-static-semantics-isfunctiondefinition">12.7.1</a>, <a
+ href="#sec-bitwise-shift-operators-static-semantics-isfunctiondefinition">12.8.1</a>, <a
+ href="#sec-relational-operators-static-semantics-isfunctiondefinition">12.9.1</a>, <a
+ href="#sec-equality-operators-static-semantics-isfunctiondefinition">12.10.1</a>, <a
+ href="#sec-binary-bitwise-operators-static-semantics-isfunctiondefinition">12.11.1</a>, <a
+ href="#sec-binary-logical-operators-static-semantics-isfunctiondefinition">12.12.1</a>, <a
+ href="#sec-conditional-operator-static-semantics-isfunctiondefinition">12.13.1</a>, <a
+ href="#sec-assignment-operators-static-semantics-isfunctiondefinition">12.14.2</a>, <a
+ href="#sec-comma-operator-static-semantics-isfunctiondefinition">12.15.1</a>, <a
+ href="#sec-function-definitions-static-semantics-isfunctiondefinition">14.1.11</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isfunctiondefinition">14.4.9</a>.</p>
+
+ <div class="gp prod"><span class="nt">ClassExpression</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassExpression</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">BindingIdentifier</span> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-isstatic">
+ <h1><span class="secnum" id="sec-14.5.9"><a href="#sec-static-semantics-isstatic"
+ title="link to this section">14.5.9</a></span> Static Semantics: IsStatic</h1>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <span class="nt">MethodDefinition</span></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <code class="t">static</code> <span class="nt">MethodDefinition</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-nonconstructormethoddefinitions">
+ <h1><span class="secnum" id="sec-14.5.10"><a href="#sec-static-semantics-nonconstructormethoddefinitions"
+ title="link to this section">14.5.10</a></span> Static Semantics: NonConstructorMethodDefinitions</h1>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>If <i>ClassElement</i> is the production <span class="prod"><span class="nt">ClassElement</span> <span
+ class="geq">:</span> <code class="t">;</code></span> , return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>false</b> and PropName of <i>ClassElement</i> is <code>"constructor"</code>,
+ return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing <i>ClassElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElementList</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>Let <i>list</i> be NonConstructorMethodDefinitions of <i>ClassElementList.</i></li>
+ <li>If <i>ClassElement</i> is the production <span class="prod"><span class="nt">ClassElement</span> <span
+ class="geq">:</span> <code class="t">;</code></span> , return <i>list</i>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>false</b> and PropName of <i>ClassElement</i> is <code>"constructor"</code>,
+ return <i>list</i>.</li>
+ <li>Append <i>ClassElement</i> to the end of <i>list</i>.</li>
+ <li>Return <i>list</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-prototypepropertynamelist">
+ <h1><span class="secnum" id="sec-14.5.11"><a href="#sec-static-semantics-prototypepropertynamelist"
+ title="link to this section">14.5.11</a></span> Static Semantics: PrototypePropertyNameList</h1>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>If PropName of <i>ClassElement</i> is <span style="font-family: sans-serif">empty</span>, return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>true</b>, return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing PropName of <i>ClassElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElementList</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>Let <i>list</i> be PrototypePropertyNameList of <i>ClassElementList.</i></li>
+ <li>If PropName of <i>ClassElement</i> is <span style="font-family: sans-serif">empty</span>, return <i>list</i>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>true</b>, return <i>list</i>.</li>
+ <li>Append PropName of <i>ClassElement</i> to the end of <i>list</i>.</li>
+ <li>Return <i>list</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-class-definitions-static-semantics-propname">
+ <h1><span class="secnum" id="sec-14.5.12"><a href="#sec-class-definitions-static-semantics-propname"
+ title="link to this section">14.5.12</a></span> Static Semantics: PropName</h1>
+
+ <p>See also: <a href="#sec-object-initializer-static-semantics-propname">12.2.5.6</a>, <a
+ href="#sec-method-definitions-static-semantics-propname">14.3.6</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-propname">14.4.10</a></p>
+
+ <div class="gp prod"><span class="nt">ClassElement</span> <span class="geq">:</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return <span style="font-family: sans-serif">empty</span>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-staticpropertynamelist">
+ <h1><span class="secnum" id="sec-14.5.13"><a href="#sec-static-semantics-staticpropertynamelist"
+ title="link to this section">14.5.13</a></span> Static Semantics: StaticPropertyNameList</h1>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>If PropName of <i>ClassElement</i> is <span style="font-family: sans-serif">empty</span>, return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>false</b>, return a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing PropName of <i>ClassElement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassElementList</span> <span class="geq">:</span> <span class="nt">ClassElementList</span> <span class="nt">ClassElement</span></div>
+ <ol class="proc">
+ <li>Let <i>list</i> be StaticPropertyNameList of <i>ClassElementList.</i></li>
+ <li>If PropName of <i>ClassElement</i> is <span style="font-family: sans-serif">empty</span>, return <i>list</i>.</li>
+ <li>If IsStatic of <i>ClassElement</i> is <b>false</b>, return <i>list</i>.</li>
+ <li>Append PropName of <i>ClassElement</i> to the end of <i>list</i>.</li>
+ <li>Return <i>list</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-classdefinitionevaluation">
+ <h1><span class="secnum" id="sec-14.5.14"><a href="#sec-runtime-semantics-classdefinitionevaluation"
+ title="link to this section">14.5.14</a></span> Runtime Semantics: ClassDefinitionEvaluation</h1>
+
+ <p>With parameter <var>className</var>.</p>
+
+ <div class="gp prod"><span class="nt">ClassTail</span> <span class="geq">:</span> <span class="nt">ClassHeritage</span><sub>opt</sub> <code class="t">{</code> <span class="nt">ClassBody</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>lex</i> be the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <a
+ href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>classScope</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>lex</i>).</li>
+ <li>Let <i>classScopeEnvRec</i> be <i>classScope</i>’s environment record.</li>
+ <li>If <i>className</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Perform <i>classScopeEnvRec.</i>CreateImmutableBinding(<i>className</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>If <i>ClassHeritage</i><sub>opt</sub> is not present, then
+ <ol class="block">
+ <li>Let <i>protoParent</i> be the intrinsic object %ObjectPrototype%.</li>
+ <li>Let <i>constructorParent</i> be the intrinsic object %FunctionPrototype%.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>classScope</i>.</li>
+ <li>Let <i>superclass</i> be the result of evaluating <i>ClassHeritage</i>.</li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>lex</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>superclass</i>).</li>
+ <li>If <i>superclass</i> is <b>null</b>, then
+ <ol class="block">
+ <li>Let <i>protoParent</i> be <b>null</b>.</li>
+ <li>Let <i>constructorParent</i> be the intrinsic object %FunctionPrototype%.</li>
+ </ol>
+ </li>
+ <li>Else if <a href="#sec-isconstructor">IsConstructor</a>(<i>superclass</i>) is <b>false</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Else
+ <ol class="block">
+ <li>If <i>superclass</i> has a [[FunctionKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> whose value is "<code>generator</code>", throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>protoParent</i> be <a href="#sec-get-o-p">Get</a>(<i>superclass</i>, <code>"prototype"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>protoParent</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>protoParent</i>) is neither Object nor Null,
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>constructorParent</i> be <i>superclass</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>proto</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<i>protoParent</i>).</li>
+ <li>If <i>ClassBody</i><sub>opt</sub> is not present, let <i>constructor</i> be <span style="font-family:
+ sans-serif">empty</span>.</li>
+ <li>Else, let <i>constructor</i> be ConstructorMethod of <i>ClassBody</i>.</li>
+ <li>If <i>constructor</i> is <span style="font-family: sans-serif">empty</span>, then,
+ <ol class="block">
+ <li>If <i>ClassHeritage</i><sub>opt</sub> is present, then
+ <ol class="block">
+ <li>Let <i>constructor</i> be the result of parsing the String <code>"constructor(... args){ super</code>
+ <code>(...args);}"</code> using the syntactic grammar with the goal symbol <i>MethodDefinition.</i></li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>constructor</i> be the result of parsing the String <code>"constructor( ){ }"</code> using the
+ syntactic grammar with the goal symbol <i>MethodDefinition.</i></li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>classScope</i>.</li>
+ <li>Let <i>constructorInfo</i> be the result of performing DefineMethod for <i>constructor</i> with arguments <i>proto</i>
+ and <i>constructorParent</i> as the optional <i>functionPrototype</i> argument.</li>
+ <li>Let <i>F</i> be <i>constructorInfo</i>.[[closure]]</li>
+ <li>If <i>ClassHeritage</i><sub>opt</sub> is present, set <i>F</i>’s [[ConstructorKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to "<code>derived</code>".</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>F</i>, <b>false</b>, <i>proto</i>).</li>
+ <li>Perform <a href="#sec-makeclassconstructor">MakeClassConstructor</a>(<i>F</i>).</li>
+ <li>Perform <a href="#sec-createmethodproperty">CreateMethodProperty</a>(<i>proto</i>, <code>"constructor"</code>,
+ <i>F</i>)<i>.</i></li>
+ <li>If <i>ClassBody</i><sub>opt</sub> is not present, let <i>methods</i> be a new empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Else, let <i>methods</i> be NonConstructorMethodDefinitions of <i>ClassBody</i>.</li>
+ <li>For each <i>ClassElement</i> <i>m</i> in order from <i>methods</i>
+ <ol class="block">
+ <li>If IsStatic of <i>m</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing PropertyDefinitionEvaluation for <i>m</i> with arguments
+ <i>proto</i> and <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be the result of performing PropertyDefinitionEvaluation for <i>m</i> with arguments
+ <i>F</i> and <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>lex</i>.</li>
+ <li>Return <i>status</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a> to <i>lex</i>.</li>
+ <li>If <i>className</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Perform <i>classScopeEnvRec.</i>InitializeBinding(<i>className</i>, <i>F</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-bindingclassdeclarationevaluation">
+ <h1><span class="secnum" id="sec-14.5.15"><a href="#sec-runtime-semantics-bindingclassdeclarationevaluation"
+ title="link to this section">14.5.15</a></span> Runtime Semantics: BindingClassDeclarationEvaluation</h1>
+ <div class="gp prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">BindingIdentifier</span> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Let <i>className</i> be StringValue of <i>BindingIdentifier</i>.</li>
+ <li>Let <i>value</i> be the result of ClassDefinitionEvaluation of <i>ClassTail</i> with argument <i>className.</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>value</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, then perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>value</i>, <i>className</i>).</li>
+ <li>Let <i>env</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>status</i> be <a href="#sec-initializeboundname">InitializeBoundName</a>(<i>className</i>, <i>value</i>,
+ <i>env</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <i>value</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Return the result of ClassDefinitionEvaluation of <i>ClassTail</i> with argument <b>undefined</b><i>.</i></li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <span class="prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span>
+ <code class="t">class</code> <span class="nt">ClassTail</span> <code class="t">only</code> <code class="t">occurs</code>
+ <code class="t">as</code> <code class="t">part</code> <code class="t">of</code> <code class="t">an</code> <span
+ class="nt">ExportDeclaration</span></span> <span style="font-family: sans-serif">and the setting of a name property and
+ establishing its binding are handled as part of the evaluation action for that production. See <a
+ href="#sec-exports-runtime-semantics-evaluation">15.2.3.11</a>.</span></p>
+ </div>
+ </section>
+
+ <section id="sec-class-definitions-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-14.5.16"><a href="#sec-class-definitions-runtime-semantics-evaluation"
+ title="link to this section">14.5.16</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">ClassDeclaration</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">BindingIdentifier</span> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>Let <i>status</i> be the result of BindingClassDeclarationEvaluation of this <i>ClassDeclaration.</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ </ol>
+
+ <p class="Note"><i>NOTE ClassDeclaration</i> <b>: <code>class</code></b> <i>ClassTail only occurs as part of an
+ ExportDeclaration</i> <span style="font-family: sans-serif">and is never directly evaluated.</span></p>
+
+ <div class="gp prod"><span class="nt">ClassExpression</span> <span class="geq">:</span> <code class="t">class</code> <span class="nt">BindingIdentifier</span><sub>opt</sub> <span class="nt">ClassTail</span></div>
+ <ol class="proc">
+ <li>If <i>BindingIdentifier</i><sub>opt</sub> is not present, let <i>className</i> be <b>undefined</b>.</li>
+ <li>Else, let <i>className</i> be StringValue of <i>BindingIdentifier</i>.</li>
+ <li>Let <i>value</i> be the result of ClassDefinitionEvaluation of <i>ClassTail</i> with argument <i>className</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>If <i>className</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>value</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>value</i>, <i>className</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>value</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If the class definition included a <code>"name"</code> static method then that method is
+ not over-written with a <code>"name"</code> data property for the class name.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-tail-position-calls">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.6"><a href="#sec-tail-position-calls" title="link to this section">14.6</a></span> Tail
+ Position Calls</h1>
+ </div>
+
+ <section id="sec-isintailposition">
+ <h1><span class="secnum" id="sec-14.6.1"><a href="#sec-isintailposition" title="link to this section">14.6.1</a></span>
+ Static Semantics: IsInTailPosition(nonterminal)</h1>
+
+ <p>The abstract operation IsInTailPosition with argument <var>nonterminal</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>nonterminal</i> is a parsed grammar production.</li>
+ <li>If the source code matching <i>nonterminal</i> is not <a href="#sec-strict-mode-code">strict code</a>, return
+ <b>false.</b></li>
+ <li>If <i>nonterminal</i> is not contained within a <i>FunctionBody</i> or <i>ConciseBody</i>, return <b>false</b>.</li>
+ <li>Let <i>body</i> be the <i>FunctionBody</i> or <i>ConciseBody</i> that most closely contains <i>nonterminal</i>.</li>
+ <li>If <i>body</i> is the <i>FunctionBody</i> of a <i>GeneratorBody</i>, return <b>false</b>.</li>
+ <li>Return the result of HasProductionInTailPosition of <i>body</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Tail Position calls are only defined in <a href="#sec-strict-mode-code">strict mode
+ code</a> because of a common non-standard language extension (<a href="#sec-addrestrictedfunctionproperties">see
+ 9.2.8</a>) that enables observation of the chain of caller contexts.</p>
+ </div>
+ </section>
+
+ <section id="sec-static-semantics-hasproductionintailposition">
+ <div class="front">
+ <h1><span class="secnum" id="sec-14.6.2"><a href="#sec-static-semantics-hasproductionintailposition"
+ title="link to this section">14.6.2</a></span> Static Semantics: HasProductionInTailPosition</h1>
+
+ <p>With parameter <var>nonterminal</var>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <i>nonterminal</i> is a parsed grammar production that represent a specific range of
+ source text. When the following algorithms compare <i>nonterminal</i> to other grammar symbols they are testing whether
+ the same source text was matched by both symbols.</p>
+ </div>
+ </div>
+
+ <section id="sec-statement-rules">
+ <h1><span class="secnum" id="sec-14.6.2.1"><a href="#sec-statement-rules" title="link to this section">14.6.2.1</a></span>
+ Statement Rules</h1>
+ <div class="gp prod"><span class="nt">ConciseBody</span> <span class="geq">:</span> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>AssignmentExpression</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">StatementList</span> <span class="geq">:</span> <span class="nt">StatementList</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be HasProductionInTailPosition of <i>StatementList</i> with argument <i>nonterminal</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return HasProductionInTailPosition of <i>StatementListItem</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">FunctionStatementList</span> <span class="geq">:</span> <span
+ class="grhsannot">[empty]</span></span></p>
+
+ <p><span class="prod"><span class="nt">StatementListItem</span> <span class="geq">:</span> <span
+ class="nt">Declaration</span></span></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Statement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">VariableStatement</span></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span></div>
+ <div class="rhs"><span class="nt">ContinueStatement</span></div>
+ <div class="rhs"><span class="nt">BreakStatement</span></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ <div class="rhs"><span class="nt">Block</span> <code class="t">:</code> <code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><span class="nt">ReturnStatement</span> <code class="t">:</code> <code class="t">return</code> <code class="t">;</code></div>
+ <div class="rhs"><span class="nt">LabelledItem</span> <code class="t">:</code> <span class="nt">FunctionDeclaration</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">in</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span> <code class="t">of</code> <span class="nt">AssignmentExpression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><span class="nt">CaseBlock</span> <code class="t">:</code> <code class="t">{</code> <code class="t">}</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span> <code class="t">else</code> <span class="nt">Statement</span></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be HasProductionInTailPosition of the first <i>Statement</i> with argument <i>nonterminal</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return HasProductionInTailPosition of the second <i>Statement</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">IfStatement</span> <span class="geq">:</span> <code class="t">if</code> <code
+ class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span
+ class="nt">Statement</span></span></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IterationStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">do</code> <span class="nt">Statement</span> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <div class="rhs"><code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span> <span class="nt">Expression</span><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span></div>
+ <div class="rhs"><span class="nt">WithStatement</span> <code class="t">:</code> <code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">Statement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>Statement</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LabelledStatement</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LabelIdentifier</span> <code class="t">:</code> <span class="nt">LabelledItem</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>LabelledItem</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ReturnStatement</span> <span class="geq">:</span> <code class="t">return</code> <span class="nt">Expression</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>Expression</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">SwitchStatement</span> <span class="geq">:</span> <code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code> <span class="nt">CaseBlock</span></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>CaseBlock</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseBlock</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">CaseClauses</span><sub>opt</sub> <span class="nt">DefaultClause</span> <span class="nt">CaseClauses</span><sub>opt</sub> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be <b>false</b>.</li>
+ <li>If the first <i>CaseClauses</i> is present, let <i>has</i> be HasProductionInTailPosition of the first
+ <i>CaseClauses</i> with argument <i>nonterminal</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Let <i>has</i> be HasProductionInTailPosition of the <i>DefaultClause</i> with argument <i>nonterminal</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>If the second <i>CaseClauses</i> is present, let <i>has</i> be HasProductionInTailPosition of the second
+ <i>CaseClauses</i> with argument <i>nonterminal</i>.</li>
+ <li>Return <i>has</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">CaseClauses</span> <span class="geq">:</span> <span class="nt">CaseClauses</span> <span class="nt">CaseClause</span></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be HasProductionInTailPosition of <i>CaseClauses</i> with argument <i>nonterminal</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return HasProductionInTailPosition of <i>CaseClause</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">CaseClause</span> <span class="geq">:</span> <code class="t">case</code> <span
+ class="nt">Expression</span> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></span></p>
+
+ <div class="gp prod"><span class="nt">DefaultClause</span> <span class="geq">:</span> <code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If <i>StatementList</i> is present, return HasProductionInTailPosition of <i>StatementList</i> with argument
+ <i>nonterminal</i>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>Catch</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span
+ class="nt">Block</span> <span class="nt">Finally</span></span></p>
+
+ <div class="gp prod"><span class="nt">TryStatement</span> <span class="geq">:</span> <code class="t">try</code> <span class="nt">Block</span> <span class="nt">Catch</span> <span class="nt">Finally</span></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>Finally</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>Block</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-expression-rules">
+ <h1><span class="secnum" id="sec-14.6.2.2"><a href="#sec-expression-rules"
+ title="link to this section">14.6.2.2</a></span> Expression Rules</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A potential tail position call that is immediately followed by return <a
+ href="#sec-getvalue">GetValue</a> of the call result is also a possible tail position call. Function calls cannot return
+ reference values, so such a <a href="#sec-getvalue">GetValue</a> operation will always returns the same value as the
+ actual function call result.</p>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AssignmentExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">YieldExpression</span></div>
+ <div class="rhs"><span class="nt">ArrowFunction</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">=</code> <span class="nt">AssignmentExpression</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <span class="nt">AssignmentOperator</span> <span class="nt">AssignmentExpression</span></div>
+ <div class="rhs"><span class="nt">BitwiseANDExpression</span> <code class="t">:</code> <span class="nt">BitwiseANDExpression</span> <code class="t">&</code> <span class="nt">EqualityExpression</span></div>
+ <div class="rhs"><span class="nt">BitwiseXORExpression</span> <code class="t">:</code> <span class="nt">BitwiseXORExpression</span> <code class="t">^</code> <span class="nt">BitwiseANDExpression</span></div>
+ <div class="rhs"><span class="nt">BitwiseORExpression</span> <code class="t">:</code> <span class="nt">BitwiseORExpression</span> <code class="t">|</code> <span class="nt">BitwiseXORExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EqualityExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">==</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">!=</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">===</code> <span class="nt">RelationalExpression</span></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span> <code class="t">!==</code> <span class="nt">RelationalExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RelationalExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t"><</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">></code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t"><=</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">>=</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">instanceof</code> <span class="nt">ShiftExpression</span></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span> <code class="t">in</code> <span class="nt">ShiftExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ShiftExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t"><<</code> <span class="nt">AdditiveExpression</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t">>></code> <span class="nt">AdditiveExpression</span></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span> <code class="t">>>></code> <span class="nt">AdditiveExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AdditiveExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span> <code class="t">+</code> <span class="nt">MultiplicativeExpression</span></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span> <code class="t">-</code> <span class="nt">MultiplicativeExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiplicativeExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MultiplicativeExpression</span> <span class="nt">MultiplicativeOperator</span> <span class="nt">UnaryExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">UnaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">delete</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">void</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">typeof</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">++</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">--</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">~</code> <span class="nt">UnaryExpression</span></div>
+ <div class="rhs"><code class="t">!</code> <span class="nt">UnaryExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PostfixExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">++</code></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span> <code class="t">--</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CallExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">SuperCall</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">NewExpression</span> <code class="t">:</code> <code class="t">new</code> <span class="nt">NewExpression</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">[</code> <span class="nt">Expression</span> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">SuperProperty</span></div>
+ <div class="rhs"><span class="nt">MetaProperty</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PrimaryExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">this</code></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span></div>
+ <div class="rhs"><span class="nt">Literal</span></div>
+ <div class="rhs"><span class="nt">ArrayLiteral</span></div>
+ <div class="rhs"><span class="nt">ObjectLiteral</span></div>
+ <div class="rhs"><span class="nt">FunctionExpression</span></div>
+ <div class="rhs"><span class="nt">ClassExpression</span></div>
+ <div class="rhs"><span class="nt">GeneratorExpression</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Expression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">AssignmentExpression</span></div>
+ <div class="rhs"><span class="nt">Expression</span> <code class="t">,</code> <span class="nt">AssignmentExpression</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>AssignmentExpression</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ConditionalExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">?</code> <span class="nt">AssignmentExpression</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>has</i> be HasProductionInTailPosition of the first <i>AssignmentExpression</i> with argument
+ <i>nonterminal</i>.</li>
+ <li>If <i>has</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return HasProductionInTailPosition of the second <i>AssignmentExpression</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LogicalANDExpression</span> <span class="geq">:</span> <span class="nt">LogicalANDExpression</span> <code class="t">&&</code> <span class="nt">BitwiseORExpression</span></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>BitwiseORExpression</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">LogicalORExpression</span> <span class="geq">:</span> <span class="nt">LogicalORExpression</span> <code class="t">||</code> <span class="nt">LogicalANDExpression</span></div>
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>LogicalANDExpression</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CallExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">Arguments</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span> <span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>If this <i>CallExpression</i> is <i>nonterminal</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MemberExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span> <span class="nt">TemplateLiteral</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>If this <i>MemberExpression</i> is <i>nonterminal</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">PrimaryExpression</span> <span class="geq">:</span> <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span></div>
+ <ol class="proc">
+ <li>Let <i>expr</i> be CoveredParenthesizedExpression of <i>CoverParenthesizedExpressionAndArrowParameterList</i>.</li>
+ <li>Return HasProductionInTailPosition of <i>expr</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ParenthesizedExpression</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span> <code class="t">)</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return HasProductionInTailPosition of <i>Expression</i> with argument <i>nonterminal</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-preparefortailcall">
+ <h1><span class="secnum" id="sec-14.6.3"><a href="#sec-preparefortailcall" title="link to this section">14.6.3</a></span>
+ Runtime Semantics: PrepareForTailCall ( )</h1>
+
+ <p>The abstract operation PrepareForTailCall performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>leafContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <i>leafContext</i>.</li>
+ <li>Pop <i>leafContext</i> from <a href="#sec-execution-contexts">the execution context stack</a>. The <a
+ href="#sec-execution-contexts">execution context</a> now on the top of the stack becomes <a
+ href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>leafContext</i> has no further use. It will never be activated as
+ <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ </ol>
+
+ <p>A tail position call must either release any transient internal resources associated with the currently executing
+ function <a href="#sec-execution-contexts">execution context</a> before invoking the target function or reuse those
+ resources in support of the target function.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For example, a tail position call should only grow an implementation’s activation
+ record stack by the amount that the size of the target function’s activation record exceeds the size of the calling
+ function’s activation record. If the target function’s activation record is smaller, then the total size of
+ the stack should decrease.</p>
+ </div>
+ </section>
+ </section>
+</section>
+
+<section id="sec-ecmascript-language-scripts-and-modules">
+ <div class="front">
+ <h1><span class="secnum" id="sec-15"><a href="#sec-ecmascript-language-scripts-and-modules"
+ title="link to this section">15</a></span> ECMAScript Language: Scripts and Modules</h1>
+ </div>
+
+ <section id="sec-scripts">
+ <div class="front">
+ <h1><span class="secnum" id="sec-15.1"><a href="#sec-scripts" title="link to this section">15.1</a></span> Scripts</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Script</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ScriptBody</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ScriptBody</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">StatementList</span></div>
+ </div>
+ </div>
+
+ <section id="sec-scripts-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-15.1.1"><a href="#sec-scripts-static-semantics-early-errors"
+ title="link to this section">15.1.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">ScriptBody</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the LexicallyDeclaredNames of <span class="nt">StatementList</span> contains any duplicate
+ entries.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the <span style="font-family: Times New Roman">LexicallyDeclaredNames</span>
+ of <span class="nt">StatementList</span> also occurs in the <span style="font-family: Times New
+ Roman">VarDeclaredNames</span> of <span class="nt">StatementList</span>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <span class="nt">StatementList</span> <span style="font-family: Times New
+ Roman">Contains</span> <code>super</code> unless the source code containing <code>super</code> is eval code that is
+ being processed by a direct <code>eval</code> that is contained in function code. However, such function code does not
+ include <span class="nt">ArrowFunction</span> function code.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <span class="nt">StatementList</span> <span style="font-family: Times New
+ Roman">Contains</span> <span class="nt">NewTarget</span> unless the source code containing <span
+ class="nt">NewTarget</span> is eval code that is being processed by a direct <code>eval</code> that is contained in
+ function code. However, such function code does not include <span class="nt">ArrowFunction</span> function code.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsDuplicateLabels of <span class="nt">StatementList</span> <span style="font-family:
+ Times New Roman">with argument «</span> <span style="font-family: Times New Roman">» is
+ <b>true</b>.</span></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsUndefinedBreakTarget of <span class="nt">StatementList</span> <span
+ style="font-family: Times New Roman">with argument «</span> <span style="font-family: Times New Roman">» is
+ <b>true</b>.</span></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsUndefinedContinueTarget of <span style="font-family: Times New
+ Roman"><i>StatementList</i> with arguments « » and « » is <b>true</b>.</span></p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-scripts-static-semantics-isstrict">
+ <h1><span class="secnum" id="sec-15.1.2"><a href="#sec-scripts-static-semantics-isstrict"
+ title="link to this section">15.1.2</a></span> Static Semantics: IsStrict</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-isstrict">14.1.13</a>, <a
+ href="#sec-module-semantics-static-semantics-isstrict">15.2.1.9</a>.</p>
+
+ <div class="gp prod"><span class="nt">ScriptBody</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>If this <i>ScriptBody</i> is contained in <a href="#sec-strict-mode-code">strict code</a> or if <i>StatementList</i>
+ is <a href="#sec-strict-mode-code">strict code</a>, return <b>true</b>. Otherwise, return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-scripts-static-semantics-lexicallydeclarednames">
+ <h1><span class="secnum" id="sec-15.1.3"><a href="#sec-scripts-static-semantics-lexicallydeclarednames"
+ title="link to this section">15.1.3</a></span> Static Semantics: LexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallydeclarednames">13.11.5</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallydeclarednames">13.12.6</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallydeclarednames">14.1.14</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">14.2.10</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallydeclarednames">15.2.1.11</a>.</p>
+
+ <div class="gp prod"><span class="nt">ScriptBody</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return TopLevelLexicallyDeclaredNames of <i>StatementList</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> At the top level of a <i>Script</i>, function declarations are treated like var
+ declarations rather than like lexical declarations.</p>
+ </div>
+ </section>
+
+ <section id="sec-scripts-static-semantics-lexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-15.1.4"><a href="#sec-scripts-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">15.1.4</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations">15.2.1.12</a>, <a
+ href="#sec-exports-static-semantics-lexicallyscopeddeclarations">15.2.3.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">ScriptBody</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return TopLevelLexicallyScopedDeclarations of <i>StatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-scripts-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-15.1.5"><a href="#sec-scripts-static-semantics-vardeclarednames"
+ title="link to this section">15.1.5</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-module-semantics-static-semantics-vardeclarednames">15.2.1.13</a>.</p>
+
+ <div class="gp prod"><span class="nt">ScriptBody</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return TopLevelVarDeclaredNames of <i>StatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-scripts-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-15.1.6"><a href="#sec-scripts-static-semantics-varscopeddeclarations"
+ title="link to this section">15.1.6</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-module-semantics-static-semantics-varscopeddeclarations">15.2.1.14</a>.</p>
+
+ <div class="gp prod"><span class="nt">ScriptBody</span> <span class="geq">:</span> <span class="nt">StatementList</span></div>
+ <ol class="proc">
+ <li>Return TopLevelVarScopedDeclarations of <i>StatementList</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-scriptevaluation">
+ <h1><span class="secnum" id="sec-15.1.7"><a href="#sec-runtime-semantics-scriptevaluation"
+ title="link to this section">15.1.7</a></span> Runtime Semantics: ScriptEvaluation</h1>
+
+ <p>With argument <var>realm</var>.</p>
+
+ <div class="gp prod"><span class="nt">Script</span> <span class="geq">:</span> <span class="nt">ScriptBody</span><sub>opt</sub></div>
+ <ol class="proc">
+ <li>If <i>ScriptBody</i> is not present, return <a href="#sec-normalcompletion">NormalCompletion</a>(<span
+ style="font-family: sans-serif">empty</span>).</li>
+ <li>Let <i>globalEnv</i> be <i>realm</i>.[[globalEnv]].</li>
+ <li>Let <i>scriptCxt</i> be a new <a href="#sec-execution-contexts">ECMAScript code execution context</a>.</li>
+ <li>Set the Function of <i>scriptCxt</i> to <b>null</b>.</li>
+ <li>Set the <a href="#sec-code-realms">Realm</a> of <i>scriptCxt</i> to <i>realm</i>.</li>
+ <li>Set the <a href="#sec-execution-contexts">VariableEnvironment</a> of <i>scriptCxt</i> to <i>globalEnv</i>.</li>
+ <li>Set the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>scriptCxt</i> to <i>globalEnv</i>.</li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <a href="#sec-execution-contexts">the currently running execution
+ context</a>.</li>
+ <li>Push <i>scriptCxt</i> on to <a href="#sec-execution-contexts">the execution context stack</a>; <i>scriptCxt</i> is now
+ <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>result</i> be <a
+ href="#sec-globaldeclarationinstantiation">GlobalDeclarationInstantiation</a>(<i>ScriptBody</i>,
+ <i>globalEnv</i>).</li>
+ <li>If <i>result</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, then
+ <ol class="block">
+ <li>Let <i>result</i> be the result of evaluating <i>ScriptBody</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>result</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>result</i>.[[value]] is <span
+ style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <i>scriptCxt</i> and remove it from <a
+ href="#sec-execution-contexts">the execution context stack</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-execution-contexts">the execution context stack</a> is
+ not empty.</li>
+ <li>Resume the context that is now on the top of <a href="#sec-execution-contexts">the execution context stack</a> as <a
+ href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-globaldeclarationinstantiation">
+ <h1><span class="secnum" id="sec-15.1.8"><a href="#sec-globaldeclarationinstantiation"
+ title="link to this section">15.1.8</a></span> Runtime Semantics: GlobalDeclarationInstantiation (script, env)</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When an <a href="#sec-execution-contexts">execution context</a> is established for
+ evaluating scripts, declarations are instantiated in the current global environment. Each global binding declared in the
+ code is instantiated.</p>
+ </div>
+
+ <p>GlobalDeclarationInstantiation is performed as follows using arguments <var>script</var> and <var>env</var>.
+ <var>script</var> is the <span class="nt">ScriptBody</span> for which the <a href="#sec-execution-contexts">execution
+ context</a> is being established. <var>env</var> is the global <a href="#sec-lexical-environments">lexical environment</a>
+ in which bindings are to be created.</p>
+
+ <ol class="proc">
+ <li>Let <i>envRec</i> be <i>env</i>’s environment record.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>envRec</i> is a <a href="#sec-global-environment-records">global
+ environment record</a>.</li>
+ <li>Let <i>lexNames</i> be the LexicallyDeclaredNames of <i>script</i>.</li>
+ <li>Let <i>varNames</i> be the VarDeclaredNames of <i>script</i>.</li>
+ <li>For each <i>name</i> in <i>lexNames</i>, do
+ <ol class="block">
+ <li>If <i>envRec.</i><a href="#sec-hasvardeclaration">HasVarDeclaration</a>(<i>name</i>) is <b>true</b>, throw a
+ <b>SyntaxError</b> exception.</li>
+ <li>If <i>envRec.</i><a href="#sec-haslexicaldeclaration">HasLexicalDeclaration</a>(<i>name</i>) is <b>true</b>, throw
+ a <b>SyntaxError</b> exception.</li>
+ <li>If <i>envRec.</i><a href="#sec-hasrestrictedglobalproperty">HasRestrictedGlobalProperty</a>(<i>name</i>) is
+ <b>true</b>, throw a <b>SyntaxError</b> exception.</li>
+ </ol>
+ </li>
+ <li>For each <i>name</i> in <i>varNames</i>, do
+ <ol class="block">
+ <li>If <i>envRec.</i><a href="#sec-haslexicaldeclaration">HasLexicalDeclaration</a>(<i>name</i>) is <b>true</b>, throw
+ a <b>SyntaxError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Let <i>varDeclarations</i> be the VarScopedDeclarations of <i>script</i>.</li>
+ <li>Let <i>functionsToInitialize</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>declaredFunctionNames</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each <i>d</i> in <i>varDeclarations</i>, in reverse list order do
+ <ol class="block">
+ <li>If <i>d</i> is neither a <i>VariableDeclaration</i> or a <i>ForBinding</i>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>d</i> is either a <i>FunctionDeclaration</i> or a
+ <i>GeneratorDeclaration</i>.</li>
+ <li>NOTE	If there are multiple <span style="font-family: Times New Roman"><i>FunctionDeclarations</i></span>
+ for the same name, the last declaration is used.</li>
+ <li>Let <i>fn</i> be the sole element of the BoundNames of <i>d.</i></li>
+ <li>If <i>fn</i> is not an element of <i>declaredFunctionNames</i>, then
+ <ol class="block">
+ <li>Let <i>fnDefinable</i> be <i>envRec.</i><a
+ href="#sec-candeclareglobalfunction">CanDeclareGlobalFunction</a>(<i>fn</i>).</li>
+ <li>If <i>fnDefinable</i> is <b>false</b>, throw <b>TypeError</b> exception.</li>
+ <li>Append <i>fn</i> to <i>declaredFunctionNames</i>.</li>
+ <li>Insert <i>d</i> as the first element of <i>functionsToInitialize</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>declaredVarNames</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each <i>d</i> in <i>varDeclarations</i>, do
+ <ol class="block">
+ <li>If <i>d</i> is a <i>VariableDeclaration</i> or a <i>ForBinding</i>, then
+ <ol class="block">
+ <li>For each String <i>vn</i> in the BoundNames of <i>d</i>, do
+ <ol class="block">
+ <li>If <i>vn</i> is not an element of <i>declaredFunctionNames</i>, then
+ <ol class="block">
+ <li>Let <i>vnDefinable</i> be <i>envRec.</i><a
+ href="#sec-candeclareglobalvar">CanDeclareGlobalVar</a>(<i>vn</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>vnDefinable</i>).</li>
+ <li>If <i>vnDefinable</i> is <b>false</b>, throw <b>TypeError</b> exception.</li>
+ <li>If <i>vn</i> is not an element of <i>declaredVarNames</i>, then
+ <ol class="block">
+ <li>Append <i>vn</i> to <i>declaredVarNames</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>NOTE: No abnormal terminations occur after this algorithm step if the global object is an ordinary object. However, if
+ the global object is a Proxy exotic object it may exhibit behaviours that cause abnormal terminations in some of the
+ following steps.</li>
+ <li>Let <i>lexDeclarations</i> be the LexicallyScopedDeclarations of <i>script</i>.</li>
+ <li>For each element <i>d</i> in <i>lexDeclarations</i> do
+ <ol class="block">
+ <li>NOTE Lexically declared names are only instantiated here but not initialized.</li>
+ <li>For each element <i>dn</i> of the BoundNames of <i>d</i> do
+ <ol class="block">
+ <li>If IsConstantDeclaration of <i>d</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateImmutableBinding(<i>dn</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateMutableBinding(<i>dn</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>For each production <i>f</i> in <i>functionsToInitialize</i>, do
+ <ol class="block">
+ <li>Let <i>fn</i> be the sole element of the BoundNames of <i>f.</i></li>
+ <li>Let <i>fo</i> be the result of performing InstantiateFunctionObject for <i>f</i> with argument <i>env</i>.</li>
+ <li>Let <i>status</i> be <i>envRec</i>.<a
+ href="#sec-createglobalfunctionbinding">CreateGlobalFunctionBinding</a>(<i>fn</i>, <i>fo</i>, <b>false</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>For each String <i>vn</i> in <i>declaredVarNames</i>, in list order do
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec.</i><a href="#sec-createglobalvarbinding">CreateGlobalVarBinding</a>(<i>vn</i>,
+ <b>false</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>)</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Early errors specified in <a href="#sec-scripts-static-semantics-early-errors">15.1.1</a>
+ prevent name conflicts between function/var declarations and let/const/class declarations as well as redeclaration of
+ let/const/class bindings for declaration contained within a single <i>Script</i>. However, such conflicts and
+ redeclarations that span more than one <i>Script</i> are detected as runtime errors during GlobalDeclarationInstantiation.
+ If any such errors are detected, no bindings are instantiated for the script. However, if the global object is defined
+ using Proxy exotic objects then the runtime tests for conflicting declarations may be unreliable resulting in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a> and some global declarations not being
+ instantiated. If this occurs, the code for the <i>Script</i> is not evaluated.</p>
+
+ <p>Unlike explicit var or function declarations, properties that are directly created on the global object result in
+ global bindings that may be shadowed by let/const/class declarations.</p>
+ </div>
+ </section>
+
+ <section id="sec-scriptevaluationjob">
+ <h1><span class="secnum" id="sec-15.1.9"><a href="#sec-scriptevaluationjob" title="link to this section">15.1.9</a></span>
+ Runtime Semantics: ScriptEvaluationJob ( <span style="font-family: sans-serif">sourceText</span> )</h1>
+
+ <p>The job ScriptEvaluationJob with parameter <var>sourceText</var> parses, validates, and evaluates <var>sourceText</var>
+ as a <span class="nt">Script</span>.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>sourceText</i> is an ECMAScript source text (see <a
+ href="#sec-ecmascript-language-source-code">clause 10</a>).</li>
+ <li>Parse <i>sourceText</i> using <i>Script</i> as the goal symbol and analyze the parse result for any Early Error
+ conditions. If the parse was successful and no early errors were found, let <i>code</i> be the resulting parse tree.
+ Otherwise, let <i>code</i> be an indication of one or more parsing errors and/or early errors. Parsing and early error
+ detection may be interweaved in an implementation dependent manner. If more than one parse or early error is present,
+ the number and ordering of reported errors is implementation dependent but at least one error must be reported.</li>
+ <li>If <i>code</i> is an error indication, then
+ <ol class="block">
+ <li>Report or log the error(s) in an implementation dependent manner.</li>
+ <li>Let <i>status</i> be <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>realm</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-code-realms">Realm</a>.</li>
+ <li>Let <i>status</i> be the result of ScriptEvaluation of <i>code</i> with argument <i>realm</i>.</li>
+ </ol>
+ </li>
+ <li>NextJob <i>status</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An implementation may parse a <i>sourceText</i> as a <i>Script</i> and analyze it for
+ Early Error conditions prior to the execution of the ScriptEvaluationJob for that <i>sourceText</i>. However, the
+ reporting of any errors must be deferred until the ScriptEvaluationJob is actually executed.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-modules">
+ <div class="front">
+ <h1><span class="secnum" id="sec-15.2"><a href="#sec-modules" title="link to this section">15.2</a></span> Modules</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Module</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ModuleBody</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleBody</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ModuleItemList</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItemList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ModuleItem</span></div>
+ <div class="rhs"><span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">ExportDeclaration</span></div>
+ <div class="rhs"><span class="nt">StatementListItem</span></div>
+ </div>
+ </div>
+
+ <section id="sec-module-semantics">
+ <div class="front">
+ <h1><span class="secnum" id="sec-15.2.1"><a href="#sec-module-semantics" title="link to this section">15.2.1</a></span>
+ Module Semantics</h1>
+ </div>
+
+ <section id="sec-module-semantics-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-15.2.1.1"><a href="#sec-module-semantics-static-semantics-early-errors"
+ title="link to this section">15.2.1.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">ModuleBody</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the LexicallyDeclaredNames of <span class="nt">ModuleItemList</span> contains any duplicate
+ entries.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the LexicallyDeclaredNames of <span class="nt">ModuleItemList</span> also
+ occurs in the VarDeclaredNames of <span class="nt">ModuleItemList</span>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if the ExportedNames of <span class="nt">ModuleItemList</span> contains any duplicate
+ entries.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the ExportedBindings of <span class="nt">ModuleItemList</span> does not also
+ occur in either the VarDeclaredNames of <var>ModuleItemList,</var> or the LexicallyDeclaredNames of <span
+ class="nt">ModuleItemList</span>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <span class="nt">ModuleItemList</span> Contains <code>super</code>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if <span style="font-family: Times New Roman"><i>ModuleItemList</i> Contains
+ <i>NewTarget</i></span></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsDuplicateLabels of <span class="nt">ModuleItemList</span> <span style="font-family:
+ Times New Roman">with argument «</span> <span style="font-family: Times New Roman">» is
+ <b>true</b>.</span></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsUndefinedBreakTarget of <span class="nt">ModuleItemList</span> <span
+ style="font-family: Times New Roman">with argument «</span> <span style="font-family: Times New Roman">»
+ is <b>true</b>.</span></p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if ContainsUndefinedContinueTarget of <span class="nt">ModuleItemList</span> <span
+ style="font-family: Times New Roman">with arguments « » and « » is <b>true</b>.</span></p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The duplicate ExportedNames rule implies that multiple <code>export default</code>
+ <i>ExportDeclaration</i> items within a <i>ModuleBody</i> is a Syntax Error. Additional error conditions relating to
+ conflicting or duplicate declarations are checked during module linking prior to evaluation of a <i>Module</i>. If any
+ such errors are detected the <i>Module</i> is not evaluated.</p>
+ </div>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-containsduplicatelabels">
+ <h1><span class="secnum" id="sec-15.2.1.2"><a href="#sec-module-semantics-static-semantics-containsduplicatelabels"
+ title="link to this section">15.2.1.2</a></span> Static Semantics: ContainsDuplicateLabels</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsduplicatelabels">13.0.1</a>, <a
+ href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-if-statement-static-semantics-containsduplicatelabels">13.5.2</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsduplicatelabels">13.6.1.1</a>, <a
+ href="#sec-while-statement-static-semantics-containsduplicatelabels">13.6.2.1</a>, <a
+ href="#sec-for-statement-static-semantics-containsduplicatelabels">13.6.3.2</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsduplicatelabels">13.6.4.3</a>, <a
+ href="#sec-with-statement-static-semantics-containsduplicatelabels">13.10.2</a>, <a
+ href="#sec-switch-statement-static-semantics-containsduplicatelabels">13.11.2</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsduplicatelabels">13.12.2</a>, <a
+ href="#sec-try-statement-static-semantics-containsduplicatelabels">13.14.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>hasDuplicates</i> be ContainsDuplicateLabels of <i>ModuleItemList</i> with argument <i>labelSet</i>.</li>
+ <li>If <i>hasDuplicates</i> is <b>true</b> return <b>true</b>.</li>
+ <li>Return ContainsDuplicateLabels of <i>ModuleItem</i> with argument <i>labelSet.</i></li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">ExportDeclaration</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-containsundefinedbreaktarget">
+ <h1><span class="secnum" id="sec-15.2.1.3"><a href="#sec-module-semantics-static-semantics-containsundefinedbreaktarget"
+ title="link to this section">15.2.1.3</a></span> Static Semantics: ContainsUndefinedBreakTarget</h1>
+
+ <p>With argument <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedbreaktarget">13.0.2</a>, <a
+ href="#sec-block-static-semantics-containsundefinedbreaktarget">13.1.3</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedbreaktarget">13.5.3</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedbreaktarget">13.6.1.2</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedbreaktarget">13.6.2.2</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedbreaktarget">13.6.3.3</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedbreaktarget">13.6.4.4</a>, <a
+ href="#sec-break-statement-static-semantics-containsundefinedbreaktarget">13.8.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedbreaktarget">13.10.3</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedbreaktarget">13.11.3</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedbreaktarget">13.12.3</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedbreaktarget">13.14.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedBreakTarget of <i>ModuleItemList</i> with argument
+ <i>labelSet</i>.</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedBreakTarget of <i>ModuleItem</i> with argument <i>labelSet.</i></li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">ExportDeclaration</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-containsundefinedcontinuetarget">
+ <h1><span class="secnum" id="sec-15.2.1.4"><a
+ href="#sec-module-semantics-static-semantics-containsundefinedcontinuetarget"
+ title="link to this section">15.2.1.4</a></span> Static Semantics: ContainsUndefinedContinueTarget</h1>
+
+ <p>With arguments <var>iterationSet</var> and <var>labelSet</var>.</p>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-containsundefinedcontinuetarget">13.0.3</a>, <a
+ href="#sec-block-static-semantics-containsundefinedcontinuetarget">13.1.4</a>, <a
+ href="#sec-if-statement-static-semantics-containsundefinedcontinuetarget">13.5.4</a>, <a
+ href="#sec-do-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.1.3</a>, <a
+ href="#sec-while-statement-static-semantics-containsundefinedcontinuetarget">13.6.2.3</a>, <a
+ href="#sec-for-statement-static-semantics-containsundefinedcontinuetarget">13.6.3.4</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-containsundefinedcontinuetarget">13.6.4.5</a>, <a
+ href="#sec-continue-statement-static-semantics-containsundefinedcontinuetarget">13.7.2</a>, <a
+ href="#sec-with-statement-static-semantics-containsundefinedcontinuetarget">13.10.4</a>, <a
+ href="#sec-switch-statement-static-semantics-containsundefinedcontinuetarget">13.11.4</a>, <a
+ href="#sec-labelled-statements-static-semantics-containsundefinedcontinuetarget">13.12.4</a>, <a
+ href="#sec-try-statement-static-semantics-containsundefinedcontinuetarget">13.14.4</a>.</p>
+
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>hasUndefinedLabels</i> be ContainsUndefinedContinueTarget of <i>ModuleItemList</i> with arguments
+ <i>iterationSet</i> and « ».</li>
+ <li>If <i>hasUndefinedLabels</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return ContainsUndefinedContinueTarget of <i>ModuleItem</i> with arguments <i>iterationSet</i> and
+ « »<i>.</i></li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">ExportDeclaration</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-exportedbindings">
+ <h1><span class="secnum" id="sec-15.2.1.5"><a href="#sec-module-semantics-static-semantics-exportedbindings"
+ title="link to this section">15.2.1.5</a></span> Static Semantics: ExportedBindings</h1>
+
+ <p>See also: <a href="#sec-exports-static-semantics-exportedbindings">15.2.3.3</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> ExportedBindings are the locally bound names that are explicitly associated with a
+ <i>Module</i>’s ExportedNames.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be ExportedBindings of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>names</i> the elements of the ExportedBindings of <i>ModuleItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">StatementListItem</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-exportednames">
+ <h1><span class="secnum" id="sec-15.2.1.6"><a href="#sec-module-semantics-static-semantics-exportednames"
+ title="link to this section">15.2.1.6</a></span> Static Semantics: ExportedNames</h1>
+
+ <p>See also: <a href="#sec-exports-static-semantics-exportednames">15.2.3.4</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> ExportedNames are the externally visible names that a <i>Module</i> explicitly maps to
+ one of its local name bindings.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be ExportedNames of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>names</i> the elements of the ExportedNames of <i>ModuleItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ExportDeclaration</span></div>
+ <ol class="proc">
+ <li>Return the ExportedNames of <i>ExportDeclaration</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">StatementListItem</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-exportentries">
+ <h1><span class="secnum" id="sec-15.2.1.7"><a href="#sec-module-semantics-static-semantics-exportentries"
+ title="link to this section">15.2.1.7</a></span> Static Semantics: ExportEntries</h1>
+
+ <p>See also: <a href="#sec-exports-static-semantics-exportentries">15.2.3.5</a>.</p>
+
+ <div class="gp prod"><span class="nt">Module</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>entries</i> be ExportEntries of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>entries</i> the elements of the ExportEntries of <i>ModuleItem.</i></li>
+ <li>Return <i>entries</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">StatementListItem</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-importentries">
+ <h1><span class="secnum" id="sec-15.2.1.8"><a href="#sec-module-semantics-static-semantics-importentries"
+ title="link to this section">15.2.1.8</a></span> Static Semantics: ImportEntries</h1>
+
+ <p>See also: <a href="#sec-imports-static-semantics-importentries">15.2.2.3</a>.</p>
+
+ <div class="gp prod"><span class="nt">Module</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>entries</i> be ImportEntries of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>entries</i> the elements of the ImportEntries of <i>ModuleItem.</i></li>
+ <li>Return <i>entries</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ExportDeclaration</span></div>
+ <div class="rhs"><span class="nt">StatementListItem</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-isstrict">
+ <h1><span class="secnum" id="sec-15.2.1.9"><a href="#sec-module-semantics-static-semantics-isstrict"
+ title="link to this section">15.2.1.9</a></span> Static Semantics: IsStrict</h1>
+
+ <p>See also: <a href="#sec-function-definitions-static-semantics-isstrict">14.1.13</a>, <a
+ href="#sec-scripts-static-semantics-isstrict">15.1.2</a>.</p>
+
+ <p><span class="prod"><span class="nt">Module</span> <span class="geq">:</span> <span
+ class="grhsannot">[empty]</span></span></p>
+
+ <div class="gp prod"><span class="nt">ModuleBody</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span></div>
+ <ol class="proc">
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-modulerequests">
+ <h1><span class="secnum" id="sec-15.2.1.10"><a href="#sec-module-semantics-static-semantics-modulerequests"
+ title="link to this section">15.2.1.10</a></span> Static Semantics: ModuleRequests</h1>
+
+ <p>See also: <a href="#sec-imports-static-semantics-modulerequests">15.2.2.5</a>,<a
+ href="#sec-exports-static-semantics-modulerequests">15.2.3.9</a>.</p>
+
+ <div class="gp prod"><span class="nt">Module</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Return ModuleRequests of <i>ModuleItem</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>moduleNames</i> be ModuleRequests of <i>ModuleItemList</i>.</li>
+ <li>Let <i>additionalNames</i> be ModuleRequests of <i>ModuleItem.</i></li>
+ <li>Append to <i>moduleNames</i> each element of <i>additionalNames</i> that is not already an element of
+ <i>moduleNames.</i></li>
+ <li>Return <i>moduleNames</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-lexicallydeclarednames">
+ <h1><span class="secnum" id="sec-15.2.1.11"><a href="#sec-module-semantics-static-semantics-lexicallydeclarednames"
+ title="link to this section">15.2.1.11</a></span> Static Semantics: LexicallyDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-containsduplicatelabels">13.1.2</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallydeclarednames">13.11.5</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallydeclarednames">13.12.6</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallydeclarednames">14.1.14</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallydeclarednames">14.2.10</a>, <a
+ href="#sec-scripts-static-semantics-lexicallydeclarednames">15.1.3</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The LexicallyDeclaredNames of a <i>Module</i> includes the names of all of its imported
+ bindings.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be LexicallyDeclaredNames of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>names</i> the elements of the LexicallyDeclaredNames of <i>ModuleItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ImportDeclaration</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>ImportDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ExportDeclaration</span></div>
+ <ol class="proc">
+ <li>If <i>ExportDeclaration</i> is <code>export</code> <i>VariableStatement</i><span style="font-family:
+ sans-serif">,</span> return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return the BoundNames of <i>ExportDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">StatementListItem</span></div>
+ <ol class="proc">
+ <li>Return LexicallyDeclaredNames of <i>StatementListItem</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> At the top level of a <i>Module</i>, function declarations are treated like lexical
+ declarations rather than like var declarations.</p>
+ </div>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-lexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-15.2.1.12"><a href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">15.2.1.12</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a>, <a
+ href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a>, <a
+ href="#sec-exports-static-semantics-lexicallyscopeddeclarations">15.2.3.8</a>.</p>
+
+ <div class="gp prod"><span class="nt">Module</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be LexicallyScopedDeclarations of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the LexicallyScopedDeclarations of <i>ModuleItem.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ImportDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-vardeclarednames">
+ <h1><span class="secnum" id="sec-15.2.1.13"><a href="#sec-module-semantics-static-semantics-vardeclarednames"
+ title="link to this section">15.2.1.13</a></span> Static Semantics: VarDeclaredNames</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-vardeclarednames">13.0.5</a>, <a
+ href="#sec-block-static-semantics-vardeclarednames">13.1.11</a>, <a
+ href="#sec-variable-statement-static-semantics-vardeclarednames">13.2.2.2</a>, <a
+ href="#sec-if-statement-static-semantics-vardeclarednames">13.5.5</a>, <a
+ href="#sec-do-while-statement-static-semantics-vardeclarednames">13.6.1.4</a>, <a
+ href="#sec-while-statement-static-semantics-vardeclarednames">13.6.2.4</a>, <a
+ href="#sec-for-statement-static-semantics-vardeclarednames">13.6.3.5</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-vardeclarednames">13.6.4.7</a>, <a
+ href="#sec-with-statement-static-semantics-vardeclarednames">13.10.5</a>, <a
+ href="#sec-switch-statement-static-semantics-vardeclarednames">13.11.7</a>, <a
+ href="#sec-labelled-statements-static-semantics-vardeclarednames">13.12.12</a>, <a
+ href="#sec-try-statement-static-semantics-vardeclarednames">13.14.5</a>, <a
+ href="#sec-function-definitions-static-semantics-vardeclarednames">14.1.16</a>, 0, <a
+ href="#sec-scripts-static-semantics-vardeclarednames">15.1.5</a>.</p>
+
+ <div class="gp prod"><span class="nt">Module</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span
+ class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></span></p>
+
+ <ol class="proc">
+ <li>Let <i>names</i> be VarDeclaredNames of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>names</i> the elements of the VarDeclaredNames of <i>ModuleItem.</i></li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ImportDeclaration</span></div>
+ <ol class="proc">
+ <li>Return an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ExportDeclaration</span></div>
+ <ol class="proc">
+ <li>If <i>ExportDeclaration</i> is <code>export</code> <i>VariableStatement</i>, return BoundNames of
+ <i>ExportDeclaration</i>.</li>
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-module-semantics-static-semantics-varscopeddeclarations">
+ <h1><span class="secnum" id="sec-15.2.1.14"><a href="#sec-module-semantics-static-semantics-varscopeddeclarations"
+ title="link to this section">15.2.1.14</a></span> Static Semantics: VarScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-statement-semantics-static-semantics-varscopeddeclarations">13.0.6</a>, <a
+ href="#sec-block-static-semantics-varscopeddeclarations">13.1.12</a>, <a
+ href="#sec-variable-statement-static-semantics-varscopeddeclarations">13.2.2.3</a>, <a
+ href="#sec-if-statement-static-semantics-varscopeddeclarations">13.5.6</a>, <a
+ href="#sec-do-while-statement-static-semantics-varscopeddeclarations">13.6.1.5</a>, <a
+ href="#sec-while-statement-static-semantics-varscopeddeclarations">13.6.2.5</a>, <a
+ href="#sec-for-statement-static-semantics-varscopeddeclarations">13.6.3.6</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-varscopeddeclarations">13.6.4.8</a>, <a
+ href="#sec-with-statement-static-semantics-varscopeddeclarations">13.10.6</a>, <a
+ href="#sec-switch-statement-static-semantics-varscopeddeclarations">13.11.8</a>, <a
+ href="#sec-labelled-statements-static-semantics-varscopeddeclarations">13.12.13</a>, <a
+ href="#sec-try-statement-static-semantics-varscopeddeclarations">13.14.6</a>, <a
+ href="#sec-function-definitions-static-semantics-varscopeddeclarations">14.1.17</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-varscopeddeclarations">14.2.12</a>, <a
+ href="#sec-scripts-static-semantics-varscopeddeclarations">15.1.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">Module</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>declarations</i> be VarScopedDeclarations of <i>ModuleItemList</i>.</li>
+ <li>Append to <i>declarations</i> the elements of the VarScopedDeclarations of <i>ModuleItem.</i></li>
+ <li>Return <i>declarations</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ImportDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ExportDeclaration</span></div>
+ <ol class="proc">
+ <li>If <i>ExportDeclaration</i> is <code>export</code> <i>VariableStatement</i>, return VarScopedDeclarations of
+ <i>VariableStatement</i>.</li>
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-abstract-module-records">
+ <h1><span class="secnum" id="sec-15.2.1.15"><a href="#sec-abstract-module-records"
+ title="link to this section">15.2.1.15</a></span> Abstract Module Records</h1>
+
+ <p>A Module Record encapsulates structural information about the imports and exports of a single module. This information
+ is used to link the imports and exports of sets of connected modules. A Module Record includes four fields that are only
+ used when evaluating a module.</p>
+
+ <p>For specification purposes Module Record values are values of the Record specification type and can be thought of as
+ existing in a simple object-oriented hierarchy where Module Record is an abstract class with concrete subclasses. This
+ specification only defines a single Module Record concrete subclass name Source Text Module Record. Other specifications
+ and implementations may define additional Module Record subclass corresponding to alternative module definition facilities
+ that they defined.</p>
+
+ <p>Module Record defines the fields listed in <a href="#table-36">Table 36</a>. All Module Definition subclasses include
+ at least those fields. Module Record also defines the abstract method list in <a href="#table-37">Table 37</a>. All Module
+ definition subclasses must provide concrete implementations of these abstract methods.</p>
+
+ <figure>
+ <figcaption><span id="table-36">Table 36</span> — Module Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[Realm]]</td>
+ <td><a href="#sec-code-realms">Realm</a> Record | <span class="value">undefined</span></td>
+ <td>The <a href="#sec-code-realms">Realm</a> within which this module was created. <span class="value">undefined</span> if not yet assigned.</td>
+ </tr>
+ <tr>
+ <td>[[Environment]]</td>
+ <td><a href="#sec-lexical-environments">Lexical Environment</a> | <span class="value">undefined</span></td>
+ <td>The <a href="#sec-lexical-environments">Lexical Environment</a> containing the top level bindings for this module. This field is set when the module is instantiated.</td>
+ </tr>
+ <tr>
+ <td>[[Namespace]]</td>
+ <td>Object | <span class="value">undefined</span></td>
+ <td>The Module Namespace Object (<a href="#sec-module-namespace-objects">26.3</a>) if one has been created for this module. Otherwise <span class="value">undefined</span>.</td>
+ </tr>
+ <tr>
+ <td>[[Evaluated]]</td>
+ <td>Boolean</td>
+ <td>Initially <span class="value">false</span>, <span class="value">true</span> if evaluation of this module has started. Remains <span class="value">true</span> when evaluation completes, even if it is an <a href="#sec-completion-record-specification-type">abrupt completion</a>.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <figure>
+ <figcaption><span id="table-37">Table 37</span> — Abstract Methods of Environment Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Method</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Purpose</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black"><a href="#sec-getexportednames">GetExportedNames</a>(exportStarSet)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black">Return a list of all names that are either directly or indirectly exported from this module.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-resolveexport">ResolveExport</a>(exportName, resolveSet, exportStarSet)</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Return the binding of a name exported by this modules. Bindings are represented by a Record of the form {[[module]]: Module Record, [[bindingName]]: String}</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-moduledeclarationinstantiation">ModuleDeclarationInstantiation</a>()</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">Transitively resolve all module dependencies and create a Module <a href="#sec-environment-records">Environment Record</a> for the module.</td>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black"><a href="#sec-moduleevaluation">ModuleEvaluation</a>()</td>
+
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">
+ <p>Do nothing if this module has already been evaluated. Otherwise, transitively evaluate all module dependences
+ of this module and then evaluate this module.</p>
+
+ <p><a href="#sec-moduledeclarationinstantiation">ModuleDeclarationInstantiation</a> must be completed prior to
+ invoking this method.</p>
+ </td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-source-text-module-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-15.2.1.16"><a href="#sec-source-text-module-records"
+ title="link to this section">15.2.1.16</a></span> Source Text Module Records</h1>
+
+ <p>A Source Text Module Record is used to represent information about a module that was defined from ECMAScript source
+ text (10) that was parsed using the goal symbol <span class="nt">Module</span>. Its fields contain digested information
+ about the names that are imported by the module and its concrete methods use this digest to link, instantiate, and
+ evaluate the module.</p>
+
+ <p>In addition to the fields, defined in <a href="#table-36">Table 36</a>, that are common to all Module Records, Source
+ Test Module Records have the additional fields listed in <a href="#table-38">Table 38</a>. Each of these fields
+ initially has the value <span class="value">undefined</span>.</p>
+
+ <figure>
+ <figcaption><span id="table-38">Table 38</span> — Additional Fields of Source Text Module Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">[[ECMAScriptCode]]</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">a parse result</td>
+ <td style="border-bottom: 1px solid black; border-left: 1px solid black; border-right: 1px solid black; border-top: 1px solid black">The result of parsing the source text of this module using <span class="nt">Module</span> as the goal symbol.</td>
+ </tr>
+ <tr>
+ <td>[[RequestedModules]]</td>
+ <td><a href="#sec-list-and-record-specification-type">List</a> of String</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of all the <span class="nt">ModuleSpecifier</span> strings used by the module represented by this record to request the importation of a module. The <a href="#sec-list-and-record-specification-type">List</a> is source code occurrence ordered.</td>
+ </tr>
+ <tr>
+ <td>[[ImportEntries]]</td>
+ <td><a href="#sec-list-and-record-specification-type">List</a> of ImportEntry Records</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of ImportEntry records derived from the code of this module. Module names within the ImportEntry records have been host normalized.</td>
+ </tr>
+ <tr>
+ <td>[[LocalExportEntries]]</td>
+ <td><a href="#sec-list-and-record-specification-type">List</a> of ExportEntry Records</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of ExportEntry records derived from the code of this module that correspond to declarations that occur within the module. Module names within the ImportEntry records have been host normalized.</td>
+ </tr>
+ <tr>
+ <td>[[IndirectExportEntries]]</td>
+ <td><a href="#sec-list-and-record-specification-type">List</a> of ExportEntry Records</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of ExportEntry records derived from the code of this module that correspond to reexported imports that occur within the module. Module names within the ImportEntry records have been host normalized.</td>
+ </tr>
+ <tr>
+ <td>[[StarExportEntries]]</td>
+ <td><a href="#sec-list-and-record-specification-type">List</a> of ExportEntry Records</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of ExportEntry records derived from the code of this module that correspond to export * declarations that occur within the module. Module names within the ImportEntry records have been host normalized.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>An ImportEntry Record is a Record that digests information about a single declarative import. Each ImportEntry Record
+ has the fields defined in <a href="#table-39">Table 39</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-39">Table 39</span> — ImportEntry Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value Type</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[ModuleRequest]]</td>
+ <td>String</td>
+ <td>String value of the <span class="nt">ModuleSpecifier</span> of the <span class="nt">ImportDeclaration</span>.</td>
+ </tr>
+ <tr>
+ <td>[[ImportName]]</td>
+ <td>String</td>
+ <td>The name under which the desired binding is exported by the module identified by [[ModuleRequest]]. The value <code>"*"</code> indicates that the import request is for the target module’s namespace object.</td>
+ </tr>
+ <tr>
+ <td>[[LocalName]]</td>
+ <td>String</td>
+ <td>The name that is used to locally access the imported value from within the importing module.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <a href="#table-40">Table 40</a> gives examples of ImportEntry records fields used to
+ represent the syntactic import forms:</p>
+ </div>
+
+ <figure>
+ <figcaption><span id="table-40">Table 40</span> (Informative) — Import Forms Mappings to ImportEntry Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">
+ <p class="Note"><b><i>Import Statement Form</i></b></p>
+ </th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">
+ <p class="Note"><b>[[ModuleRequest]]</b></p>
+ </th>
+ <th style="border-bottom: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">
+ <p class="Note"><b>[[ImportName]]</b></p>
+ </th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">
+ <p class="Note"><b>[[LocalName]]</b></p>
+ </th>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>import v from "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"mod"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"default"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"v"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>import * as ns from "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"mod"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"*"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"ns"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>import {x} from "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"mod"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>import {x as v} from "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"mod"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"v"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>import "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note">An ImportEntry Record is not created.</p>
+ </td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>An ExportEntry Record is a Record that digests information about a single declarative export. Each ExportEntry Record
+ has the fields defined in <a href="#table-41">Table 41</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-41">Table 41</span> — ExportEntry Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000"><span style="background-color: #C0C0C0"><b><i>Value</i></b></span> <span style="background-color: #C0C0C0"><b><i>Type</i></b></span></th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[ExportName]]</td>
+ <td>String</td>
+ <td>The name used to export this binding by this module.</td>
+ </tr>
+ <tr>
+ <td>[[ModuleRequest]]</td>
+ <td>String | null</td>
+ <td>The String value of the <span class="nt">ModuleSpecifier</span> of the <span class="nt">ExportDeclaration</span>. <span class="value">null</span> if the <span class="nt">ExportDeclaration</span> does not have a <span class="nt">ModuleSpecifier</span>.</td>
+ </tr>
+ <tr>
+ <td>[[ImportName]]</td>
+ <td>String | null</td>
+ <td>The name under which the desired binding is exported by the module identified by [[ModuleRequest]]. <span class="value">null</span> if the <span class="nt">ExportDeclaration</span> does not have a <span class="nt">ModuleSpecifier</span>. <code>"*"</code> indicates that the export request is for all exported bindings.</td>
+ </tr>
+ <tr>
+ <td>[[LocalName]]</td>
+ <td>String | null</td>
+ <td>The name that is used to locally access the exported value from within the importing module. <span class="value">null</span> if the exported value is not locally accessible from within the module.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <a href="#table-42">Table 42</a> gives examples of the ExportEntry record fields used
+ to represent the syntactic export forms:</p>
+ </div>
+
+ <figure>
+ <figcaption><span id="table-42">Table 42</span> (Informative) — Export Forms Mappings to ExportEntry Records</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">
+ <p class="Note"><b><i>Export Statement Form</i></b></p>
+ </th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 0px solid black; border-top: 2px solid #000000">
+ <p class="Note"><b>[[ExportName]]</b></p>
+ </th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">
+ <p class="Note"><b>[[ModuleRequest]]</b></p>
+ </th>
+ <th style="border-bottom: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">
+ <p class="Note"><b>[[ImportName]]</b></p>
+ </th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">
+ <p class="Note"><b>[[LocalName]]</b></p>
+ </th>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export var v;</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"v"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"v"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export default function f(){};</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"default"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"f"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export default function(){};</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"default"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"*default*"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export default 42;</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"default"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"*default*"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export {x};</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export {v as x};</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"v"</code></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export {x} from "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"mod"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export {v as x} from "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"x"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"mod"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"v"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <p class="Note"><code>export * from "mod";</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"mod"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><code>"*"</code></p>
+ </td>
+
+ <td>
+ <p class="Note"><b>null</b></p>
+ </td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The following definitions specify the required concrete methods and other abstract operations for Source Text Module
+ Records</p>
+ </div>
+
+ <section id="sec-parsemodule">
+ <h1><span class="secnum" id="sec-15.2.1.16.1"><a href="#sec-parsemodule"
+ title="link to this section">15.2.1.16.1</a></span> Runtime Semantics: ParseModule ( sourceText )</h1>
+
+ <p>The abstract operation ParseModule with argument <var>sourceText</var> creates a Source Text Module Record based upon
+ the result of parsing <var>sourceText</var> as a <var>Module.</var> ParseModule performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-algorithm-conventions">Assert</a>:
+ <i>sourceText</i> is an ECMAScript source text (see <a href="#sec-ecmascript-language-source-code">clause
+ 10</a>).</li>
+ <li>Parse <i>sourceText</i> using <i>Module</i> as the goal symbol and analyze the parse result for any Early Error
+ conditions. If the parse was successful and no early errors were found, let <i>body</i> be the resulting parse
+ tree. Otherwise, let <i>body</i> be an indication of one or more parsing errors and/or early errors. Parsing and
+ early error detection may be interweaved in an implementation dependent manner. If more than one parse or early
+ error is present, the number and ordering of reported errors is implementation dependent but at least one error
+ must be reported.</li>
+ <li>If <i>body</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a> or error
+ indication, then
+ <ol class="block">
+ <li>Throw a <b>SyntaxError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Let <i>requestedModules</i> be the ModuleRequests of <i>body</i>.</li>
+ <li>Let <i>importEntries</i> be ImportEntries of <i>body</i>.</li>
+ <li>Let <i>indirectExportEntries</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>localExportEntries</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>starExportEntries</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>exportEntries</i> be ExportEntries of <i>body</i>.</li>
+ <li>For each record <i>ee</i> in <i>exportEntries</i>, do
+ <ol class="block">
+ <li>If <i>ee</i>.[[ModuleRequest]] is <b>null</b>, then
+ <ol class="block">
+ <li>Append <i>ee</i> to <i>localExportEntries</i>.</li>
+ </ol>
+ </li>
+ <li>Else, if <i>ee</i>.[[ImportName]] is <code>"*"</code>, then
+ <ol class="block">
+ <li>Append <i>ee</i> to <i>starExportEntries</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Append <i>ee</i> to <i>indirectExportEntries</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return Source Text Module Record {[[Realm]]: <b>undefined</b>, [[Environment]]: <b>undefined</b>, [[Namespace]]:
+ <b>undefined</b>, [[Evaluated]]: <b>false</b>, [[ECMAScriptCode]]: <i>body</i>, [[RequestedModules]]:
+ <i>requestedModules</i>, [[ImportEntries]]: <i>importEntries</i>, [[LocalExportEntries]]:
+ <i>localExportEntries</i>, [[StarExportEntries]]: <i>starExportEntries</i>, [[IndirectExportEntries]]:
+ <i>indirectExportEntries</i>}.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An implementation may parse the source code identified by a host supplied module
+ identifier as a <i>Module</i> and analyze it for Early Error conditions prior to the evaluation of ParseModule for
+ that module source text. However, the reporting of any errors must be deferred until the point where this
+ specification actually performs ParseModule upon that source text.</p>
+ </div>
+ </section>
+
+ <section id="sec-getexportednames">
+ <h1><span class="secnum" id="sec-15.2.1.16.2"><a href="#sec-getexportednames"
+ title="link to this section">15.2.1.16.2</a></span> GetExportedNames( exportStarSet ) Concrete Method</h1>
+
+ <p>The GetExportedNames concrete method of a Source Text Module Record with argument <var>exportStarSet</var> performs
+ the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>module</i> be this Source Text Module Record.</li>
+ <li>If <i>exportStarSet</i> contains <i>module</i>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: We’ve reached the starting point of an import *
+ circularity.</li>
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </li>
+ <li>Append <i>module</i> to <i>exportStarSet</i>.</li>
+ <li>Let <i>exportedNames</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each ExportEntry Record <i>e</i> in <i>module</i>.[[LocalExportEntries]], do
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i> provides the leaf binding for this export.</li>
+ <li>Append <i>e</i>.[[ExportName]] to <i>exportedNames</i>.</li>
+ </ol>
+ </li>
+ <li>For each ExportEntry Record <i>e</i> in <i>module</i>.[[IndirectExportEntries]], do
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i> imports a specific binding for this
+ export.</li>
+ <li>Append <i>e</i>.[[ExportName]] to <i>exportedNames</i>.</li>
+ </ol>
+ </li>
+ <li>For each ExportEntry Record <i>e</i> in <i>module</i>.[[StarExportEntries]], do
+ <ol class="block">
+ <li>Let <i>requestedModule</i> be <a
+ href="#sec-hostresolveimportedmodule">HostResolveImportedModule</a>(<i>module</i>,
+ <i>e</i>.[[ModuleRequest]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>requestedModule</i>).</li>
+ <li>Let <i>starNames</i> be <i>requestedModule.</i>GetExportedNames(<i>exportStarSet</i>).</li>
+ <li>For each element <i>n</i> of <i>starNames</i>, do
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>n</i>, <code>"default"</code>) is <b>false</b>, then
+ <ol class="block">
+ <li>If <i>n</i> is not an element of <i>exportedNames</i>, then
+ <ol class="block">
+ <li>Append <i>n</i> to <i>exportedNames</i>.Return <i>exportedNames</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>exportedNames</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> GetExportedNames does not filter out or throw an exception for names that have
+ ambiguous star export bindings.</p>
+ </div>
+ </section>
+
+ <section id="sec-resolveexport">
+ <h1><span class="secnum" id="sec-15.2.1.16.3"><a href="#sec-resolveexport"
+ title="link to this section">15.2.1.16.3</a></span> ResolveExport( exportName, resolveSet, exportStarSet ) Concrete
+ Method</h1>
+
+ <p>The ResolveExport concrete method of a Source Text Module Record with arguments <var>exportName</var>,
+ <var>resolveSet</var>, and <var>exportStarSet</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>module</i> be this Source Text Module Record.</li>
+ <li>For each Record {[[module]], [[exportName]]} <i>r</i> in <i>resolveSet</i>, do:
+ <ol class="block">
+ <li>If <i>module</i> and <i>r</i>.[[module]] are the same Module Record and <a
+ href="#sec-samevalue">SameValue</a>(<i>exportName</i>, <i>r</i>.[[exportName]]) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: this is a circular import request.</li>
+ <li>Return <b>null</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Append the Record {[[module]]: <i>module</i>, [[exportName]]: <i>exportName</i>} to <i>resolveSet</i>.</li>
+ <li>For each ExportEntry Record <i>e</i> in <i>module</i>.[[LocalExportEntries]], do
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>exportName</i>, <i>e</i>.[[ExportName]]) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i> provides the leaf binding for this
+ export.</li>
+ <li>Return Record{[[module]]: <i>module,</i> [[bindingName]]: <i>e</i>.[[LocalName]]}.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>For each ExportEntry Record <i>e</i> in <i>module</i>.[[IndirectExportEntries]], do
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>exportName</i>, <i>e</i>.[[ExportName]]) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i> imports a specific binding for this
+ export.</li>
+ <li>Let <i>importedModule</i> be <a
+ href="#sec-hostresolveimportedmodule">HostResolveImportedModule</a>(<i>module</i>,
+ <i>e</i>.[[ModuleRequest]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>importedModule</i>).</li>
+ <li>Let <i>indirectResolution</i> be <i>importedModule.</i>ResolveExport(<i>e</i>.[[ImportName]],
+ <i>resolveSet</i>, <i>exportStarSet</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>indirectResolution</i>).</li>
+ <li>If <i>indirectResolution</i> is not <b>null</b>, return <i>indirectResolution</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>exportName</i>, <code>"default"</code>) is <b>true</b>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: A <code>default</code> export was not explicitly defined by
+ this module.</li>
+ <li>Throw a <b>SyntaxError</b> exception.</li>
+ <li>NOTE A <code>default</code> export cannot be provided by an <code>export *</code>.</li>
+ </ol>
+ </li>
+ <li>If <i>exportStarSet</i> contains <i>module</i>, then return <b>null</b>.</li>
+ <li>Append <i>module</i> to <i>exportStarSet</i>.</li>
+ <li>Let <i>starResolution</i> be <b>null</b>.</li>
+ <li>For each ExportEntry Record <i>e</i> in <i>module</i>.[[StarExportEntries]], do
+ <ol class="block">
+ <li>Let <i>importedModule</i> be <a
+ href="#sec-hostresolveimportedmodule">HostResolveImportedModule</a>(<i>module</i>,
+ <i>e</i>.[[ModuleRequest]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>importedModule</i>).</li>
+ <li>Let <i>resolution</i> be <i>importedModule</i>.ResolveExport(<i>exportName</i>, <i>resolveSet</i>,
+ <i>exportStarSetCopy</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resolution</i>).</li>
+ <li>If <i>resolution</i> is <code>"ambiguous"</code>, return <code>"ambiguous"</code>.</li>
+ <li>If <i>resolution</i> is not <b>null</b>, then
+ <ol class="block">
+ <li>If <i>starResolution</i> is <b>null</b>, let <i>starResolution</i> be <i>resolution</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: there is more than one * import that includes the
+ requested name.</li>
+ <li>If <i>resolution</i>.[[module]] and <i>starResolution</i>.[[module]] are not the same Module Record or <a
+ href="#sec-samevalue">SameValue</a>(<i>resolution.</i>[[exportName]],
+ <i>starResolution</i>.[[exportName]]) is <b>false</b>, return <code>"ambiguous"</code>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>starResolution</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> ResolveExport attempts to resolve an imported binding to the actual defining module
+ and local binding name. The defining module may be the module represented by the Module Record this method was invoked
+ on or some other module that is imported by that module. The parameter <i>resolveSet</i> is use to detect unresolved
+ circular import/export paths. If a pair consisting of <span style="font-family: sans-serif">specific module
+ record</span> and <i>exportName</i> is reached that is already in <i>resolveSet</i>, an import circularity has been
+ encountered. Before recursively calling ResolveExport, a pair consisting of <i>module</i> and <i>exportName</i> is
+ added to <i>resolveSet</i>.</p>
+
+ <p>If a defining module is found a Record {[[module]]<i>,</i> [[bindingName]]} is returned. This record identifies the
+ resolved binding of the originally requested export. If no definition was found or the request is found to be
+ circular, <b>null</b> is returned. If the request is found to be ambiguous, the string <code>"ambiguous"</code> is
+ returned.</p>
+ </div>
+ </section>
+
+ <section id="sec-moduledeclarationinstantiation">
+ <h1><span class="secnum" id="sec-15.2.1.16.4"><a href="#sec-moduledeclarationinstantiation"
+ title="link to this section">15.2.1.16.4</a></span> ModuleDeclarationInstantiation( ) Concrete Method</h1>
+
+ <p>The ModuleDeclarationInstantiation concrete method of a Source Text Module Record performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>module</i> be this Source Text Module Record.</li>
+ <li>Let <i>realm</i> be <i>module</i>.[[Realm]].</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>realm</i> is not <b>undefined</b>.</li>
+ <li>Let <i>code</i> be <i>module</i>.[[ECMAScriptCode]].</li>
+ <li>If <i>module</i>.[[Environment]] is not <b>undefined</b>, return <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>).</li>
+ <li>Let <i>env</i> be <a href="#sec-newmoduleenvironment">NewModuleEnvironment</a>(<i>realm</i>.[[globalEnv]]).</li>
+ <li>Set <i>module</i>.[[Environment]] to <i>env</i>.</li>
+ <li>For each String <i>required</i> that is an element of <i>module</i>.[[RequestedModules]] do,
+ <ol class="block">
+ <li>NOTE: Before instantiating a module, all of the modules it requested must be available. An implementation may
+ perform this test at any time prior to this point,</li>
+ <li>Let <i>requiredModule</i> be <a
+ href="#sec-hostresolveimportedmodule">HostResolveImportedModule</a>(<i>module</i>, <i>required</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>requiredModule</i>).</li>
+ <li>Let <i>status</i> be <i>requiredModule</i>.ModuleDeclarationInstantiation().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>For each ExportEntry Record <i>e</i> in <i>module</i>.[[IndirectExportEntries]], do
+ <ol class="block">
+ <li>Let <i>resolution</i> be <i>module</i>.<a href="#sec-resolveexport">ResolveExport</a>(<i>e</i>.[[ExportName]],
+ «‍ », «‍ »).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resolution</i>).</li>
+ <li>If <i>resolution</i> is <b>null</b> or <i>resolution</i> is <code>"ambiguous"</code>, throw a
+ <b>SyntaxError</b> exception.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: all named exports from <i>module</i> are resolvable.</li>
+ <li>Let <i>envRec</i> be <i>env</i>’s environment record.</li>
+ <li>For each ImportEntry Record <i>in</i> in <i>module</i>.[[ImportEntries]], do
+ <ol class="block">
+ <li>Let <i>importedModule</i> be <a
+ href="#sec-hostresolveimportedmodule">HostResolveImportedModule</a>(<i>module</i>,
+ <i>in</i>.[[ModuleRequest]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>importedModule</i>).</li>
+ <li>If <i>in</i>.[[ImportName]] is <code>"*"</code>, then
+ <ol class="block">
+ <li>Let <i>namespace</i> be <a
+ href="#sec-getmodulenamespace">GetModuleNamespace</a>(<i>importedModule</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>module</i>).</li>
+ <li>Let <i>status</i> be <i>envRec</i>.CreateImmutableBinding(<i>in</i>.[[LocalName]], <b>true</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><a href="#sec-call">Call</a> <i>envRec</i>.InitializeBinding(<i>in</i>.[[LocalName]],
+ <i>namespace</i>).</li>
+ </ol>
+ </li>
+ <li>else,
+ <ol class="block">
+ <li>Let <i>resolution</i> be <i>importedModule</i>.<a
+ href="#sec-resolveexport">ResolveExport</a>(<i>in</i>.[[ImportName]], « », «‍
+ »).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resolution</i>).</li>
+ <li>If <i>resolution</i> is <b>null</b> or <i>resolution</i> is <code>"ambiguous"</code>, throw a
+ <b>SyntaxError</b> exception.</li>
+ <li><a href="#sec-call">Call</a> <i>envRec</i>.<a
+ href="#sec-createimportbinding">CreateImportBinding</a>(<i>in</i>.[[LocalName]],
+ <i>resolution</i>.[[module]], <i>resolution</i>.[[bindingName]]).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>varDeclarations</i> be the VarScopedDeclarations of <i>code</i>.</li>
+ <li>For each element <i>d</i> in <i>varDeclarations</i> do
+ <ol class="block">
+ <li>For each element <i>dn</i> of the BoundNames of <i>d</i> do
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateMutableBinding(<i>dn</i>, <b>false</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><a href="#sec-call">Call</a> <i>envRec</i>.InitializeBinding(<i>dn</i>, <b>undefined</b>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>lexDeclarations</i> be the LexicallyScopedDeclarations of <i>code</i>.</li>
+ <li>For each element <i>d</i> in <i>lexDeclarations</i> do
+ <ol class="block">
+ <li>For each element <i>dn</i> of the BoundNames of <i>d</i> do
+ <ol class="block">
+ <li>If IsConstantDeclaration of <i>d</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateImmutableBinding(<i>dn</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>envRec</i>.CreateMutableBinding(<i>dn</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>If <i>d</i> is a <i>GeneratorDeclaration</i> production or a <i>FunctionDeclaration</i> production, then
+ <ol class="block">
+ <li>Let <i>fo</i> be the result of performing InstantiateFunctionObject for <i>d</i> with argument
+ <i>env</i>.</li>
+ <li><a href="#sec-call">Call</a> <i>envRec</i>.InitializeBinding(<i>dn</i>, <i>fo</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-moduleevaluation">
+ <h1><span class="secnum" id="sec-15.2.1.16.5"><a href="#sec-moduleevaluation"
+ title="link to this section">15.2.1.16.5</a></span> ModuleEvaluation() Concrete Method</h1>
+
+ <p>The ModuleEvaluation concrete method of a Source Text Module Record performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>module</i> be this Source Text Module Record.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: ModuleDeclarationInstantion has already been invoked on
+ <i>module</i> and successfully completed.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i>.[[Realm]] is not <b>undefined</b>.</li>
+ <li>If <i>module.</i>[[Evaluated]] is <b>true</b>, return <b>undefined</b>.</li>
+ <li>Set <i>module.</i>[[Evaluated]] to <b>true</b>.</li>
+ <li>For each String <i>required</i> that is an element of <i>module</i>.[[RequestedModules]] do,
+ <ol class="block">
+ <li>Let <i>requiredModule</i> be <a
+ href="#sec-hostresolveimportedmodule">HostResolveImportedModule</a>(<i>module</i>, <i>required</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>requiredModule</i>).</li>
+ <li>Let <i>status</i> be <i>requiredModule.</i>ModuleEvaluation().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>moduleCxt</i> be a new <a href="#sec-execution-contexts">ECMAScript code execution context</a>.</li>
+ <li>Set the Function of <i>moduleCxt</i> to <b>null</b>.</li>
+ <li>Set the <a href="#sec-code-realms">Realm</a> of <i>moduleCxt</i> to <i>module</i>.[[Realm]].</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i> has been linked and declarations in its module
+ environment have been instantiated.</li>
+ <li>Set the <a href="#sec-execution-contexts">VariableEnvironment</a> of <i>moduleCxt</i> to
+ <i>module</i>.[[Environment]].</li>
+ <li>Set the <a href="#sec-execution-contexts">LexicalEnvironment</a> of <i>moduleCxt</i> to
+ <i>module</i>.[[Environment]].</li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <a href="#sec-execution-contexts">the currently running execution
+ context</a>.</li>
+ <li>Push <i>moduleCxt</i> on to <a href="#sec-execution-contexts">the execution context stack</a>; <i>moduleCxt</i> is
+ now <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>result</i> be the result of evaluating <i>module</i>.[[ECMAScriptCode]].</li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <i>moduleCxt</i> and remove it from <a
+ href="#sec-execution-contexts">the execution context stack</a>.</li>
+ <li>Resume the context that is now on the top of <a href="#sec-execution-contexts">the execution context stack</a> as
+ <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-hostresolveimportedmodule">
+ <h1><span class="secnum" id="sec-15.2.1.17"><a href="#sec-hostresolveimportedmodule"
+ title="link to this section">15.2.1.17</a></span> Runtime Semantics: HostResolveImportedModule (referencingModule,
+ specifier )</h1>
+
+ <p>HostResolveImportedModule is an implementation defined abstract operation that provides the concrete Module Record
+ subclass instance that corresponds to the <span class="nt">ModuleSpecifier</span> <var>String, specifier, occurring within
+ the context of the module represented by the Module Record referencingModule.</var></p>
+
+ <p>The implementation of HostResolveImportedModule must conform to the following requirements:</p>
+
+ <ul>
+ <li>
+ <p>The normal return value must be an instance of a concrete subclass of Module Record.</p>
+ </li>
+
+ <li>
+ <p>If a Module Record corresponding to the pair <i>referencingModule, specifier</i> does not exist or cannot be
+ created, an exception must be thrown,</p>
+ </li>
+
+ <li>
+ <p>This operation must be idempotent if it completes normally. Each time it is called with a specific
+ <i>referencingModule, specifier</i> pair as arguments it must return the same Module Record instance.</p>
+ </li>
+ </ul>
+
+ <p>Multiple different <var>referencingModule, specifier</var> pairs may map to the same Module Record instance. The actual
+ mapping semantic is implementation defined but typically a normalization process is applied to <var>specifier</var> as
+ part of the mapping process. A typical normalization process would include actions such as alphabetic case folding and
+ expansion of relative and abbreviated path specifiers.</p>
+ </section>
+
+ <section id="sec-getmodulenamespace">
+ <h1><span class="secnum" id="sec-15.2.1.18"><a href="#sec-getmodulenamespace"
+ title="link to this section">15.2.1.18</a></span> Runtime Semantics: GetModuleNamespace( module )</h1>
+
+ <p>The abstract operation GetModuleNamespace called with argument <var>module</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>module</i> is a instance of a concrete subclass of Module
+ Record.</li>
+ <li>Let <i>namespace</i> be <i>module</i>.[[Namespace]].</li>
+ <li>If <i>namespace</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>exportedNames</i> be <i>module</i>.<a href="#sec-getexportednames">GetExportedNames</a>(«
+ »).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exportedNames</i>).</li>
+ <li>Let <i>unambiguousNames</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each <i>name</i> that is an element of <i>exportedNames</i>,
+ <ol class="block">
+ <li>Let <i>resolution</i> be <i>module</i>.<a href="#sec-resolveexport">ResolveExport</a>(<i>name</i>, «
+ », « »).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resolution</i>).</li>
+ <li>If <i>resolution</i> is <b>null</b>, throw a <b>SyntaxError</b> exception.</li>
+ <li>If <i>resolution</i> is not <code>"ambiguous"</code>, append <i>name</i> to <i>unambiguousNames</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>namespace</i> be <a href="#sec-modulenamespacecreate">ModuleNamespaceCreate</a>(<i>module</i>,
+ <i>unambiguousNames</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>namespace</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-toplevelmoduleevaluationjob">
+ <h1><span class="secnum" id="sec-15.2.1.19"><a href="#sec-toplevelmoduleevaluationjob"
+ title="link to this section">15.2.1.19</a></span> Runtime Semantics: TopLevelModuleEvaluationJob ( <span
+ style="font-family: sans-serif">sourceText</span>)</h1>
+
+ <p>A TopLevelModuleEvaluationJob with parameter <var>sourceText</var> is a job that parses, validates, and evaluates
+ <var>sourceText</var> as a <span class="nt">Module</span>.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>sourceText</i> is an ECMAScript source text (see <a
+ href="#sec-ecmascript-language-source-code">clause 10</a>).</li>
+ <li>Let <i>realm</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-code-realms">Realm</a>.</li>
+ <li>Let <i>m</i> be <a href="#sec-parsemodule">ParseModule</a>(<i>sourceText</i>).</li>
+ <li>If <i>m</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a> or any other
+ implementation defined error indication, then
+ <ol class="block">
+ <li>Report or log the error(s) in an implementation dependent manner.</li>
+ <li>NextJob <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </li>
+ <li>Set <i>m</i>.[[Realm]] to <i>realm</i>.</li>
+ <li>Let <i>status</i> be <i>m</i>.<a
+ href="#sec-moduledeclarationinstantiation">ModuleDeclarationInstantiation</a>().</li>
+ <li>If <i>status</i> is not an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: all dependencies of <i>m</i> have been transitively resolved
+ and <i>m</i> is ready for evaluation.</li>
+ <li>Let <i>status</i> be <i>m</i>.<a href="#sec-moduleevaluation">ModuleEvaluation</a>().</li>
+ </ol>
+ </li>
+ <li>NextJob <i>status</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An implementation may parse a <i>sourceText</i> as a <i>Module,</i> analyze it for Early
+ Error conditions, and instantiate it prior to the execution of the TopLevelModuleEvaluationJob for that
+ <i>sourceText</i>. An implementation may also resolve, pre-parse and pre-analyze, and pre-instantiate module
+ dependencies of <i>sourceText</i>. However, the reporting of any errors detected by these actions must be deferred until
+ the TopLevelModuleEvaluationJob is actually executed.</p>
+ </div>
+ </section>
+
+ <section id="sec-module-semantics-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-15.2.1.20"><a href="#sec-module-semantics-runtime-semantics-evaluation"
+ title="link to this section">15.2.1.20</a></span> Runtime Semantics: Evaluation</h1>
+ <div class="gp prod"><span class="nt">Module</span> <span class="geq">:</span> <span class="grhsannot">[empty]</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleItemList</span> <span class="geq">:</span> <span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ <ol class="proc">
+ <li>Let <i>sl</i> be the result of evaluating <i>ModuleItemList</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>sl</i>).</li>
+ <li>Let <i>s</i> be the result of evaluating <i>ModuleItem</i>.</li>
+ <li>If <i>s</i>.[[type]] is <span style="font-family: sans-serif">throw</span>, return <i>s</i>.</li>
+ <li>If <i>s</i>.[[value]] is <span style="font-family: sans-serif">empty</span>, let <i>V</i> = <i>sl</i>.[[value]],
+ otherwise let <i>V</i> = <i>s</i>.[[value]].</li>
+ <li>Return <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <i>s</i>.[[type]], [[value]]:
+ <i>V</i>, [[target]]: <i>s</i>.[[target]]}.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Steps 5 and 6 of the above algorithm ensure that the value of a <i>ModuleItemList</i> is
+ the value of the last value producing item in the <i>ModuleItemList</i>.</p>
+ </div>
+
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ImportDeclaration</span></div>
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-imports">
+ <div class="front">
+ <h1><span class="secnum" id="sec-15.2.2"><a href="#sec-imports" title="link to this section">15.2.2</a></span>
+ Imports</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ImportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">import</code> <span class="nt">ImportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">import</code> <span class="nt">ModuleSpecifier</span> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ImportClause</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportedDefaultBinding</span></div>
+ <div class="rhs"><span class="nt">NameSpaceImport</span></div>
+ <div class="rhs"><span class="nt">NamedImports</span></div>
+ <div class="rhs"><span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NameSpaceImport</span></div>
+ <div class="rhs"><span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NamedImports</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ImportedDefaultBinding</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportedBinding</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NameSpaceImport</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">*</code> <code class="t">as</code> <span class="nt">ImportedBinding</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NamedImports</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ImportsList</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ImportsList</span> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FromClause</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">from</code> <span class="nt">ModuleSpecifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ImportsList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportSpecifier</span></div>
+ <div class="rhs"><span class="nt">ImportsList</span> <code class="t">,</code> <span class="nt">ImportSpecifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ImportSpecifier</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ImportedBinding</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">ImportedBinding</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ModuleSpecifier</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ImportedBinding</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span></div>
+ </div>
+ </div>
+
+ <section id="sec-imports-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-15.2.2.1"><a href="#sec-imports-static-semantics-early-errors"
+ title="link to this section">15.2.2.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">ModuleItem</span> <span class="geq">:</span> <span class="nt">ImportDeclaration</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if the BoundNames of <span class="nt">ImportDeclaration</span> contains any duplicate
+ entries.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-imports-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-15.2.2.2"><a href="#sec-imports-static-semantics-boundnames"
+ title="link to this section">15.2.2.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-exports-static-semantics-boundnames">15.2.3.2</a>.</p>
+
+ <div class="gp prod"><span class="nt">ImportDeclaration</span> <span class="geq">:</span> <code class="t">import</code> <span class="nt">ImportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>ImportClause</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportDeclaration</span> <span class="geq">:</span> <code class="t">import</code> <span class="nt">ModuleSpecifier</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportClause</span> <span class="geq">:</span> <span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NameSpaceImport</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the BoundNames of <i>ImportedDefaultBinding</i>.</li>
+ <li>Append to <i>names</i> the elements of the BoundNames of <i>NameSpaceImport</i>.</li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportClause</span> <span class="geq">:</span> <span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NamedImports</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the BoundNames of <i>ImportedDefaultBinding</i>.</li>
+ <li>Append to <i>names</i> the elements of the BoundNames of <i>NamedImports</i>.</li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">NamedImports</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportsList</span> <span class="geq">:</span> <span class="nt">ImportsList</span> <code class="t">,</code> <span class="nt">ImportSpecifier</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the BoundNames of <i>ImportsList</i>.</li>
+ <li>Append to <i>names</i> the elements of the BoundNames of <i>ImportSpecifier</i>.</li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">ImportedBinding</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>ImportedBinding</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-imports-static-semantics-importentries">
+ <h1><span class="secnum" id="sec-15.2.2.3"><a href="#sec-imports-static-semantics-importentries"
+ title="link to this section">15.2.2.3</a></span> Static Semantics: ImportEntries</h1>
+
+ <p>See also: <a href="#sec-module-semantics-static-semantics-exportentries">15.2.1.7</a>.</p>
+
+ <div class="gp prod"><span class="nt">ImportDeclaration</span> <span class="geq">:</span> <code class="t">import</code> <span class="nt">ImportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>module</i> be the sole element of ModuleRequests of <i>FromClause</i>.</li>
+ <li>Return ImportEntriesForModule of <i>ImportClause</i> with argument <i>module</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportDeclaration</span> <span class="geq">:</span> <code class="t">import</code> <span class="nt">ModuleSpecifier</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-importentriesformodule">
+ <h1><span class="secnum" id="sec-15.2.2.4"><a href="#sec-static-semantics-importentriesformodule"
+ title="link to this section">15.2.2.4</a></span> Static Semantics: ImportEntriesForModule</h1>
+
+ <p>With parameter <var>module</var>.</p>
+
+ <div class="gp prod"><span class="nt">ImportClause</span> <span class="geq">:</span> <span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NameSpaceImport</span></div>
+ <ol class="proc">
+ <li>Let <i>entries</i> be ImportEntriesForModule of <i>ImportedDefaultBinding</i> with argument <i>module</i>.</li>
+ <li>Append to <i>entries</i> the elements of the ImportEntriesForModule of <i>NameSpaceImport</i> with argument
+ <i>module</i>.</li>
+ <li>Return <i>entries</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportClause</span> <span class="geq">:</span> <span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NamedImports</span></div>
+ <ol class="proc">
+ <li>Let <i>entries</i> be ImportEntriesForModule of <i>ImportedDefaultBinding</i> with argument <i>module</i>.</li>
+ <li>Append to <i>entries</i> the elements of the ImportEntriesForModule of <i>NamedImports</i> with argument
+ <i>module</i>.</li>
+ <li>Return <i>entries</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">ImportedDefaultBinding</span> <span class="geq">:</span> <span
+ class="nt">ImportedBinding</span></span></p>
+
+ <ol class="proc">
+ <li>Let <i>localName</i> be the sole element of BoundNames of <i>ImportedBinding</i>.</li>
+ <li>Let <i>defaultEntry</i> be the Record {[[ModuleRequest]]: <i>module</i>, [[ImportName]]: <code>"default"</code>,
+ [[LocalName]]: <i>localName</i> }.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>defaultEntry.</i></li>
+ </ol>
+ <div class="gp prod"><span class="nt">NameSpaceImport</span> <span class="geq">:</span> <code class="t">*</code> <code class="t">as</code> <span class="nt">ImportedBinding</span></div>
+ <ol class="proc">
+ <li>Let <i>localName</i> be the StringValue of <i>ImportedBinding</i>.</li>
+ <li>Let <i>entry</i> be the Record {[[ModuleRequest]]: <i>module</i>, [[ImportName]]: <code>"*"</code>, [[LocalName]]:
+ <i>localName</i> }.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>entry</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">NamedImports</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportsList</span> <span class="geq">:</span> <span class="nt">ImportsList</span> <code class="t">,</code> <span class="nt">ImportSpecifier</span></div>
+ <ol class="proc">
+ <li>Let <i>specs</i> be the ImportEntriesForModule of <i>ImportsList</i> with argument <i>module</i>.</li>
+ <li>Append to <i>specs</i> the elements of the ImportEntriesForModule of <i>ImportSpecifier</i> with argument
+ <i>module</i>.</li>
+ <li>Return <i>specs</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportSpecifier</span> <span class="geq">:</span> <span class="nt">ImportedBinding</span></div>
+ <ol class="proc">
+ <li>Let <i>localName</i> be the sole element of BoundNames of <i>ImportedBinding</i>.</li>
+ <li>Let <i>entry</i> be the Record {[[ModuleRequest]]: <i>module</i>, [[ImportName]]: <i>localName</i> , [[LocalName]]:
+ <i>localName</i> }.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>entry</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ImportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">ImportedBinding</span></div>
+ <ol class="proc">
+ <li>Let <i>importName</i> be the StringValue of <i>IdentifierName</i>.</li>
+ <li>Let <i>localName</i> be the StringValue of <i>ImportedBinding</i>.</li>
+ <li>Let <i>entry</i> be the Record {[[ModuleRequest]]: <i>module</i>, [[ImportName]]: <i>importName</i>, [[LocalName]]:
+ <i>localName</i> }.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>entry</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-imports-static-semantics-modulerequests">
+ <h1><span class="secnum" id="sec-15.2.2.5"><a href="#sec-imports-static-semantics-modulerequests"
+ title="link to this section">15.2.2.5</a></span> Static Semantics: ModuleRequests</h1>
+
+ <p>See also: <a href="#sec-module-semantics-static-semantics-modulerequests">15.2.1.10</a>,<a
+ href="#sec-exports-static-semantics-modulerequests">15.2.3.9</a>.</p>
+
+ <div class="gp prod"><span class="nt">ImportDeclaration</span> <span class="geq">:</span> <code class="t">import</code> <span class="nt">ImportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return ModuleRequests of <i>FromClause</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ModuleSpecifier</span> <span class="geq">:</span> <span class="nt">StringLiteral</span></div>
+ <ol class="proc">
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the StringValue of
+ <i>StringLiteral</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-imports-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-15.2.2.6"><a href="#sec-imports-runtime-semantics-evaluation"
+ title="link to this section">15.2.2.6</a></span> Runtime Semantics: Evaluation</h1>
+
+ <p>See <a href="#sec-hostresolveimportedmodule">15.2.1.17</a>.</p>
+ </section>
+ </section>
+
+ <section id="sec-exports">
+ <div class="front">
+ <h1><span class="secnum" id="sec-15.2.3"><a href="#sec-exports" title="link to this section">15.2.3</a></span>
+ Exports</h1>
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">Declaration</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">HoistableDeclaration</span><sub>[Default]</sub></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">ClassDeclaration</span><sub>[Default]</sub></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="grhsannot">[lookahead ∉ {<code class="t">function</code>, <code class="t">class</code>}]</span> <span class="nt">AssignmentExpression</span><sub>[In]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportClause</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ExportsList</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ExportsList</span> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportsList</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">ExportSpecifier</span></div>
+ <div class="rhs"><span class="nt">ExportsList</span> <code class="t">,</code> <span class="nt">ExportSpecifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportSpecifier</span> <span class="geq">:</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">IdentifierName</span></div>
+ </div>
+ </div>
+
+ <section id="sec-exports-static-semantics-early-errors">
+ <h1><span class="secnum" id="sec-15.2.3.1"><a href="#sec-exports-static-semantics-early-errors"
+ title="link to this section">15.2.3.1</a></span> Static Semantics: Early Errors</h1>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <ul>
+ <li>
+ <p>For each <span class="nt">IdentifierName</span> <var>n</var> in ReferencedBindings of <span class="prod"><span
+ class="nt">ExportClause</span> <span class="geq">:</span> <span class="nt">It</span> <code class="t">is</code> <code
+ class="t">a</code> <span class="nt">Syntax</span> <span class="nt">Error</span> <code class="t">if</code> <span
+ class="nt">StringValue</span> <code class="t">of</code></span> <var>n</var> is a <span class="nt">ReservedWord</span>
+ or if the StringValue of <var>n</var> is one of: <code>"implements"</code>, <code>"interface"</code>,
+ <code>"let"</code>, <code>"package"</code>, <code>"private"</code>, <code>"protected"</code>, <code>"public"</code>,
+ <code>"static"</code>, or <code>"yield"</code>.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The above rule means that each ReferencedBindings of <i>ExportClause</i> is treated as
+ an <i>IdentifierReference</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-exports-static-semantics-boundnames">
+ <h1><span class="secnum" id="sec-15.2.3.2"><a href="#sec-exports-static-semantics-boundnames"
+ title="link to this section">15.2.3.2</a></span> Static Semantics: BoundNames</h1>
+
+ <p>See also: <a href="#sec-identifiers-static-semantics-boundnames">12.1.2</a>, <a
+ href="#sec-let-and-const-declarations-static-semantics-boundnames">13.2.1.2</a>, <a
+ href="#sec-variable-statement-static-semantics-boundnames">13.2.2.1</a>, <a
+ href="#sec-destructuring-binding-patterns-static-semantics-boundnames">13.2.3.1</a>, <a
+ href="#sec-for-in-and-for-of-statements-static-semantics-boundnames">13.6.4.2</a>, <a
+ href="#sec-function-definitions-static-semantics-boundnames">14.1.3</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-boundnames">14.2.2</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-boundnames">14.4.2</a>, <a
+ href="#sec-class-definitions-static-semantics-boundnames">14.5.2</a>, <a
+ href="#sec-imports-static-semantics-boundnames">15.2.2.2</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>VariableStatement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>Declaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">HoistableDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>declarationNames</i> be the BoundNames of <i>HoistableDeclaration</i>.</li>
+ <li>If <i>declarationNames</i> does not include the element <code>"*default*"</code>, append <code>"*default*"</code> to
+ <i>declarationNames</i>.</li>
+ <li>Return <i>declarationNames</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">ClassDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>declarationNames</i> be the BoundNames of <i>ClassDeclaration</i>.</li>
+ <li>If <i>declarationNames</i> does not include the element <code>"*default*"</code>, append <code>"*default*"</code> to
+ <i>declarationNames</i>.</li>
+ <li>Return <i>declarationNames</i>.</li>
+ </ol>
+
+ <p><span style="font-family: Times New Roman"><span class="prod"><span class="nt">ExportDeclaration</span> <span
+ class="geq">:</span></span></span> <code>export default</code> <span class="nt">AssignmentExpression</span>
+ <code>;</code></p>
+
+ <ol class="proc">
+ <li>Return «<code>"*default*"</code>».</li>
+ </ol>
+ </section>
+
+ <section id="sec-exports-static-semantics-exportedbindings">
+ <h1><span class="secnum" id="sec-15.2.3.3"><a href="#sec-exports-static-semantics-exportedbindings"
+ title="link to this section">15.2.3.3</a></span> Static Semantics: ExportedBindings</h1>
+
+ <p>See also: <a href="#sec-module-semantics-static-semantics-exportedbindings">15.2.1.5</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return the ExportedBindings of <i>ExportClause</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>VariableStatement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>Declaration</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code>
+ <code class="t">default</code> <span class="nt">HoistableDeclaration</span></span></p>
+
+ <p><span class="prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code>
+ <code class="t">default</code> <span class="nt">ClassDeclaration</span></span></p>
+
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">AssignmentExpression</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return the BoundNames of this <i>ExportDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportClause</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportsList</span> <span class="geq">:</span> <span class="nt">ExportsList</span> <code class="t">,</code> <span class="nt">ExportSpecifier</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the ExportedBindings of <i>ExportsList</i>.</li>
+ <li>Append to <i>names</i> the elements of the ExportedBindings of <i>ExportSpecifier</i>.</li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the StringValue of
+ <i>IdentifierName</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the StringValue of the first
+ <i>IdentifierName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-exports-static-semantics-exportednames">
+ <h1><span class="secnum" id="sec-15.2.3.4"><a href="#sec-exports-static-semantics-exportednames"
+ title="link to this section">15.2.3.4</a></span> Static Semantics: ExportedNames</h1>
+
+ <p>See also: <a href="#sec-module-semantics-static-semantics-exportednames">15.2.1.6</a>.</p>
+
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return the ExportedNames of <i>ExportClause</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>VariableStatement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return the BoundNames of <i>Declaration</i>.</li>
+ </ol>
+
+ <p><span class="prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code>
+ <code class="t">default</code> <span class="nt">HoistableDeclaration</span></span></p>
+
+ <p><span class="prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code>
+ <code class="t">default</code> <span class="nt">ClassDeclaration</span></span></p>
+
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">AssignmentExpression</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return «<code>"default"</code>».</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportClause</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportsList</span> <span class="geq">:</span> <span class="nt">ExportsList</span> <code class="t">,</code> <span class="nt">ExportSpecifier</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the ExportedNames of <i>ExportsList</i>.</li>
+ <li>Append to <i>names</i> the elements of the ExportedNames of <i>ExportSpecifier</i>.</li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the StringValue of
+ <i>IdentifierName</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the StringValue of the second
+ <i>IdentifierName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-exports-static-semantics-exportentries">
+ <h1><span class="secnum" id="sec-15.2.3.5"><a href="#sec-exports-static-semantics-exportentries"
+ title="link to this section">15.2.3.5</a></span> Static Semantics: ExportEntries</h1>
+
+ <p>See also: <a href="#sec-module-semantics-static-semantics-exportentries">15.2.1.7</a>.</p>
+
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>module</i> be the sole element of ModuleRequests of <i>FromClause</i>.</li>
+ <li>Let <i>entry</i> be the Record {[[ModuleRequest]]: <i>module</i>, [[ImportName]]: <code>"*"</code>, [[LocalName]]:
+ <b>null</b>, [[ExportName]]: <b>null</b> }.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>entry</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Let <i>module</i> be the sole element of ModuleRequests of <i>FromClause</i>.</li>
+ <li>Return ExportEntriesForModule of <i>ExportClause</i> with argument <i>module</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return ExportEntriesForModule of <i>ExportClause</i> with argument <b>null</b>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <ol class="proc">
+ <li>Let <i>entries</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>names</i> be the BoundNames of <i>VariableStatement</i>.</li>
+ <li>Repeat for each <i>name</i> in <i>names,</i>
+ <ol class="block">
+ <li>Append to <i>entries</i> the Record {[[ModuleRequest]]: <b>null</b>, [[ImportName]]: <b>null</b>, [[LocalName]]:
+ <i>name</i>, [[ExportName]]: <i>name</i> }.</li>
+ </ol>
+ </li>
+ <li>Return <i>entries</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Let <i>entries</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>names</i> be the BoundNames of <i>Declaration</i>.</li>
+ <li>Repeat for each <i>name</i> in <i>names,</i>
+ <ol class="block">
+ <li>Append to <i>entries</i> the Record {[[ModuleRequest]]: <b>null</b>, [[ImportName]]: <b>null</b>, [[LocalName]]:
+ <i>name</i>, [[ExportName]]: <i>name</i> }.</li>
+ </ol>
+ </li>
+ <li>Return <i>entries</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">HoistableDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>HoistableDeclaration</i>.</li>
+ <li>Let <i>localName</i> be the sole element of <i>names</i>.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing the Record {[[ModuleRequest]]:
+ <b>null</b>, [[ImportName]]: <b>null</b>, [[LocalName]]: <i>localName</i>, [[ExportName]]:
+ <code>"default"</code>}.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">ClassDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be BoundNames of <i>ClassDeclaration</i>.</li>
+ <li>Let <i>localName</i> be the sole element of <i>names</i>.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing the Record {[[ModuleRequest]]:
+ <b>null</b>, [[ImportName]]: <b>null</b>, [[LocalName]]: <i>localName</i>, [[ExportName]]:
+ <code>"default"</code>}.</li>
+ </ol>
+
+ <p><span style="font-family: Times New Roman"><span class="prod"><span class="nt">ExportDeclaration</span> <span
+ class="geq">:</span></span></span> <code>export default</code> <span
+ class="nt">AssignmentExpression</span><code>;</code></p>
+
+ <ol class="proc">
+ <li>Let <i>entry</i> be the Record {[[ModuleRequest]]: <b>null</b>, [[ImportName]]: <b>null</b>, [[LocalName]]:
+ <code>"*default*"</code>, [[ExportName]]: <code>"default"</code>}.</li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>entry</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <code>"*default*"</code> is used within this specification as a synthetic name for
+ anonymous default export values.</p>
+ </div>
+ </section>
+
+ <section id="sec-static-semantics-exportentriesformodule">
+ <h1><span class="secnum" id="sec-15.2.3.6"><a href="#sec-static-semantics-exportentriesformodule"
+ title="link to this section">15.2.3.6</a></span> Static Semantics: ExportEntriesForModule</h1>
+
+ <p>With parameter <var>module</var>.</p>
+
+ <div class="gp prod"><span class="nt">ExportClause</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportsList</span> <span class="geq">:</span> <span class="nt">ExportsList</span> <code class="t">,</code> <span class="nt">ExportSpecifier</span></div>
+ <ol class="proc">
+ <li>Let <i>specs</i> be the ExportEntriesForModule of <i>ExportsList</i> with argument <i>module</i>.</li>
+ <li>Append to <i>specs</i> the elements of the ExportEntriesForModule of <i>ExportSpecifier</i> with argument
+ <i>module</i>.</li>
+ <li>Return <i>specs</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Let <i>sourceName</i> be the StringValue of <i>IdentifierName</i>.</li>
+ <li>If <i>module</i> is <b>null</b>, then
+ <ol class="block">
+ <li>Let <i>localName</i> be <i>sourceName</i>.</li>
+ <li>Let <i>importName</i> be <b>null</b>.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>localName</i> be <b>null</b>.</li>
+ <li>Let <i>importName</i> be <i>sourceName</i>.</li>
+ </ol>
+ </li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing the Record {[[ModuleRequest]]:
+ <i>module</i>, [[ImportName]]: <i>importName</i>, [[LocalName]]: <i>localName</i>, [[ExportName]]: <i>sourceName</i>
+ }.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Let <i>sourceName</i> be the StringValue of the first <i>IdentifierName</i>.</li>
+ <li>Let <i>exportName</i> be the StringValue of the second <i>IdentifierName</i>.</li>
+ <li>If <i>module</i> is <b>null</b>, then
+ <ol class="block">
+ <li>Let <i>localName</i> be <i>sourceName</i>.</li>
+ <li>Let <i>importName</i> be <b>null</b>.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>localName</i> be <b>null</b>.</li>
+ <li>Let <i>importName</i> be <i>sourceName</i>.</li>
+ </ol>
+ </li>
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing the Record {[[ModuleRequest]]:
+ <i>module</i>, [[ImportName]]: <i>importName</i>, [[LocalName]]: <i>localName</i>, [[ExportName]]: <i>exportName</i>
+ }.</li>
+ </ol>
+ </section>
+
+ <section id="sec-exports-static-semantics-isconstantdeclaration">
+ <h1><span class="secnum" id="sec-15.2.3.7"><a href="#sec-exports-static-semantics-isconstantdeclaration"
+ title="link to this section">15.2.3.7</a></span> Static Semantics: IsConstantDeclaration</h1>
+
+ <p>See also: <a href="#sec-let-and-const-declarations-static-semantics-isconstantdeclaration">13.2.1.3</a>, <a
+ href="#sec-function-definitions-static-semantics-isconstantdeclaration">14.1.10</a>, <a
+ href="#sec-generator-function-definitions-static-semantics-isconstantdeclaration">14.4.8</a>, <a
+ href="#sec-class-definitions-static-semantics-isconstantdeclaration">14.5.7</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">AssignmentExpression</span> <code class="t">;</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> It is not necessary to treat <code>export</code> <code>default</code>
+ <i>AssignmentExpression</i> as a constant declaration because there is no syntax that permits assignment to the internal
+ bound name used to reference a module’s default object.</p>
+ </div>
+ </section>
+
+ <section id="sec-exports-static-semantics-lexicallyscopeddeclarations">
+ <h1><span class="secnum" id="sec-15.2.3.8"><a href="#sec-exports-static-semantics-lexicallyscopeddeclarations"
+ title="link to this section">15.2.3.8</a></span> Static Semantics: LexicallyScopedDeclarations</h1>
+
+ <p>See also: <a href="#sec-block-static-semantics-lexicallyscopeddeclarations">13.1.6</a>, <a
+ href="#sec-switch-statement-static-semantics-lexicallyscopeddeclarations">13.11.6</a>, <a
+ href="#sec-labelled-statements-static-semantics-lexicallyscopeddeclarations">13.12.7</a>, <a
+ href="#sec-function-definitions-static-semantics-lexicallyscopeddeclarations">14.1.15</a>, <a
+ href="#sec-arrow-function-definitions-static-semantics-lexicallyscopeddeclarations">14.2.11</a>, <a
+ href="#sec-scripts-static-semantics-lexicallyscopeddeclarations">15.1.4</a>, <a
+ href="#sec-module-semantics-static-semantics-lexicallyscopeddeclarations">15.2.1.12</a>.</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing DeclarationPart of
+ <i>Declaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">HoistableDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing DeclarationPart of
+ <i>HoistableDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">ClassDeclaration</span></div>
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing <i>ClassDeclaration</i>.</li>
+ </ol>
+
+ <p><span style="font-family: Times New Roman"><span class="prod"><span class="nt">ExportDeclaration</span> <span
+ class="geq">:</span></span></span> <code>export default</code> <span class="nt">AssignmentExpression</span>
+ <code>;</code></p>
+
+ <ol class="proc">
+ <li>Return a new <a href="#sec-list-and-record-specification-type">List</a> containing this
+ <i>ExportDeclaration</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-exports-static-semantics-modulerequests">
+ <h1><span class="secnum" id="sec-15.2.3.9"><a href="#sec-exports-static-semantics-modulerequests"
+ title="link to this section">15.2.3.9</a></span> Static Semantics: ModuleRequests</h1>
+
+ <p>See also: <a href="#sec-module-semantics-static-semantics-modulerequests">15.2.1.10</a>, <a
+ href="#sec-imports-static-semantics-modulerequests">15.2.2.5</a>.</p>
+
+ <p><span class="prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code>
+ <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></span></p>
+
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <ol class="proc">
+ <li>Return the ModuleRequests of <i>FromClause</i>.</li>
+ </ol>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">Declaration</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">HoistableDeclaration</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">ClassDeclaration</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">AssignmentExpression</span> <code class="t">;</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-static-semantics-referencedbindings">
+ <h1><span class="secnum" id="sec-15.2.3.10"><a href="#sec-static-semantics-referencedbindings"
+ title="link to this section">15.2.3.10</a></span> Static Semantics: ReferencedBindings</h1>
+ <div class="gp prod"><span class="nt">ExportClause</span> <span class="geq">:</span> <code class="t">{</code> <code class="t">}</code></div>
+ <ol class="proc">
+ <li>Return a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportsList</span> <span class="geq">:</span> <span class="nt">ExportsList</span> <code class="t">,</code> <span class="nt">ExportSpecifier</span></div>
+ <ol class="proc">
+ <li>Let <i>names</i> be the ReferencedBindings of <i>ExportsList</i>.</li>
+ <li>Append to <i>names</i> the elements of the ReferencedBindings of <i>ExportSpecifier</i>.</li>
+ <li>Return <i>names</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the <i>IdentifierName</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> <span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">IdentifierName</span></div>
+ <ol class="proc">
+ <li>Return a <a href="#sec-list-and-record-specification-type">List</a> containing the first <i>IdentifierName</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-exports-runtime-semantics-evaluation">
+ <h1><span class="secnum" id="sec-15.2.3.11"><a href="#sec-exports-runtime-semantics-evaluation"
+ title="link to this section">15.2.3.11</a></span> Runtime Semantics: Evaluation</h1>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ </div>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>VariableStatement</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <span class="nt">Declaration</span></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>Declaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">HoistableDeclaration</span></div>
+ <ol class="proc">
+ <li>Return the result of evaluating <i>HoistableDeclaration</i>.</li>
+ </ol>
+ <div class="gp prod"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> <code class="t">export</code> <code class="t">default</code> <span class="nt">ClassDeclaration</span></div>
+ <ol class="proc">
+ <li>Let <i>value</i> be the result of BindingClassDeclarationEvaluation of <i>ClassDeclaration</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>Let <i>className</i> be the sole element of BoundNames of <i>ClassDeclaration</i>.</li>
+ <li>If <i>className</i> is <code>"*default*"</code>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>value</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>value</i>, <code>"default"</code>).</li>
+ <li>Let <i>env</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>status</i> be <a href="#sec-initializeboundname">InitializeBoundName</a>(<code>"*default*"</code>,
+ <i>value</i>, <i>env</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+
+ <p><span style="font-family: Times New Roman"><span class="prod"><span class="nt">ExportDeclaration</span> <span
+ class="geq">:</span></span></span> <code>export default</code> <span class="nt">AssignmentExpression</span>
+ <code>;</code></p>
+
+ <ol class="proc">
+ <li>Let <i>rhs</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>value</i> be <a href="#sec-getvalue">GetValue</a>(<i>rhs</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>AssignmentExpression)</i> is
+ <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>value</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>value</i>, <code>"default"</code>).</li>
+ </ol>
+ </li>
+ <li>Let <i>env</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>status</i> be <a href="#sec-initializeboundname">InitializeBoundName</a>(<code>"*default*"</code>,
+ <i>value</i>, <i>env</i>).</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+</section>
+
+<section id="sec-error-handling-and-language-extensions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-16"><a href="#sec-error-handling-and-language-extensions"
+ title="link to this section">16</a></span> Error Handling and Language Extensions</h1>
+
+ <p>An implementation must report most errors at the time the relevant ECMAScript language construct is evaluated. An <i>early
+ error</i> is an error that can be detected and reported prior to the evaluation of any construct in the <span
+ class="nt">Script</span> containing the error. The presence of an early error prevents the evaluation of the construct. An
+ implementation must report early errors in a <span class="nt">Script</span> as part of the <a
+ href="#sec-scriptevaluationjob">ScriptEvaluationJob</a> for that <span class="nt">Script</span>. Early errors in a <span
+ class="nt">Module</span> are reported at the point when the <span class="nt">Module</span> would be evaluated and the <span
+ class="nt">Module</span> is never initialized. Early errors in <b>eval</b> code are reported at the time <code>eval</code> is
+ called and prevent evaluation of the <b>eval</b> code. All errors that are not early errors are runtime errors.</p>
+
+ <p>An implementation must report as an early error any occurrence of a condition that is listed in a “Static Semantics:
+ Early Errors” subclause of this specification.</p>
+
+ <p>An implementation shall not treat other kinds of errors as early errors even if the compiler can prove that a construct
+ cannot execute without error under any circumstances. An implementation may issue an early warning in such a case, but it
+ should not report the error until the relevant construct is actually executed.</p>
+
+ <p>An implementation shall report all errors as specified, except for the following:</p>
+
+ <ul>
+ <li>
+ <p>Except as restricted in <a href="#sec-forbidden-extensions">16.1</a>, an implementation may extend <i>Script</i>
+ syntax, <i>Module</i> syntax, and regular expression pattern or flag syntax. To permit this, all operations (such as
+ calling <code>eval</code>, using a regular expression literal, or using the <code>Function</code> or <code>RegExp</code>
+ constructor) that are allowed to throw <b>SyntaxError</b> are permitted to exhibit implementation-defined behaviour
+ instead of throwing <b>SyntaxError</b> when they encounter an implementation-defined extension to the script syntax or
+ regular expression pattern or flag syntax.</p>
+ </li>
+
+ <li>
+ <p>Except as restricted in <a href="#sec-forbidden-extensions">16.1</a>, an implementation may provide additional types,
+ values, objects, properties, and functions beyond those described in this specification. This may cause constructs (such
+ as looking up a variable in the global scope) to have implementation-defined behaviour instead of throwing an error (such
+ as <b>ReferenceError</b>).</p>
+ </li>
+ </ul>
+
+ <p>An implementation may define behaviour other than throwing <b>RangeError</b> for <code>toFixed</code>,
+ <code>toExponential</code>, and <code>toPrecision</code> when the <var>fractionDigits</var> or <var>precision</var> argument
+ is outside the specified range.</p>
+ </div>
+
+ <section id="sec-forbidden-extensions">
+ <h1><span class="secnum" id="sec-16.1"><a href="#sec-forbidden-extensions" title="link to this section">16.1</a></span>
+ Forbidden Extensions</h1>
+
+ <p>An implementation must not extend this specification in the following ways:</p>
+
+ <ul>
+ <li>
+ <p>Other than as defined in this specification, ECMAScript Function objects defined using syntactic constructors in <a
+ href="#sec-strict-mode-code">strict code</a> must not be created with own properties named <code>"caller"</code> or
+ <code>"arguments"</code> other than those that are created by applying the <a
+ href="#sec-addrestrictedfunctionproperties">AddRestrictedFunctionProperties</a> abstract operation (<a
+ href="#sec-addrestrictedfunctionproperties">9.2.8</a>) to the function. Such own properties also must not be created for
+ function objects defined in non-<a href="#sec-strict-mode-code">strict code</a> using an <span
+ class="nt">ArrowFunction</span>, <span class="nt">MethodDefinition</span>, <span class="nt">GeneratorDeclaration</span>,
+ <span class="nt">GeneratorExpression</span>, <span class="nt">ClassDeclaration</span>, or <span
+ class="nt">ClassExpression</span>. Built-in functions, strict mode functions created using the <code>Function</code>
+ constructor, generator functions created using the <code>Generator</code> constructor, and functions created using the
+ <code>bind</code> method also must not be created with such own properties.</p>
+ </li>
+
+ <li>
+ <p>If an implementation extends non-strict mode or built-in function objects with an own property named
+ <code>"caller"</code> the value of that property, as observed using [[Get]] or [[GetOwnProperty]], must not be a strict
+ mode function object. If it is an accessor property, the function that is the value of the property’s [[Get]]
+ attribute must never return a strict mode function when called.</p>
+ </li>
+
+ <li>
+ <p>The behaviour of the following methods must not be extended except as specified in ECMA-402: <code><a
+ href="#sec-object.prototype.tolocalestring">Object.prototype.toLocaleString</a></code>, <code><a
+ href="#sec-array.prototype.tolocalestring">Array.prototype.toLocaleString</a></code>, <code><a
+ href="#sec-number.prototype.tolocalestring">Number.prototype.toLocaleString</a></code>, <code><a
+ href="#sec-date.prototype.tolocaledatestring">Date.prototype.toLocaleDateString</a></code>, <code><a
+ href="#sec-date.prototype.tolocalestring">Date.prototype.toLocaleString</a></code>, <code><a
+ href="#sec-date.prototype.tolocaletimestring">Date.prototype.toLocaleTimeString</a></code>, <code><a
+ href="#sec-string.prototype.localecompare">String.prototype.localeCompare</a></code>.</p>
+ </li>
+
+ <li>
+ <p>The RegExp pattern grammars in <a href="#sec-patterns">21.2.1</a> and <a
+ href="#sec-regular-expressions-patterns">B.1.4</a> must not be extended to recognize any of the source characters A-Z or
+ a-z as <span class="nt">IdentityEscape</span><sub>[U]</sub> when the U grammar parameter is present.</p>
+ </li>
+
+ <li>
+ <p>The Syntactic Grammar must not be extended in any manner that allows the token <code>:</code> to immediate follow
+ source text that matches the <span class="nt">BindingIdentifier</span> nonterminal symbol.</p>
+ </li>
+
+ <li>
+ <p>When processing <a href="#sec-strict-mode-code">strict mode code</a>, the syntax of <i>NumericLiteral</i> must not be
+ extended to include <i>LegacyOctalIntegerLiteral</i> as defined in <a
+ href="#sec-additional-syntax-numeric-literals">B.1.1</a>.</p>
+ </li>
+
+ <li>
+ <p><span class="nt">TemplateCharacter</span> (<a href="#sec-template-literal-lexical-components">11.8.6</a>) must not be
+ extended to include <i>Legacy<span style="font-family: Times New Roman">OctalEscapeSequence</span></i> as defined in <a
+ href="#sec-additional-syntax-string-literals">B.1.2</a>.</p>
+ </li>
+
+ <li>
+ <p>When processing <a href="#sec-strict-mode-code">strict mode code</a>, the extensions defined in <a
+ href="#sec-__proto__-property-names-in-object-initializers">B.3.1</a>, <a
+ href="#sec-labelled-function-declarations">B.3.2</a>, <a
+ href="#sec-block-level-function-declarations-web-legacy-compatibility-semantics">B.3.3</a>, and <a
+ href="#sec-functiondeclarations-in-ifstatement-statement-clauses">B.3.4</a> must not be supported.</p>
+ </li>
+
+ <li>
+ <p>When parsing for the <span class="nt">Module</span> goal symbol, the lexical grammar extensions defined in <a
+ href="#sec-html-like-comments">B.1.3</a> must not be supported.</p>
+ </li>
+ </ul>
+ </section>
+</section>
+
+<section id="sec-ecmascript-standard-built-in-objects">
+ <h1><span class="secnum" id="sec-17"><a href="#sec-ecmascript-standard-built-in-objects"
+ title="link to this section">17</a></span> ECMAScript Standard Built-in Objects</h1>
+
+ <p>There are certain built-in objects available whenever an ECMAScript <span class="nt">Script</span> or <span
+ class="nt">Module</span> begins execution. One, the global object, is part of the <a href="#sec-lexical-environments">lexical
+ environment</a> of the executing program. Others are accessible as initial properties of the global object or indirectly as
+ properties of accessible built-in objects.</p>
+
+ <p>Unless specified otherwise, a built-in object that is callable as a function is a built-in Function object with the
+ characteristics described in <a href="#sec-built-in-function-objects">9.3</a>. Unless specified otherwise, the [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of a built-in object initially has the value
+ <b>true</b>. Every built-in Function object has a [[Realm]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> whose value is the code <a href="#sec-code-realms">Realm</a> for which the object was initially created.</p>
+
+ <p>Many built-in objects are functions: they can be invoked with arguments. Some of them furthermore are constructors: they are
+ functions intended for use with the <code>new</code> operator. For each built-in function, this specification describes the
+ arguments required by that function and properties of the Function object. For each built-in constructor, this specification
+ furthermore describes properties of the prototype object of that constructor and properties of specific object instances
+ returned by a <code>new</code> expression that invokes that constructor.</p>
+
+ <p>Unless otherwise specified in the description of a particular function, if a built-in function or constructor is given fewer
+ arguments than the function is specified to require, the function or constructor shall behave exactly as if it had been given
+ sufficient additional arguments, each such argument being the <b>undefined</b> value. Such missing arguments are considered to
+ be “not present” and may be identified in that manner by specification algorithms. In the description of a
+ particular function, the terms “<code>this</code> value” and “<span style="font-family: Times New
+ Roman">NewTarget</span>” have the meanings given in <a href="#sec-built-in-function-objects">9.3</a>.</p>
+
+ <p>Unless otherwise specified in the description of a particular function, if a built-in function or constructor described is
+ given more arguments than the function is specified to allow, the extra arguments are evaluated by the call and then ignored by
+ the function. However, an implementation may define implementation specific behaviour relating to such arguments as long as the
+ behaviour is not the throwing of a <b>TypeError</b> exception that is predicated simply on the presence of an extra
+ argument.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Implementations that add additional capabilities to the set of built-in functions are
+ encouraged to do so by adding new functions rather than adding new parameters to existing functions.</p>
+ </div>
+
+ <p>Unless otherwise specified every built-in function and every built-in constructor has the Function prototype object, which is
+ the initial value of the expression <code>Function.prototype</code> (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>), as the value of its [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>Unless otherwise specified every built-in prototype object has the Object prototype object, which is the initial value of the
+ expression <code>Object.prototype</code> (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>), as the value of
+ its [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, except the Object prototype
+ object itself.</p>
+
+ <p>Built-in function objects that are not identified as constructors do not implement the [[Construct]] internal method unless
+ otherwise specified in the description of a particular function.</p>
+
+ <p>Unless otherwise specified, each built-in function defined in clauses 18 through 26 is created as if by calling the <a
+ href="#sec-createbuiltinfunction">CreateBuiltinFunction</a> abstract operation (<a
+ href="#sec-createbuiltinfunction">9.3.3</a>).</p>
+
+ <p>Every built-in Function object, including constructors, has a <code>length</code> property whose value is an integer. Unless
+ otherwise specified, this value is equal to the largest number of named arguments shown in the subclause headings for the
+ function description, including optional parameters. However, rest parameters shown using the form “...name” are not
+ included in the default argument count.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For example, the Function object that is the initial value of the <code>slice</code> property
+ of the String prototype object is described under the subclause heading “<a
+ href="#sec-string.prototype.slice">String.prototype.slice</a> (start, end)” which shows the two named arguments start
+ and end; therefore the value of the <code>length</code> property of that Function object is <code>2</code>.</p>
+ </div>
+
+ <p>Unless otherwise specified, the <code>length</code> property of a built-in Function object has the attributes
+ { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>true</b> }.</p>
+
+ <p>Every built-in Function object, including constructors, that is not identified as an anonymous function has a
+ <code>name</code> property whose value is a String. Unless otherwise specified, this value is the name that is given to the
+ function in this specification. For functions that are specified as properties of objects, the name value is the property name
+ string used to access the function. Functions that are specified as get or set accessor functions of built-in properties have
+ "<code>get</code> " or "<code>set</code> " prepended to the property name string. The value of the <code>name</code> property is
+ explicitly specified for each built-in functions whose <a href="#sec-object-type">property key</a> is a symbol value.</p>
+
+ <p>Unless otherwise specified, the <code>name</code> property of a built-in Function object, if it exists, has the attributes
+ { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>true</b> }.</p>
+
+ <p>Every other data property described in clauses 18 through 26 and in Annex { REF _Ref406169814 \n \h }B.2 has the attributes {
+ [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>true</b> } unless otherwise specified.</p>
+
+ <p>Every accessor property described in clauses 18 through 26 and in Annex { REF _Ref406169814 \n \h }B.2 has the attributes
+ {[[Enumerable]]: <b>false</b>, [[Configurable]]: <b>true</b> } unless otherwise specified. If only a get accessor function is
+ described, the set accessor function is the default value, <b>undefined</b>. If only a set accessor is described the get
+ accessor is the default value, <b>undefined</b>.</p>
+</section>
+
+<section id="sec-global-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18"><a href="#sec-global-object" title="link to this section">18</a></span> The Global
+ Object</h1>
+
+ <p>The unique <i>global object</i> is created before control enters any <a href="#sec-execution-contexts">execution
+ context</a>.</p>
+
+ <p>The global object does not have a [[Construct]] internal method; it is not possible to use the global object as a
+ constructor with the <code>new</code> operator.</p>
+
+ <p>The global object does not have a [[Call]] internal method; it is not possible to invoke the global object as a
+ function.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the global
+ object is implementation-dependent.</p>
+
+ <p>In addition to the properties defined in this specification the global object may have additional host defined properties.
+ This may include a property whose value is the global object itself; for example, in the HTML document object model the
+ <code>window</code> property of the global object is the global object itself.</p>
+ </div>
+
+ <section id="sec-value-properties-of-the-global-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18.1"><a href="#sec-value-properties-of-the-global-object"
+ title="link to this section">18.1</a></span> Value Properties of the Global Object</h1>
+ </div>
+
+ <section id="sec-value-properties-of-the-global-object-infinity">
+ <h1><span class="secnum" id="sec-18.1.1"><a href="#sec-value-properties-of-the-global-object-infinity"
+ title="link to this section">18.1.1</a></span> Infinity</h1>
+
+ <p>The value of <code>Infinity</code> is <b>+∞</b> (<a href="#sec-ecmascript-language-types-number-type">see
+ 6.1.6</a>). This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-value-properties-of-the-global-object-nan">
+ <h1><span class="secnum" id="sec-18.1.2"><a href="#sec-value-properties-of-the-global-object-nan"
+ title="link to this section">18.1.2</a></span> NaN</h1>
+
+ <p>The value of <code>NaN</code> is <b>NaN</b> (<a href="#sec-ecmascript-language-types-number-type">see 6.1.6</a>). This
+ property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b>
+ }.</p>
+ </section>
+
+ <section id="sec-undefined">
+ <h1><span class="secnum" id="sec-18.1.3"><a href="#sec-undefined" title="link to this section">18.1.3</a></span>
+ undefined</h1>
+
+ <p>The value of <code>undefined</code> is <b>undefined</b> (<a href="#sec-ecmascript-language-types-undefined-type">see
+ 6.1.1</a>). This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-function-properties-of-the-global-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18.2"><a href="#sec-function-properties-of-the-global-object"
+ title="link to this section">18.2</a></span> Function Properties of the Global Object</h1>
+ </div>
+
+ <section id="sec-eval-x">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18.2.1"><a href="#sec-eval-x" title="link to this section">18.2.1</a></span> eval
+ (x)</h1>
+
+ <p>The <code>eval</code> function is the %eval% intrinsic object. When the <code>eval</code> function is called with one
+ argument <var>x</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>evalRealm</i> be the value of the active function object’s [[Realm]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>strictCaller</i> be <b>false</b>.</li>
+ <li>Let <i>directEval</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-performeval">PerformEval</a>(<i>x</i>, <i>evalRealm</i>, <i>strictCaller</i>,
+ <i>directEval</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-performeval">
+ <h1><span class="secnum" id="sec-18.2.1.1"><a href="#sec-performeval" title="link to this section">18.2.1.1</a></span>
+ Runtime Semantics: PerformEval( x, evalRealm, strictCaller, direct)</h1>
+
+ <p>The abstract operation PerformEval with arguments <var>x</var>, <var>evalRealm</var>, <var>strictCaller</var>, and
+ <var>direct</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If <i>direct</i> is <b>false</b> then <i>strictCaller</i> is also
+ <b>false</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is not String, return <i>x</i>.</li>
+ <li>Let <i>script</i> be the ECMAScript code that is the result of parsing <i>x</i>, interpreted as UTF-16 encoded
+ Unicode text as described in <a href="#sec-ecmascript-language-types-string-type">6.1.4</a><i>,</i> for the goal
+ symbol <i>Script</i>. If the parse fails or any early errors are detected, throw a <b>SyntaxError</b> exception (but
+ <a href="#sec-error-handling-and-language-extensions">see also clause 16</a>).</li>
+ <li>If <i>script</i> Contains <i>ScriptBody</i> is <b>false</b>, return <b>undefined</b>.</li>
+ <li>Let <i>body</i> be the <i>ScriptBody</i> of <i>script.</i></li>
+ <li>If <i>strictCaller</i> is <b>true</b>, let <i>strictEval</i> be <b>true.</b></li>
+ <li>Else, let <i>strictEval</i> be IsStrict of <i>script</i>.</li>
+ <li>Let <i>ctx</i> be <a href="#sec-execution-contexts">the running execution context</a>. If <i>direct</i> is
+ <b>true</b> <i>ctx</i> will be the <a href="#sec-execution-contexts">execution context</a> that performed the direct
+ <code>eval</code>. If <i>direct</i> is <b>false</b> <i>ctx</i> will be the <a
+ href="#sec-execution-contexts">execution context</a> for the invocation of the eval function.</li>
+ <li>If <i>direct</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>lexEnv</i> be <a href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>ctx’s</i>
+ <a href="#sec-execution-contexts">LexicalEnvironment</a>).</li>
+ <li>Let <i>varEnv</i> be <i>ctx’s</i> <a href="#sec-execution-contexts">VariableEnvironment</a>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>lexEnv</i> be <a
+ href="#sec-newdeclarativeenvironment">NewDeclarativeEnvironment</a>(<i>evalRealm</i>.[[globalEnv]]).</li>
+ <li>Let <i>varEnv</i> be <i>evalRealm</i>.[[globalEnv]].</li>
+ </ol>
+ </li>
+ <li>If <i>strictEval</i> is <b>true</b>, let <i>varEnv</i> be <i>lexEnv</i>.</li>
+ <li>If <i>ctx</i> is not already <a href="#sec-execution-contexts">suspended</a>, <a
+ href="#sec-execution-contexts">Suspend</a> <i>ctx</i>.</li>
+ <li>Let <i>evalCxt</i> be a new <a href="#sec-execution-contexts">ECMAScript code execution context</a>.</li>
+ <li>Set the <i>evalCxt’s</i> <a href="#sec-code-realms">Realm</a> to <i>evalRealm</i>.</li>
+ <li>Set the <i>evalCxt’s</i> <a href="#sec-execution-contexts">VariableEnvironment</a> to <i>varEnv</i>.</li>
+ <li>Set the <i>evalCxt’s</i> <a href="#sec-execution-contexts">LexicalEnvironment</a> to <i>lexEnv</i>.</li>
+ <li>Push <i>evalCxt</i> on to <a href="#sec-execution-contexts">the execution context stack</a>; <i>evalCxt</i> is now
+ <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Let <i>result</i> be <a href="#sec-evaldeclarationinstantiation">EvalDeclarationInstantiation</a>(<i>body</i>,
+ <i>varEnv</i>, <i>lexEnv</i>, <i>strictEval</i>).</li>
+ <li>If <i>result</i>.[[type]] is <span style="font-family: sans-serif">normal</span>, then
+ <ol class="block">
+ <li>Let <i>result</i> be the result of evaluating <i>body</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>result</i>.[[type]] is <span style="font-family: sans-serif">normal</span> and <i>result</i>.[[value]] is
+ <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <i>evalCxt</i> and remove it from <a
+ href="#sec-execution-contexts">the execution context stack</a>.</li>
+ <li>Resume the context that is now on the top of <a href="#sec-execution-contexts">the execution context stack</a> as <a
+ href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The eval code cannot instantiate variable or function bindings in the variable
+ environment of the calling context that invoked the eval if the calling context is evaluating formal parameter
+ initializers or if either the code of the calling context or the eval code is <a href="#sec-strict-mode-code">strict
+ code</a>. Instead such bindings are instantiated in a new <a href="#sec-execution-contexts">VariableEnvironment</a> that
+ is only accessible to the eval code. Bindings introduced by <code>let</code>, <code>const</code>, or <code>class</code>
+ declarations are always instantiated in a new <a href="#sec-execution-contexts">LexicalEnvironment</a>.</p>
+ </div>
+ </section>
+
+ <section id="sec-evaldeclarationinstantiation">
+ <h1><span class="secnum" id="sec-18.2.1.2"><a href="#sec-evaldeclarationinstantiation"
+ title="link to this section">18.2.1.2</a></span> Runtime Semantics: EvalDeclarationInstantiation( body, varEnv,
+ lexEnv, strict)</h1>
+
+ <p>When the abstract operation EvalDeclarationInstantiation is call with arguments <var>body</var>, <var>varEnv</var>,
+ <var>lexEnv</var>, and <var>strict</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>lexNames</i> be the LexicallyDeclaredNames of <i>body</i>.</li>
+ <li>Let <i>varNames</i> be the VarDeclaredNames of <i>body</i>.</li>
+ <li>Let <i>varDeclarations</i> be the VarScopedDeclarations of <i>body</i>.</li>
+ <li>Let <i>lexEnvRec</i> be <i>lexEnv</i>’s environment record.</li>
+ <li>Let <i>varEnvRec</i> be <i>varEnv</i>’s environment record.</li>
+ <li>If <i>strict</i> is <b>false</b>, then
+ <ol class="block">
+ <li>If <i>varEnvRec</i> is a <a href="#sec-global-environment-records">global environment record</a>, then
+ <ol class="block">
+ <li>For each <i>name</i> in <i>varNames</i>, do
+ <ol class="block">
+ <li>If <i>varEnvRec.</i><a href="#sec-haslexicaldeclaration">HasLexicalDeclaration</a>(<i>name</i>) is
+ <b>true</b>, throw a <b>SyntaxError</b> exception.</li>
+ <li>NOTE: <code>eval</code> will not create a global var declaration that would be shadowed by a global
+ lexical declaration.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>thisLex</i> be <i>lexEnv</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: the following loop will terminate.</li>
+ <li>Repeat while <i>thisLex</i> is not the same as <i>varEnv,</i>
+ <ol class="block">
+ <li>Let <i>thisEnvRec</i> be <i>thisLex</i>’s environment record.</li>
+ <li>If <i>thisEnvRec</i> is not an <a href="#sec-object-environment-records">object environment record</a>, then
+ <ol class="block">
+ <li>NOTE: The environment of with statements can not contain any lexical declaration so it doesn’t
+ need to be checked for var/let hoisting conflicts.</li>
+ <li>For each <i>name</i> in <i>varNames</i>, do
+ <ol class="block">
+ <li>If <i>thisEnvRec.</i>HasBinding(<i>name</i>) is <b>true</b>, throw a <b>SyntaxError</b>
+ exception.</li>
+ <li>NOTE: A direct <code>eval</code> will not hoist var declaration over a like-named lexical
+ declaration.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>thisLex</i> be <i>thisLex</i>’s <a href="#sec-lexical-environments">outer environment
+ reference</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>functionsToInitialize</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>declaredFunctionNames</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each <i>d</i> in <i>varDeclarations</i>, in reverse list order do
+ <ol class="block">
+ <li>If <i>d</i> is neither a <i>VariableDeclaration</i> or a <i>ForBinding</i>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>d</i> is either a <i>FunctionDeclaration</i> or a
+ <i>GeneratorDeclaration</i>.</li>
+ <li>NOTE	If there are multiple <span style="font-family: Times New Roman"><i>FunctionDeclarations</i></span>
+ for the same name, the last declaration is used.</li>
+ <li>Let <i>fn</i> be the sole element of the BoundNames of <i>d.</i></li>
+ <li>If <i>fn</i> is not an element of <i>declaredFunctionNames</i>, then
+ <ol class="block">
+ <li>If <i>varEnvRec</i> is a <a href="#sec-global-environment-records">global environment record</a>, then
+ <ol class="block">
+ <li>Let <i>fnDefinable</i> be <i>varEnvRec</i>.<a
+ href="#sec-candeclareglobalfunction">CanDeclareGlobalFunction</a>(<i>fn</i>).</li>
+ <li>If <i>fnDefinable</i> is <b>false</b>, throw <b>SyntaxError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Append <i>fn</i> to <i>declaredFunctionNames</i>.</li>
+ <li>Insert <i>d</i> as the first element of <i>functionsToInitialize</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>declaredVarNames</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each <i>d</i> in <i>varDeclarations</i>, do
+ <ol class="block">
+ <li>If <i>d</i> is a <i>VariableDeclaration</i> or a <i>ForBinding</i>, then
+ <ol class="block">
+ <li>For each String <i>vn</i> in the BoundNames of <i>d</i>, do
+ <ol class="block">
+ <li>If <i>vn</i> is not an element of <i>declaredFunctionNames</i>, then
+ <ol class="block">
+ <li>If <i>varEnvRec</i> is a <a href="#sec-global-environment-records">global environment record</a>,
+ then
+ <ol class="block">
+ <li>Let <i>vnDefinable</i> be <i>varEnvRec.</i><a
+ href="#sec-candeclareglobalvar">CanDeclareGlobalVar</a>(<i>vn</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>vnDefinable</i>).</li>
+ <li>If <i>vnDefinable</i> is <b>false</b>, throw <b>SyntaxError</b> exception.</li>
+ </ol>
+ </li>
+ <li>If <i>vn</i> is not an element of <i>declaredVarNames</i>, then
+ <ol class="block">
+ <li>Append <i>vn</i> to <i>declaredVarNames</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>NOTE: No abnormal terminations occur after this algorithm step unless <span style="font-family: Times New
+ Roman"><i>varEnvRec</i></span> is a <a href="#sec-global-environment-records">global environment record</a> and the
+ global object is a Proxy exotic object.</li>
+ <li>Let <i>lexDeclarations</i> be the LexicallyScopedDeclarations of <i>body</i>.</li>
+ <li>For each element <i>d</i> in <i>lexDeclarations</i> do
+ <ol class="block">
+ <li>NOTE Lexically declared names are only instantiated here but not initialized.</li>
+ <li>For each element <i>dn</i> of the BoundNames of <i>d</i> do
+ <ol class="block">
+ <li>If IsConstantDeclaration of <i>d</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>lexEnvRec</i>.CreateImmutableBinding(<i>dn</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>lexEnvRec</i>.CreateMutableBinding(<i>dn</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>For each production <i>f</i> in <i>functionsToInitialize</i>, do
+ <ol class="block">
+ <li>Let <i>fn</i> be the sole element of the BoundNames of <i>f.</i></li>
+ <li>Let <i>fo</i> be the result of performing InstantiateFunctionObject for <i>f</i> with argument
+ <i>lexEnv</i>.</li>
+ <li>If <i>varEnvRec</i> is a <a href="#sec-global-environment-records">global environment record</a>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>varEnvRec</i>.<a
+ href="#sec-createglobalfunctionbinding">CreateGlobalFunctionBinding</a>(<i>fn</i>, <i>fo</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>bindingExists</i> be <i>varEnvRec</i>.HasBinding(<i>fn</i>).</li>
+ <li>If <i>bindingExists</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>varEnvRec</i>.CreateMutableBinding(<i>fn</i>, <b>true</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a> because of validation preceding
+ step 12.</li>
+ <li>Let <i>status</i> be <i>varEnvRec</i>.InitializeBinding(<i>fn</i>, <i>fo</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>status</i> be <i>varEnvRec</i>.SetMutableBinding(<i>fn</i>, <i>fo</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>For each String <i>vn</i> in <i>declaredVarNames</i>, in list order do
+ <ol class="block">
+ <li>If <i>varEnvRec</i> is a <a href="#sec-global-environment-records">global environment record</a>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>varEnvRec.</i><a
+ href="#sec-createglobalvarbinding">CreateGlobalVarBinding</a>(<i>vn</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>bindingExists</i> be <i>varEnvRec</i>.HasBinding(<i>vn</i>).</li>
+ <li>If <i>bindingExists</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>varEnvRec</i>.CreateMutableBinding(<i>vn</i>, <b>true</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a> because of validation preceding
+ step 12.</li>
+ <li>Let <i>status</i> be <i>varEnvRec</i>.InitializeBinding(<i>vn</i>, <b>undefined</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family: sans-serif">empty</span>)</li>
+ </ol>
+
+ <p class="Note"><i>NOTE	An alternative version of this algorithm is described in <a
+ href="#sec-variablestatements-in-catch-blocks">B.3.5</a>.</i></p>
+ </section>
+ </section>
+
+ <section id="sec-isfinite-number">
+ <h1><span class="secnum" id="sec-18.2.2"><a href="#sec-isfinite-number" title="link to this section">18.2.2</a></span>
+ isFinite (number)</h1>
+
+ <p>Returns <b>false</b> if the argument coerces to <b>NaN</b>, <b>+∞</b>, or <b>−∞</b>, and otherwise
+ returns <b>true</b>.</p>
+
+ <ol class="proc">
+ <li>Let <i>num</i> be <a href="#sec-tonumber">ToNumber</a>(<i>number</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>num</i>).</li>
+ <li>If <i>num</i> is <b>NaN</b>, <b>+∞</b>, or <b>−∞</b>, return <b>false</b>.</li>
+ <li>Otherwise, return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isnan-number">
+ <h1><span class="secnum" id="sec-18.2.3"><a href="#sec-isnan-number" title="link to this section">18.2.3</a></span> isNaN
+ (number)</h1>
+
+ <p>Returns <b>true</b> if the argument coerces to <b>NaN</b>, and otherwise returns <b>false</b>.</p>
+
+ <ol class="proc">
+ <li>Let <i>num</i> be <a href="#sec-tonumber">ToNumber</a>(<i>number</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>num</i>).</li>
+ <li>If <i>num</i> is <b>NaN</b>, return <b>true</b>.</li>
+ <li>Otherwise, return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A reliable way for ECMAScript code to test if a value <code>X</code> is a <b>NaN</b> is an
+ expression of the form <code>X !== X</code>. The result will be <b>true</b> if and only if <code>X</code> is a
+ <b>NaN</b>.</p>
+ </div>
+ </section>
+
+ <section id="sec-parsefloat-string">
+ <h1><span class="secnum" id="sec-18.2.4"><a href="#sec-parsefloat-string" title="link to this section">18.2.4</a></span>
+ parseFloat (string)</h1>
+
+ <p>The <code>parseFloat</code> function produces a Number value dictated by interpretation of the contents of the
+ <var>string</var> argument as a decimal literal.</p>
+
+ <p>When the <code>parseFloat</code> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>inputString</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>inputString</i>).</li>
+ <li>Let <i>trimmedString</i> be a substring of <i>inputString</i> consisting of the leftmost code unit that is not a
+ <i>StrWhiteSpaceChar</i> and all code units to the right of that code unit. (In other words, remove leading white
+ space.) If <i>inputString</i> does not contain any such code units, let <i>trimmedString</i> be the empty string.</li>
+ <li>If neither <i>trimmedString</i> nor any prefix of <i>trimmedString</i> satisfies the syntax of a
+ <i>StrDecimalLiteral</i> (<a href="#sec-tonumber-applied-to-the-string-type">see 7.1.3.1</a>), return <b>NaN</b>.</li>
+ <li>Let <i>numberString</i> be the longest prefix of <i>trimmedString</i>, which might be <i>trimmedString</i> itself,
+ that satisfies the syntax of a <i>StrDecimalLiteral</i>.</li>
+ <li>Let <i>mathFloat</i> be MV of <i>numberString</i>.</li>
+ <li>If <i>mathFloat</i>=0, then
+ <ol class="block">
+ <li>If the first code unit of <i>trimmedString</i> is <code>"-"</code>, return −0.</li>
+ <li>Return +0.</li>
+ </ol>
+ </li>
+ <li>Return the Number value for <i>mathFloat</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <code>parseFloat</code> may interpret only a leading portion of <i>string</i> as a Number
+ value; it ignores any code units that cannot be interpreted as part of the notation of an decimal literal, and no
+ indication is given that any such code units were ignored.</p>
+ </div>
+ </section>
+
+ <section id="sec-parseint-string-radix">
+ <h1><span class="secnum" id="sec-18.2.5"><a href="#sec-parseint-string-radix" title="link to this section">18.2.5</a></span>
+ parseInt (string , radix)</h1>
+
+ <p>The <code>parseInt</code> function produces an integer value dictated by interpretation of the contents of the
+ <var>string</var> argument according to the specified <var>radix</var>. Leading white space in <var>string</var> is ignored.
+ If <var>radix</var> is <b>undefined</b> or 0, it is assumed to be <span style="font-family: Times New Roman">10</span>
+ except when the number begins with the code unit pairs <code>0x</code> or <code>0X</code>, in which case a radix of 16 is
+ assumed. If <var>radix</var> is <span style="font-family: Times New Roman">16,</span> the number may also optionally begin
+ with the code unit pairs <code>0x</code> or <code>0X</code>.</p>
+
+ <p>When the <code>parseInt</code> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>inputString</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>string</i>).</li>
+ <li>Let <i>S</i> be a newly created substring of <i>inputString</i> consisting of the first code unit that is not a
+ <i>StrWhiteSpaceChar</i> and all code units following that code unit. (In other words, remove leading white space.) If
+ <i>inputString</i> does not contain any such code unit, let <i>S</i> be the empty string.</li>
+ <li>Let <i>sign</i> be 1.</li>
+ <li>If <i>S</i> is not empty and the first code unit of <i>S</i> is 0x002D <b>(</b>HYPHEN-MINUS<b>)</b>, let <i>sign</i>
+ be −1.</li>
+ <li>If <i>S</i> is not empty and the first code unit of <i>S</i> is 0x002B <b>(</b>PLUS SIGN<b>)</b> or 0x002D
+ <b>(</b>HYPHEN-MINUS<b>)</b>, remove the first code unit from <i>S</i>.</li>
+ <li>Let <i>R</i> = <a href="#sec-toint32">ToInt32</a>(<i>radix</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>R</i>).</li>
+ <li>Let <i>stripPrefix</i> be <b>true</b>.</li>
+ <li>If <i>R</i> ≠ 0, then
+ <ol class="block">
+ <li>If <i>R</i> < 2 or <i>R</i> > 36, return <b>NaN</b>.</li>
+ <li>If <i>R</i> ≠ 16, let <i>stripPrefix</i> be <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Else <i>R</i> = 0,
+ <ol class="block">
+ <li>Let <i>R</i> = 10.</li>
+ </ol>
+ </li>
+ <li>If <i>stripPrefix</i> is <b>true</b>, then
+ <ol class="block">
+ <li>If the length of <i>S</i> is at least 2 and the first two code units of <i>S</i> are either
+ “<b>0x</b>” or “<b>0X</b>”, remove the first two code units from <i>S</i> and let <i>R</i>
+ = 16.</li>
+ </ol>
+ </li>
+ <li>If <i>S</i> contains a code unit that is not a radix-<i>R</i> digit, let <i>Z</i> be the substring of <i>S</i>
+ consisting of all code units before the first such code unit; otherwise, let <i>Z</i> be <i>S</i>.</li>
+ <li>If <i>Z</i> is empty, return <b>NaN</b>.</li>
+ <li>Let <i>mathInt</i> be the mathematical integer value that is represented by <i>Z</i> in radix-<i>R</i> notation, using
+ the letters <b>A</b>-<b>Z</b> and <b>a</b>-<b>z</b> for digits with values 10 through 35. (However, if <i>R</i> is 10
+ and <i>Z</i> contains more than 20 significant digits, every significant digit after the 20th may be replaced by a
+ <b>0</b> digit, at the option of the implementation; and if <i>R</i> is not 2, 4, 8, 10, 16, or 32, then
+ <i>mathInt</i> may be an implementation-dependent approximation to the mathematical integer value that is represented
+ by <i>Z</i> in radix-<i>R</i> notation.)</li>
+ <li>If <i>mathInt</i> = 0, then
+ <ol class="block">
+ <li>If <i>sign</i> = −1, return −0.</li>
+ <li>Return +0.</li>
+ </ol>
+ </li>
+ <li>Let <i>number</i> be the Number value for <i>mathInt</i>.</li>
+ <li>Return <i>sign</i> × <i>number</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <code>parseInt</code> may interpret only a leading portion of <i>string</i> as an integer
+ value; it ignores any code units that cannot be interpreted as part of the notation of an integer, and no indication is
+ given that any such code units were ignored.</p>
+ </div>
+ </section>
+
+ <section id="sec-uri-handling-functions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18.2.6"><a href="#sec-uri-handling-functions"
+ title="link to this section">18.2.6</a></span> URI Handling Functions</h1>
+
+ <p>Uniform Resource Identifiers, or URIs, are Strings that identify resources (e.g. web pages or files) and transport
+ protocols by which to access them (e.g. HTTP or FTP) on the Internet. The ECMAScript language itself does not provide any
+ support for using URIs except for functions that encode and decode URIs as described in <a
+ href="#sec-decodeuri-encodeduri">18.2.6.2</a>, <a href="#sec-decodeuricomponent-encodeduricomponent">18.2.6.3</a>, <a
+ href="#sec-encodeuri-uri">18.2.6.4</a> and <a href="#sec-encodeuricomponent-uricomponent">18.2.6.5</a></p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Many implementations of ECMAScript provide additional functions and methods that
+ manipulate web pages; these functions are beyond the scope of this standard.</p>
+ </div>
+ </div>
+
+ <section id="sec-uri-syntax-and-semantics">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18.2.6.1"><a href="#sec-uri-syntax-and-semantics"
+ title="link to this section">18.2.6.1</a></span> URI Syntax and Semantics</h1>
+
+ <p>A URI is composed of a sequence of components separated by component separators. The general form is:</p>
+
+ <div class="gp prod"><span class="nt">Scheme</span> <span class="geq">:</span> <span class="nt">First</span> <code class="t">/</code> <span class="nt">Second</span> <code class="t">;</code> <span class="nt">Third</span> <code class="t">?</code> <span class="nt">Fourth</span></div>
+
+ <p>where the italicized names represent components and “<code>:</code>”, “<code>/</code>”,
+ “<code>;</code>” and “<code>?</code>” are reserved for use as separators. The
+ <code>encodeURI</code> and <code>decodeURI</code> functions are intended to work with complete URIs; they assume that
+ any reserved code units in the URI are intended to have special meaning and so are not encoded. The
+ <code>encodeURIComponent</code> and <code>decodeURIComponent</code> functions are intended to work with the individual
+ component parts of a URI; they assume that any reserved code units represent text and so must be encoded so that they
+ are not interpreted as reserved code units when the component is part of a complete URI.</p>
+
+ <p>The following lexical grammar specifies the form of encoded URIs.</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uri</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">uriCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uriCharacters</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">uriCharacter</span> <span class="nt">uriCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uriCharacter</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">uriReserved</span></div>
+ <div class="rhs"><span class="nt">uriUnescaped</span></div>
+ <div class="rhs"><span class="nt">uriEscaped</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uriReserved</span> <span class="geq">:::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">;</code> <code class="t">/</code> <code class="t">?</code> <code class="t">:</code> <code class="t">@</code> <code class="t">&</code> <code class="t">=</code> <code class="t">+</code> <code class="t">$</code> <code class="t">,</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uriUnescaped</span> <span class="geq">:::</span></div>
+ <div class="rhs"><span class="nt">uriAlpha</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><span class="nt">uriMark</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uriEscaped</span> <span class="geq">:::</span></div>
+ <div class="rhs"><code class="t">%</code> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uriAlpha</span> <span class="geq">:::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">a</code> <code class="t">b</code> <code class="t">c</code> <code class="t">d</code> <code class="t">e</code> <code class="t">f</code> <code class="t">g</code> <code class="t">h</code> <code class="t">i</code> <code class="t">j</code> <code class="t">k</code> <code class="t">l</code> <code class="t">m</code> <code class="t">n</code> <code class="t">o</code> <code class="t">p</code> <code class="t">q</code> <code class="t">r</code> <code class="t">s</code> <code class="t">t</code> <code class="t">u</code> <code class="t">v</code> <code class="t">w</code> <code class="t">x</code> <code class="t">y</code> <code class="t">z</code></div>
+ <div class="rhs"><code class="t">A</code> <code class="t">B</code> <code class="t">C</code> <code class="t">D</code> <code class="t">E</code> <code class="t">F</code> <code class="t">G</code> <code class="t">H</code> <code class="t">I</code> <code class="t">J</code> <code class="t">K</code> <code class="t">L</code> <code class="t">M</code> <code class="t">N</code> <code class="t">O</code> <code class="t">P</code> <code class="t">Q</code> <code class="t">R</code> <code class="t">S</code> <code class="t">T</code> <code class="t">U</code> <code class="t">V</code> <code class="t">W</code> <code class="t">X</code> <code class="t">Y</code> <code class="t">Z</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">uriMark</span> <span class="geq">:::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">-</code> <code class="t">_</code> <code class="t">.</code> <code class="t">!</code> <code class="t">~</code> <code class="t">*</code> <code class="t">'</code> <code class="t">(</code> <code class="t">)</code></div>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The above syntax is based upon RFC 2396 and does not reflect changes introduced by the
+ more recent RFC 3986.</p>
+ </div>
+
+ <p><b>Runtime Semantics</b></p>
+
+ <p>When a code unit to be included in a URI is not listed above or is not intended to have the special meaning sometimes
+ given to the reserved code units, that code unit must be encoded. The code unit is transformed into its UTF-8 encoding,
+ with surrogate pairs first converted from UTF-16 to the corresponding code point value. (Note that for code units in the
+ range [0,127] this results in a single octet with the same value.) The resulting sequence of octets is then transformed
+ into a String with each octet represented by an escape sequence of the form “<code><b>%</b>xx</code>”.</p>
+ </div>
+
+ <section id="sec-encode">
+ <h1><span class="secnum" id="sec-18.2.6.1.1"><a href="#sec-encode" title="link to this section">18.2.6.1.1</a></span>
+ Runtime Semantics: Encode Abstract Operation</h1>
+
+ <p>The encoding and escaping process is described by the abstract operation Encode taking two String arguments
+ <var>string</var> and <var>unescapedSet</var>.</p>
+
+ <ol class="proc">
+ <li>Let <i>strLen</i> be the number of code units in <i>string</i>.</li>
+ <li>Let <i>R</i> be the empty String.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>If <i>k</i> equals <i>strLen</i>, return <i>R</i>.</li>
+ <li>Let <i>C</i> be the code unit at index <i>k</i> within <i>string</i>.</li>
+ <li>If <i>C</i> is in <i>unescapedSet</i>, then
+ <ol class="block">
+ <li>Let <i>S</i> be a String containing only the code unit <i>C</i>.</li>
+ <li>Let <i>R</i> be a new String value computed by concatenating the previous value of <i>R</i> and
+ <i>S</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>C</i> is not in <i>unescapedSet</i>,
+ <ol class="block">
+ <li>If the code unit value of <i>C</i> is not less than 0xDC00 and not greater than 0xDFFF, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>If the code unit value of <i>C</i> is less than 0xD800 or greater than 0xDBFF, then
+ <ol class="block">
+ <li>Let <i>V</i> be the code unit value of <i>C</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Increase <i>k</i> by 1.</li>
+ <li>If <i>k</i> equals <i>strLen</i>, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>Let <i>kChar</i> be the code unit value of the code unit at index <i>k</i> within <i>string</i>.</li>
+ <li>If <i>kChar</i> is less than 0xDC00 or greater than 0xDFFF, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>Let <i>V</i> be (((the code unit value of <i>C</i>) – 0xD800) × 0x400 + (<i>kChar</i>
+ – 0xDC00) + 0x10000).</li>
+ </ol>
+ </li>
+ <li>Let <i>Octets</i> be the array of octets resulting by applying the UTF-8 transformation to <i>V</i>, and
+ let <i>L</i> be the array size.</li>
+ <li>Let <i>j</i> be 0.</li>
+ <li>Repeat, while <i>j</i> < <i>L</i>
+ <ol class="block">
+ <li>Let <i>jOctet</i> be the value at index <i>j</i> within <i>Octets</i>.</li>
+ <li>Let <i>S</i> be a String containing three code units “<b>%</b><i>XY</i>” where <i>XY</i>
+ are two uppercase hexadecimal digits encoding the value of <i>jOctet</i>.</li>
+ <li>Let <i>R</i> be a new String value computed by concatenating the previous value of <i>R</i> and
+ <i>S</i>.</li>
+ <li>Increase <i>j</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-decode">
+ <h1><span class="secnum" id="sec-18.2.6.1.2"><a href="#sec-decode" title="link to this section">18.2.6.1.2</a></span>
+ Runtime Semantics: Decode Abstract Operation</h1>
+
+ <p>The unescaping and decoding process is described by the abstract operation Decode taking two String arguments
+ <var>string</var> and <var>reservedSet</var>.</p>
+
+ <ol class="proc">
+ <li>Let <i>strLen</i> be the number of code units in <i>string</i>.</li>
+ <li>Let <i>R</i> be the empty String.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>If <i>k</i> equals <i>strLen</i>, return <i>R</i>.</li>
+ <li>Let <i>C</i> be the code unit at index <i>k</i> within <i>string</i>.</li>
+ <li>If <i>C</i> is not ‘<b>%</b>’, then
+ <ol class="block">
+ <li>Let <i>S</i> be the String containing only the code unit <i>C</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>C</i> is ‘<b>%</b>’,
+ <ol class="block">
+ <li>Let <i>start</i> be <i>k</i>.</li>
+ <li>If <i>k</i> + 2 is greater than or equal to <i>strLen</i>, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>If the code units at index (<i>k</i>+1) and (<i>k</i> + 2) within <i>string</i> do not represent
+ hexadecimal digits, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>Let <i>B</i> be the 8-bit value represented by the two hexadecimal digits at index (<i>k</i> + 1) and
+ (<i>k</i> + 2).</li>
+ <li>Increment <i>k</i> by 2.</li>
+ <li>If the most significant bit in <i>B</i> is 0, then
+ <ol class="block">
+ <li>Let <i>C</i> be the code unit with code unit value <i>B</i>.</li>
+ <li>If <i>C</i> is not in <i>reservedSet</i>, then
+ <ol class="block">
+ <li>Let <i>S</i> be the String containing only the code unit <i>C</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>C</i> is in <i>reservedSet</i>,
+ <ol class="block">
+ <li>Let <i>S</i> be the substring of <i>string</i> from index <i>start</i> to index <i>k</i>
+ inclusive.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else the most significant bit in <i>B</i> is 1,
+ <ol class="block">
+ <li>Let <i>n</i> be the smallest nonnegative integer such that (<i>B</i> << <i>n</i>) & 0x80 is
+ equal to 0.</li>
+ <li>If <i>n</i> equals 1 or <i>n</i> is greater than 4, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>Let <i>Octets</i> be an array of 8-bit integers of size <i>n</i>.</li>
+ <li>Put <i>B</i> into <i>Octets</i> at index 0.</li>
+ <li>If <i>k</i> + (3 × (<i>n</i> – 1)) is greater than or equal to <i>strLen</i>, throw a
+ <b><a href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b>
+ exception.</li>
+ <li>Let <i>j</i> be 1.</li>
+ <li>Repeat, while <i>j</i> < <i>n</i>
+ <ol class="block">
+ <li>Increment <i>k</i> by 1.</li>
+ <li>If the code unit at index <i>k</i> within <i>string</i> is not <b><code>"%</code>"</b>, throw a
+ <b><a href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b>
+ exception.</li>
+ <li>If the code units at index (<i>k</i> +1) and (<i>k</i> + 2) within <i>string</i> do not represent
+ hexadecimal digits, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>Let <i>B</i> be the 8-bit value represented by the two hexadecimal digits at index (<i>k</i> + 1)
+ and (<i>k</i> + 2).</li>
+ <li>If the two most significant bits in <i>B</i> are not 10, throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>Increment <i>k</i> by 2.</li>
+ <li>Put <i>B</i> into <i>Octets</i> at index <i>j</i>.</li>
+ <li>Increment <i>j</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>V</i> be the value obtained by applying the UTF-8 transformation to <i>Octets</i>, that is,
+ from an array of octets into a 21-bit value. If <i>Octets</i> does not contain a valid UTF-8 encoding
+ of a Unicode code point throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> exception.</li>
+ <li>If <i>V</i> < 0x10000, then
+ <ol class="block">
+ <li>Let <i>C</i> be the code unit <i>V</i>.</li>
+ <li>If <i>C</i> is not in <i>reservedSet</i>, then
+ <ol class="block">
+ <li>Let <i>S</i> be the String containing only the code unit <i>C</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>C</i> is in <i>reservedSet</i>,
+ <ol class="block">
+ <li>Let <i>S</i> be the substring of <i>string</i> from index <i>start</i> to index <i>k</i>
+ inclusive.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else <i>V</i> ≥ 0x10000,
+ <ol class="block">
+ <li>Let <i>L</i> be (((<i>V</i> – 0x10000) & 0x3FF) + 0xDC00).</li>
+ <li>Let <i>H</i> be ((((<i>V</i> – 0x10000) >> 10) & 0x3FF) + 0xD800).</li>
+ <li>Let <i>S</i> be the String containing the two code units <i>H</i> and <i>L</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>R</i> be a new String value computed by concatenating the previous value of <i>R</i> and <i>S</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This syntax of Uniform Resource Identifiers is based upon RFC 2396 and does not
+ reflect the more recent RFC 3986 which replaces RFC 2396. A formal description and implementation of UTF-8 is given in
+ RFC 3629.</p>
+
+ <p>In UTF-8, characters are encoded using sequences of 1 to 6 octets. The only octet of a "sequence" of one has the
+ higher-order bit set to 0, the remaining 7 bits being used to encode the character value. In a sequence of n octets,
+ n>1, the initial octet has the n higher-order bits set to 1, followed by a bit set to 0. The remaining bits of that
+ octet contain bits from the value of the character to be encoded. The following octets all have the higher-order bit
+ set to 1 and the following bit set to 0, leaving 6 bits in each to contain bits from the character to be encoded. The
+ possible UTF-8 encodings of ECMAScript characters are specified in <a href="#table-43">Table 43</a>.</p>
+ </div>
+
+ <figure>
+ <figcaption><span id="table-43">Table 43</span> — UTF-8 Encodings</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 0px solid black; border-left: 0px solid black; border-top: 0px solid black">Code Unit Value</th>
+ <th style="border-bottom: 0px solid black; border-top: 0px solid black">Representation</th>
+ <th style="border-bottom: 0px solid black; border-top: 0px solid black">1<sup>st</sup> Octet</th>
+ <th style="border-bottom: 0px solid black; border-top: 0px solid black">2<sup>nd</sup> Octet</th>
+ <th style="border-bottom: 0px solid black; border-top: 0px solid black">3<sup>rd</sup> Octet</th>
+ <th style="border-bottom: 0px solid black; border-right: 0px solid black; border-top: 0px solid black">4<sup>th</sup> Octet</th>
+ </tr>
+ <tr>
+ <td><code>0x0000 - 0x007F</code></td>
+ <td><code>00000000</code> <code><b>0</b><i>zzzzzzz</i></code></td>
+ <td><code><b>0</b><i>zzzzzzz</i></code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>0x0080 - 0x07FF</code></td>
+ <td><code><b>00000</b><i>yyy yyzzzzzz</i></code></td>
+ <td><code><b>110</b><i>yyyyy</i></code></td>
+ <td><code><b>10</b><i>zzzzzz</i></code></td>
+ <td></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>0x0800 - 0xD7FF</code></td>
+ <td><span style="font-family: monospace"><i>xxxxyyyy yyzzzzzz</i></span></td>
+ <td><code><b>1110</b><i>xxxx</i></code></td>
+ <td><code><b>10</b><i>yyyyyy</i></code></td>
+ <td><code><b>10</b><i>zzzzzz</i></code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td>
+ <p><code>0xD800 - 0xDBFF</code></p>
+
+ <p><i>followed by</i></p>
+
+ <p><code>0xDC00 – 0xDFFF</code></p>
+ </td>
+
+ <td>
+ <p><code><b>110110</b><i>vv vvwwwwxx</i></code></p>
+
+ <p><i>followed by</i></p>
+
+ <p><code><b>110111</b><i>yy yyzzzzzz</i></code></p>
+ </td>
+
+ <td><code><b>11110</b><i>uuu</i></code></td>
+ <td><code><b>10</b><i>uuwwww</i></code></td>
+ <td><code><b>10</b><i>xxyyyy</i></code></td>
+ <td><code><b>10</b><i>zzzzzz</i></code></td>
+ </tr>
+ <tr>
+ <td>
+ <p><code>0xD800 - 0xDBFF</code></p>
+
+ <p><i>not followed by</i></p>
+
+ <p><code>0xDC00 – 0xDFFF</code></p>
+ </td>
+
+ <td><span style="font-family: sans-serif"><i>causes</i></span> <code><b><a href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b></code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>0xDC00 – 0xDFFF</code></td>
+ <td><span style="font-family: sans-serif"><i>causes</i></span> <code><b><a href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b></code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>0xE000 - 0xFFFF</code></td>
+ <td><span style="font-family: monospace"><i>xxxxyyyy yyzzzzzz</i></span></td>
+ <td><code><b>1110</b><i>xxxx</i></code></td>
+ <td><code><b>10</b><i>yyyyyy</i></code></td>
+ <td><code><b>10</b><i>zzzzzz</i></code></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p class="Note">Where</p>
+
+ <p class="Note"><i>uuuuu</i> = <i>vvvv</i> + 1</p>
+
+ <p class="Note">to account for the addition of 0x10000 as in Surrogates, section 3.7, of the Unicode Standard.</p>
+
+ <p class="Note">The range of code unit values 0xD800-0xDFFF is used to encode surrogate pairs; the above transformation
+ combines a UTF-16 surrogate pair into a UTF-32 representation and encodes the resulting 21-bit value in UTF-8. Decoding
+ reconstructs the surrogate pair.</p>
+
+ <p class="Note">RFC 3629 prohibits the decoding of invalid UTF-8 octet sequences. For example, the invalid sequence C0
+ 80 must not decode into the code unit 0x0000. Implementations of the Decode algorithm are required to throw a <b><a
+ href="#sec-constructor-properties-of-the-global-object-urierror">URIError</a></b> when encountering such invalid
+ sequences.</p>
+ </section>
+ </section>
+
+ <section id="sec-decodeuri-encodeduri">
+ <h1><span class="secnum" id="sec-18.2.6.2"><a href="#sec-decodeuri-encodeduri"
+ title="link to this section">18.2.6.2</a></span> decodeURI (encodedURI)</h1>
+
+ <p>The <code>decodeURI</code> function computes a new version of a URI in which each escape sequence and UTF-8 encoding of
+ the sort that might be introduced by the <code>encodeURI</code> function is replaced with the UTF-16 encoding of the code
+ points that it represents. Escape sequences that could not have been introduced by <code>encodeURI</code> are not
+ replaced.</p>
+
+ <p>When the <code>decodeURI</code> function is called with one argument <var>encodedURI</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>uriString</i> be <a href="#sec-tostring">ToString</a>(<i>encodedURI</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>uriString</i>).</li>
+ <li>Let <i>reservedURISet</i> be a String containing one instance of each code unit valid in <i>uriReserved</i> plus
+ “<code>#</code>”.</li>
+ <li>Return <a href="#sec-decode">Decode</a>(<i>uriString</i>, <i>reservedURISet</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The code point “<code>#</code>” is not decoded from escape sequences even
+ though it is not a reserved URI code point.</p>
+ </div>
+ </section>
+
+ <section id="sec-decodeuricomponent-encodeduricomponent">
+ <h1><span class="secnum" id="sec-18.2.6.3"><a href="#sec-decodeuricomponent-encodeduricomponent"
+ title="link to this section">18.2.6.3</a></span> decodeURIComponent (encodedURIComponent)</h1>
+
+ <p>The <code>decodeURIComponent</code> function computes a new version of a URI in which each escape sequence and UTF-8
+ encoding of the sort that might be introduced by the <code>encodeURIComponent</code> function is replaced with the UTF-16
+ encoding of the code points that it represents.</p>
+
+ <p>When the <code>decodeURIComponent</code> function is called with one argument <var>encodedURIComponent</var>, the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>componentString</i> be <a href="#sec-tostring">ToString</a>(<i>encodedURIComponent</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>componentString</i>).</li>
+ <li>Let <i>reservedURIComponentSet</i> be the empty String.</li>
+ <li>Return <a href="#sec-decode">Decode</a>(<i>componentString</i>, <i>reservedURIComponentSet</i>)</li>
+ </ol>
+ </section>
+
+ <section id="sec-encodeuri-uri">
+ <h1><span class="secnum" id="sec-18.2.6.4"><a href="#sec-encodeuri-uri" title="link to this section">18.2.6.4</a></span>
+ encodeURI (uri)</h1>
+
+ <p>The <code>encodeURI</code> function computes a new version of an UTF-16 encoded (<a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>) URI in which each instance of certain code points is replaced
+ by one, two, three, or four escape sequences representing the UTF-8 encoding of the code points.</p>
+
+ <p>When the <code>encodeURI</code> function is called with one argument <span class="nt">uri</span>, the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>uriString</i> be <a href="#sec-tostring">ToString</a>(<i>uri</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>uriString</i>).</li>
+ <li>Let <i>unescapedURISet</i> be a String containing one instance of each code unit valid in <i>uriReserved</i> and
+ <i>uriUnescaped</i> plus "<code>#</code>".</li>
+ <li>Return <a href="#sec-encode">Encode</a>(<i>uriString</i>, <i>unescapedURISet</i>)</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The code point <span style="font-family: sans-serif">"</span><code>#</code><span
+ style="font-family: sans-serif">"</span> is not encoded to an escape sequence even though it is not a reserved or
+ unescaped URI code point.</p>
+ </div>
+ </section>
+
+ <section id="sec-encodeuricomponent-uricomponent">
+ <h1><span class="secnum" id="sec-18.2.6.5"><a href="#sec-encodeuricomponent-uricomponent"
+ title="link to this section">18.2.6.5</a></span> encodeURIComponent (uriComponent)</h1>
+
+ <p>The <code>encodeURIComponent</code> function computes a new version of an UTF-16 encoded (<a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>) URI in which each instance of certain code points is replaced
+ by one, two, three, or four escape sequences representing the UTF-8 encoding of the code point.</p>
+
+ <p>When the <code>encodeURIComponent</code> function is called with one argument <span class="nt">uriComponent</span>, the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>componentString</i> be <a href="#sec-tostring">ToString</a>(<i>uriComponent</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>componentString</i>).</li>
+ <li>Let <i>unescapedURIComponentSet</i> be a String containing one instance of each code unit valid in
+ <i>uriUnescaped</i>.</li>
+ <li>Return <a href="#sec-encode">Encode</a>(<i>componentString</i>, <i>unescapedURIComponentSet</i>)</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18.3"><a href="#sec-constructor-properties-of-the-global-object"
+ title="link to this section">18.3</a></span> Constructor Properties of the Global Object</h1>
+ </div>
+
+ <section id="sec-constructor-properties-of-the-global-object-array">
+ <h1><span class="secnum" id="sec-18.3.1"><a href="#sec-constructor-properties-of-the-global-object-array"
+ title="link to this section">18.3.1</a></span> Array ( . . . )</h1>
+
+ <p>See <a href="#sec-array-constructor">22.1.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-arraybuffer">
+ <h1><span class="secnum" id="sec-18.3.2"><a href="#sec-constructor-properties-of-the-global-object-arraybuffer"
+ title="link to this section">18.3.2</a></span> ArrayBuffer ( . . . )</h1>
+
+ <p>See <a href="#sec-arraybuffer-constructor">24.1.2</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-boolean">
+ <h1><span class="secnum" id="sec-18.3.3"><a href="#sec-constructor-properties-of-the-global-object-boolean"
+ title="link to this section">18.3.3</a></span> Boolean ( . . . )</h1>
+
+ <p>See <a href="#sec-boolean-constructor">19.3.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-dataview">
+ <h1><span class="secnum" id="sec-18.3.4"><a href="#sec-constructor-properties-of-the-global-object-dataview"
+ title="link to this section">18.3.4</a></span> DataView ( . . . )</h1>
+
+ <p>See <a href="#sec-dataview-constructor">24.2.2</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-date">
+ <h1><span class="secnum" id="sec-18.3.5"><a href="#sec-constructor-properties-of-the-global-object-date"
+ title="link to this section">18.3.5</a></span> Date ( . . . )</h1>
+
+ <p>See <a href="#sec-date-constructor">20.3.2</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-error">
+ <h1><span class="secnum" id="sec-18.3.6"><a href="#sec-constructor-properties-of-the-global-object-error"
+ title="link to this section">18.3.6</a></span> Error ( . . . )</h1>
+
+ <p>See <a href="#sec-error-constructor">19.5.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-evalerror">
+ <h1><span class="secnum" id="sec-18.3.7"><a href="#sec-constructor-properties-of-the-global-object-evalerror"
+ title="link to this section">18.3.7</a></span> EvalError ( . . . )</h1>
+
+ <p>See <a href="#sec-native-error-types-used-in-this-standard-evalerror">19.5.5.1</a>.</p>
+ </section>
+
+ <section id="sec-float32array">
+ <h1><span class="secnum" id="sec-18.3.8"><a href="#sec-float32array" title="link to this section">18.3.8</a></span>
+ Float32Array ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-float64array">
+ <h1><span class="secnum" id="sec-18.3.9"><a href="#sec-float64array" title="link to this section">18.3.9</a></span>
+ Float64Array ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-function">
+ <h1><span class="secnum" id="sec-18.3.10"><a href="#sec-constructor-properties-of-the-global-object-function"
+ title="link to this section">18.3.10</a></span> Function ( . . . )</h1>
+
+ <p>See <a href="#sec-function-constructor">19.2.1</a>.</p>
+ </section>
+
+ <section id="sec-int8array">
+ <h1><span class="secnum" id="sec-18.3.11"><a href="#sec-int8array" title="link to this section">18.3.11</a></span> Int8Array
+ ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-int16array">
+ <h1><span class="secnum" id="sec-18.3.12"><a href="#sec-int16array" title="link to this section">18.3.12</a></span>
+ Int16Array ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-int32array">
+ <h1><span class="secnum" id="sec-18.3.13"><a href="#sec-int32array" title="link to this section">18.3.13</a></span>
+ Int32Array ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-map">
+ <h1><span class="secnum" id="sec-18.3.14"><a href="#sec-map" title="link to this section">18.3.14</a></span> Map ( . . .
+ )</h1>
+
+ <p>See <a href="#sec-map-constructor">23.1.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-number">
+ <h1><span class="secnum" id="sec-18.3.15"><a href="#sec-constructor-properties-of-the-global-object-number"
+ title="link to this section">18.3.15</a></span> Number ( . . . )</h1>
+
+ <p>See <a href="#sec-number-constructor">20.1.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-object">
+ <h1><span class="secnum" id="sec-18.3.16"><a href="#sec-constructor-properties-of-the-global-object-object"
+ title="link to this section">18.3.16</a></span> Object ( . . . )</h1>
+
+ <p>See <a href="#sec-object-constructor">19.1.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-proxy">
+ <h1><span class="secnum" id="sec-18.3.17"><a href="#sec-constructor-properties-of-the-global-object-proxy"
+ title="link to this section">18.3.17</a></span> Proxy ( . . . )</h1>
+
+ <p>See <a href="#sec-proxy-constructor">26.2.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-promise">
+ <h1><span class="secnum" id="sec-18.3.18"><a href="#sec-constructor-properties-of-the-global-object-promise"
+ title="link to this section">18.3.18</a></span> Promise ( . . . )</h1>
+
+ <p>See <a href="#sec-promise-constructor">25.4.3</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-rangeerror">
+ <h1><span class="secnum" id="sec-18.3.19"><a href="#sec-constructor-properties-of-the-global-object-rangeerror"
+ title="link to this section">18.3.19</a></span> RangeError ( . . . )</h1>
+
+ <p>See <a href="#sec-native-error-types-used-in-this-standard-rangeerror">19.5.5.2</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-referenceerror">
+ <h1><span class="secnum" id="sec-18.3.20"><a href="#sec-constructor-properties-of-the-global-object-referenceerror"
+ title="link to this section">18.3.20</a></span> ReferenceError ( . . . )</h1>
+
+ <p>See <a href="#sec-native-error-types-used-in-this-standard-referenceerror">19.5.5.3</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-regexp">
+ <h1><span class="secnum" id="sec-18.3.21"><a href="#sec-constructor-properties-of-the-global-object-regexp"
+ title="link to this section">18.3.21</a></span> RegExp ( . . . )</h1>
+
+ <p>See <a href="#sec-regexp-constructor">21.2.3</a>.</p>
+ </section>
+
+ <section id="sec-set">
+ <h1><span class="secnum" id="sec-18.3.22"><a href="#sec-set" title="link to this section">18.3.22</a></span> Set ( . . .
+ )</h1>
+
+ <p>See <a href="#sec-set-constructor">23.2.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-string">
+ <h1><span class="secnum" id="sec-18.3.23"><a href="#sec-constructor-properties-of-the-global-object-string"
+ title="link to this section">18.3.23</a></span> String ( . . . )</h1>
+
+ <p>See <a href="#sec-string-constructor">21.1.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-symbol">
+ <h1><span class="secnum" id="sec-18.3.24"><a href="#sec-constructor-properties-of-the-global-object-symbol"
+ title="link to this section">18.3.24</a></span> Symbol ( . . . )</h1>
+
+ <p>See <a href="#sec-symbol-constructor">19.4.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-syntaxerror">
+ <h1><span class="secnum" id="sec-18.3.25"><a href="#sec-constructor-properties-of-the-global-object-syntaxerror"
+ title="link to this section">18.3.25</a></span> SyntaxError ( . . . )</h1>
+
+ <p>See <a href="#sec-native-error-types-used-in-this-standard-syntaxerror">19.5.5.4</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-typeerror">
+ <h1><span class="secnum" id="sec-18.3.26"><a href="#sec-constructor-properties-of-the-global-object-typeerror"
+ title="link to this section">18.3.26</a></span> TypeError ( . . . )</h1>
+
+ <p>See <a href="#sec-native-error-types-used-in-this-standard-typeerror">19.5.5.5</a>.</p>
+ </section>
+
+ <section id="sec-uint8array">
+ <h1><span class="secnum" id="sec-18.3.27"><a href="#sec-uint8array" title="link to this section">18.3.27</a></span>
+ Uint8Array ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-uint8clampedarray">
+ <h1><span class="secnum" id="sec-18.3.28"><a href="#sec-uint8clampedarray" title="link to this section">18.3.28</a></span>
+ Uint8ClampedArray ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-uint16array">
+ <h1><span class="secnum" id="sec-18.3.29"><a href="#sec-uint16array" title="link to this section">18.3.29</a></span>
+ Uint16Array ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-uint32array">
+ <h1><span class="secnum" id="sec-18.3.30"><a href="#sec-uint32array" title="link to this section">18.3.30</a></span>
+ Uint32Array ( . . . )</h1>
+
+ <p>See <a href="#sec-typedarray-constructors">22.2.4</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-urierror">
+ <h1><span class="secnum" id="sec-18.3.31"><a href="#sec-constructor-properties-of-the-global-object-urierror"
+ title="link to this section">18.3.31</a></span> URIError ( . . . )</h1>
+
+ <p>See <a href="#sec-native-error-types-used-in-this-standard-urierror">19.5.5.6</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-weakmap">
+ <h1><span class="secnum" id="sec-18.3.32"><a href="#sec-constructor-properties-of-the-global-object-weakmap"
+ title="link to this section">18.3.32</a></span> WeakMap ( . . . )</h1>
+
+ <p>See <a href="#sec-weakmap-constructor">23.3.1</a>.</p>
+ </section>
+
+ <section id="sec-constructor-properties-of-the-global-object-weakset">
+ <h1><span class="secnum" id="sec-18.3.33"><a href="#sec-constructor-properties-of-the-global-object-weakset"
+ title="link to this section">18.3.33</a></span> WeakSet ( . . . )</h1>
+
+ <p>See <a href="#sec-weakset-objects">23.4</a>.</p>
+ </section>
+ </section>
+
+ <section id="sec-other-properties-of-the-global-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-18.4"><a href="#sec-other-properties-of-the-global-object"
+ title="link to this section">18.4</a></span> Other Properties of the Global Object</h1>
+ </div>
+
+ <section id="sec-json">
+ <h1><span class="secnum" id="sec-18.4.1"><a href="#sec-json" title="link to this section">18.4.1</a></span> JSON</h1>
+
+ <p>See <a href="#sec-json-object">24.3</a>.</p>
+ </section>
+
+ <section id="sec-math">
+ <h1><span class="secnum" id="sec-18.4.2"><a href="#sec-math" title="link to this section">18.4.2</a></span> Math</h1>
+
+ <p>See <a href="#sec-math-object">20.2</a>.</p>
+ </section>
+
+ <section id="sec-reflect">
+ <h1><span class="secnum" id="sec-18.4.3"><a href="#sec-reflect" title="link to this section">18.4.3</a></span> Reflect</h1>
+
+ <p>See <a href="#sec-reflect-object">26.1</a>.</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-fundamental-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19"><a href="#sec-fundamental-objects" title="link to this section">19</a></span> Fundamental
+ Objects</h1>
+ </div>
+
+ <section id="sec-object-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.1"><a href="#sec-object-objects" title="link to this section">19.1</a></span> Object
+ Objects</h1>
+ </div>
+
+ <section id="sec-object-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.1.1"><a href="#sec-object-constructor" title="link to this section">19.1.1</a></span>
+ The Object Constructor</h1>
+
+ <p>The Object constructor is the %Object% intrinsic object and the initial value of the <code>Object</code> property of
+ the global object. When called as a constructor it creates new ordinary object. When <code>Object</code> is called as a
+ function rather than as a constructor, it performs a type conversion.</p>
+
+ <p>The <code>Object</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition.</p>
+ </div>
+
+ <section id="sec-object-value">
+ <h1><span class="secnum" id="sec-19.1.1.1"><a href="#sec-object-value" title="link to this section">19.1.1.1</a></span>
+ Object ( [ value ] )</h1>
+
+ <p>When <code>Object</code> function is called with optional argument <var>value</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is neither <b>undefined</b> nor the active function<i>,</i> then
+ <ol class="block">
+ <li>Return <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%ObjectPrototype%"</code>).</li>
+ </ol>
+ </li>
+ <li>If <i>value</i> is <b>null</b>, <b>undefined</b> or not supplied, return <a
+ href="#sec-objectcreate">ObjectCreate</a>(%ObjectPrototype%).</li>
+ <li>Return <a href="#sec-toobject">ToObject</a>(<i>value</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-object-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.1.2"><a href="#sec-properties-of-the-object-constructor"
+ title="link to this section">19.1.2</a></span> Properties of the Object Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Object constructor is the intrinsic object %FunctionPrototype%.</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>1</b>), the Object constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-object.assign">
+ <h1><span class="secnum" id="sec-19.1.2.1"><a href="#sec-object.assign" title="link to this section">19.1.2.1</a></span>
+ Object.assign ( target, ...sources )</h1>
+
+ <p>The <b>assign</b> function is used to copy the values of all of the enumerable own properties from one or more source
+ objects to a <var>target</var> object. When the <b>assign</b> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>to</i> be <a href="#sec-toobject">ToObject</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>to</i>).</li>
+ <li>If only one argument was passed, return <i>to</i>.</li>
+ <li>Let <i>sources</i> be the <a href="#sec-list-and-record-specification-type">List</a> of argument values starting
+ with the second argument.</li>
+ <li>For each element <i>nextSource</i> of <i>sources</i>, in ascending index order,
+ <ol class="block">
+ <li>If <i>nextSource</i> is <b>undefined</b> or <b>null</b>, let <i>keys</i> be an empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>from</i> be <a href="#sec-toobject">ToObject</a>(<i>nextSource</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>from</i>).</li>
+ <li>Let <i>keys</i> be <i>from</i>.[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keys</i>).</li>
+ </ol>
+ </li>
+ <li>Repeat for each element <i>nextKey</i> of <i>keys</i> in <a
+ href="#sec-list-and-record-specification-type">List</a> order,
+ <ol class="block">
+ <li>Let <i>desc</i> be <i>from</i>.[[GetOwnProperty]](<i>nextKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>if <i>desc</i> is not <b>undefined</b> and <i>desc</i>.[[Enumerable]] is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>propValue</i> be <a href="#sec-get-o-p">Get</a>(<i>from</i>, <i>nextKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>to</i>, <i>nextKey</i>, <i>propValue</i>,
+ <b>true</b>);</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>to</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>assign</code> method is <b>2</b>.</p>
+ </section>
+
+ <section id="sec-object.create">
+ <h1><span class="secnum" id="sec-19.1.2.2"><a href="#sec-object.create" title="link to this section">19.1.2.2</a></span>
+ Object.create ( O [ , Properties ] )</h1>
+
+ <p>The <b>create</b> function creates a new object with a specified prototype. When the <b>create</b> function is called,
+ the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object or Null throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>obj</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<i>O</i>).</li>
+ <li>If the argument <i>Properties</i> is present and not <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-objectdefineproperties">ObjectDefineProperties</a>(<i>obj</i>, <i>Properties</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.defineproperties">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.1.2.3"><a href="#sec-object.defineproperties"
+ title="link to this section">19.1.2.3</a></span> Object.defineProperties ( O, Properties )</h1>
+
+ <p>The <b>defineProperties</b> function is used to add own properties and/or update the attributes of existing own
+ properties of an object. When the <b>defineProperties</b> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-objectdefineproperties">ObjectDefineProperties</a>(<i>O</i>, <i>Properties</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-objectdefineproperties">
+ <h1><span class="secnum" id="sec-19.1.2.3.1"><a href="#sec-objectdefineproperties"
+ title="link to this section">19.1.2.3.1</a></span> Runtime Semantics: ObjectDefineProperties Abstract Operation</h1>
+
+ <p>The abstract operation ObjectDefineProperties with arguments <i>O</i> and <i>Properties</i> performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>props</i> be <a href="#sec-toobject">ToObject</a>(<i>Properties</i>).</li>
+ <li>Let <i>keys</i> be <i>props</i>.[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keys</i>).</li>
+ <li>Let <i>descriptors</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Repeat for each element <i>nextKey</i> of <i>keys</i> in <a
+ href="#sec-list-and-record-specification-type">List</a> order,
+ <ol class="block">
+ <li>Let <i>propDesc</i> be <i>props</i>.[[GetOwnProperty]](<i>nextKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propDesc</i>).</li>
+ <li>If <i>propDesc</i> is not <b>undefined</b> and <i>propDesc</i>.[[Enumerable]] is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>descObj</i> be <a href="#sec-get-o-p">Get</a>( <i>props</i>, <i>nextKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>descObj</i>).</li>
+ <li>Let <i>desc</i> be <a href="#sec-topropertydescriptor">ToPropertyDescriptor</a>(<i>descObj</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>Append the pair (a two element <a href="#sec-list-and-record-specification-type">List</a>) consisting of
+ <i>nextKey</i> and <i>desc</i> to the end of <i>descriptors</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>For each <i>pair</i> from <i>descriptors</i> in list order,
+ <ol class="block">
+ <li>Let <i>P</i> be the first element of <i>pair</i>.</li>
+ <li>Let <i>desc</i> be the second element of <i>pair</i>.</li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>O</i>,<i>P</i>,
+ <i>desc</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-object.defineproperty">
+ <h1><span class="secnum" id="sec-19.1.2.4"><a href="#sec-object.defineproperty"
+ title="link to this section">19.1.2.4</a></span> Object.defineProperty ( O, P, Attributes )</h1>
+
+ <p>The <b>defineProperty</b> function is used to add an own property and/or update the attributes of an existing own
+ property of an object. When the <b>defineProperty</b> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>Let <i>desc</i> be <a href="#sec-topropertydescriptor">ToPropertyDescriptor</a>(<i>Attributes</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>Let <i>success</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>O,key</i>,
+ <i>desc</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>success</i>).</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.freeze">
+ <h1><span class="secnum" id="sec-19.1.2.5"><a href="#sec-object.freeze" title="link to this section">19.1.2.5</a></span>
+ Object.freeze ( O )</h1>
+
+ <p>When the <b>freeze</b> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <i>O</i>.</li>
+ <li>Let <i>status</i> be <a href="#sec-setintegritylevel">SetIntegrityLevel</a>( <i>O</i>, "<code>frozen</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.getownpropertydescriptor">
+ <h1><span class="secnum" id="sec-19.1.2.6"><a href="#sec-object.getownpropertydescriptor"
+ title="link to this section">19.1.2.6</a></span> Object.getOwnPropertyDescriptor ( O, P )</h1>
+
+ <p>When the <code>getOwnPropertyDescriptor</code> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-toobject">ToObject</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>Let <i>desc</i> be <i>obj.</i>[[GetOwnProperty]](<i>key</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>Return <a href="#sec-frompropertydescriptor">FromPropertyDescriptor</a>(<i>desc</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.getownpropertynames">
+ <h1><span class="secnum" id="sec-19.1.2.7"><a href="#sec-object.getownpropertynames"
+ title="link to this section">19.1.2.7</a></span> Object.getOwnPropertyNames ( O )</h1>
+
+ <p>When the <b>getOwnPropertyNames</b> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-getownpropertykeys">GetOwnPropertyKeys</a>(<i>O</i>, String).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.getownpropertysymbols">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.1.2.8"><a href="#sec-object.getownpropertysymbols"
+ title="link to this section">19.1.2.8</a></span> Object.getOwnPropertySymbols ( O )</h1>
+
+ <p>When the <b>getOwnPropertySymbols</b> function is called with argument <var>O</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-getownpropertykeys">GetOwnPropertyKeys</a>(<i>O</i>, Symbol).</li>
+ </ol>
+ </div>
+
+ <section id="sec-getownpropertykeys">
+ <h1><span class="secnum" id="sec-19.1.2.8.1"><a href="#sec-getownpropertykeys"
+ title="link to this section">19.1.2.8.1</a></span> Runtime Semantics: GetOwnPropertyKeys ( O, Type )</h1>
+
+ <p>The abstract operation GetOwnPropertyKeys is called with arguments <var>O</var> and <span class="nt">Type</span>
+ where <var>O</var> is an Object and <span class="nt">Type</span> is one of the ECMAScript specification types String or
+ Symbol. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-toobject">ToObject</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>Let <i>keys</i> be <i>obj.</i>[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keys</i>).</li>
+ <li>Let <i>nameList</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Repeat for each element <i>nextKey</i> of <i>keys</i> in <a
+ href="#sec-list-and-record-specification-type">List</a> order,
+ <ol class="block">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>nextKey</i>) is <i>Type</i>, then
+ <ol class="block">
+ <li>Append <i>nextKey</i> as the last element of <i>nameList</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-createarrayfromlist">CreateArrayFromList</a>(<i>nameList</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-object.getprototypeof">
+ <h1><span class="secnum" id="sec-19.1.2.9"><a href="#sec-object.getprototypeof"
+ title="link to this section">19.1.2.9</a></span> Object.getPrototypeOf ( O )</h1>
+
+ <p>When the <code>getPrototypeOf</code> function is called with argument <var>O</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-toobject">ToObject</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>Return <i>obj.</i>[[GetPrototypeOf]]().</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.is">
+ <h1><span class="secnum" id="sec-19.1.2.10"><a href="#sec-object.is" title="link to this section">19.1.2.10</a></span>
+ Object.is ( value1, value2 )</h1>
+
+ <p>When the <b>is</b> function is called with arguments <var>value1</var> and <var>value2</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-samevalue">SameValue</a>(<i>value1</i>, <i>value2</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.isextensible">
+ <h1><span class="secnum" id="sec-19.1.2.11"><a href="#sec-object.isextensible"
+ title="link to this section">19.1.2.11</a></span> Object.isExtensible ( O )</h1>
+
+ <p>When the <b>isExtensible</b> function is called with argument <var>O</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <b>false</b>.</li>
+ <li>Return <a href="#sec-isextensible-o">IsExtensible</a>(<i>O</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.isfrozen">
+ <h1><span class="secnum" id="sec-19.1.2.12"><a href="#sec-object.isfrozen"
+ title="link to this section">19.1.2.12</a></span> Object.isFrozen ( O )</h1>
+
+ <p>When the <b>isFrozen</b> function is called with argument <var>O</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <b>true</b>.</li>
+ <li>Return <a href="#sec-testintegritylevel">TestIntegrityLevel</a>(<i>O</i>, "<code>frozen</code>").</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.issealed">
+ <h1><span class="secnum" id="sec-19.1.2.13"><a href="#sec-object.issealed"
+ title="link to this section">19.1.2.13</a></span> Object.isSealed ( O )</h1>
+
+ <p>When the <b>isSealed</b> function is called with argument <var>O</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <b>true</b>.</li>
+ <li>Return <a href="#sec-testintegritylevel">TestIntegrityLevel</a>(<i>O</i>, "<code>sealed</code>").</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.keys">
+ <h1><span class="secnum" id="sec-19.1.2.14"><a href="#sec-object.keys" title="link to this section">19.1.2.14</a></span>
+ Object.keys ( O )</h1>
+
+ <p>When the <b>keys</b> function is called with argument <var>O</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-toobject">ToObject</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>Let <i>nameList</i> be <a href="#sec-enumerableownnames">EnumerableOwnNames</a>(<i>obj</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nameList</i>).</li>
+ <li>Return <a href="#sec-createarrayfromlist">CreateArrayFromList</a>(<i>nameList</i>).</li>
+ </ol>
+
+ <p>If an implementation defines a specific order of enumeration for the for-in statement, the same order must be used for
+ the elements of the array returned in step 4.</p>
+ </section>
+
+ <section id="sec-object.preventextensions">
+ <h1><span class="secnum" id="sec-19.1.2.15"><a href="#sec-object.preventextensions"
+ title="link to this section">19.1.2.15</a></span> Object.preventExtensions ( O )</h1>
+
+ <p>When the <b>preventExtensions</b> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <i>O</i>.</li>
+ <li>Let <i>status</i> be <i>O</i>.[[PreventExtensions]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.prototype">
+ <h1><span class="secnum" id="sec-19.1.2.16"><a href="#sec-object.prototype"
+ title="link to this section">19.1.2.16</a></span> Object.prototype</h1>
+
+ <p>The initial value of <code>Object.prototype</code> is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+
+ <p>This property has the attributes {[[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-object.seal">
+ <h1><span class="secnum" id="sec-19.1.2.17"><a href="#sec-object.seal" title="link to this section">19.1.2.17</a></span>
+ Object.seal ( O )</h1>
+
+ <p>When the <b>seal</b> function is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <i>O</i>.</li>
+ <li>Let <i>status</i> be <a href="#sec-setintegritylevel">SetIntegrityLevel</a>( <i>O</i>, "<code>sealed</code>").</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-object.setprototypeof">
+ <h1><span class="secnum" id="sec-19.1.2.18"><a href="#sec-object.setprototypeof"
+ title="link to this section">19.1.2.18</a></span> Object.setPrototypeOf ( O, proto )</h1>
+
+ <p>When the <code>setPrototypeOf</code> function is called with arguments <span style="font-family: Times New
+ Roman"><i>O</i> and</span> proto, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<i>O</i>)<i>.</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>proto</i>) is neither Object nor Null, throw a
+ <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <i>O</i>.</li>
+ <li>Let <i>status</i> be <i>O</i>.[[SetPrototypeOf]](<i>proto</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-object-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.1.3"><a href="#sec-properties-of-the-object-prototype-object"
+ title="link to this section">19.1.3</a></span> Properties of the Object Prototype Object</h1>
+
+ <p>The Object prototype object is the intrinsic object %ObjectPrototype%. The Object prototype object is an ordinary
+ object.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Object prototype object is <b>null</b> and the initial value of the [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <b>true</b>.</p>
+ </div>
+
+ <section id="sec-object.prototype.constructor">
+ <h1><span class="secnum" id="sec-19.1.3.1"><a href="#sec-object.prototype.constructor"
+ title="link to this section">19.1.3.1</a></span> Object.prototype.constructor</h1>
+
+ <p>The initial value of <code>Object.prototype.constructor</code> is the intrinsic object %Object%.</p>
+ </section>
+
+ <section id="sec-object.prototype.hasownproperty">
+ <h1><span class="secnum" id="sec-19.1.3.2"><a href="#sec-object.prototype.hasownproperty"
+ title="link to this section">19.1.3.2</a></span> Object.prototype.hasOwnProperty ( V )</h1>
+
+ <p>When the <code>hasOwnProperty</code> method is called with argument <var>V</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>P</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>V</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Return <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>O</i>, <i>P</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The ordering of steps 1 and 3 is chosen to ensure that any exception that would have
+ been thrown by step 1 in previous editions of this specification will continue to be thrown even if the <b>this</b>
+ value is <b>undefined</b> or <b>null</b>.</p>
+ </div>
+ </section>
+
+ <section id="sec-object.prototype.isprototypeof">
+ <h1><span class="secnum" id="sec-19.1.3.3"><a href="#sec-object.prototype.isprototypeof"
+ title="link to this section">19.1.3.3</a></span> Object.prototype.isPrototypeOf ( V )</h1>
+
+ <p>When the <code>isPrototypeOf</code> method is called with argument <var>V</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>V</i>) is not Object, return <b>false</b>.</li>
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>V</i> be <i>V</i>.[[GetPrototypeOf]]().</li>
+ <li>If <i>V</i> is <b>null</b>, return <b>false</b></li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>O</i>, <i>V</i>) is <b>true</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The ordering of steps 1 and 2 preserves the behaviour specified by previous editions of
+ this specification for the case where V is not an object and the <b>this</b> value is <b>undefined</b> or null.</p>
+ </div>
+ </section>
+
+ <section id="sec-object.prototype.propertyisenumerable">
+ <h1><span class="secnum" id="sec-19.1.3.4"><a href="#sec-object.prototype.propertyisenumerable"
+ title="link to this section">19.1.3.4</a></span> Object.prototype.propertyIsEnumerable ( V )</h1>
+
+ <p>When the <code>propertyIsEnumerable</code> method is called with argument <var>V</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>P</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>V</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>desc</i> be <i>O</i>.[[GetOwnProperty]](<i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>If <i>desc</i> is <b>undefined</b>, return <b>false</b>.</li>
+ <li>Return the value of <i>desc</i>.[[Enumerable]].</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> This method does not consider objects in the prototype chain.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The ordering of steps 1 and 3 is chosen to ensure that any exception that would have
+ been thrown by step 1 in previous editions of this specification will continue to be thrown even if the <b>this</b>
+ value is <b>undefined</b> or <b>null</b>.</p>
+ </div>
+ </section>
+
+ <section id="sec-object.prototype.tolocalestring">
+ <h1><span class="secnum" id="sec-19.1.3.5"><a href="#sec-object.prototype.tolocalestring"
+ title="link to this section">19.1.3.5</a></span> Object.prototype.toLocaleString ( [ reserved1 [ , reserved2 ] ]
+ )</h1>
+
+ <p>When the <b>toLocaleString</b> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-invoke">Invoke</a>(<i>O</i>, <code>"toString"</code>).</li>
+ </ol>
+
+ <p>The optional parameters to this function are not used but are intended to correspond to the parameter pattern used by
+ ECMA-402 <code>toLocalString</code> functions. Implementations that do not include ECMA-402 support must not use those
+ parameter positions for other purposes.</p>
+
+ <p>The <code>length</code> property of the <code>toLocaleString</code> method is <b>0</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> This function provides a generic <code>toLocaleString</code> implementation for
+ objects that have no locale-specific <code>toString</code> behaviour. <code>Array</code>, <code>Number</code>,
+ <code>Date</code><span style="font-family: sans-serif">, and</span> <code>Typed Arrays</code> provide their own
+ locale-sensitive <code>toLocaleString</code> methods.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> ECMA-402 intentionally does not provide an alternative to this default
+ implementation.</p>
+ </div>
+ </section>
+
+ <section id="sec-object.prototype.tostring">
+ <h1><span class="secnum" id="sec-19.1.3.6"><a href="#sec-object.prototype.tostring"
+ title="link to this section">19.1.3.6</a></span> Object.prototype.toString ( )</h1>
+
+ <p>When the <code>toString</code> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If the <b>this</b> value is <b>undefined</b>, return <code>"[object Undefined]"</code>.</li>
+ <li>If the <b>this</b> value is <b>null</b>, return <code>"[object Null]"</code>.</li>
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li>Let <i>isArray</i> be <a href="#sec-isarray">IsArray</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isArray</i>).</li>
+ <li>If <i>isArray</i> is <b>true</b>, let <i>builtinTag</i> be <code>"Array"</code>.</li>
+ <li>Else, if <i>O</i> is an exotic String object, let <i>builtinTag</i> be <code>"String"</code>.</li>
+ <li>Else, if <i>O</i> has an [[ParameterMap]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, let <i>builtinTag</i> be <code>"Arguments"</code>.</li>
+ <li>Else, if <i>O</i> has a [[Call]] internal method, let <i>builtinTag</i> be <code>"Function"</code>.</li>
+ <li>Else, if <i>O</i> has an [[ErrorData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>,
+ let <i>builtinTag</i> be <code>"Error"</code>.</li>
+ <li>Else, if <i>O</i> has a [[BooleanData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>,
+ let <i>builtinTag</i> be <code>"Boolean"</code>.</li>
+ <li>Else, if <i>O</i> has a [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>,
+ let <i>builtinTag</i> be <code>"Number"</code>.</li>
+ <li>Else, if <i>O</i> has a [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>,
+ let <i>builtinTag</i> be <code>"Date"</code>.</li>
+ <li>Else, if <i>O</i> has a [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, let <i>builtinTag</i> be <code>"RegExp"</code>.</li>
+ <li>Else, let <i>builtinTag</i> be <code>"Object"</code>.</li>
+ <li>Let <i>tag</i> be Get (<i>O</i>, @@toStringTag).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>tag</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>tag</i>) is not String, let <i>tag</i> be
+ <i>builtinTag</i>.</li>
+ <li>Return the String that is the result of concatenating <code>"[object "</code>, <i>tag</i>, and
+ <code>"]"</code>.</li>
+ </ol>
+
+ <p>This function is the %ObjProto_toString% intrinsic object.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Historically, this function was occasionally used to access the string value of the
+ [[Class]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> that was used in previous editions
+ of this specification as a nominal type tag for various built-in objects. The above definition of <code>toString</code>
+ preserves compatibility for legacy code that uses <code>toString</code> as a test for those specific kinds of built-in
+ objects. It does not provide a reliable type testing mechanism for other kinds of built-in or program defined objects.
+ In addition, programs can use @@toStringTag in ways that will invalidate the reliability of such legacy type tests.</p>
+ </div>
+ </section>
+
+ <section id="sec-object.prototype.valueof">
+ <h1><span class="secnum" id="sec-19.1.3.7"><a href="#sec-object.prototype.valueof"
+ title="link to this section">19.1.3.7</a></span> Object.prototype.valueOf ( )</h1>
+
+ <p>When the <b>valueOf</b> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-object-instances">
+ <h1><span class="secnum" id="sec-19.1.4"><a href="#sec-properties-of-object-instances"
+ title="link to this section">19.1.4</a></span> Properties of Object Instances</h1>
+
+ <p>Object instances have no special properties beyond those inherited from the Object prototype object.</p>
+ </section>
+ </section>
+
+ <section id="sec-function-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.2"><a href="#sec-function-objects" title="link to this section">19.2</a></span> Function
+ Objects</h1>
+ </div>
+
+ <section id="sec-function-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.2.1"><a href="#sec-function-constructor"
+ title="link to this section">19.2.1</a></span> The Function Constructor</h1>
+
+ <p>The Function constructor is the %Function% intrinsic object and the initial value of the <code>Function</code> property
+ of the global object. When <code>Function</code> is called as a function rather than as a constructor, it creates and
+ initializes a new Function object. Thus the function call <code><b>Function(</b>…<b>)</b></code> is equivalent to
+ the object creation expression <code><b>new Function(</b>…<b>)</b></code> with the same arguments.</p>
+
+ <p>The <code>Function</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>Function</code> behaviour must include a <code>super</code> call to the <code>Function</code> constructor to create
+ and initialize a subclass instances with the internal slots necessary for built-in function behaviour. All ECMAScript
+ syntactic forms for defining function objects create instances of <code>Function</code>. There is no syntactic means to
+ create instances of <code>Function</code> subclasses except for the built-in Generator Function subclass.</p>
+ </div>
+
+ <section id="sec-function-p1-p2-pn-body">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.2.1.1"><a href="#sec-function-p1-p2-pn-body"
+ title="link to this section">19.2.1.1</a></span> Function ( p1, p2, … , pn, body )</h1>
+
+ <p>The last argument specifies the body (executable code) of a function; any preceding arguments specify formal
+ parameters.</p>
+
+ <p>When the <code>Function</code> function is called with some arguments <var>p1</var>, <var>p2</var>, … ,
+ <var>pn</var>, <var>body</var> (where <var>n</var> might be <span style="font-family: Times New Roman">0</span>, that
+ is, there are no “<var>p</var>” arguments, and where <var>body</var> might also not be provided), the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the active function object.</li>
+ <li>Let <i>args</i> be the <i>argumentsList</i> that was passed to this function by [[Call]] or [[Construct]].</li>
+ <li>Return <a href="#sec-createdynamicfunction">CreateDynamicFunction</a>(<i>C</i>, NewTarget, <code>"normal"</code>,
+ <i>args</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> It is permissible but not necessary to have one argument for each formal parameter to
+ be specified. For example, all three of the following expressions produce the same result:</p>
+
+ <pre>new Function("a", "b", "c", "return a+b+c")</pre>
+ <pre>new Function("a, b, c", "return a+b+c")</pre>
+ <pre>new Function("a,b", "c", "return a+b+c")</pre>
+ </div>
+ </div>
+
+ <section id="sec-createdynamicfunction">
+ <h1><span class="secnum" id="sec-19.2.1.1.1"><a href="#sec-createdynamicfunction"
+ title="link to this section">19.2.1.1.1</a></span> RuntimeSemantics: CreateDynamicFunction(constructor, newTarget,
+ kind, args)</h1>
+
+ <p>The abstract operation CreateDynamicFunction is called with arguments <var>constructor</var>, <var>newTarget</var>,
+ <var>kind</var>, and <var>args</var>. <var>constructor</var> is the constructor function that is performing this action,
+ <var>newTarget</var> is the constructor that <code>new</code> was initially applied to, <var>kind</var> is either
+ <code>"normal"</code> or <code>"generator"</code>, and <var>args</var> is a <a
+ href="#sec-list-and-record-specification-type">List</a> containing the actual argument values that were passed to
+ <var>constructor</var>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>newTarget</i> is <b>undefined</b><i>,</i> let <i>newTarget</i> be <i>constructor</i>.</li>
+ <li>If <i>kind</i> is <code>"normal"</code>, then
+ <ol class="block">
+ <li>Let <i>goal</i> be the grammar symbol <i>FunctionBody.</i></li>
+ <li>Let <i>parameterGoal</i> be the grammar symbol <i>FormalParameters</i>.</li>
+ <li>Let <i>fallbackProto</i> be <code>"%FunctionPrototype%"</code>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>goal</i> be the grammar symbol <i>GeneratorBody</i><sub>[Yield]</sub>.</li>
+ <li>Let <i>parameterGoal</i> be the grammar symbol <i>FormalParameters</i><span style="font-family:
+ sans-serif"><sub>[Yield,</sub></span> <span style="font-family:
+ sans-serif"><sub>GeneratorParameter]</sub></span>.</li>
+ <li>Let <i>fallbackProto</i> be <code>"%Generator%"</code>.</li>
+ </ol>
+ </li>
+ <li>Let <i>argCount</i> be the number of elements in <i>args</i>.</li>
+ <li>Let <i>P</i> be the empty String.</li>
+ <li>If <i>argCount</i> = 0, let <i>bodyText</i> be the empty String.</li>
+ <li>Else if <i>argCount</i> = 1, let <i>bodyText</i> be <i>args</i>[0].</li>
+ <li>Else <i>argCount</i> > 1,
+ <ol class="block">
+ <li>Let <i>firstArg</i> be <i>args</i>[0].</li>
+ <li>Let <i>P</i> be <a href="#sec-tostring">ToString</a>(<i>firstArg</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>Let <i>k</i> be 1.</li>
+ <li>Repeat, while <i>k</i> < <i>argCount</i>-1
+ <ol class="block">
+ <li>Let <i>nextArg</i> be <i>args</i>[<i>k</i>].</li>
+ <li>Let <i>nextArgString</i> be <a href="#sec-tostring">ToString</a>(<i>nextArg</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextArgString</i>).</li>
+ <li>Let <i>P</i> be the result of concatenating the previous value of <i>P</i>, the String <code>","</code> (a
+ comma), and <i>nextArgString</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>bodyText</i> be <i>args</i>[<i>k</i>].</li>
+ </ol>
+ </li>
+ <li>Let <i>bodyText</i> be <a href="#sec-tostring">ToString</a>(<i>bodyText</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>bodyText</i>).</li>
+ <li>Let <i>body</i> be the result of parsing <i>bodyText</i>, interpreted as UTF-16 encoded Unicode text as described
+ in <a href="#sec-ecmascript-language-types-string-type">6.1.4</a><i>,</i> using <i>goal</i> as the goal symbol.
+ Throw a <b>SyntaxError</b> exception if the parse fails or if any static semantics errors are detected.</li>
+ <li>If <i>bodyText</i> is <a href="#sec-strict-mode-code">strict mode code</a> (<a href="#sec-strict-mode-code">see
+ 10.2.1</a>) then let <i>strict</i> be <b>true</b>, else let <i>strict</i> be <b>false</b>.</li>
+ <li>Let <i>parameters</i> be the result of parsing <i>P</i>, interpreted as UTF-16 encoded Unicode text as described
+ in <a href="#sec-ecmascript-language-types-string-type">6.1.4</a><i>,</i> using <i>parameterGoal</i> as the goal
+ symbol. Throw a <b>SyntaxError</b> exception if the parse fails or if any static semantics errors are detected. If
+ <i>strict</i> is <b>true</b>, the Early Error rules for <span class="prod"><span
+ class="nt">StrictFormalParameters</span> <span class="geq">:</span> <span
+ class="nt">FormalParameters</span></span> are applied.</li>
+ <li>If any element of the BoundNames of <i>parameters</i> also occurs in the LexicallyDeclaredNames of <i>body</i>,
+ throw a <b>SyntaxError</b> exception.</li>
+ <li>If <i>body</i> Contains <i>SuperCall</i> is <i><b>true</b>,</i> throw a <b>SyntaxError</b> exception.</li>
+ <li>If <i>parameters</i> Contains <i>SuperCall</i> is <i><b>true</b>,</i> throw a <b>SyntaxError</b> exception.</li>
+ <li>If <i>body</i> Contains <i>SuperProperty</i> is <i><b>true</b>,</i> throw a <b>SyntaxError</b> exception.</li>
+ <li>If <i>parameters</i> Contains <i>SuperProperty</i> is <i><b>true</b>,</i> throw a <b>SyntaxError</b>
+ exception.</li>
+ <li>If <i>strict</i> is <b>true</b>, then
+ <ol class="block">
+ <li>If BoundNames of <i>parameters</i> contains any duplicate elements<i>,</i> throw a <b>SyntaxError</b>
+ exception.</li>
+ </ol>
+ </li>
+ <li>Let <i>proto</i> be <a href="#sec-getprototypefromconstructor">GetPrototypeFromConstructor</a>(<i>newTarget</i>,
+ <i>fallbackProto</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>Let <i>F</i> be <a href="#sec-functionallocate">FunctionAllocate</a>(<i>proto</i>, <i>strict</i>,
+ <i>kind</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>F</i>).</li>
+ <li>Let <i>realmF</i> be the value of <i>F’s</i> [[Realm]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>scope</i> be <i>realmF</i>.[[globalEnv]].</li>
+ <li>Perform <a href="#sec-functioninitialize">FunctionInitialize</a>(<i>F</i>, <span style="font-family:
+ sans-serif">Normal</span>, <i>parameters</i>, <i>body, scope</i>).</li>
+ <li>If <i>kind</i> is <code>"generator"</code> , then
+ <ol class="block">
+ <li>Let <i>prototype</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<span style="font-family:
+ sans-serif">%GeneratorPrototype%</span>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>prototype</i>).</li>
+ <li>Perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>F</i>, <b>true</b>, <i>prototype</i>).</li>
+ </ol>
+ </li>
+ <li>Else, perform <a href="#sec-makeconstructor">MakeConstructor</a>(<i>F</i>).</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>F</i>, <code>"<b>anonymous</b>"</code>).</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A <code>prototype</code> property is automatically created for every function created
+ using CreateDynamicFunction , to provide for the possibility that the function will be used as a constructor.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-function-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.2.2"><a href="#sec-properties-of-the-function-constructor"
+ title="link to this section">19.2.2</a></span> Properties of the Function Constructor</h1>
+
+ <p>The <code>Function</code> constructor is itself a built-in function object. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the <code>Function</code> constructor is
+ %FunctionPrototype%, the intrinsic Function prototype object (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>The value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Function constructor is <b>true</b>.</p>
+
+ <p>The Function constructor has the following properties:</p>
+ </div>
+
+ <section id="sec-function.length">
+ <h1><span class="secnum" id="sec-19.2.2.1"><a href="#sec-function.length" title="link to this section">19.2.2.1</a></span>
+ Function.length</h1>
+
+ <p>This is a data property with a value of 1. This property has the attributes { [[Writable]]: <span
+ class="value">false</span>, [[Enumerable]]: <span class="value">false</span>, [[Configurable]]: <span
+ class="value">true</span> }.</p>
+ </section>
+
+ <section id="sec-function.prototype">
+ <h1><span class="secnum" id="sec-19.2.2.2"><a href="#sec-function.prototype"
+ title="link to this section">19.2.2.2</a></span> Function.prototype</h1>
+
+ <p>The value of <code>Function.prototype</code> is %FunctionPrototype%, the intrinsic Function prototype object (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">false</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-function-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.2.3"><a href="#sec-properties-of-the-function-prototype-object"
+ title="link to this section">19.2.3</a></span> Properties of the Function Prototype Object</h1>
+
+ <p>The Function prototype object is the intrinsic object %FunctionPrototype%. The Function prototype object is itself a
+ built-in Function object. When invoked, it accepts any arguments and returns <span class="value">undefined</span>. It does
+ not have a [[Construct]] internal method so it is not a constructor.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The Function prototype object is specified to be a function object to ensure
+ compatibility with ECMAScript code that was created prior to the 6<sup>th</sup> Edition of this specification.</p>
+ </div>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Function prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The initial value of the [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Function prototype object is <span
+ class="value">true</span>.</p>
+
+ <p>The Function prototype object does not have a <code>prototype</code> property.</p>
+
+ <p>The value of the <code>length</code> property of the Function prototype object is <b>0</b>.</p>
+
+ <p>The value of the <code>name</code> property of the Function prototype object is the empty String.</p>
+ </div>
+
+ <section id="sec-function.prototype.apply">
+ <h1><span class="secnum" id="sec-19.2.3.1"><a href="#sec-function.prototype.apply"
+ title="link to this section">19.2.3.1</a></span> Function.prototype.apply ( thisArg, argArray )</h1>
+
+ <p>When the <code>apply</code> method is called on an object <var>func</var> with arguments <var>thisArg</var> and
+ <var>argArray</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>func</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <i>argArray</i> is <b>null</b> or <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-call">Call</a>(<i>func</i>, <i>thisArg</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>argList</i> be <a href="#sec-createlistfromarraylike">CreateListFromArrayLike</a>(<i>argArray</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>argList</i> ).</li>
+ <li>Perform <a href="#sec-preparefortailcall">PrepareForTailCall</a>().</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>func</i>, <i>thisArg</i>, <i>argList</i>).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>apply</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The thisArg value is passed without modification as the <b>this</b> value. This is a
+ change from Edition 3, where an <b>undefined</b> or <b>null</b> thisArg is replaced with the global object and <a
+ href="#sec-toobject">ToObject</a> is applied to all other values and that result is passed as the <b>this</b> value.
+ Even though the thisArg is passed without modification, non-strict mode functions still perform these transformations
+ upon entry to the function.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> If <i>func</i> is an arrow function or a <a
+ href="#sec-bound-function-exotic-objects">bound function</a> then the <i>thisArg</i> will be ignored by the function
+ [[Call]] in step 6.</p>
+ </div>
+ </section>
+
+ <section id="sec-function.prototype.bind">
+ <h1><span class="secnum" id="sec-19.2.3.2"><a href="#sec-function.prototype.bind"
+ title="link to this section">19.2.3.2</a></span> Function.prototype.bind ( thisArg , ...args)</h1>
+
+ <p>When the <code>bind</code> method is called with argument <var>thisArg</var> and zero or more <var>args</var>, it
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>Target</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>Target</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>args</i> be a new (possibly empty) <a href="#sec-list-and-record-specification-type">List</a> consisting of
+ all of the argument values provided after <i>thisArg</i> in order.</li>
+ <li>Let <i>F</i> be <a href="#sec-boundfunctioncreate">BoundFunctionCreate</a>(<i>Target</i>, <i>thisArg</i>,
+ <i>args</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>F</i>).</li>
+ <li>Let <i>targetHasLength</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>Target</i>,
+ <code>"length"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetHasLength</i>).</li>
+ <li>If <i>targetHasLength</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>targetLen</i> be <a href="#sec-get-o-p">Get</a>(<i>Target</i>, <code>"length"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetLen</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>targetLen</i>) is not Number, let <i>L</i> be
+ 0.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>targetLen</i> be <a href="#sec-tointeger">ToInteger</a>(<i>targetLen</i>).</li>
+ <li>Let <i>L</i> be the larger of 0 and the result of <i>targetLen</i> minus the number of elements of
+ <i>args</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else let <i>L</i> be 0.</li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>F</i>, <code>"length"</code>,
+ PropertyDescriptor {[[Value]]: <i>L</i>, [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>true</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Let <i>targetName</i> be <a href="#sec-get-o-p">Get</a>(<i>Target</i>, <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetName</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>targetName</i>) is not String, let <i>targetName</i>
+ be the empty string.</li>
+ <li>Perform <a href="#sec-setfunctionname">SetFunctionName</a>(<i>F</i>, <i>targetName</i>, <code>"bound"</code>).</li>
+ <li>Return <i>F</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>bind</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> Function objects created using <code>Function.prototype.bind</code> are exotic
+ objects. They also do not have a <code>prototype</code> property.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> If <i>Target</i> is an arrow function or a <a
+ href="#sec-bound-function-exotic-objects">bound function</a> then the <i>thisArg</i> passed to this method will not be
+ used by subsequent calls to <i>F</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-function.prototype.call">
+ <h1><span class="secnum" id="sec-19.2.3.3"><a href="#sec-function.prototype.call"
+ title="link to this section">19.2.3.3</a></span> Function.prototype.call (thisArg , ...args)</h1>
+
+ <p>When the <code>call</code> method is called on an object <var>func</var> with argument, <var>thisArg</var> and zero or
+ more <var>args</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>func</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>argList</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If this method was called with more than one argument then in left to right order, starting with the second
+ argument, append each argument as the last element of <i>argList</i></li>
+ <li>Perform <a href="#sec-preparefortailcall">PrepareForTailCall</a>().</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>func</i>, <i>thisArg</i>, <i>argList</i>).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>call</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The thisArg value is passed without modification as the <b>this</b> value. This is a
+ change from Edition 3, where an <b>undefined</b> or <b>null</b> thisArg is replaced with the global object and <a
+ href="#sec-toobject">ToObject</a> is applied to all other values and that result is passed as the <b>this</b> value.
+ Even though the thisArg is passed without modification, non-strict mode functions still perform these transformations
+ upon entry to the function.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> If <i>func</i> is an arrow function or a <a
+ href="#sec-bound-function-exotic-objects">bound function</a> then the <i>thisArg</i> will be ignored by the function
+ [[Call]] in step 5.</p>
+ </div>
+ </section>
+
+ <section id="sec-function.prototype.constructor">
+ <h1><span class="secnum" id="sec-19.2.3.4"><a href="#sec-function.prototype.constructor"
+ title="link to this section">19.2.3.4</a></span> Function.prototype.constructor</h1>
+
+ <p>The initial value of <code>Function.prototype.constructor</code> is the intrinsic object %Function%.</p>
+ </section>
+
+ <section id="sec-function.prototype.tostring">
+ <h1><span class="secnum" id="sec-19.2.3.5"><a href="#sec-function.prototype.tostring"
+ title="link to this section">19.2.3.5</a></span> Function.prototype.toString ( )</h1>
+
+ <p>When the <code>toString</code> method is called on an object <var>func</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>func</i> is a <a href="#sec-bound-function-exotic-objects">Bound Function</a> exotic object, then
+ <ol class="block">
+ <li>Return an implementation-dependent String source code representation of <i>func</i>. The representation must
+ conform to the rules below. It is implementation dependent whether the representation includes <a
+ href="#sec-bound-function-exotic-objects">bound function</a> information or information about the target
+ function.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>func</i>) is Object and is either a built-in function
+ object or has an [[ECMAScriptCode]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>,
+ then
+ <ol class="block">
+ <li>Return an implementation-dependent String source code representation of <i>func</i>. The representation must
+ conform to the rules below.</li>
+ </ol>
+ </li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+
+ <p><code>toString</code> Representation Requirements:</p>
+
+ <ul>
+ <li>
+ <p>The string representation must have the syntax of a <i>FunctionDeclaration</i> <i>FunctionExpression</i>,
+ <i>GeneratorDeclaration, GeneratorExpression, ClassDeclaration</i>, <i>ClassExpression</i>, <i>ArrowFunction</i>,
+ <i>MethodDefinition</i>, or <i>GeneratorMethod</i> depending upon the actual characteristics of the object.</p>
+ </li>
+
+ <li>
+ <p>T<span style="font-family: Times New Roman">he use and placement of white space, line terminators, and semicolons
+ within the representation String is implementation-dependent.</span></p>
+ </li>
+
+ <li>
+ <p>If the object was defined using ECMAScript code and the returned string representation is not in the form of a
+ <i>MethodDefinition</i> or <i>GeneratorMethod</i> then the representation must be such that if the string is
+ evaluated, using <code>eval</code> in a lexical context that is equivalent to the lexical context used to create the
+ original object, it will result in a new functionally equivalent object. In that case the returned source code must
+ not mention freely any variables that were not mentioned freely by the original function’s source code, even if
+ these “extra” names were originally in scope.</p>
+ </li>
+
+ <li>
+ <p>If the implementation cannot produce a source code string that meets these criteria then it must return a string
+ for which <code>eval</code> will throw a <span style="font-family: sans-serif"><b>SyntaxError</b></span>
+ exception.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-function.prototype-@@hasinstance">
+ <h1><span class="secnum" id="sec-19.2.3.6"><a href="#sec-function.prototype-@@hasinstance"
+ title="link to this section">19.2.3.6</a></span> Function.prototype[@@hasInstance] ( V )</h1>
+
+ <p>When the @@hasInstance method of an object <var>F</var> is called with value <var>V</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>F</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-ordinaryhasinstance">OrdinaryHasInstance</a>(<i>F</i>, <i>V</i>).</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.hasInstance]"</code>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <span class="value">false</span>,
+ [[Configurable]]: <span class="value">false</span> }.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This is the default implementation of <code>@@hasInstance</code> that most functions
+ inherit. <code>@@hasInstance</code> is called by the <code>instanceof</code> operator to determine whether a value is an
+ instance of a specific constructor. An expression such as</p>
+
+ <pre>v instanceof F</pre>
+
+ <p>evaluates as</p>
+
+ <pre>F[@@hasInstance](v)</pre>
+
+ <p>A constructor function can control which objects are recognized as its instances by <code>instanceof</code> by
+ exposing a different <code>@@hasInstance</code> method on the function.</p>
+
+ <p>This property is non-writable and non-configurable to prevent tampering that could be used to globally expose the
+ target function of a <a href="#sec-bound-function-exotic-objects">bound function</a>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-function-instances">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.2.4"><a href="#sec-function-instances" title="link to this section">19.2.4</a></span>
+ Function Instances</h1>
+
+ <p>Every function instance is an <a href="#sec-ecmascript-function-objects">ECMAScript function object</a> and has the
+ internal slots listed in <a href="#table-27">Table 27</a>. Function instances created using the <code><a
+ href="#sec-function.prototype.bind">Function.prototype.bind</a></code> method (<a
+ href="#sec-function.prototype.bind">19.2.3.2</a>) have the internal slots listed in <a href="#table-28">Table 28</a>.</p>
+
+ <p>The Function instances have the following properties:</p>
+ </div>
+
+ <section id="sec-function-instances-length">
+ <h1><span class="secnum" id="sec-19.2.4.1"><a href="#sec-function-instances-length"
+ title="link to this section">19.2.4.1</a></span> length</h1>
+
+ <p>The value of the <code>length</code> property is an integer that indicates the typical number of arguments expected by
+ the function. However, the language permits the function to be invoked with some other number of arguments. The behaviour
+ of a function when invoked on a number of arguments other than the number specified by its <code>length</code> property
+ depends on the function. This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>true</b> }.</p>
+ </section>
+
+ <section id="sec-name">
+ <h1><span class="secnum" id="sec-19.2.4.2"><a href="#sec-name" title="link to this section">19.2.4.2</a></span> name</h1>
+
+ <p>The value of the <code>name</code> property is an String that is descriptive of the function. The name has no semantic
+ significance but is typically a variable or property name that is used to refer to the function at its point of definition
+ in ECMAScript code. This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>true</b> }.</p>
+
+ <p>Anonymous functions objects that do not have a contextual name associated with them by this specification do not have a
+ <code>name</code> own property but inherit the <code>name</code> property of %FunctionPrototype%.</p>
+ </section>
+
+ <section id="sec-function-instances-prototype">
+ <h1><span class="secnum" id="sec-19.2.4.3"><a href="#sec-function-instances-prototype"
+ title="link to this section">19.2.4.3</a></span> prototype</h1>
+
+ <p>Function instances that can be used as a constructor have a <code>prototype</code> property. Whenever such a function
+ instance is created another ordinary object is also created and is the initial value of the function’s
+ <code>prototype</code> property. Unless otherwise specified, the value of the prototype property is used to initialize the
+ [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of a newly created ordinary
+ object before the Function object is invoked as a constructor for that newly created object.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Function objects created using <code><a
+ href="#sec-function.prototype.bind">Function.prototype.bind</a></code>, or by evaluating a <i>MethodDefinition</i> (that
+ are not a <i>GeneratorMethod</i>) or an <i>ArrowFunction</i> grammar production do not have a <code>prototype</code>
+ property.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-boolean-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.3"><a href="#sec-boolean-objects" title="link to this section">19.3</a></span> Boolean
+ Objects</h1>
+ </div>
+
+ <section id="sec-boolean-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.3.1"><a href="#sec-boolean-constructor" title="link to this section">19.3.1</a></span>
+ The Boolean Constructor</h1>
+
+ <p>The Boolean constructor is the %Boolean% intrinsic object and the initial value of the <code>Boolean</code> property of
+ the global object. When called as a constructor it creates and initializes a new Boolean object. When <code>Boolean</code>
+ is called as a function rather than as a constructor, it performs a type conversion.</p>
+
+ <p>The <code>Boolean</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>Boolean</code> behaviour must include a <code>super</code> call to the <code>Boolean</code> constructor to create
+ and initialize the subclass instance with a [[BooleanData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </div>
+
+ <section id="sec-boolean-constructor-boolean-value">
+ <h1><span class="secnum" id="sec-19.3.1.1"><a href="#sec-boolean-constructor-boolean-value"
+ title="link to this section">19.3.1.1</a></span> Boolean ( value )</h1>
+
+ <p>When <code>Boolean</code> is called with argument <var>value</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>b</i> be <a href="#sec-toboolean">ToBoolean</a>(<i>value</i>).</li>
+ <li>If NewTarget is <b>undefined</b><i>,</i> return <i>b</i>.</li>
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%BooleanPrototype%"</code>, «[[BooleanData]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Set the value of <i>O’s</i> [[BooleanData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>b</i>.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-boolean-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.3.2"><a href="#sec-properties-of-the-boolean-constructor"
+ title="link to this section">19.3.2</a></span> Properties of the Boolean Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Boolean constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>1</b>), the Boolean constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-boolean.prototype">
+ <h1><span class="secnum" id="sec-19.3.2.1"><a href="#sec-boolean.prototype"
+ title="link to this section">19.3.2.1</a></span> Boolean.prototype</h1>
+
+ <p>The initial value of <code>Boolean.prototype</code> is the intrinsic object %BooleanPrototype% (<a
+ href="#sec-properties-of-the-boolean-prototype-object">19.3.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-boolean-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.3.3"><a href="#sec-properties-of-the-boolean-prototype-object"
+ title="link to this section">19.3.3</a></span> Properties of the Boolean Prototype Object</h1>
+
+ <p>The Boolean prototype object is the intrinsic object %BooleanPrototype%. The Boolean prototype object is an ordinary
+ object. It is not a Boolean instance and does not have a [[BooleanData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Boolean prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">thisBooleanValue(<i>value</i>)</span> performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Boolean, return <i>value</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object and <i>value</i> has a
+ [[BooleanData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>value</i>’s [[BooleanData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is a Boolean value.</li>
+ <li>Return the value of <i>value’s</i> [[BooleanData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </div>
+
+ <section id="sec-boolean.prototype.constructor">
+ <h1><span class="secnum" id="sec-19.3.3.1"><a href="#sec-boolean.prototype.constructor"
+ title="link to this section">19.3.3.1</a></span> Boolean.prototype.constructor</h1>
+
+ <p>The initial value of <code>Boolean.prototype.constructor</code> is the intrinsic object %Boolean%.</p>
+ </section>
+
+ <section id="sec-boolean.prototype.tostring">
+ <h1><span class="secnum" id="sec-19.3.3.2"><a href="#sec-boolean.prototype.tostring"
+ title="link to this section">19.3.3.2</a></span> Boolean.prototype.toString ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>b</i> be thisBooleanValue(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>b</i>).</li>
+ <li>If <i>b</i> is <b>true</b>, return <code>"true"</code>; else return <code>"false"</code>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-boolean.prototype.valueof">
+ <h1><span class="secnum" id="sec-19.3.3.3"><a href="#sec-boolean.prototype.valueof"
+ title="link to this section">19.3.3.3</a></span> Boolean.prototype.valueOf ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return thisBooleanValue(<b>this</b> value).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-boolean-instances">
+ <h1><span class="secnum" id="sec-19.3.4"><a href="#sec-properties-of-boolean-instances"
+ title="link to this section">19.3.4</a></span> Properties of Boolean Instances</h1>
+
+ <p>Boolean instances are ordinary objects that inherit properties from the Boolean prototype object. Boolean instances have
+ a [[BooleanData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>. The [[BooleanData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the Boolean value represented by this Boolean
+ object.</p>
+ </section>
+ </section>
+
+ <section id="sec-symbol-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.4"><a href="#sec-symbol-objects" title="link to this section">19.4</a></span> Symbol
+ Objects</h1>
+ </div>
+
+ <section id="sec-symbol-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.4.1"><a href="#sec-symbol-constructor" title="link to this section">19.4.1</a></span>
+ The Symbol Constructor</h1>
+
+ <p>The Symbol constructor is the %Symbol% intrinsic object and the initial value of the <code>Symbol</code> property of
+ the global object. When <code>Symbol</code> is called as a function, it returns a new Symbol value.</p>
+
+ <p>The <code>Symbol</code> constructor is not intended to be used with the <code>new</code> operator or to be subclassed.
+ It may be used as the value of an <code>extends</code> clause of a class definition but a <code>super</code> call to the
+ <code>Symbol</code> constructor will cause an exception.</p>
+ </div>
+
+ <section id="sec-symbol-description">
+ <h1><span class="secnum" id="sec-19.4.1.1"><a href="#sec-symbol-description"
+ title="link to this section">19.4.1.1</a></span> Symbol ( [ description ] )</h1>
+
+ <p>When <code>Symbol</code> is called with optional argument <var>description</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is not <b>undefined</b><i>,</i> throw a <b>TypeError</b> exception.</li>
+ <li>If <i>description</i> is <b>undefined</b>, let <i>descString</i> be <b>undefined</b>.</li>
+ <li>Else, let <i>descString</i> be <a href="#sec-tostring">ToString</a>(<i>description</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>descString</i>).</li>
+ <li>Return a new unique Symbol value whose [[Description]] value is <i>descString</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-symbol-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.4.2"><a href="#sec-properties-of-the-symbol-constructor"
+ title="link to this section">19.4.2</a></span> Properties of the Symbol Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Symbol constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>0</b>), the Symbol constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-symbol.for">
+ <h1><span class="secnum" id="sec-19.4.2.1"><a href="#sec-symbol.for" title="link to this section">19.4.2.1</a></span>
+ Symbol.for ( key )</h1>
+
+ <p>When <code>Symbol.for</code> is called with argument <var>key</var> it performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>stringKey</i> be <a href="#sec-tostring">ToString</a>(<i>key</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>stringKey</i>).</li>
+ <li>For each element <i>e</i> of the GlobalSymbolRegistry <a href="#sec-list-and-record-specification-type">List</a>,
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>e</i>.[[key]], <i>stringKey</i>) is <b>true</b>, return
+ <i>e</i>.[[symbol]].</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: GlobalSymbolRegistry does not currently contain an entry for
+ <i>stringKey</i>.</li>
+ <li>Let <i>newSymbol</i> be a new unique Symbol value whose [[Description]] value is <i>stringKey</i>.</li>
+ <li>Append the record { [[key]]: <i>stringKey</i>, [[symbol]]: <i>newSymbol</i> } to the GlobalSymbolRegistry <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return <i>newSymbol</i>.</li>
+ </ol>
+
+ <p>The GlobalSymbolRegistry is a <a href="#sec-list-and-record-specification-type">List</a> that is globally available. It
+ is shared by all Code Realms. Prior to the evaluation of any ECMAScript code it is initialized as an empty <a
+ href="#sec-list-and-record-specification-type">List</a>. Elements of the GlobalSymbolRegistry are Records with the
+ structure defined in <a href="#table-44">Table 44</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-44">Table 44</span> — GlobalSymbolRegistry Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Usage</th>
+ </tr>
+ <tr>
+ <td>[[key]]</td>
+ <td>A String</td>
+ <td>A string key used to globally identify a Symbol.</td>
+ </tr>
+ <tr>
+ <td>[[symbol]]</td>
+ <td>A Symbol</td>
+ <td>A symbol that can be retrieved from any <a href="#sec-code-realms">Realm</a>.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-symbol.hasinstance">
+ <h1><span class="secnum" id="sec-19.4.2.2"><a href="#sec-symbol.hasinstance"
+ title="link to this section">19.4.2.2</a></span> Symbol.hasInstance</h1>
+
+ <p>The initial value of <code>Symbol.hasInstance</code> is the well known symbol @@hasInstance (<a href="#table-1">Table
+ 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.isconcatspreadable">
+ <h1><span class="secnum" id="sec-19.4.2.3"><a href="#sec-symbol.isconcatspreadable"
+ title="link to this section">19.4.2.3</a></span> Symbol.isConcatSpreadable</h1>
+
+ <p>The initial value of <code>Symbol.isConcatSpreadable</code> is the well known symbol @@isConcatSpreadable (<a
+ href="#table-1">Table 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.iterator">
+ <h1><span class="secnum" id="sec-19.4.2.4"><a href="#sec-symbol.iterator" title="link to this section">19.4.2.4</a></span>
+ Symbol.iterator</h1>
+
+ <p>The initial value of <code>Symbol.iterator</code> is the well known symbol @@iterator (<a href="#table-1">Table
+ 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.keyfor">
+ <h1><span class="secnum" id="sec-19.4.2.5"><a href="#sec-symbol.keyfor" title="link to this section">19.4.2.5</a></span>
+ Symbol.keyFor ( sym )</h1>
+
+ <p>When <code>Symbol.keyFor</code> is called with argument <var>sym</var> it performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>sym</i>) is not Symbol, throw a <b>TypeError</b>
+ exception.</li>
+ <li>For each element <i>e</i> of the GlobalSymbolRegistry <a href="#sec-list-and-record-specification-type">List</a> (<a
+ href="#sec-symbol.for">see 19.4.2.1</a>),
+ <ol class="block">
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>e</i>.[[symbol]], <i>sym</i>) is <b>true</b>, return
+ <i>e</i>.[[key]].</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: GlobalSymbolRegistry does not currently contain an entry for
+ <i>sym</i>.</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-symbol.match">
+ <h1><span class="secnum" id="sec-19.4.2.6"><a href="#sec-symbol.match" title="link to this section">19.4.2.6</a></span>
+ Symbol.match</h1>
+
+ <p>The initial value of <code>Symbol.match</code> is the well known symbol @@match (<a href="#table-1">Table 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.prototype">
+ <h1><span class="secnum" id="sec-19.4.2.7"><a href="#sec-symbol.prototype"
+ title="link to this section">19.4.2.7</a></span> Symbol.prototype</h1>
+
+ <p>The initial value of <code>Symbol.prototype</code> is the intrinsic object %SymbolPrototype% (<a
+ href="#sec-properties-of-the-symbol-prototype-object">19.4.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.replace">
+ <h1><span class="secnum" id="sec-19.4.2.8"><a href="#sec-symbol.replace" title="link to this section">19.4.2.8</a></span>
+ Symbol.replace</h1>
+
+ <p>The initial value of <code>Symbol.replace</code>is the well known symbol @@replace (<a href="#table-1">Table
+ 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.search">
+ <h1><span class="secnum" id="sec-19.4.2.9"><a href="#sec-symbol.search" title="link to this section">19.4.2.9</a></span>
+ Symbol.search</h1>
+
+ <p>The initial value of <code>Symbol.search</code> is the well known symbol @@search (<a href="#table-1">Table 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.species">
+ <h1><span class="secnum" id="sec-19.4.2.10"><a href="#sec-symbol.species"
+ title="link to this section">19.4.2.10</a></span> Symbol.species</h1>
+
+ <p>The initial value of <code>Symbol.species</code> is the well known symbol @@species (<a href="#table-1">Table
+ 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.split">
+ <h1><span class="secnum" id="sec-19.4.2.11"><a href="#sec-symbol.split" title="link to this section">19.4.2.11</a></span>
+ Symbol.split</h1>
+
+ <p>The initial value of <code>Symbol.split</code> is the well known symbol @@split (<a href="#table-1">Table 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.toprimitive">
+ <h1><span class="secnum" id="sec-19.4.2.12"><a href="#sec-symbol.toprimitive"
+ title="link to this section">19.4.2.12</a></span> Symbol.toPrimitive</h1>
+
+ <p>The initial value of <code>Symbol.toPrimitive</code> is the well known symbol @@toPrimitive (<a href="#table-1">Table
+ 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.tostringtag">
+ <h1><span class="secnum" id="sec-19.4.2.13"><a href="#sec-symbol.tostringtag"
+ title="link to this section">19.4.2.13</a></span> Symbol.toStringTag</h1>
+
+ <p>The initial value of <code>Symbol.toStringTag</code> is the well known symbol @@toStringTag (<a href="#table-1">Table
+ 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-symbol.unscopables">
+ <h1><span class="secnum" id="sec-19.4.2.14"><a href="#sec-symbol.unscopables"
+ title="link to this section">19.4.2.14</a></span> Symbol.unscopables</h1>
+
+ <p>The initial value of <code>Symbol.</code>unscopables is the well known symbol @@unscopables (<a href="#table-1">Table
+ 1</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-symbol-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.4.3"><a href="#sec-properties-of-the-symbol-prototype-object"
+ title="link to this section">19.4.3</a></span> Properties of the Symbol Prototype Object</h1>
+
+ <p>The Symbol prototype object is the intrinsic object %SymbolPrototype%. The Symbol prototype object is an ordinary
+ object. It is not a Symbol instance and does not have a [[SymbolData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Symbol prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+ </div>
+
+ <section id="sec-symbol.prototype.constructor">
+ <h1><span class="secnum" id="sec-19.4.3.1"><a href="#sec-symbol.prototype.constructor"
+ title="link to this section">19.4.3.1</a></span> Symbol.prototype.constructor</h1>
+
+ <p>The initial value of <code>Symbol.prototype.constructor</code> is the intrinsic object %Symbol%.</p>
+ </section>
+
+ <section id="sec-symbol.prototype.tostring">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.4.3.2"><a href="#sec-symbol.prototype.tostring"
+ title="link to this section">19.4.3.2</a></span> Symbol.prototype.toString ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>s</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>s</i>) is Symbol, let <i>sym</i> be <i>s</i>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>s</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>s</i> does not have a [[SymbolData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>sym</i> be the value of <i>s’s</i> [[SymbolData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-symboldescriptivestring">SymbolDescriptiveString</a>(<i>sym</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-symboldescriptivestring">
+ <h1><span class="secnum" id="sec-19.4.3.2.1"><a href="#sec-symboldescriptivestring"
+ title="link to this section">19.4.3.2.1</a></span> Runtime Semantics: SymbolDescriptiveString ( sym )</h1>
+
+ <p>When the abstract operation SymbolDescriptiveString is called with argument <var>sym</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>sym</i>) is Symbol.</li>
+ <li>Let <i>desc</i> be <i>sym’s</i> [[Description]] value.</li>
+ <li>If <i>desc</i> is <b>undefined</b>, let <i>desc</i> be the empty string.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>desc</i>) is String.</li>
+ <li>Return the <i>result</i> be the result of concatenating the strings <code>"Symbol("</code>, <i>desc</i>, and
+ <code>")"</code>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-symbol.prototype.valueof">
+ <h1><span class="secnum" id="sec-19.4.3.3"><a href="#sec-symbol.prototype.valueof"
+ title="link to this section">19.4.3.3</a></span> Symbol.prototype.valueOf ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>s</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>s</i>) is Symbol, return <i>s</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>s</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>s</i> does not have a [[SymbolData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Return the value of <i>s’s</i> [[SymbolData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-symbol.prototype-@@toprimitive">
+ <h1><span class="secnum" id="sec-19.4.3.4"><a href="#sec-symbol.prototype-@@toprimitive"
+ title="link to this section">19.4.3.4</a></span> Symbol.prototype [ @@toPrimitive ] ( hint )</h1>
+
+ <p>This function is called by ECMAScript language operators to convert an object to a primitive value. The allowed values
+ for <var>hint</var> are "<code>default</code>", "<code>number</code>", and "<code>string</code>".</p>
+
+ <p>When the <code>@@toPrimitive</code> method is called with argument <var>hint</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>s</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>s</i>) is Symbol, return <i>s</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>s</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>s</i> does not have a [[SymbolData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Return the value of <i>s’s</i> [[SymbolData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.toPrimitive]"</code>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+
+ <section id="sec-symbol.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-19.4.3.5"><a href="#sec-symbol.prototype-@@tostringtag"
+ title="link to this section">19.4.3.5</a></span> Symbol.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Symbol</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-symbol-instances">
+ <h1><span class="secnum" id="sec-19.4.4"><a href="#sec-properties-of-symbol-instances"
+ title="link to this section">19.4.4</a></span> Properties of Symbol Instances</h1>
+
+ <p>Symbol instances are ordinary objects that inherit properties from the Symbol prototype object. Symbol instances have a
+ [[SymbolData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>. The [[SymbolData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the Symbol value represented by this Symbol
+ object.</p>
+ </section>
+ </section>
+
+ <section id="sec-error-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5"><a href="#sec-error-objects" title="link to this section">19.5</a></span> Error
+ Objects</h1>
+
+ <p>Instances of Error objects are thrown as exceptions when runtime errors occur. The Error objects may also serve as base
+ objects for user-defined exception classes.</p>
+ </div>
+
+ <section id="sec-error-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.1"><a href="#sec-error-constructor" title="link to this section">19.5.1</a></span>
+ The Error Constructor</h1>
+
+ <p>The Error constructor is the %Error% intrinsic object and the initial value of the <code>Error</code> property of the
+ global object. When <code>Error</code> is called as a function rather than as a constructor, it creates and initializes a
+ new Error object. Thus the function call <code><b>Error(</b>…<b>)</b></code> is equivalent to the object creation
+ expression <code><b>new Error(</b>…<b>)</b></code> with the same arguments.</p>
+
+ <p>The <code>Error</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>Error</code> behaviour must include a <code>super</code> call to the <code>Error</code> constructor to create and
+ initialize subclass instances with a [[ErrorData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </div>
+
+ <section id="sec-error-message">
+ <h1><span class="secnum" id="sec-19.5.1.1"><a href="#sec-error-message" title="link to this section">19.5.1.1</a></span>
+ Error ( message )</h1>
+
+ <p>When the <code>Error</code> function is called with argument <i>message</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b><i>,</i> let <i>newTarget</i> be the active function object, else let
+ <i>newTarget</i> be NewTarget.</li>
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(<i>newTarget</i>,
+ <code>"%ErrorPrototype%"</code>, «[[ErrorData]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <i>message</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>msg</i> be <a href="#sec-tostring">ToString</a>(<i>message</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>msg</i>).</li>
+ <li>Let <i>msgDesc</i> be the PropertyDescriptor{[[Value]]: <i>msg</i>, [[Writable]]: <b>true</b>, [[Enumerable]]:
+ <b>false</b>, [[Configurable]]: <b>true</b>}.</li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>O</i>,
+ "<code>message</code>", <i>msgDesc</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-error-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.2"><a href="#sec-properties-of-the-error-constructor"
+ title="link to this section">19.5.2</a></span> Properties of the Error Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Error
+ constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>1</b>), the Error constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-error.prototype">
+ <h1><span class="secnum" id="sec-19.5.2.1"><a href="#sec-error.prototype" title="link to this section">19.5.2.1</a></span>
+ Error.prototype</h1>
+
+ <p>The initial value of <code>Error.prototype</code> is the intrinsic object %ErrorPrototype% (<a
+ href="#sec-properties-of-the-error-prototype-object">19.5.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-error-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.3"><a href="#sec-properties-of-the-error-prototype-object"
+ title="link to this section">19.5.3</a></span> Properties of the Error Prototype Object</h1>
+
+ <p>The Error prototype object is the intrinsic object %ErrorPrototype%. The Error prototype object is an ordinary object.
+ It is not an Error instance and does not have an [[ErrorData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Error
+ prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+ </div>
+
+ <section id="sec-error.prototype.constructor">
+ <h1><span class="secnum" id="sec-19.5.3.1"><a href="#sec-error.prototype.constructor"
+ title="link to this section">19.5.3.1</a></span> Error.prototype.constructor</h1>
+
+ <p>The initial value of <code>Error.prototype.constructor</code> is the intrinsic object %Error%.</p>
+ </section>
+
+ <section id="sec-error.prototype.message">
+ <h1><span class="secnum" id="sec-19.5.3.2"><a href="#sec-error.prototype.message"
+ title="link to this section">19.5.3.2</a></span> Error.prototype.message</h1>
+
+ <p>The initial value of <code>Error.prototype.message</code> is the empty String.</p>
+ </section>
+
+ <section id="sec-error.prototype.name">
+ <h1><span class="secnum" id="sec-19.5.3.3"><a href="#sec-error.prototype.name"
+ title="link to this section">19.5.3.3</a></span> Error.prototype.name</h1>
+
+ <p>The initial value of <code>Error.prototype.name</code> is <code>"<b>Error</b>"</code>.</p>
+ </section>
+
+ <section id="sec-error.prototype.tostring">
+ <h1><span class="secnum" id="sec-19.5.3.4"><a href="#sec-error.prototype.tostring"
+ title="link to this section">19.5.3.4</a></span> Error.prototype.toString ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>name</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>name</i>).</li>
+ <li>If <i>name</i> is <b>undefined</b>, let <i>name</i> be <code>"<b>Error</b>"</code>; otherwise let <i>name</i> be <a
+ href="#sec-tostring">ToString</a>(<i>name</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>name</i>).</li>
+ <li>Let <i>msg</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <code>"message"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>msg</i>).</li>
+ <li>If <i>msg</i> is <b>undefined</b>, let <i>msg</i> be the empty String; otherwise let <i>msg</i> be <a
+ href="#sec-tostring">ToString</a>(<i>msg</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>msg</i>).</li>
+ <li>If <i>name</i> is the empty String, return <i>msg</i><code>.</code></li>
+ <li>If <i>msg</i> is the empty String, return <i>name</i><code>.</code></li>
+ <li>Return the result of concatenating <i>name</i>, the code unit 0x003A (COLON), the code unit 0x0020 (SPACE), and
+ <i>msg</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-error-instances">
+ <h1><span class="secnum" id="sec-19.5.4"><a href="#sec-properties-of-error-instances"
+ title="link to this section">19.5.4</a></span> Properties of Error Instances</h1>
+
+ <p>Error instances are ordinary objects that inherit properties from the Error prototype object and have an [[ErrorData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value is <span
+ class="value">undefined</span>. The only specified uses of [[ErrorData]] is to identify Error and <i>NativeError</i>
+ instances as Error objects within <code><a href="#sec-object.prototype.tostring">Object.prototype.toString</a></code>.</p>
+ </section>
+
+ <section id="sec-native-error-types-used-in-this-standard">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.5"><a href="#sec-native-error-types-used-in-this-standard"
+ title="link to this section">19.5.5</a></span> Native Error Types Used in This Standard</h1>
+
+ <p>A new instance of one of the <i>NativeError</i> objects below is thrown when a runtime error is detected. All of these
+ objects share the same structure, as described in <a href="#sec-nativeerror-object-structure">19.5.6</a>.</p>
+ </div>
+
+ <section id="sec-native-error-types-used-in-this-standard-evalerror">
+ <h1><span class="secnum" id="sec-19.5.5.1"><a href="#sec-native-error-types-used-in-this-standard-evalerror"
+ title="link to this section">19.5.5.1</a></span> EvalError</h1>
+
+ <p>This exception is not currently used within this specification. This object remains for compatibility with previous
+ editions of this specification.</p>
+ </section>
+
+ <section id="sec-native-error-types-used-in-this-standard-rangeerror">
+ <h1><span class="secnum" id="sec-19.5.5.2"><a href="#sec-native-error-types-used-in-this-standard-rangeerror"
+ title="link to this section">19.5.5.2</a></span> RangeError</h1>
+
+ <p>Indicates a value that is not in the set or range of allowable values.</p>
+ </section>
+
+ <section id="sec-native-error-types-used-in-this-standard-referenceerror">
+ <h1><span class="secnum" id="sec-19.5.5.3"><a href="#sec-native-error-types-used-in-this-standard-referenceerror"
+ title="link to this section">19.5.5.3</a></span> ReferenceError</h1>
+
+ <p>Indicate that an invalid reference value has been detected.</p>
+ </section>
+
+ <section id="sec-native-error-types-used-in-this-standard-syntaxerror">
+ <h1><span class="secnum" id="sec-19.5.5.4"><a href="#sec-native-error-types-used-in-this-standard-syntaxerror"
+ title="link to this section">19.5.5.4</a></span> SyntaxError</h1>
+
+ <p>Indicates that a parsing error has occurred.</p>
+ </section>
+
+ <section id="sec-native-error-types-used-in-this-standard-typeerror">
+ <h1><span class="secnum" id="sec-19.5.5.5"><a href="#sec-native-error-types-used-in-this-standard-typeerror"
+ title="link to this section">19.5.5.5</a></span> TypeError</h1>
+
+ <p>Indicates the actual type of an operand is different than the expected type.</p>
+ </section>
+
+ <section id="sec-native-error-types-used-in-this-standard-urierror">
+ <h1><span class="secnum" id="sec-19.5.5.6"><a href="#sec-native-error-types-used-in-this-standard-urierror"
+ title="link to this section">19.5.5.6</a></span> URIError</h1>
+
+ <p>Indicates that one of the global URI handling functions was used in a way that is incompatible with its definition.</p>
+ </section>
+ </section>
+
+ <section id="sec-nativeerror-object-structure">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.6"><a href="#sec-nativeerror-object-structure"
+ title="link to this section">19.5.6</a></span> <i>NativeError</i> Object Structure</h1>
+
+ <p>When an ECMAScript implementation detects a runtime error, it throws a new instance of one of the <i>NativeError</i>
+ objects defined in <a href="#sec-native-error-types-used-in-this-standard">19.5.5</a>. Each of these objects has the
+ structure described below, differing only in the name used as the constructor name instead of <i>NativeError</i>, in the
+ <b>name</b> property of the prototype object, and in the implementation-defined <code>message</code> property of the
+ prototype object.</p>
+
+ <p>For each error object, references to <i>NativeError</i> in the definition should be replaced with the appropriate error
+ object name from <a href="#sec-native-error-types-used-in-this-standard">19.5.5</a>.</p>
+ </div>
+
+ <section id="sec-nativeerror-constructors">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.6.1"><a href="#sec-nativeerror-constructors"
+ title="link to this section">19.5.6.1</a></span> <i>NativeError</i> Constructors</h1>
+
+ <p>When a <i>NativeError</i> constructor is called as a function rather than as a constructor, it creates and
+ initializes a new <i>NativeError</i> object. A call of the object as a function is equivalent to calling it as a
+ constructor with the same arguments. Thus the function call <i>NativeError</i><code><b>(</b>…<b>)</b></code> is
+ equivalent to the object creation expression <code>new</code> <i>NativeError</i><code><b>(</b>…<b>)</b></code>
+ with the same arguments.</p>
+
+ <p>Each <i>NativeError</i> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <i>NativeError</i> behaviour must include a <code>super</code> call to the <i>NativeError</i> constructor to create and
+ initialize subclass instances with a [[ErrorData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </div>
+
+ <section id="sec-nativeerror">
+ <h1><span class="secnum" id="sec-19.5.6.1.1"><a href="#sec-nativeerror"
+ title="link to this section">19.5.6.1.1</a></span> NativeError ( message )</h1>
+
+ <p>When a <i>NativeError</i> function is called with argument <i>message</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b><i>,</i> let <i>newTarget</i> be the active function object, else let
+ <i>newTarget</i> be NewTarget.</li>
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(<i>newTarget</i>,
+ <code>"%<i>NativeError</i>Prototype%"</code>, «[[ErrorData]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <i>message</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>msg</i> be <a href="#sec-tostring">ToString</a>(<i>message</i>).</li>
+ <li>Let <i>msgDesc</i> be the PropertyDescriptor{[[Value]]: <i>msg</i>, [[Writable]]: <b>true</b>, [[Enumerable]]:
+ <b>false</b>, [[Configurable]]: <b>true</b>}.</li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>O</i>,
+ "<code>message</code>", <i>msgDesc</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ </ol>
+ </li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+
+ <p>The actual value of the string passed in step 2 is either <code>"%EvalErrorPrototype%"</code>,
+ <code>"%RangeErrorPrototype%"</code>, <code>"%ReferenceErrorPrototype%"</code>, <code>"%SyntaxErrorPrototype%"</code>,
+ <code>"%TypeErrorPrototype%"</code>, or <code>"%URIErrorPrototype%"</code> corresponding to which <i>NativeError</i>
+ constructor is being defined.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-nativeerror-constructors">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.6.2"><a href="#sec-properties-of-the-nativeerror-constructors"
+ title="link to this section">19.5.6.2</a></span> Properties of the <i>NativeError</i> Constructors</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of a
+ <i>NativeError</i> constructor is the intrinsic object %Error% (<a href="#sec-error-constructor">19.5.1</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>1</b>), each <i>NativeError</i> constructor has the
+ following properties:</p>
+ </div>
+
+ <section id="sec-nativeerror.prototype">
+ <h1><span class="secnum" id="sec-19.5.6.2.1"><a href="#sec-nativeerror.prototype"
+ title="link to this section">19.5.6.2.1</a></span> NativeError.prototype</h1>
+
+ <p>The initial value of <b><i>NativeError</i><code>.prototype</code></b> is a <i>NativeError</i> prototype object (<a
+ href="#sec-properties-of-the-nativeerror-prototype-objects">19.5.6.3</a>). Each <i>NativeError</i> constructor has a
+ distinct prototype object.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-nativeerror-prototype-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-19.5.6.3"><a href="#sec-properties-of-the-nativeerror-prototype-objects"
+ title="link to this section">19.5.6.3</a></span> Properties of the <i>NativeError</i> Prototype Objects</h1>
+
+ <p>Each <i>NativeError</i> prototype object is an ordinary object. It is not an Error instance and does not have an
+ [[ErrorData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of each
+ <i>NativeError</i> prototype object is the intrinsic object %ErrorPrototype% (<a
+ href="#sec-properties-of-the-error-prototype-object">19.5.3</a>).</p>
+ </div>
+
+ <section id="sec-nativeerror.prototype.constructor">
+ <h1><span class="secnum" id="sec-19.5.6.3.1"><a href="#sec-nativeerror.prototype.constructor"
+ title="link to this section">19.5.6.3.1</a></span> <i>NativeError</i>.prototype.constructor</h1>
+
+ <p>The initial value of the <code>constructor</code> property of the prototype for a given <i>NativeError</i>
+ constructor is the corresponding intrinsic object %<i>NativeError</i>% (<a
+ href="#sec-nativeerror-constructors">19.5.6.1</a>).</p>
+ </section>
+
+ <section id="sec-nativeerror.prototype.message">
+ <h1><span class="secnum" id="sec-19.5.6.3.2"><a href="#sec-nativeerror.prototype.message"
+ title="link to this section">19.5.6.3.2</a></span> <i>NativeError</i>.prototype.message</h1>
+
+ <p>The initial value of the <code>message</code> property of the prototype for a given <i>NativeError</i> constructor is
+ the empty String.</p>
+ </section>
+
+ <section id="sec-nativeerror.prototype.name">
+ <h1><span class="secnum" id="sec-19.5.6.3.3"><a href="#sec-nativeerror.prototype.name"
+ title="link to this section">19.5.6.3.3</a></span> <i>NativeError</i>.prototype.name</h1>
+
+ <p>The initial value of the <code>name</code> property of the prototype for a given <i>NativeError</i> constructor is a
+ string consisting of the name of the constructor (the name used instead of <i>NativeError</i>).</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-nativeerror-instances">
+ <h1><span class="secnum" id="sec-19.5.6.4"><a href="#sec-properties-of-nativeerror-instances"
+ title="link to this section">19.5.6.4</a></span> Properties of <i>NativeError</i> Instances</h1>
+
+ <p><i>NativeError</i> instances are ordinary objects that inherit properties from their <i>NativeError</i> prototype
+ object and have an [[ErrorData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value
+ is <span class="value">undefined</span>. The only specified use of [[ErrorData]] is by <code><a
+ href="#sec-object.prototype.tostring">Object.prototype.toString</a></code> (<a
+ href="#sec-object.prototype.tostring">19.1.3.6</a>) to identify Error or <i>NativeError</i> instances.</p>
+ </section>
+ </section>
+ </section>
+</section>
+
+<section id="sec-numbers-and-dates">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20"><a href="#sec-numbers-and-dates" title="link to this section">20</a></span> Numbers and
+ Dates</h1>
+ </div>
+
+ <section id="sec-number-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.1"><a href="#sec-number-objects" title="link to this section">20.1</a></span> Number
+ Objects</h1>
+ </div>
+
+ <section id="sec-number-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.1.1"><a href="#sec-number-constructor" title="link to this section">20.1.1</a></span>
+ The Number Constructor</h1>
+
+ <p>The Number constructor is the %Number% intrinsic object and the initial value of the <code>Number</code> property of
+ the global object. When called as a constructor, it creates and initializes a new Number object. When <code>Number</code>
+ is called as a function rather than as a constructor, it performs a type conversion.</p>
+
+ <p>The <code>Number</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>Number</code> behaviour must include a <code>super</code> call to the <code>Number</code> constructor to create and
+ initialize the subclass instance with a [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </div>
+
+ <section id="sec-number-constructor-number-value">
+ <h1><span class="secnum" id="sec-20.1.1.1"><a href="#sec-number-constructor-number-value"
+ title="link to this section">20.1.1.1</a></span> Number ( [ value ] )</h1>
+
+ <p>When <code>Number</code> is called with argument <var>number</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If no arguments were passed to this function invocation, let <i>n</i> be +0.</li>
+ <li>Else, let <i>n</i> be <a href="#sec-tonumber">ToNumber</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>n</i>).</li>
+ <li>If NewTarget is <b>undefined</b><i>,</i> return <i>n</i>.</li>
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%NumberPrototype%"</code>, «[[NumberData]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Set the value of <i>O’s</i> [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>n</i>.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-number-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.1.2"><a href="#sec-properties-of-the-number-constructor"
+ title="link to this section">20.1.2</a></span> Properties of the Number Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Number constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>1</b>), the Number constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-number.epsilon">
+ <h1><span class="secnum" id="sec-20.1.2.1"><a href="#sec-number.epsilon" title="link to this section">20.1.2.1</a></span>
+ Number.EPSILON</h1>
+
+ <p>The value of Number.EPSILON is the difference between 1 and the smallest value greater than 1 that is representable as
+ a Number value, which is approximately 2.2204460492503130808472633361816 x 10‍<sup>−‍16</sup>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.isfinite">
+ <h1><span class="secnum" id="sec-20.1.2.2"><a href="#sec-number.isfinite" title="link to this section">20.1.2.2</a></span>
+ Number.isFinite ( number )</h1>
+
+ <p>When the <code>Number.isFinite</code> is called with one argument <var>number</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>number</i>) is not Number, return <b>false</b>.</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+∞</b>, or <b>−∞</b>, return <b>false</b>.</li>
+ <li>Otherwise, return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-number.isinteger">
+ <h1><span class="secnum" id="sec-20.1.2.3"><a href="#sec-number.isinteger"
+ title="link to this section">20.1.2.3</a></span> Number.isInteger ( number )</h1>
+
+ <p>When the <code>Number.isInteger</code> is called with one argument <var>number</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>number</i>) is not Number, return <b>false</b>.</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+∞</b>, or <b>−∞</b>, return <b>false</b>.</li>
+ <li>Let <i>integer</i> be <a href="#sec-tointeger">ToInteger</a>(<i>number</i>).</li>
+ <li>If <i>integer</i> is not equal to <i>number</i>, return <b>false</b>.</li>
+ <li>Otherwise, return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-number.isnan">
+ <h1><span class="secnum" id="sec-20.1.2.4"><a href="#sec-number.isnan" title="link to this section">20.1.2.4</a></span>
+ Number.isNaN ( number )</h1>
+
+ <p>When the <code>Number.isNaN</code> is called with one argument <var>number</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>number</i>) is not Number, return <b>false</b>.</li>
+ <li>If <i>number</i> is <b>NaN</b>, return <b>true</b>.</li>
+ <li>Otherwise, return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This function differs from the global isNaN function (<a
+ href="#sec-isnan-number">18.2.3</a>) is that it does not convert its argument to a Number before determining whether it
+ is NaN.</p>
+ </div>
+ </section>
+
+ <section id="sec-number.issafeinteger">
+ <h1><span class="secnum" id="sec-20.1.2.5"><a href="#sec-number.issafeinteger"
+ title="link to this section">20.1.2.5</a></span> Number.isSafeInteger ( number )</h1>
+
+ <p>When the <code>Number.isSafeInteger</code> is called with one argument <var>number</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>number</i>) is not Number, return <b>false</b>.</li>
+ <li>If <i>number</i> is <b>NaN</b>, <b>+∞</b>, or <b>−∞</b>, return <b>false</b>.</li>
+ <li>Let <i>integer</i> be <a href="#sec-tointeger">ToInteger</a>(<i>number</i>).</li>
+ <li>If <i>integer</i> is not equal to <i>number</i>, return <b>false</b>.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>integer</i>) ≤ 2<sup>53</sup>−1, return
+ <b>true</b>.</li>
+ <li>Otherwise, return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-number.max_safe_integer">
+ <h1><span class="secnum" id="sec-20.1.2.6"><a href="#sec-number.max_safe_integer"
+ title="link to this section">20.1.2.6</a></span> Number.MAX_SAFE_INTEGER</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of <code>Number.MAX_SAFE_INTEGER</code> is the largest integer n such that n
+ and n + 1 are both exactly representable as a Number value.</p>
+ </div>
+
+ <p>The value of Number.MAX_SAFE_INTEGER is 9007199254740991 (2<sup>53</sup>−1).</p>
+
+ <p><br>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.max_value">
+ <h1><span class="secnum" id="sec-20.1.2.7"><a href="#sec-number.max_value"
+ title="link to this section">20.1.2.7</a></span> Number.MAX_VALUE</h1>
+
+ <p>The value of <code>Number.MAX_VALUE</code> is the largest positive finite value of the Number type, which is
+ approximately <span style="font-family: Times New Roman">1.7976931348623157 × 10<sup>308</sup></span>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.min_safe_integer">
+ <h1><span class="secnum" id="sec-20.1.2.8"><a href="#sec-number.min_safe_integer"
+ title="link to this section">20.1.2.8</a></span> Number.MIN_SAFE_INTEGER</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of <code>Number.MIN_SAFE_INTEGER</code> is the smallest integer n such that
+ n and n − 1 are both exactly representable as a Number value.</p>
+ </div>
+
+ <p>The value of Number.MIN_SAFE_INTEGER is −9007199254740991 (−(2<sup>53</sup>−1)).</p>
+
+ <p><br>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.min_value">
+ <h1><span class="secnum" id="sec-20.1.2.9"><a href="#sec-number.min_value"
+ title="link to this section">20.1.2.9</a></span> Number.MIN_VALUE</h1>
+
+ <p>The value of <code>Number.MIN_VALUE</code> is the smallest positive value of the Number type, which is approximately
+ <span style="font-family: Times New Roman">5 × 10<sup>−324</sup></span>.</p>
+
+ <p>In the IEEE-764 double precision binary representation, the smallest possible value is a denormalized number. If an
+ implementation does not support denormalized values, the value of <code>Number.MIN_VALUE</code> must be the smallest
+ non-zero positive value that can actually be represented by the implementation.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.nan">
+ <h1><span class="secnum" id="sec-20.1.2.10"><a href="#sec-number.nan" title="link to this section">20.1.2.10</a></span>
+ Number.NaN</h1>
+
+ <p>The value of <code>Number.NaN</code> is <b>NaN</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.negative_infinity">
+ <h1><span class="secnum" id="sec-20.1.2.11"><a href="#sec-number.negative_infinity"
+ title="link to this section">20.1.2.11</a></span> Number.NEGATIVE_INFINITY</h1>
+
+ <p>The value of Number.NEGATIVE_INFINITY is −∞.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.parsefloat">
+ <h1><span class="secnum" id="sec-20.1.2.12"><a href="#sec-number.parsefloat"
+ title="link to this section">20.1.2.12</a></span> Number.parseFloat ( string )</h1>
+
+ <p>The value of the <code>Number.parseFloat</code> data property is the same built-in function object that is the value of
+ the <code>parseFloat</code> property of the global object defined in <a href="#sec-parsefloat-string">18.2.4</a>.</p>
+ </section>
+
+ <section id="sec-number.parseint">
+ <h1><span class="secnum" id="sec-20.1.2.13"><a href="#sec-number.parseint"
+ title="link to this section">20.1.2.13</a></span> Number.parseInt ( string, radix )</h1>
+
+ <p>The value of the <code>Number.parseInt</code> data property is the same built-in function object that is the value of
+ the <code>parseInt</code> property of the global object defined in <a href="#sec-parseint-string-radix">18.2.5</a>.</p>
+ </section>
+
+ <section id="sec-number.positive_infinity">
+ <h1><span class="secnum" id="sec-20.1.2.14"><a href="#sec-number.positive_infinity"
+ title="link to this section">20.1.2.14</a></span> Number.POSITIVE_INFINITY</h1>
+
+ <p>The value of Number.POSITIVE_INFINITY is +∞.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-number.prototype">
+ <h1><span class="secnum" id="sec-20.1.2.15"><a href="#sec-number.prototype"
+ title="link to this section">20.1.2.15</a></span> Number.prototype</h1>
+
+ <p>The initial value of <code>Number.prototype</code> is the intrinsic object %NumberPrototype% (<a
+ href="#sec-properties-of-the-number-prototype-object">20.1.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-number-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.1.3"><a href="#sec-properties-of-the-number-prototype-object"
+ title="link to this section">20.1.3</a></span> Properties of the Number Prototype Object</h1>
+
+ <p>The Number prototype object is the intrinsic object %NumberPrototype%. The Number prototype object is an ordinary
+ object. It is not a Number instance and does not have a [[NumberData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Number prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+
+ <p>Unless explicitly stated otherwise, the methods of the Number prototype object defined below are not generic and the
+ <b>this</b> value passed to them must be either a Number value or an object that has a [[NumberData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> that has been initialized to a Number value.</p>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">thisNumberValue(<i>value</i>)</span> performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Number, return <i>value</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object and <i>value</i> has a
+ [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>value</i>’s [[NumberData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is a Number value.</li>
+ <li>Return the value of <i>value’s</i> [[NumberData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+
+ <p>The phrase “this Number value” within the specification of a method refers to the result returned by
+ calling the abstract operation <span style="font-family: Times New Roman">thisNumberValue</span> with the <b>this</b>
+ value of the method invocation passed as the argument.</p>
+ </div>
+
+ <section id="sec-number.prototype.constructor">
+ <h1><span class="secnum" id="sec-20.1.3.1"><a href="#sec-number.prototype.constructor"
+ title="link to this section">20.1.3.1</a></span> Number.prototype.constructor</h1>
+
+ <p>The initial value of <code>Number.prototype.constructor</code> is the intrinsic object %Number%.</p>
+ </section>
+
+ <section id="sec-number.prototype.toexponential">
+ <h1><span class="secnum" id="sec-20.1.3.2"><a href="#sec-number.prototype.toexponential"
+ title="link to this section">20.1.3.2</a></span> Number.prototype.toExponential ( fractionDigits )</h1>
+
+ <p>Return a String containing this Number value represented in decimal exponential notation with one digit before the
+ significand's decimal point and <var>fractionDigits</var> digits after the significand's decimal point. If
+ <var>fractionDigits</var> is <b>undefined</b>, include as many significand digits as necessary to uniquely specify the
+ Number (just like in <a href="#sec-tostring">ToString</a> except that in this case the Number is always output in
+ exponential notation). Specifically, perform the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>x</i> be thisNumberValue(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li>Let <i>f</i> be <a href="#sec-tointeger">ToInteger</a>(<i>fractionDigits</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>f</i> is 0, when <i>fractionDigits</i> is <b>undefined</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>f</i>).</li>
+ <li>If <i>x</i> is <b>NaN</b>, return the String <code>"NaN"</code>.</li>
+ <li>Let <i>s</i> be the empty String.</li>
+ <li>If <i>x</i> <i><</i> 0, then
+ <ol class="block">
+ <li>Let <i>s</i> be <code>"-"</code>.</li>
+ <li>Let <i>x</i> = –<i>x</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>x</i> = +∞, then
+ <ol class="block">
+ <li>Return the concatenation of the Strings <i>s</i> and <code>"Infinity"</code>.</li>
+ </ol>
+ </li>
+ <li>If <i>f</i> < 0 or <i>f</i> > 20, throw a <b>RangeError</b> exception. However, an implementation is permitted
+ to extend the behaviour of <code>toExponential</code> for values of <i>f</i> less than 0 or greater than 20. In this
+ case <code>toExponential</code> would not necessarily throw <b>RangeError</b> for such values.</li>
+ <li>If <i>x</i> = 0, then
+ <ol class="block">
+ <li>Let <i>m</i> be the String consisting of <i>f</i>+1 occurrences of the code unit 0x0030.</li>
+ <li>Let <i>e</i> = 0.</li>
+ </ol>
+ </li>
+ <li>Else <i>x</i> ≠ 0,
+ <ol class="block">
+ <li>If <i>fractionDigits</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>e</i> and <i>n</i> be integers such that 10<sup><i>f</i></sup> ≤ <i>n</i> <
+ 10<sup><i>f</i>+1</sup> and for which the exact mathematical value of <i>n</i> ×
+ 10<sup><i>e</i>–<i>f</i></sup> – <i>x</i> is as close to zero as possible. If there are two such
+ sets of <i>e</i> and <i>n</i>, pick the <i>e</i> and <i>n</i> for which <i>n</i> ×
+ 10<sup><i>e</i>–<i>f</i></sup> is larger.</li>
+ </ol>
+ </li>
+ <li>Else <i>fractionDigits</i> is <b>undefined</b>,
+ <ol class="block">
+ <li>Let <i>e</i>, <i>n</i>, and <i>f</i> be integers such that <i>f</i> ≥ 0, 10<sup><i>f</i></sup> ≤
+ <i>n</i> < 10<sup><i>f</i>+1</sup>, the Number value for n × 10<sup><i>e</i>–<i>f</i></sup>
+ is <i>x</i>, and <i>f</i> is as small as possible. Note that the decimal representation of <i>n</i> has
+ <i>f</i>+1 digits, <i>n</i> is not divisible by 10, and the least significant digit of <i>n</i> is not
+ necessarily uniquely determined by these criteria.</li>
+ </ol>
+ </li>
+ <li>Let <i>m</i> be the String consisting of the digits of the decimal representation of <i>n</i> (in order, with no
+ leading zeroes).</li>
+ </ol>
+ </li>
+ <li>If <i>f</i> ≠ 0, then
+ <ol class="block">
+ <li>Let <i>a</i> be the first element of <i>m</i>, and let <i>b</i> be the remaining <i>f</i> elements of
+ <i>m</i>.</li>
+ <li>Let <i>m</i> be the concatenation of the three Strings <i>a</i>, <code>"."</code>, and <i>b</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>e</i> = 0, then
+ <ol class="block">
+ <li>Let <i>c</i> = <code>"+".</code></li>
+ <li>Let <i>d</i> = <code>"0".</code></li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>If <i>e</i> > 0, let <i>c</i> = <code>"+".</code></li>
+ <li>Else <i>e</i> ≤ 0,
+ <ol class="block">
+ <li>Let <i>c</i> = <code>"-"</code>.</li>
+ <li>Let <i>e</i> = –<i>e</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>d</i> be the String consisting of the digits of the decimal representation of <i>e</i> (in order, with no
+ leading zeroes).</li>
+ </ol>
+ </li>
+ <li>Let <i>m</i> be the concatenation of the four Strings <i>m</i>, <code>"e"</code>, <i>c</i>, and <i>d</i>.</li>
+ <li>Return the concatenation of the Strings <i>s</i> and <i>m</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>toExponential</code> method is <b>1</b>.</p>
+
+ <p>If the <code>toExponential</code> method is called with more than one argument, then the behaviour is undefined (see <a
+ href="#sec-ecmascript-standard-built-in-objects">clause 17</a>).</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For implementations that provide more accurate conversions than required by the rules
+ above, it is recommended that the following alternative version of step 12.b.i be used as a guideline:</p>
+
+ <ol class="proc">
+ <li>Let <i>e</i>, <i>n</i>, and <i>f</i> be integers such that <i>f</i> ≥ 0, 10<sup><i>f</i></sup> ≤ n <
+ 10<sup><i>f</i>+1</sup>, the Number value for n × 10<sup><i>e</i>–<i>f</i></sup> is x, and <i>f</i> is
+ as small as possible. If there are multiple possibilities for <i>n</i>, choose the value of <i>n</i> for which
+ <i>n</i> × 10<sup><i>e</i>–<i>f</i></sup> is closest in value to <i>x</i>. If there are two such
+ possible values of <i>n</i>, choose the one that is even.</li>
+ </ol>
+ </div>
+ </section>
+
+ <section id="sec-number.prototype.tofixed">
+ <h1><span class="secnum" id="sec-20.1.3.3"><a href="#sec-number.prototype.tofixed"
+ title="link to this section">20.1.3.3</a></span> Number.prototype.toFixed ( fractionDigits )</h1>
+
+ <div class="note">
+ <p><span class="nh">Note</span> <b>toFixed</b> returns a String containing this Number value represented in decimal
+ fixed-point notation with <i>fractionDigits</i> digits after the decimal point. If <i>fractionDigits</i> is
+ <b>undefined</b>, 0 is assumed.</p>
+ </div>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>x</i> be thisNumberValue(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li>Let <i>f</i> be <a href="#sec-tointeger">ToInteger</a>(<i>fractionDigits</i>). (If <i>fractionDigits</i> is
+ <b>undefined</b>, this step produces the value <code>0</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>f</i>).</li>
+ <li>If <i>f</i> < 0 or <i>f</i> > 20, throw a <b>RangeError</b> exception. However, an implementation is permitted
+ to extend the behaviour of <code>toFixed</code> for values of <i>f</i> less than 0 or greater than 20. In this case
+ <code>toFixed</code> would not necessarily throw <b>RangeError</b> for such values.</li>
+ <li>If <i>x</i> is <b>NaN</b>, return the String <code>"NaN"</code>.</li>
+ <li>Let <i>s</i> be the empty String.</li>
+ <li>If <i>x</i> < 0, then
+ <ol class="block">
+ <li>Let <i>s</i> be "<code>-</code>".</li>
+ <li>Let <i>x</i> = –<i>x</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>x</i> ≥ 10<sup>21</sup>, then
+ <ol class="block">
+ <li>Let <i>m</i> = <a href="#sec-tostring">ToString</a>(<i>x</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>x</i> < 10<sup>21</sup>,
+ <ol class="block">
+ <li>Let <i>n</i> be an integer for which the exact mathematical value of <i>n</i> ÷ 10<sup>f</sup> –
+ <i>x</i> is as close to zero as possible. If there are two such <i>n</i>, pick the larger <i>n</i>.</li>
+ <li>If <i>n</i> = 0, let <i>m</i> be the String <code>"0"</code>. Otherwise, let <i>m</i> be the String consisting
+ of the digits of the decimal representation of <i>n</i> (in order, with no leading zeroes).</li>
+ <li>If <i>f</i> ≠ 0, then
+ <ol class="block">
+ <li>Let <i>k</i> be the number of elements in <i>m</i>.</li>
+ <li>If <i>k</i> ≤ <i>f</i>, then
+ <ol class="block">
+ <li>Let <i>z</i> be the String consisting of <i>f</i>+1–<i>k</i> occurrences of the code unit
+ 0x0030.</li>
+ <li>Let <i>m</i> be the concatenation of Strings <i>z</i> and <i>m</i>.</li>
+ <li>Let <i>k</i> = <i>f</i> + 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>a</i> be the first <i>k</i>–<i>f</i> elements of <i>m</i>, and let <i>b</i> be the remaining
+ <i>f</i> elements of <i>m</i>.</li>
+ <li>Let <i>m</i> be the concatenation of the three Strings <i>a</i>, <code>"."</code>, and <i>b</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return the concatenation of the Strings <i>s</i> and <i>m</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>toFixed</code> method is <b>1</b>.</p>
+
+ <p>If the <code>toFixed</code> method is called with more than one argument, then the behaviour is undefined (see <a
+ href="#sec-ecmascript-standard-built-in-objects">clause 17</a>).</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The output of <code>toFixed</code> may be more precise than <code>toString</code> for
+ some values because toString only prints enough significant digits to distinguish the number from adjacent number
+ values. For example,</p>
+
+ <p>(<code>1000000000000000128).toString()</code> returns <code>"1000000000000000100"</code>,<br>while
+ (<code>1000000000000000128).toFixed(0)</code> returns <code>"1000000000000000128"</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-number.prototype.tolocalestring">
+ <h1><span class="secnum" id="sec-20.1.3.4"><a href="#sec-number.prototype.tolocalestring"
+ title="link to this section">20.1.3.4</a></span> Number.prototype.toLocaleString( [ reserved1 [ , reserved2 ] ])</h1>
+
+ <p>An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the
+ <code>Number.prototype.toLocaleString</code> method as specified in the ECMA-402 specification. If an ECMAScript
+ implementation does not include the ECMA-402 API the following specification of the <code>toLocaleString</code> method is
+ used.</p>
+
+ <p>Produces a String value that represents this Number value formatted according to the conventions of the host
+ environment’s current locale. This function is implementation-dependent, and it is permissible, but not encouraged,
+ for it to return the same thing as <code>toString</code>.</p>
+
+ <p>The meanings of the optional parameters to this method are defined in the ECMA-402 specification; implementations that
+ do not include ECMA-402 support must not use those parameter positions for anything else.</p>
+
+ <p>The <code>length</code> property of the <code>toLocaleString</code> method is <b>0</b>.</p>
+ </section>
+
+ <section id="sec-number.prototype.toprecision">
+ <h1><span class="secnum" id="sec-20.1.3.5"><a href="#sec-number.prototype.toprecision"
+ title="link to this section">20.1.3.5</a></span> Number.prototype.toPrecision ( precision )</h1>
+
+ <p>Return a String containing this Number value represented either in decimal exponential notation with one digit before
+ the significand's decimal point and <span style="font-family: Times New Roman"><i>precision</i>–1</span> digits
+ after the significand's decimal point or in decimal fixed notation with <var>precision</var> significant digits. If
+ <var>precision</var> is <b>undefined</b>, call <a href="#sec-tostring">ToString</a> (<a href="#sec-tostring">7.1.12</a>)
+ instead. Specifically, perform the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>x</i> be thisNumberValue(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li>If <i>precision</i> is <b>undefined</b>, return <a href="#sec-tostring">ToString</a>(<i>x</i>).</li>
+ <li>Let <i>p</i> be <a href="#sec-tointeger">ToInteger</a>(<i>precision</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>p</i>).</li>
+ <li>If <i>x</i> is <b>NaN</b>, return the String <code>"NaN"</code>.</li>
+ <li>Let <i>s</i> be the empty String.</li>
+ <li>If <i>x</i> < 0, then
+ <ol class="block">
+ <li>Let <i>s</i> be code unit 0x002D <b>(</b>HYPHEN-MINUS<b>)</b>.</li>
+ <li>Let <i>x</i> = –<i>x</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>x</i> = +∞, then
+ <ol class="block">
+ <li>Return the String that is the concatenation of <i>s</i> and <code>"Infinity"</code>.</li>
+ </ol>
+ </li>
+ <li>If <i>p</i> < 1 or <i>p</i> > 21, throw a <b>RangeError</b> exception. However, an implementation is permitted
+ to extend the behaviour of <code>toPrecision</code> for values of <i>p</i> less than 1 or greater than 21. In this
+ case <code>toPrecision</code> would not necessarily throw <b>RangeError</b> for such values.</li>
+ <li>If <i>x</i> = 0, then
+ <ol class="block">
+ <li>Let <i>m</i> be the String consisting of <i>p</i> occurrences of the code unit 0x0030 (DIGIT ZERO).</li>
+ <li>Let <i>e</i> = 0.</li>
+ </ol>
+ </li>
+ <li>Else <i>x</i> ≠ 0,
+ <ol class="block">
+ <li>Let <i>e</i> and <i>n</i> be integers such that 10<sup><i>p</i>–1</sup> ≤ <i>n</i> <
+ 10<sup><i>p</i></sup> and for which the exact mathematical value of <i>n</i> ×
+ 10<sup><i>e</i>–<i>p</i>+1</sup> – <i>x</i> is as close to zero as possible. If there are two such
+ sets of <i>e</i> and <i>n</i>, pick the <i>e</i> and <i>n</i> for which <i>n</i> ×
+ 10<sup><i>e</i>–<i>p</i>+1</sup> is larger.</li>
+ <li>Let <i>m</i> be the String consisting of the digits of the decimal representation of <i>n</i> (in order, with no
+ leading zeroes).</li>
+ <li>If <i>e</i> < –6 or <i>e</i> ≥ <i>p</i>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>e</i> ≠ 0</li>
+ <li>Let <i>a</i> be the first element of <i>m</i>, and let <i>b</i> be the remaining <i>p</i>–1 elements
+ of <i>m</i>.</li>
+ <li>Let <i>m</i> be the concatenation of <i>a</i>, code unit 0x002E <b>(</b>FULL STOP<b>)</b>, and
+ <i>b</i>.</li>
+ <li>If <i>e</i> > 0, then
+ <ol class="block">
+ <li>Let <i>c</i> be code unit 0x002B <b>(</b>PLUS SIGN<b>)</b>.</li>
+ </ol>
+ </li>
+ <li>Else <i>e</i> < 0,
+ <ol class="block">
+ <li>Let <i>c</i> be code unit 0x002D <b>(</b>HYPHEN-MINUS<b>)</b>.</li>
+ <li>Let <i>e</i> = –<i>e</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>d</i> be the String consisting of the digits of the decimal representation of <i>e</i> (in order,
+ with no leading zeroes).</li>
+ <li>Return the concatenation of <i>s</i>, <i>m</i>, code unit 0x0065 <b>(</b>LATIN SMALL LETTER E<b>)</b>,
+ <i>c</i>, and <i>d</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>e</i> = <i>p</i>–1, return the concatenation of the Strings <i>s</i> and <i>m</i>.</li>
+ <li>If <i>e</i> ≥ 0, then
+ <ol class="block">
+ <li>Let <i>m</i> be the concatenation of the first <i>e</i>+1 elements of <i>m</i>, the code unit 0x002E
+ <b>(</b>FULL STOP<b>)</b>, and the remaining <i>p</i>– (<i>e</i>+1) elements of <i>m</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>e</i> < 0,
+ <ol class="block">
+ <li>Let <i>m</i> be the String formed by the concatenation of code unit 0x0030 <b>(</b>DIGIT ZERO<b>),</b> code unit
+ 0x002E <b>(</b>FULL STOP<b>)</b>, –(<i>e</i>+1) occurrences of code unit 0x0030 <b>(</b>DIGIT
+ ZERO<b>)</b>, and the String <i>m</i>.</li>
+ </ol>
+ </li>
+ <li>Return the String that is the concatenation of <i>s</i> and <i>m</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>toPrecision</code> method is <b>1</b>.</p>
+
+ <p>If the <code>toPrecision</code> method is called with more than one argument, then the behaviour is undefined (see <a
+ href="#sec-ecmascript-standard-built-in-objects">clause 17</a>).</p>
+ </section>
+
+ <section id="sec-number.prototype.tostring">
+ <h1><span class="secnum" id="sec-20.1.3.6"><a href="#sec-number.prototype.tostring"
+ title="link to this section">20.1.3.6</a></span> Number.prototype.toString ( [ radix ] )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The optional <i>radix</i> should be an integer value in the inclusive range 2 to 36. If
+ <i>radix</i> not present or is <b>undefined</b> the Number 10 is used as the value of <i>radix</i>.</p>
+ </div>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>x</i> be thisNumberValue(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>x</i>).</li>
+ <li>If <i>radix</i> is not present, let <i>radixNumber</i> be 10.</li>
+ <li>Else if <i>radix</i> is <b>undefined</b>, let <i>radixNumber</i> be 10.</li>
+ <li>Else let <i>radixNumber</i> be <a href="#sec-tointeger">ToInteger</a>(<i>radix</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>radixNumber</i>).</li>
+ <li>If <i>radixNumber</i> < 2 or <i>radixNumber</i> > 36, throw a <b>RangeError</b> exception.</li>
+ <li>If <i>radixNumber</i> = 10, return <a href="#sec-tostring">ToString</a>(<i>x</i>).</li>
+ <li>Return the String representation of this Number value using the radix specified by <i>radixNumber</i>. Letters
+ <code>a</code>-<code>z</code> are used for digits with values 10 through 35. The precise algorithm is
+ implementation-dependent, however the algorithm should be a generalization of that specified in <a
+ href="#sec-tostring-applied-to-the-number-type">7.1.12.1</a>.</li>
+ </ol>
+
+ <p>The <code>toString</code> function is not generic; it throws a <b>TypeError</b> exception if its <b>this</b> value is
+ not a Number or a Number object. Therefore, it cannot be transferred to other kinds of objects for use as a method.</p>
+ </section>
+
+ <section id="sec-number.prototype.valueof">
+ <h1><span class="secnum" id="sec-20.1.3.7"><a href="#sec-number.prototype.valueof"
+ title="link to this section">20.1.3.7</a></span> Number.prototype.valueOf ( )</h1>
+ <ol class="proc">
+ <li>Let <i>x</i> be thisNumberValue(<b>this</b> value).</li>
+ <li>Return <i>x</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-number-instances">
+ <h1><span class="secnum" id="sec-20.1.4"><a href="#sec-properties-of-number-instances"
+ title="link to this section">20.1.4</a></span> Properties of Number Instances</h1>
+
+ <p>Number instances are ordinary objects that inherit properties from the Number prototype object. Number instances also
+ have a [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>. The [[NumberData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the Number value represented by this Number
+ object.</p>
+ </section>
+ </section>
+
+ <section id="sec-math-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.2"><a href="#sec-math-object" title="link to this section">20.2</a></span> The Math
+ Object</h1>
+
+ <p>The Math object is the %Math% intrinsic object and the initial value of the <code>Math</code> property of the global
+ object.The Math object is a single ordinary object.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Math
+ object is the intrinsic object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+
+ <p>The Math object is not a function object. It does not have a [[Construct]] internal method; it is not possible to use the
+ Math object as a constructor with the <code>new</code> operator. The Math object also does not have a [[Call]] internal
+ method; it is not possible to invoke the Math object as a function.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In this specification, the phrase “the Number value for <i>x</i>” has a
+ technical meaning defined in <a href="#sec-ecmascript-language-types-number-type">6.1.6</a>.</p>
+ </div>
+ </div>
+
+ <section id="sec-value-properties-of-the-math-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.2.1"><a href="#sec-value-properties-of-the-math-object"
+ title="link to this section">20.2.1</a></span> Value Properties of the Math Object</h1>
+ </div>
+
+ <section id="sec-math.e">
+ <h1><span class="secnum" id="sec-20.2.1.1"><a href="#sec-math.e" title="link to this section">20.2.1.1</a></span>
+ Math.E</h1>
+
+ <p>The Number value for <var>e</var>, the base of the natural logarithms, which is approximately
+ 2.7182818284590452354.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-math.ln10">
+ <h1><span class="secnum" id="sec-20.2.1.2"><a href="#sec-math.ln10" title="link to this section">20.2.1.2</a></span>
+ Math.LN10</h1>
+
+ <p>The Number value for the natural logarithm of 10, which is approximately 2.302585092994046.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-math.ln2">
+ <h1><span class="secnum" id="sec-20.2.1.3"><a href="#sec-math.ln2" title="link to this section">20.2.1.3</a></span>
+ Math.LN2</h1>
+
+ <p>The Number value for the natural logarithm of 2, which is approximately 0.6931471805599453.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-math.log10e">
+ <h1><span class="secnum" id="sec-20.2.1.4"><a href="#sec-math.log10e" title="link to this section">20.2.1.4</a></span>
+ Math.LOG10E</h1>
+
+ <p>The Number value for the base-<span style="font-family: Times New Roman">10</span> logarithm of <var>e</var>, the base
+ of the natural logarithms; this value is approximately <span style="font-family: Times New
+ Roman">0.4342944819032518</span>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of <code>Math.LOG10E</code> is approximately the reciprocal of the value of
+ <code>Math.LN10</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.log2e">
+ <h1><span class="secnum" id="sec-20.2.1.5"><a href="#sec-math.log2e" title="link to this section">20.2.1.5</a></span>
+ Math.LOG2E</h1>
+
+ <p>The Number value for the base-<span style="font-family: Times New Roman">2</span> logarithm of <var>e</var>, the base
+ of the natural logarithms; this value is approximately <span style="font-family: Times New
+ Roman">1.4426950408889634</span>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of <code>Math.LOG2E</code> is approximately the reciprocal of the value of
+ <code>Math.LN2</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.pi">
+ <h1><span class="secnum" id="sec-20.2.1.6"><a href="#sec-math.pi" title="link to this section">20.2.1.6</a></span>
+ Math.PI</h1>
+
+ <p>The Number value for <span style="font-family: Times New Roman">π</span>, the ratio of the circumference of a circle
+ to its diameter, which is approximately <span style="font-family: Times New Roman">3.1415926535897932</span>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-math.sqrt1_2">
+ <h1><span class="secnum" id="sec-20.2.1.7"><a href="#sec-math.sqrt1_2" title="link to this section">20.2.1.7</a></span>
+ Math.SQRT1_2</h1>
+
+ <p>The Number value for the square root of <span style="font-family: Times New Roman">½</span>, which is
+ approximately <span style="font-family: Times New Roman">0.7071067811865476</span>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of <code>Math.SQRT1_2</code> is approximately the reciprocal of the value of
+ <code>Math.SQRT2</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.sqrt2">
+ <h1><span class="secnum" id="sec-20.2.1.8"><a href="#sec-math.sqrt2" title="link to this section">20.2.1.8</a></span>
+ Math.SQRT2</h1>
+
+ <p>The Number value for the square root of <span style="font-family: Times New Roman">2</span>, which is approximately
+ <span style="font-family: Times New Roman">1.4142135623730951</span>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-math-@@tostringtag">
+ <h1><span class="secnum" id="sec-20.2.1.9"><a href="#sec-math-@@tostringtag"
+ title="link to this section">20.2.1.9</a></span> Math [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Math</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-function-properties-of-the-math-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.2.2"><a href="#sec-function-properties-of-the-math-object"
+ title="link to this section">20.2.2</a></span> Function Properties of the Math Object</h1>
+
+ <p>Each of the following <code>Math</code> object functions applies the <a href="#sec-tonumber">ToNumber</a> abstract
+ operation to each of its arguments (in left-to-right order if there is more than one). If <a
+ href="#sec-tonumber">ToNumber</a> returns an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ that <a href="#sec-completion-record-specification-type">Completion Record</a> is immediately returned. Otherwise, the
+ function performs a computation on the resulting Number value(s). The value returned by each function is a Number.</p>
+
+ <p>In the function descriptions below, the symbols NaN, −0, +0, −∞ and +∞ refer to the Number
+ values described in <a href="#sec-ecmascript-language-types-number-type">6.1.6</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The behaviour of the functions <code>acos</code>, <code>acosh</code>, <code>asin</code>,
+ <code>asinh</code>, <code>atan</code>, <code>atanh</code>, <code>atan2</code>, <code>cbrt</code>, <code>cos</code>,
+ <code>cosh</code>, <code>exp</code>, <code>expm1</code>, <code>hypot</code>, <code>log</code>,<code>log1p</code>,
+ <code>log2</code>, <code>log10</code>, <code>pow</code>, <code>random</code>, <code>sin</code>, <code>sinh</code>,
+ <code>sqrt</code>, <code>tan</code>, and <code>tanh</code> is not precisely specified here except to require specific
+ results for certain argument values that represent boundary cases of interest. For other argument values, these
+ functions are intended to compute approximations to the results of familiar mathematical functions, but some latitude is
+ allowed in the choice of approximation algorithms. The general intent is that an implementer should be able to use the
+ same mathematical library for ECMAScript on a given hardware platform that is available to C programmers on that
+ platform.</p>
+ </div>
+
+ <p>Although the choice of algorithms is left to the implementation, it is recommended (but not specified by this standard)
+ that implementations use the approximation algorithms for IEEE 754 arithmetic contained in <code>fdlibm</code>, the freely
+ distributable mathematical library from Sun Microsystems (<a
+ href="http://www.netlib.org/fdlibm">http://www.netlib.org/fdlibm</a><code>)</code>.</p>
+ </div>
+
+ <section id="sec-math.abs">
+ <h1><span class="secnum" id="sec-20.2.2.1"><a href="#sec-math.abs" title="link to this section">20.2.2.1</a></span>
+ Math.abs ( x )</h1>
+
+ <p>Returns the absolute value of <var>x</var>; the result has the same magnitude as <var>x</var> but has positive
+ sign.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is −0, the result is +0.</li>
+ <li>If <i>x</i> is −∞, the result is +∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.acos">
+ <h1><span class="secnum" id="sec-20.2.2.2"><a href="#sec-math.acos" title="link to this section">20.2.2.2</a></span>
+ Math.acos ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the arc cosine of <var>x</var>. The result is expressed in radians
+ and ranges from <span style="font-family: Times New Roman">+0</span> to <span style="font-family: Times New
+ Roman">+π</span>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is greater than 1, the result is NaN.</li>
+ <li>If <i>x</i> is less than <b>−</b>1, the result is NaN.</li>
+ <li>If <i>x</i> is exactly 1, the result is +0.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.acosh">
+ <h1><span class="secnum" id="sec-20.2.2.3"><a href="#sec-math.acosh" title="link to this section">20.2.2.3</a></span>
+ Math.acosh( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the inverse hyperbolic cosine of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If x is less than 1, the result is NaN.</li>
+ <li>If x is 1, the result is +0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.asin">
+ <h1><span class="secnum" id="sec-20.2.2.4"><a href="#sec-math.asin" title="link to this section">20.2.2.4</a></span>
+ Math.asin ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the arc sine of <var>x</var>. The result is expressed in radians
+ and ranges from <span style="font-family: Times New Roman">−π/2</span> to <span style="font-family: Times New
+ Roman">+π/2</span>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is greater than 1, the result is NaN.</li>
+ <li>If <i>x</i> is less than –1, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.asinh">
+ <h1><span class="secnum" id="sec-20.2.2.5"><a href="#sec-math.asinh" title="link to this section">20.2.2.5</a></span>
+ Math.asinh( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the inverse hyperbolic sine of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If x is −∞, the result is −∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.atan">
+ <h1><span class="secnum" id="sec-20.2.2.6"><a href="#sec-math.atan" title="link to this section">20.2.2.6</a></span>
+ Math.atan ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the arc tangent of <var>x</var>. The result is expressed in
+ radians and ranges from <span style="font-family: Times New Roman">−π/2</span> to <span style="font-family: Times
+ New Roman">+π/2</span>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is an implementation-dependent approximation to +π/2.</li>
+ <li>If <i>x</i> is −∞, the result is an implementation-dependent approximation to −π/2.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.atanh">
+ <h1><span class="secnum" id="sec-20.2.2.7"><a href="#sec-math.atanh" title="link to this section">20.2.2.7</a></span>
+ Math.atanh( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the inverse hyperbolic tangent of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is less than −1, the result is NaN.</li>
+ <li>If <i>x</i> is greater than 1, the result is NaN.</li>
+ <li>If <i>x</i> is −1, the result is −∞.</li>
+ <li>If <i>x</i> is +1, the result is +∞.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.atan2">
+ <h1><span class="secnum" id="sec-20.2.2.8"><a href="#sec-math.atan2" title="link to this section">20.2.2.8</a></span>
+ Math.atan2 ( y, x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the arc tangent of the quotient <span style="font-family: Times
+ New Roman"><i>y</i><b>/</b><i>x</i></span> of the arguments <var>y</var> and <var>x</var>, where the signs of <var>y</var>
+ and <var>x</var> are used to determine the quadrant of the result. Note that it is intentional and traditional for the
+ two-argument arc tangent function that the argument named <var>y</var> be first and the argument named <var>x</var> be
+ second. The result is expressed in radians and ranges from <span style="font-family: Times New Roman">−π</span>
+ to <span style="font-family: Times New Roman">+π</span>.</p>
+
+ <ul>
+ <li>If either <i>x</i> or <i>y</i> is NaN, the result is NaN.</li>
+ <li>If <i>y</i>>0 and <i>x</i> is +0, the result is an implementation-dependent approximation to +π/2.</li>
+ <li>If <i>y</i>>0 and <i>x</i> is −0, the result is an implementation-dependent approximation to +π/2.</li>
+ <li>If <i>y</i> is +0 and <i>x</i>>0, the result is +0.</li>
+ <li>If <i>y</i> is +0 and <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>y</i> is +0 and <i>x</i> is −0, the result is an implementation-dependent approximation to +π.</li>
+ <li>If <i>y</i> is +0 and <i>x</i><0, the result is an implementation-dependent approximation to +π.</li>
+ <li>If <i>y</i> is −0 and <i>x</i>>0, the result is −0.</li>
+ <li>If <i>y</i> is −0 and <i>x</i> is +0, the result is −0.</li>
+ <li>If <i>y</i> is −0 and <i>x</i> is −0, the result is an implementation-dependent approximation to
+ −π.</li>
+ <li>If <i>y</i> is −0 and <i>x</i><0, the result is an implementation-dependent approximation to
+ −π.</li>
+ <li>If <i>y</i><0 and <i>x</i> is +0, the result is an implementation-dependent approximation to −π/2.</li>
+ <li>If <i>y</i><0 and <i>x</i> is −0, the result is an implementation-dependent approximation to
+ −π/2.</li>
+ <li>If <i>y</i>>0 and <i>y</i> is finite and <i>x</i> is +∞, the result is +0.</li>
+ <li>If <i>y</i>>0 and <i>y</i> is finite and <i>x</i> is −∞, the result if an implementation-dependent
+ approximation to +π.</li>
+ <li>If <i>y</i><0 and <i>y</i> is finite and <i>x</i> is +∞, the result is −0.</li>
+ <li>If <i>y</i><0 and <i>y</i> is finite and <i>x</i> is −∞, the result is an implementation-dependent
+ approximation to −π.</li>
+ <li>If <i>y</i> is +∞ and <i>x</i> is finite, the result is an implementation-dependent approximation to
+ +π/2.</li>
+ <li>If <i>y</i> is −∞ and <i>x</i> is finite, the result is an implementation-dependent approximation to
+ −π/2.</li>
+ <li>If <i>y</i> is +∞ and <i>x</i> is +∞, the result is an implementation-dependent approximation to
+ +π/4.</li>
+ <li>If <i>y</i> is +∞ and <i>x</i> is −∞, the result is an implementation-dependent approximation to
+ +3π/4.</li>
+ <li>If <i>y</i> is −∞ and <i>x</i> is +∞, the result is an implementation-dependent approximation to
+ −π/4.</li>
+ <li>If <i>y</i> is −∞ and <i>x</i> is −∞, the result is an implementation-dependent
+ approximation to −3π/4.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.cbrt">
+ <h1><span class="secnum" id="sec-20.2.2.9"><a href="#sec-math.cbrt" title="link to this section">20.2.2.9</a></span>
+ Math.cbrt ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the cube root of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If <i>x</i> is −∞, the result is −∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.ceil">
+ <h1><span class="secnum" id="sec-20.2.2.10"><a href="#sec-math.ceil" title="link to this section">20.2.2.10</a></span>
+ Math.ceil ( x )</h1>
+
+ <p>Returns the smallest (closest to <b>−∞</b>) Number value that is not less than <var>x</var> and is equal to
+ a mathematical integer. If <var>x</var> is already an integer, the result is <var>x</var>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If <i>x</i> is −∞, the result is −∞.</li>
+ <li>If <i>x</i> is less than 0 but greater than -1, the result is −0.</li>
+ </ul>
+
+ <p>The value of <code>Math.ceil(x)</code> is the same as the value of <code>-<a
+ href="#sec-math.floor">Math.floor</a>(-x)</code>.</p>
+ </section>
+
+ <section id="sec-math.clz32">
+ <h1><span class="secnum" id="sec-20.2.2.11"><a href="#sec-math.clz32" title="link to this section">20.2.2.11</a></span>
+ Math.clz32 ( x )</h1>
+
+ <p>When <code>Math.clz32</code> is called with one argument <var>x</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>n</i> be <a href="#sec-touint32">ToUint32</a>(<i>x</i>).</li>
+ <li>Let <i>p</i> be the number of leading zero bits in the 32-bit binary representation of <i>n</i>.</li>
+ <li>Return <i>p</i>.</li>
+ </ol>
+
+ <p class="Note">NOTE If <i>n</i> is 0, <i>p</i> will be 32. If the most significant bit of the 32-bit binary encoding of
+ <i>n</i> is 1, <i>p</i> will be 0.</p>
+ </section>
+
+ <section id="sec-math.cos">
+ <h1><span class="secnum" id="sec-20.2.2.12"><a href="#sec-math.cos" title="link to this section">20.2.2.12</a></span>
+ Math.cos ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the cosine of <var>x</var>. The argument is expressed in
+ radians.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is 1.</li>
+ <li>If <i>x</i> is −0, the result is 1.</li>
+ <li>If <i>x</i> is +∞, the result is NaN.</li>
+ <li>If <i>x</i> is −∞, the result is NaN.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.cosh">
+ <h1><span class="secnum" id="sec-20.2.2.13"><a href="#sec-math.cosh" title="link to this section">20.2.2.13</a></span>
+ Math.cosh ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the hyperbolic cosine of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is 1.</li>
+ <li>If <i>x</i> is −0, the result is 1.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If <i>x</i> is −∞, the result is +∞.</li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of cosh(x) is the same as <i>(exp(x) + exp(-x))/2</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.exp">
+ <h1><span class="secnum" id="sec-20.2.2.14"><a href="#sec-math.exp" title="link to this section">20.2.2.14</a></span>
+ Math.exp ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the exponential function of <var>x</var> (<var>e</var> raised to
+ the power of <var>x</var>, where <var>e</var> is the base of the natural logarithms).</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is 1.</li>
+ <li>If <i>x</i> is −0, the result is 1.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If <i>x</i> is −∞, the result is +0.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.expm1">
+ <h1><span class="secnum" id="sec-20.2.2.15"><a href="#sec-math.expm1" title="link to this section">20.2.2.15</a></span>
+ Math.expm1 ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to subtracting 1 from the exponential function of <i>x</i> (<i>e</i>
+ raised to the power of <i>x</i>, where <i>e</i> is the base of the natural logarithms). The result is computed in a way
+ that is accurate even when the value of x is close 0.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If <i>x</i> is −∞, the result is −1.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.floor">
+ <h1><span class="secnum" id="sec-20.2.2.16"><a href="#sec-math.floor" title="link to this section">20.2.2.16</a></span>
+ Math.floor ( x )</h1>
+
+ <p>Returns the greatest (closest to <b>+∞</b>) Number value that is not greater than <var>x</var> and is equal to a
+ mathematical integer. If <var>x</var> is already an integer, the result is <var>x</var>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If <i>x</i> is −∞, the result is −∞.</li>
+ <li>If <i>x</i> is greater than 0 but less than 1, the result is +0.</li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of <code>Math.<a href="#sec-algorithm-conventions">floor</a>(x)</code> is the
+ same as the value of <code>-<a href="#sec-math.ceil">Math.ceil</a>(-x)</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.fround">
+ <h1><span class="secnum" id="sec-20.2.2.17"><a href="#sec-math.fround" title="link to this section">20.2.2.17</a></span>
+ Math.fround ( x )</h1>
+
+ <p>When <code>Math.fround</code> is called with argument <i>x</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>x</i> is NaN, return NaN.</li>
+ <li>If <i>x</i> is one of +0, −0, +∞, −∞, return <i>x</i>.</li>
+ <li>Let <i>x32</i> be the result of converting <i>x</i> to a value in IEEE-754-2008 binary32 format using
+ roundTiesToEven.</li>
+ <li>Let <i>x64</i> be the result of converting <i>x32</i> to a value in IEEE-754-2008 binary64 format.</li>
+ <li>Return the ECMAScript Number value corresponding to <i>x64</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-math.hypot">
+ <h1><span class="secnum" id="sec-20.2.2.18"><a href="#sec-math.hypot" title="link to this section">20.2.2.18</a></span>
+ Math.hypot ( value1 , value2 , …values )</h1>
+
+ <p><code>Math.hypot</code> returns an implementation-dependent approximation of the square root of the sum of squares of
+ its arguments.</p>
+
+ <ul>
+ <li>If no arguments are passed, the result is +0.</li>
+ <li>If any argument is +∞, the result is +∞.</li>
+ <li>If any argument is −∞, the result is +∞.</li>
+ <li>If no argument is +∞ or −∞, and any argument is NaN, the result is NaN.</li>
+ <li>If all arguments are either +0 or −0, the result is +0.</li>
+ </ul>
+
+ <p>The length property of the <code>hypot</code> function is 2.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Implementations should take care to avoid the loss of precision from overflows and
+ underflows that are prone to occur in naive implementations when this function is called with two or more arguments.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.imul">
+ <h1><span class="secnum" id="sec-20.2.2.19"><a href="#sec-math.imul" title="link to this section">20.2.2.19</a></span>
+ Math.imul ( x, y )</h1>
+
+ <p>When the <code>Math.imul</code> is called with arguments <var>x</var> and <var>y</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>a</i> be <a href="#sec-touint32">ToUint32</a>(<i>x</i>).</li>
+ <li>Let <i>b</i> be <a href="#sec-touint32">ToUint32</a>(<i>y</i>).</li>
+ <li>Let <i>product</i> be (<i>a</i> × <i>b</i>) <a href="#sec-algorithm-conventions">modulo</a>
+ 2<sup>32</sup>.</li>
+ <li>If <i>product</i> ≥ 2<sup>31</sup>, return <i>product</i> − 2<sup>32</sup>, otherwise return
+ <i>product</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-math.log">
+ <h1><span class="secnum" id="sec-20.2.2.20"><a href="#sec-math.log" title="link to this section">20.2.2.20</a></span>
+ Math.log ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the natural logarithm of <var>x</var>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is less than 0, the result is NaN.</li>
+ <li>If <i>x</i> is +0 or −0, the result is −∞.</li>
+ <li>If <i>x</i> is 1, the result is +0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.log1p">
+ <h1><span class="secnum" id="sec-20.2.2.21"><a href="#sec-math.log1p" title="link to this section">20.2.2.21</a></span>
+ Math.log1p ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the natural logarithm of 1 + <i>x</i>. The result is computed in a
+ way that is accurate even when the value of x is close to zero.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is less than -1, the result is NaN.</li>
+ <li>If x is -1, the result is -∞.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.log10">
+ <h1><span class="secnum" id="sec-20.2.2.22"><a href="#sec-math.log10" title="link to this section">20.2.2.22</a></span>
+ Math.log10 ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the base 10 logarithm of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is less than 0, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is −∞.</li>
+ <li>If <i>x</i> is −0, the result is −∞.</li>
+ <li>If <i>x</i> is 1, the result is +0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.log2">
+ <h1><span class="secnum" id="sec-20.2.2.23"><a href="#sec-math.log2" title="link to this section">20.2.2.23</a></span>
+ Math.log2 ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the base 2 logarithm of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is less than 0, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is −∞.</li>
+ <li>If <i>x</i> is −0, the result is −∞.</li>
+ <li>If <i>x</i> is 1, the result is +0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.max">
+ <h1><span class="secnum" id="sec-20.2.2.24"><a href="#sec-math.max" title="link to this section">20.2.2.24</a></span>
+ Math.max ( value1, value2 , …values )</h1>
+
+ <p>Given zero or more arguments, calls <a href="#sec-tonumber">ToNumber</a> on each of the arguments and returns the
+ largest of the resulting values.</p>
+
+ <ul>
+ <li>
+ <p>If no arguments are given, the result is −∞.</p>
+ </li>
+
+ <li>
+ <p>If any value is NaN, the result is NaN.</p>
+ </li>
+
+ <li>
+ <p>The comparison of values to determine the largest value is done using the Abstract Relational Comparison algorithm
+ (<a href="#sec-ispropertykey">7.2.7</a>) except that +0 is considered to be larger than −0.</p>
+ </li>
+ </ul>
+
+ <p>The <code>length</code> property of the <code>max</code> method is <b>2</b>.</p>
+ </section>
+
+ <section id="sec-math.min">
+ <h1><span class="secnum" id="sec-20.2.2.25"><a href="#sec-math.min" title="link to this section">20.2.2.25</a></span>
+ Math.min ( value1, value2 , …values )</h1>
+
+ <p>Given zero or more arguments, calls <a href="#sec-tonumber">ToNumber</a> on each of the arguments and returns the
+ smallest of the resulting values.</p>
+
+ <ul>
+ <li>
+ <p>If no arguments are given, the result is +∞.</p>
+ </li>
+
+ <li>
+ <p>If any value is NaN, the result is NaN.</p>
+ </li>
+
+ <li>
+ <p>The comparison of values to determine the smallest value is done using the Abstract Relational Comparison algorithm
+ (<a href="#sec-ispropertykey">7.2.7</a>) except that +0 is considered to be larger than −0.</p>
+ </li>
+ </ul>
+
+ <p>The <code>length</code> property of the <code>min</code> method is <b>2</b>.</p>
+ </section>
+
+ <section id="sec-math.pow">
+ <h1><span class="secnum" id="sec-20.2.2.26"><a href="#sec-math.pow" title="link to this section">20.2.2.26</a></span>
+ Math.pow ( x, y )</h1>
+
+ <p>Returns an implementation-dependent approximation to the result of raising <var>x</var> to the power <var>y</var>.</p>
+
+ <ul>
+ <li>If <i>y</i> is NaN, the result is NaN.</li>
+ <li>If <i>y</i> is +0, the result is 1, even if <i>x</i> is NaN.</li>
+ <li>If <i>y</i> is −0, the result is 1, even if <i>x</i> is NaN.</li>
+ <li>If <i>x</i> is NaN and <i>y</i> is nonzero, the result is NaN.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>x</i>)>1 and <i>y</i> is +∞, the result is
+ +∞.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>x</i>)>1 and <i>y</i> is −∞, the result is
+ +0.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>x</i>) is 1 and <i>y</i> is +∞, the result is NaN.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>x</i>) is 1 and <i>y</i> is −∞, the result is
+ NaN.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>x</i>)<1 and <i>y</i> is +∞, the result is +0.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>x</i>)<1 and <i>y</i> is −∞, the result is
+ +∞.</li>
+ <li>If <i>x</i> is +∞ and <i>y</i>>0, the result is +∞.</li>
+ <li>If <i>x</i> is +∞ and <i>y</i><0, the result is +0.</li>
+ <li>If <i>x</i> is −∞ and <i>y</i>>0 and <i>y</i> is an odd integer, the result is −∞.</li>
+ <li>If <i>x</i> is −∞ and <i>y</i>>0 and <i>y</i> is not an odd integer, the result is +∞.</li>
+ <li>If <i>x</i> is −∞ and <i>y</i><0 and <i>y</i> is an odd integer, the result is −0.</li>
+ <li>If <i>x</i> is −∞ and <i>y</i><0 and <i>y</i> is not an odd integer, the result is +0.</li>
+ <li>If <i>x</i> is +0 and <i>y</i>>0, the result is +0.</li>
+ <li>If <i>x</i> is +0 and <i>y</i><0, the result is +∞.</li>
+ <li>If <i>x</i> is −0 and <i>y</i>>0 and <i>y</i> is an odd integer, the result is −0.</li>
+ <li>If <i>x</i> is −0 and <i>y</i>>0 and <i>y</i> is not an odd integer, the result is +0.</li>
+ <li>If <i>x</i> is −0 and <i>y</i><0 and <i>y</i> is an odd integer, the result is −∞.</li>
+ <li>If <i>x</i> is −0 and <i>y</i><0 and <i>y</i> is not an odd integer, the result is +∞.</li>
+ <li>If <i>x</i><0 and <i>x</i> is finite and <i>y</i> is finite and <i>y</i> is not an integer, the result is
+ NaN.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.random">
+ <h1><span class="secnum" id="sec-20.2.2.27"><a href="#sec-math.random" title="link to this section">20.2.2.27</a></span>
+ Math.random ( )</h1>
+
+ <p>Returns a Number value with positive sign, greater than or equal to 0 but less than 1, chosen randomly or pseudo
+ randomly with approximately uniform distribution over that range, using an implementation-dependent algorithm or strategy.
+ This function takes no arguments.</p>
+
+ <p>Each <code>Math.random</code> function created for distinct code Realms must produce a distinct sequence of values from
+ successive calls.</p>
+ </section>
+
+ <section id="sec-math.round">
+ <h1><span class="secnum" id="sec-20.2.2.28"><a href="#sec-math.round" title="link to this section">20.2.2.28</a></span>
+ Math.round ( x )</h1>
+
+ <p>Returns the Number value that is closest to <var>x</var> and is equal to a mathematical integer. If two integer Number
+ values are equally close to <var>x</var>, then the result is the Number value that is closer to <span style="font-family:
+ Times New Roman">+∞</span>. If <var>x</var> is already an integer, the result is <var>x</var>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If <i>x</i> is −∞, the result is −∞.</li>
+ <li>If <i>x</i> is greater than 0 but less than 0.5, the result is +0.</li>
+ <li>If <i>x</i> is less than 0 but greater than or equal to -0.5, the result is −0.</li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> <code>Math.round(3.5)</code> returns 4, but <code>Math.round(–3.5)</code>
+ returns –3.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The value of <code>Math.round(x)</code> is not always the same as the value of
+ <code><a href="#sec-math.floor">Math.floor</a>(x+0.5)</code>. When <code>x</code> is −0 or is less than 0 but
+ greater than or equal to -0.5, <code>Math.round(x)</code> returns −0, but <code><a
+ href="#sec-math.floor">Math.floor</a>(x+0.5)</code> returns +0. <code>Math.round(x)</code> may also differ from the
+ value of <code><a href="#sec-math.floor">Math.floor</a>(x+0.5)</code><span style="font-family: sans-serif">because of
+ internal rounding when computing</span> <code>x+0.5</code><span style="font-family: sans-serif">.</span></p>
+ </div>
+ </section>
+
+ <section id="sec-math.sign">
+ <h1><span class="secnum" id="sec-20.2.2.29"><a href="#sec-math.sign" title="link to this section">20.2.2.29</a></span>
+ Math.sign(x)</h1>
+
+ <p>Returns the sign of the x, indicating whether x is positive, negative or zero.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is negative and not −0, the result is −1.</li>
+ <li>If <i>x</i> is positive and not +0, the result is +1.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.sin">
+ <h1><span class="secnum" id="sec-20.2.2.30"><a href="#sec-math.sin" title="link to this section">20.2.2.30</a></span>
+ Math.sin ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the sine of <var>x</var>. The argument is expressed in
+ radians.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞ or −∞, the result is NaN.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.sinh">
+ <h1><span class="secnum" id="sec-20.2.2.31"><a href="#sec-math.sinh" title="link to this section">20.2.2.31</a></span>
+ Math.sinh( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the hyperbolic sine of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If x is −∞, the result is −∞.</li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of sinh(x) is the same as <i>(exp(x) - exp(-x))/2</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.sqrt">
+ <h1><span class="secnum" id="sec-20.2.2.32"><a href="#sec-math.sqrt" title="link to this section">20.2.2.32</a></span>
+ Math.sqrt ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the square root of <var>x</var>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is less than 0, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.tan">
+ <h1><span class="secnum" id="sec-20.2.2.33"><a href="#sec-math.tan" title="link to this section">20.2.2.33</a></span>
+ Math.tan ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the tangent of <var>x</var>. The argument is expressed in
+ radians.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞ or −∞, the result is NaN.</li>
+ </ul>
+ </section>
+
+ <section id="sec-math.tanh">
+ <h1><span class="secnum" id="sec-20.2.2.34"><a href="#sec-math.tanh" title="link to this section">20.2.2.34</a></span>
+ Math.tanh ( x )</h1>
+
+ <p>Returns an implementation-dependent approximation to the hyperbolic tangent of <i>x</i>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +∞, the result is +1.</li>
+ <li>If <i>x</i> is −∞, the result is -1.</li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of tanh(x) is the same as <i>(exp(x) - exp(-x))/(exp(x) + exp(-x))</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-math.trunc">
+ <h1><span class="secnum" id="sec-20.2.2.35"><a href="#sec-math.trunc" title="link to this section">20.2.2.35</a></span>
+ Math.trunc ( x )</h1>
+
+ <p>Returns the integral part of the number <var>x</var>, removing any fractional digits. If <var>x</var> is already an
+ integer, the result is <var>x</var>.</p>
+
+ <ul>
+ <li>If <i>x</i> is NaN, the result is NaN.</li>
+ <li>If <i>x</i> is −0, the result is −0.</li>
+ <li>If <i>x</i> is +0, the result is +0.</li>
+ <li>If <i>x</i> is +∞, the result is +∞.</li>
+ <li>If x is −∞, the result is −∞.</li>
+ <li>If <i>x</i> is greater than 0 but less than 1, the result is +0.</li>
+ <li>If <i>x</i> is less than 0 but greater than <span style="font-family: sans-serif">−</span>1, the result is
+ <span style="font-family: sans-serif">−</span>0.</li>
+ </ul>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-date-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.3"><a href="#sec-date-objects" title="link to this section">20.3</a></span> Date
+ Objects</h1>
+ </div>
+
+ <section id="sec-overview-of-date-objects-and-definitions-of-abstract-operations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.3.1"><a href="#sec-overview-of-date-objects-and-definitions-of-abstract-operations"
+ title="link to this section">20.3.1</a></span> Overview of Date Objects and Definitions of Abstract Operations</h1>
+
+ <p>The following functions are abstract operations that operate on time values (defined in <a
+ href="#sec-time-values-and-time-range">20.3.1.1</a>). Note that, in every case, if any argument to one of these functions
+ is <b>NaN</b>, the result will be <b>NaN</b>.</p>
+ </div>
+
+ <section id="sec-time-values-and-time-range">
+ <h1><span class="secnum" id="sec-20.3.1.1"><a href="#sec-time-values-and-time-range"
+ title="link to this section">20.3.1.1</a></span> Time Values and Time Range</h1>
+
+ <p>A Date object contains a Number indicating a particular instant in time to within a millisecond. Such a Number is
+ called a <i>time value</i>. A time value may also be <b>NaN</b>, indicating that the Date object does not represent a
+ specific instant of time.</p>
+
+ <p>Time is measured in ECMAScript in milliseconds since 01 January, 1970 UTC. In time values leap seconds are ignored. It
+ is assumed that there are exactly 86,400,000 milliseconds per day. ECMAScript Number values can represent all integers
+ from –9,007,199,254,740,992 to 9,007,199,254,740,992; this range suffices to measure times to millisecond precision
+ for any instant that is within approximately 285,616 years, either forward or backward, from 01 January, 1970 UTC.</p>
+
+ <p>The actual range of times supported by ECMAScript Date objects is slightly smaller: exactly –100,000,000 days to
+ 100,000,000 days measured relative to midnight at the beginning of 01 January, 1970 UTC. This gives a range of
+ 8,640,000,000,000,000 milliseconds to either side of 01 January, 1970 UTC.</p>
+
+ <p>The exact moment of midnight at the beginning of 01 January, 1970 UTC is represented by the value <b>+0</b>.</p>
+ </section>
+
+ <section id="sec-day-number-and-time-within-day">
+ <h1><span class="secnum" id="sec-20.3.1.2"><a href="#sec-day-number-and-time-within-day"
+ title="link to this section">20.3.1.2</a></span> Day Number and Time within Day</h1>
+
+ <p>A given <a href="#sec-time-values-and-time-range">time value</a> <i>t</i> belongs to day number</p>
+
+ <div class="display">Day(<i>t</i>) = <a href="#sec-algorithm-conventions">floor</a>(<i>t</i> / msPerDay)</div>
+
+ <p>where the number of milliseconds per day is</p>
+
+ <div class="display">msPerDay = 86400000</div>
+
+ <p>The remainder is called the time within the day:</p>
+
+ <div class="display">TimeWithinDay(<i>t</i>) = <i>t</i> <a href="#sec-algorithm-conventions">modulo</a> msPerDay</div>
+ </section>
+
+ <section id="sec-year-number">
+ <h1><span class="secnum" id="sec-20.3.1.3"><a href="#sec-year-number" title="link to this section">20.3.1.3</a></span>
+ Year Number</h1>
+
+ <p>ECMAScript uses an extrapolated Gregorian system to map a day number to a year number and to determine the month and
+ date within that year. In this system, leap years are precisely those which are (divisible by <span style="font-family:
+ Times New Roman">4</span>) and ((not divisible by <span style="font-family: Times New Roman">100</span>) or (divisible by
+ <span style="font-family: Times New Roman">400</span>)). The number of days in year number <var>y</var> is therefore
+ defined by</p>
+
+ <div class="display">DaysInYear(<i>y</i>) 	= 365 if (<i>y</i> <a href="#sec-algorithm-conventions">modulo</a> 4) ≠ 0<br>= 366 if (<i>y</i> <a href="#sec-algorithm-conventions">modulo</a> 4) = 0 and (<i>y</i> <a href="#sec-algorithm-conventions">modulo</a> 100) ≠ 0<br>= 365 if (<i>y</i> <a href="#sec-algorithm-conventions">modulo</a> 100) = 0 and (<i>y</i> <a href="#sec-algorithm-conventions">modulo</a> 400) ≠ 0<br>= 366 if (<i>y</i> <a href="#sec-algorithm-conventions">modulo</a> 400) = 0</div>
+
+ <p>All non-leap years have <span style="font-family: Times New Roman">365</span> days with the usual number of days per
+ month and leap years have an extra day in February. The day number of the first day of year <var>y</var> is given by:</p>
+
+ <div class="display">DayFromYear(<i>y</i>)	 = 365 × (<i>y</i>−1970) + <a href="#sec-algorithm-conventions">floor</a>((<i>y</i>−1969)/4) − <a href="#sec-algorithm-conventions">floor</a>((<i>y</i>−1901)/100) + <a href="#sec-algorithm-conventions">floor</a>((<i>y</i>−1601)/400)</div>
+
+ <p>The <a href="#sec-time-values-and-time-range">time value</a> of the start of a year is:</p>
+
+ <div class="display">TimeFromYear(<i>y</i>)	 = <a href="#sec-day-number-and-time-within-day">msPerDay</a> × DayFromYear(<i>y</i>)</div>
+
+ <p>A <a href="#sec-time-values-and-time-range">time value</a> determines a year by:</p>
+
+ <div class="display">YearFromTime(<i>t</i>) 	= the largest integer <i>y</i> (closest to positive infinity) such that TimeFromYear(<i>y</i>) ≤ <i>t</i></div>
+
+ <p>The leap-year function is 1 for a time within a leap year and otherwise is zero:</p>
+
+ <div class="display">InLeapYear(<i>t</i>)	= 0 if DaysInYear(YearFromTime(<i>t</i>)) = 365<br>= 1 if DaysInYear(YearFromTime(<i>t</i>)) = 366</div>
+ </section>
+
+ <section id="sec-month-number">
+ <h1><span class="secnum" id="sec-20.3.1.4"><a href="#sec-month-number" title="link to this section">20.3.1.4</a></span>
+ Month Number</h1>
+
+ <p>Months are identified by an integer in the range <span style="font-family: Times New Roman">0</span> to <span
+ style="font-family: Times New Roman">11</span>, inclusive. The mapping MonthFromTime(<i>t</i>) from a <a
+ href="#sec-time-values-and-time-range">time value</a> <i>t</i> to a month number is defined by:</p>
+
+ <div class="display">MonthFromTime(<i>t</i>)	= 0	if	0	≤ DayWithinYear(<i>t</i>) < 31<br>	= 1	if	31 	≤ DayWithinYear (<i>t</i>) < 59+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 2	if	59+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 90+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 3	if	90+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 120+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 4	if	120+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 151+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 5	if	151+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 181+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 6	if	181+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 212+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 7	if	212+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 243+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 8	if	243+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 273+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 9	if	273+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 304+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 10	if	304+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 334+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)<br>	= 11	if	334+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>) 	≤ DayWithinYear (<i>t</i>) < 365+<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)</div>
+
+ <p>where</p>
+
+ <div class="display">DayWithinYear(<i>t</i>)	= <a href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>)−DayFromYear(<a href="#sec-year-number">YearFromTime</a>(<i>t)</i>)</div>
+
+ <p>A month value of <span style="font-family: Times New Roman">0</span> specifies January; <span style="font-family: Times
+ New Roman">1</span> specifies February; <span style="font-family: Times New Roman">2</span> specifies March; <span
+ style="font-family: Times New Roman">3</span> specifies April; <span style="font-family: Times New
+ Roman">4</span> specifies May; <span style="font-family: Times New Roman">5</span> specifies June; <span
+ style="font-family: Times New Roman">6</span> specifies July; <span style="font-family: Times New Roman">7</span>
+ specifies August; <span style="font-family: Times New Roman">8</span> specifies September; <span style="font-family: Times
+ New Roman">9</span> specifies October; <span style="font-family: Times New Roman">10</span> specifies November; and <span
+ style="font-family: Times New Roman">11</span> specifies December. Note that <span style="font-family: Times New
+ Roman">MonthFromTime(0) = 0</span>, corresponding to Thursday, 01 January, 1970.</p>
+ </section>
+
+ <section id="sec-date-number">
+ <h1><span class="secnum" id="sec-20.3.1.5"><a href="#sec-date-number" title="link to this section">20.3.1.5</a></span>
+ Date Number</h1>
+
+ <p>A date number is identified by an integer in the range <span style="font-family: Times New Roman">1</span> through
+ <span style="font-family: Times New Roman">31</span>, inclusive. The mapping DateFromTime(<i>t</i>) from a <a
+ href="#sec-time-values-and-time-range">time value</a> <i>t</i> to a date number is defined by:</p>
+
+ <div class="display">DateFromTime(<i>t</i>)	= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)+1		if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=0<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−30		if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=1<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−58−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=2<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−89−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=3<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−119−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=4<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−150−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=5<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−180−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=6<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−211−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=7<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−242−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=8<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−272−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=9<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−303−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=10<br>		= <a href="#sec-month-number">DayWithinYear</a>(<i>t</i>)−333−<a href="#sec-year-number">InLeapYear</a>(<i>t</i>)	if <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>)=11</div>
+ </section>
+
+ <section id="sec-week-day">
+ <h1><span class="secnum" id="sec-20.3.1.6"><a href="#sec-week-day" title="link to this section">20.3.1.6</a></span> Week
+ Day</h1>
+
+ <p>The weekday for a particular <a href="#sec-time-values-and-time-range">time value</a> <var>t</var> is defined as</p>
+
+ <div class="display">WeekDay(<i>t</i>)	 = (<a href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>) + 4) <a href="#sec-algorithm-conventions">modulo</a> 7</div>
+
+ <p>A weekday value of <span style="font-family: Times New Roman">0</span> specifies Sunday; <span style="font-family:
+ Times New Roman">1</span> specifies Monday; <span style="font-family: Times New Roman">2</span> specifies Tuesday; <span
+ style="font-family: Times New Roman">3</span> specifies Wednesday; <span style="font-family: Times New
+ Roman">4</span> specifies Thursday; <span style="font-family: Times New Roman">5</span> specifies Friday; and <span
+ style="font-family: Times New Roman">6</span> specifies Saturday. Note that <span style="font-family: Times New
+ Roman">WeekDay(0) = 4</span>, corresponding to Thursday, 01 January, 1970.</p>
+ </section>
+
+ <section id="sec-local-time-zone-adjustment">
+ <h1><span class="secnum" id="sec-20.3.1.7"><a href="#sec-local-time-zone-adjustment"
+ title="link to this section">20.3.1.7</a></span> Local Time Zone Adjustment</h1>
+
+ <p>An implementation of ECMAScript is expected to determine the local time zone adjustment. The local time zone adjustment
+ is a value LocalTZA measured in milliseconds which when added to UTC represents the local <i>standard</i> time. Daylight
+ saving time is <i>not</i> reflected by LocalTZA.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> It is recommended that implementations use the time zone information of the IANA Time
+ Zone Database <a href="http://www.iana.org/time-zones/">http://www.iana.org/time-zones/</a>.</p>
+ </div>
+ </section>
+
+ <section id="sec-daylight-saving-time-adjustment">
+ <h1><span class="secnum" id="sec-20.3.1.8"><a href="#sec-daylight-saving-time-adjustment"
+ title="link to this section">20.3.1.8</a></span> Daylight Saving Time Adjustment</h1>
+
+ <p>An implementation dependent algorithm using best available information on time zones to determine the local daylight
+ saving time adjustment DaylightSavingTA(<i>t</i>), measured in milliseconds. An implementation of ECMAScript is expected
+ to make its best effort to determine the local daylight saving time adjustment.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> It is recommended that implementations use the time zone information of the IANA Time
+ Zone Database <a href="http://www.iana.org/time-zones/">http://www.iana.org/time-zones/</a>.</p>
+ </div>
+ </section>
+
+ <section id="sec-local-time">
+ <h1><span class="secnum" id="sec-20.3.1.9"><a href="#sec-local-time" title="link to this section">20.3.1.9</a></span>
+ Local Time</h1>
+
+ <p>The abstract operation LocalTime with argument <var>t</var> converts <var>t</var> from UTC to local time by performing
+ the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Return <i>t</i> + <a href="#sec-local-time-zone-adjustment">LocalTZA</a> + <a
+ href="#sec-daylight-saving-time-adjustment">DaylightSavingTA</a>(<i>t</i>).</li>
+ </ol>
+
+ <p>The abstract operation UTC with argument <var>t</var> converts <var>t</var> from local time to UTC is defined by
+ performing the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>). <i>t</i> – <a
+ href="#sec-local-time-zone-adjustment">LocalTZA</a> – <a
+ href="#sec-daylight-saving-time-adjustment">DaylightSavingTA</a>(<i>t</i> – <a
+ href="#sec-local-time-zone-adjustment">LocalTZA</a>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> UTC(LocalTime(<i>t</i>)) is not necessarily always equal to <i>t</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-hours-minutes-second-and-milliseconds">
+ <h1><span class="secnum" id="sec-20.3.1.10"><a href="#sec-hours-minutes-second-and-milliseconds"
+ title="link to this section">20.3.1.10</a></span> Hours, Minutes, Second, and Milliseconds</h1>
+
+ <p>The following abstract operations are useful in decomposing time values:</p>
+
+ <div class="display">HourFromTime(<i>t</i>)	= <a href="#sec-algorithm-conventions">floor</a>(<i>t</i> / msPerHour) <a href="#sec-algorithm-conventions">modulo</a> HoursPerDay</div>
+ <div class="display">MinFromTime(<i>t</i>)	= <a href="#sec-algorithm-conventions">floor</a>(<i>t</i> / msPerMinute) <a href="#sec-algorithm-conventions">modulo</a> MinutesPerHour</div>
+ <div class="display">SecFromTime(<i>t</i>)	= <a href="#sec-algorithm-conventions">floor</a>(<i>t</i> / msPerSecond) <a href="#sec-algorithm-conventions">modulo</a> SecondsPerMinute</div>
+ <div class="display">msFromTime(<i>t</i>)	= <i>t</i> <a href="#sec-algorithm-conventions">modulo</a> msPerSecond</div>
+
+ <p>where</p>
+
+ <div class="display">HoursPerDay	= 24</div>
+ <div class="display">MinutesPerHour	= 60</div>
+ <div class="display">SecondsPerMinute	= 60</div>
+ <div class="display">msPerSecond	= 1000</div>
+ <div class="display">msPerMinute	= 60000	= msPerSecond × SecondsPerMinute</div>
+ <div class="display">msPerHour	= 3600000	= msPerMinute × MinutesPerHour</div>
+ </section>
+
+ <section id="sec-maketime">
+ <h1><span class="secnum" id="sec-20.3.1.11"><a href="#sec-maketime" title="link to this section">20.3.1.11</a></span>
+ MakeTime (hour, min, sec, ms)</h1>
+
+ <p>The abstract operation MakeTime calculates a number of milliseconds from its four arguments, which must be ECMAScript
+ Number values. This operator functions as follows:</p>
+
+ <ol class="proc">
+ <li>If <i>hour</i> is not finite or <i>min</i> is not finite or <i>sec</i> is not finite or <i>ms</i> is not finite,
+ return <b>NaN</b>.</li>
+ <li>Let <i>h</i> be <a href="#sec-tointeger">ToInteger</a>(<i>hour</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tointeger">ToInteger</a>(<i>min</i>).</li>
+ <li>Let <i>s</i> be <a href="#sec-tointeger">ToInteger</a>(<i>sec</i>).</li>
+ <li>Let <i>milli</i> be <a href="#sec-tointeger">ToInteger</a>(<i>ms</i>).</li>
+ <li>Let <i>t</i> be <i>h</i> <code>*</code> <a href="#sec-hours-minutes-second-and-milliseconds">msPerHour</a>
+ <code>+</code> <i>m</i> <code>*</code> <a href="#sec-hours-minutes-second-and-milliseconds">msPerMinute</a>
+ <code>+</code> <i>s</i> <code>*</code> <a href="#sec-hours-minutes-second-and-milliseconds">msPerSecond</a>
+ <code>+</code> <i>milli</i>, performing the arithmetic according to IEEE 754 rules (that is, as if using the
+ ECMAScript operators <code>*</code> and <code>+</code>).</li>
+ <li>Return <i>t</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-makeday">
+ <h1><span class="secnum" id="sec-20.3.1.12"><a href="#sec-makeday" title="link to this section">20.3.1.12</a></span>
+ MakeDay (year, month, date)</h1>
+
+ <p>The abstract operation MakeDay calculates a number of days from its three arguments, which must be ECMAScript Number
+ values. This operator functions as follows:</p>
+
+ <ol class="proc">
+ <li>If <i>year</i> is not finite or <i>month</i> is not finite or <i>date</i> is not finite, return <b>NaN</b>.</li>
+ <li>Let <i>y</i> be <a href="#sec-tointeger">ToInteger</a>(<i>year</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tointeger">ToInteger</a>(<i>month</i>).</li>
+ <li>Let <i>dt</i> be <a href="#sec-tointeger">ToInteger</a>(<i>date</i>).</li>
+ <li>Let <i>ym</i> be <i>y</i> + <a href="#sec-algorithm-conventions">floor</a>(<i>m</i> /12).</li>
+ <li>Let <i>mn</i> be <i>m</i> <a href="#sec-algorithm-conventions">modulo</a> 12.</li>
+ <li>Find a value <i>t</i> such that <a href="#sec-year-number">YearFromTime</a>(<i>t</i>) is <i>ym</i> and <a
+ href="#sec-month-number">MonthFromTime</a>(<i>t</i>) is <i>mn</i> and <a
+ href="#sec-date-number">DateFromTime</a>(<i>t</i>) is 1; but if this is not possible (because some argument is out
+ of range), return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>) + <i>dt</i> − 1.</li>
+ </ol>
+ </section>
+
+ <section id="sec-makedate">
+ <h1><span class="secnum" id="sec-20.3.1.13"><a href="#sec-makedate" title="link to this section">20.3.1.13</a></span>
+ MakeDate (day, time)</h1>
+
+ <p>The abstract operation MakeDate calculates a number of milliseconds from its two arguments, which must be ECMAScript
+ Number values. This operator functions as follows:</p>
+
+ <ol class="proc">
+ <li>If <i>day</i> is not finite or <i>time</i> is not finite, return <b>NaN</b>.</li>
+ <li>Return <i>day</i> × <a href="#sec-day-number-and-time-within-day">msPerDay</a> + <i>time</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-timeclip">
+ <h1><span class="secnum" id="sec-20.3.1.14"><a href="#sec-timeclip" title="link to this section">20.3.1.14</a></span>
+ TimeClip (time)</h1>
+
+ <p>The abstract operation TimeClip calculates a number of milliseconds from its argument, which must be an ECMAScript
+ Number value. This operator functions as follows:</p>
+
+ <ol class="proc">
+ <li>If <i>time</i> is not finite, return <b>NaN</b>.</li>
+ <li>If <a href="#sec-algorithm-conventions">abs</a>(<i>time</i>) > 8.64 <span style="font-family:
+ sans-serif">×</span> 10<sup>15</sup>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-tointeger">ToInteger</a>(<i>time</i>) + (<b>+0</b>). (Adding a positive zero converts
+ <b>−0</b> to <b>+0</b>.)</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The point of step 3 is that an implementation is permitted a choice of internal
+ representations of time values, for example as a 64-bit signed integer or as a 64-bit floating-point value. Depending on
+ the implementation, this internal representation may or may not distinguish <b>−0</b> and <b>+0</b>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date-time-string-format">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.3.1.15"><a href="#sec-date-time-string-format"
+ title="link to this section">20.3.1.15</a></span> Date Time String Format</h1>
+
+ <p>ECMAScript defines a string interchange format for date-times based upon a simplification of the ISO 8601 Extended
+ Format. The format is as follows: <code>YYYY-MM-DDTHH:mm:ss.sss<i>Z</i></code></p>
+
+ <p>Where the fields are as follows:</p>
+
+ <p><code>YYYY</code>	<span style="font-family: sans-serif">is the decimal digits of the year 0000 to 9999 in the
+ Gregorian calendar.</span></p>
+
+ <p><code>-</code>	<span style="font-family: sans-serif">“</span><code>-</code><span style="font-family:
+ sans-serif">” (hyphen) appears literally twice in the string.</span></p>
+
+ <p><code>MM</code>	<span style="font-family: sans-serif">is the month of the year from 01 (January) to 12
+ (December).</span></p>
+
+ <p><code>DD</code>	<span style="font-family: sans-serif">is the day of the month from 01 to 31.</span></p>
+
+ <p><code>T</code>	<span style="font-family: sans-serif">“</span><code>T</code><span style="font-family:
+ sans-serif">” appears literally in the string, to indicate the beginning of the time element.</span></p>
+
+ <p><code>HH</code>	<span style="font-family: sans-serif">is the number of complete hours that have passed since
+ midnight as two decimal digits from 00 to 24.</span></p>
+
+ <p><code>:</code>	<span style="font-family: sans-serif">“</span><code>:</code><span style="font-family:
+ sans-serif">” (colon) appears literally twice in the string.</span></p>
+
+ <p><code>mm</code>	<span style="font-family: sans-serif">is the number of complete minutes since the start of the
+ hour as two decimal digits from 00 to 59.</span></p>
+
+ <p><code>ss</code>	<span style="font-family: sans-serif">is the number of complete seconds since the start of the
+ minute as two decimal digits from 00 to 59.</span></p>
+
+ <p><code>.</code>	<span style="font-family: sans-serif">“</span><code>.</code><span style="font-family:
+ sans-serif">” (dot) appears literally in the string.</span></p>
+
+ <p><code>sss</code>	<span style="font-family: sans-serif">is the number of complete milliseconds since the start of
+ the second as three decimal digits.</span></p>
+
+ <p><code>Z</code>	<span style="font-family: sans-serif">is the time zone offset specified as
+ “</span><code>Z</code><span style="font-family: sans-serif">” (for UTC) or either
+ “</span><code>+</code><span style="font-family: sans-serif">” or “</span><code>-</code><span
+ style="font-family: sans-serif">” followed by a time expression</span> <code>HH:mm</code></p>
+
+ <p>This format includes date-only forms:</p>
+
+ <pre>YYYY<br>YYYY-MM<br>YYYY-MM-DD</pre>
+
+ <p>It also includes “date-time” forms that consist of one of the above date-only forms immediately followed
+ by one of the following time forms with an optional time zone offset appended:</p>
+
+ <pre>THH:mm<br>THH:mm:ss<br>THH:mm:ss.sss</pre>
+
+ <p>All numbers must be base <span style="font-family: Times New Roman">10</span>. If the <code>MM</code> or
+ <code>DD</code> fields are absent “<code>01</code>” is used as the value. If the <code>HH</code>,
+ <code>mm</code>, or <code>ss</code> fields are absent “<code>00</code>” is used as the value and the value
+ of an absent <code>sss</code> field is “<code>000</code>”. If the time zone offset is absent, the date-time
+ is interpreted as a local time.</p>
+
+ <p>Illegal values (out-of-bounds as well as syntax errors) in a format string means that the format string is not a
+ valid instance of this format.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> As every day both starts and ends with midnight, the two notations
+ <code>00:00</code> and <code>24:00</code> are available to distinguish the two midnights that can be associated with
+ one date. This means that the following two notations refer to exactly the same point in time:
+ <code>1995-02-04T24:00</code> and <code>1995-02-05T00:00</code></p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> There exists no international standard that specifies abbreviations for civil time
+ zones like CET, EST, etc. and sometimes the same abbreviation is even used for two very different time zones. For this
+ reason, ISO 8601 and this format specifies numeric representations of date and time.</p>
+ </div>
+ </div>
+
+ <section id="sec-extended-years">
+ <h1><span class="secnum" id="sec-20.3.1.15.1"><a href="#sec-extended-years"
+ title="link to this section">20.3.1.15.1</a></span> Extended years</h1>
+
+ <p>ECMAScript requires the ability to specify <span style="font-family: Times New Roman">6</span> digit years (extended
+ years); approximately <span style="font-family: Times New Roman">285,426</span> years, either forward or backward, from
+ 01 January, 1970 UTC. To represent years before <span style="font-family: Times New Roman">0</span> or after <span
+ style="font-family: Times New Roman">9999</span>, ISO 8601 permits the expansion of the year representation, but only by
+ prior agreement between the sender and the receiver. In the simplified ECMAScript format such an expanded year
+ representation shall have <span style="font-family: Times New Roman">2</span> extra year digits and is always prefixed
+ with a + or – sign. The year <span style="font-family: Times New Roman">0</span> is considered positive and hence
+ prefixed with a + sign.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Examples of extended years:</p>
+
+ <p>-283457-03-21T15:00:59.008Z	283458 B.C.<span style="font-family: Times New
+ Roman"><br></span>-000001-01-01T00:00:00Z	2 B.C.<span style="font-family: Times New
+ Roman"><br></span>+000000-01-01T00:00:00Z	1 B.C.<span style="font-family: Times New
+ Roman"><br></span>+000001-01-01T00:00:00Z	1 A.D.<span style="font-family: Times New
+ Roman"><br></span>+001970-01-01T00:00:00Z	1970 A.D.<span style="font-family: Times New
+ Roman"><br></span>+002009-12-15T00:00:00Z	2009 A.D.<span style="font-family: Times New
+ Roman"><br></span>+287396-10-12T08:59:00.992Z	287396 A.D.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-date-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.3.2"><a href="#sec-date-constructor" title="link to this section">20.3.2</a></span>
+ The Date Constructor</h1>
+
+ <p>The Date constructor is the %Date% intrinsic object and the initial value of the <code>Date</code> property of the
+ global object. When called as a constructor it creates and initializes a new Date object. When <code>Date</code> is called
+ as a function rather than as a constructor, it returns a String representing the current time (UTC).</p>
+
+ <p>The <code>Date</code> constructor is a single function whose behaviour is overloaded based upon the number and types of
+ its arguments.</p>
+
+ <p>The <code>Date</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>Date</code> behaviour must include a <code>super</code> call to the <code>Date</code> constructor to create and
+ initialize the subclass instance with a [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </div>
+
+ <section id="sec-date-year-month-date-hours-minutes-seconds-ms">
+ <h1><span class="secnum" id="sec-20.3.2.1"><a href="#sec-date-year-month-date-hours-minutes-seconds-ms"
+ title="link to this section">20.3.2.1</a></span> Date ( year, month [, date [ , hours [ , minutes [ , seconds [ , ms ]
+ ] ] ] ] )</h1>
+
+ <p>This description applies only if the Date constructor is called with at least two arguments.</p>
+
+ <p>When the <code>Date</code> function is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>numberOfArgs</i> be the number of arguments passed to this function call.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numberOfArgs</i> ≥ 2.</li>
+ <li>If NewTarget is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>y</i> be <a href="#sec-tonumber">ToNumber</a>(<i>year</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>month</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>date</i> is supplied, let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>); else let
+ <i>dt</i> be <b>1</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dt</i>).</li>
+ <li>If <i>hours</i> is supplied, let <i>h</i> be <a href="#sec-tonumber">ToNumber</a>(<i>hours</i>); else let
+ <i>h</i> be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>h</i>).</li>
+ <li>If <i>minutes</i> is supplied, let <i>min</i> be <a href="#sec-tonumber">ToNumber</a>(<i>minutes</i>); else let
+ <i>min</i> be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>min</i>).</li>
+ <li>If <i>seconds</i> is supplied, let <i>s</i> be <a href="#sec-tonumber">ToNumber</a>(<i>seconds</i>); else let
+ <i>s</i> be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>s</i>).</li>
+ <li>If <i>ms</i> is supplied, let <i>milli</i> be <a href="#sec-tonumber">ToNumber</a>(<i>ms</i>); else let
+ <i>milli</i> be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>milli</i>).</li>
+ <li>If <i>y</i> is not <b>NaN</b> and 0 ≤ <a
+ href="#sec-tointeger">ToInteger</a>(<i>y</i>) ≤ 99, let <i>yr</i> be 1900+<a
+ href="#sec-tointeger">ToInteger</a>(<i>y</i>); otherwise, let <i>yr</i> be <i>y</i>.</li>
+ <li>Let <i>finalDate</i> be <a href="#sec-makedate">MakeDate</a>(<a href="#sec-makeday">MakeDay</a>(<i>yr</i>,
+ <i>m</i>, <i>dt</i>), <a href="#sec-maketime">MakeTime</a>(<i>h</i>, <i>min</i>, <i>s</i>, <i>milli</i>)).</li>
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%DatePrototype%"</code>, «‍ [[DateValue]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i> to
+ <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<i>finalDate</i>)).</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>now</i> be the Number that is the <a href="#sec-time-values-and-time-range">time value</a> (UTC)
+ identifying the current time.</li>
+ <li>Return <a href="#sec-todatestring">ToDateString</a> (<i>now</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-date-value">
+ <h1><span class="secnum" id="sec-20.3.2.2"><a href="#sec-date-value" title="link to this section">20.3.2.2</a></span> Date
+ ( value )</h1>
+
+ <p>This description applies only if the Date constructor is called with exactly one argument.</p>
+
+ <p>When the <code>Date</code> function is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>numberOfArgs</i> be the number of arguments passed to this function call.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numberOfArgs</i> = 1.</li>
+ <li>If NewTarget is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object and <i>value</i> has a
+ [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li>Let <i>tv</i> be thisTimeValue(<i>value</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>value</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>v</i>) is String, then
+ <ol class="block">
+ <li>Let <i>tv</i> be the result of parsing <i>v</i> as a date, in exactly the same manner as for the
+ <code>parse</code> method (<a href="#sec-date.parse">20.3.3.2</a>). If the parse resulted in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>, <i>tv</i> is the <a
+ href="#sec-completion-record-specification-type">Completion Record</a>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>tv</i> be <a href="#sec-tonumber">ToNumber</a>(<i>v</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>tv</i>).</li>
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%DatePrototype%"</code>, «‍ [[DateValue]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i> to
+ <a href="#sec-timeclip">TimeClip</a>(<i>tv</i>).</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>now</i> be the Number that is the <a href="#sec-time-values-and-time-range">time value</a> (UTC)
+ identifying the current time.</li>
+ <li>Return <a href="#sec-todatestring">ToDateString</a> (<i>now</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-date-constructor-date">
+ <h1><span class="secnum" id="sec-20.3.2.3"><a href="#sec-date-constructor-date"
+ title="link to this section">20.3.2.3</a></span> Date ( )</h1>
+
+ <p>This description applies only if the Date constructor is called with no arguments.</p>
+
+ <p>When the <code>Date</code> function is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>numberOfArgs</i> be the number of arguments passed to this function call.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numberOfArgs</i> = 0.</li>
+ <li>If NewTarget is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%DatePrototype%"</code>, «‍ [[DateValue]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i> to
+ the <a href="#sec-time-values-and-time-range">time value</a> (UTC) identifying the current time.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>now</i> be the Number that is the <a href="#sec-time-values-and-time-range">time value</a> (UTC)
+ identifying the current time.</li>
+ <li>Return <a href="#sec-todatestring">ToDateString</a> (<i>now</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-date-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.3.3"><a href="#sec-properties-of-the-date-constructor"
+ title="link to this section">20.3.3</a></span> Properties of the Date Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Date
+ constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <code>7</code>), the Date constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-date.now">
+ <h1><span class="secnum" id="sec-20.3.3.1"><a href="#sec-date.now" title="link to this section">20.3.3.1</a></span>
+ Date.now ( )</h1>
+
+ <p>The <code>now</code> function return a Number value that is the <a href="#sec-time-values-and-time-range">time
+ value</a> designating the UTC date and time of the occurrence of the call to <code>now</code>.</p>
+ </section>
+
+ <section id="sec-date.parse">
+ <h1><span class="secnum" id="sec-20.3.3.2"><a href="#sec-date.parse" title="link to this section">20.3.3.2</a></span>
+ Date.parse ( string )</h1>
+
+ <p>The <code>parse</code> function applies the <a href="#sec-tostring">ToString</a> operator to its argument. If <a
+ href="#sec-tostring">ToString</a> results in an <a href="#sec-completion-record-specification-type">abrupt completion</a>
+ the <a href="#sec-completion-record-specification-type">Completion Record</a> is immediately returned. Otherwise,
+ <code>parse</code> interprets the resulting String as a date and time; it returns a Number, the UTC <a
+ href="#sec-time-values-and-time-range">time value</a> corresponding to the date and time. The String may be interpreted as
+ a local time, a UTC time, or a time in some other time zone, depending on the contents of the String. The function first
+ attempts to parse the format of the String according to the rules (including extended years) called out in Date Time
+ String Format (<a href="#sec-date-time-string-format">20.3.1.15</a>). If the String does not conform to that format the
+ function may fall back to any implementation-specific heuristics or implementation-specific date formats. Unrecognizable
+ Strings or dates containing illegal element values in the format String shall cause <code>Date.parse</code> to return
+ <b>NaN</b>.</p>
+
+ <p>If <var>x</var> is any Date object whose milliseconds amount is zero within a particular implementation of ECMAScript,
+ then all of the following expressions should produce the same numeric value in that implementation, if all the properties
+ referenced have their initial values:</p>
+
+ <pre><i>x</i>.valueOf()</pre>
+ <pre>Date.parse(<i>x</i>.toString())</pre>
+ <pre>Date.parse(<i>x</i>.toUTCString())</pre>
+ <pre>Date.parse(<i>x</i>.toISOString())</pre>
+
+ <p>However, the expression</p>
+
+ <pre>Date.parse(<i>x</i>.toLocaleString())</pre>
+
+ <p>is not required to produce the same Number value as the preceding three expressions and, in general, the value produced
+ by <code>Date.parse</code> is implementation-dependent when given any String value that does not conform to the Date Time
+ String Format (<a href="#sec-date-time-string-format">20.3.1.15</a>) and that could not be produced in that implementation
+ by the <code>toString</code> or <code>toUTCString</code> method.</p>
+ </section>
+
+ <section id="sec-date.prototype">
+ <h1><span class="secnum" id="sec-20.3.3.3"><a href="#sec-date.prototype" title="link to this section">20.3.3.3</a></span>
+ Date.prototype</h1>
+
+ <p>The initial value of <code>Date.prototype</code> is the intrinsic object %DatePrototype% (<a
+ href="#sec-properties-of-the-date-prototype-object">20.3.4</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-date.utc">
+ <h1><span class="secnum" id="sec-20.3.3.4"><a href="#sec-date.utc" title="link to this section">20.3.3.4</a></span>
+ Date.UTC ( year, month [ , date [ , hours [ , minutes [ , seconds [ , ms ] ] ] ] ] )</h1>
+
+ <p>When the <code>UTC</code> function is called with fewer than two arguments, the behaviour is implementation-dependent.
+ When the <code>UTC</code> function is called with two to seven arguments, it computes the date from <var>year</var>,
+ <var>month</var> and (optionally) <var>date</var>, <var>hours</var>, <var>minutes</var>, <var>seconds</var> and
+ <var>ms</var>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>y</i> be <a href="#sec-tonumber">ToNumber</a>(<i>year</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>month</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>date</i> is supplied, let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>); else let <i>dt</i>
+ be <b>1</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dt</i>).</li>
+ <li>If <i>hours</i> is supplied, let <i>h</i> be <a href="#sec-tonumber">ToNumber</a>(<i>hours</i>); else let <i>h</i>
+ be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>h</i>).</li>
+ <li>If <i>minutes</i> is supplied, let <i>min</i> be <a href="#sec-tonumber">ToNumber</a>(<i>minutes</i>); else let
+ <i>min</i> be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>min</i>).</li>
+ <li>If <i>seconds</i> is supplied, let <i>s</i> be <a href="#sec-tonumber">ToNumber</a>(<i>seconds</i>); else let
+ <i>s</i> be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>s</i>).</li>
+ <li>If <i>ms</i> is supplied, let <i>milli</i> be <a href="#sec-tonumber">ToNumber</a>(<i>ms</i>); else let <i>milli</i>
+ be <b>0</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>milli</i>).</li>
+ <li>If <i>y</i> is not <b>NaN</b> and 0 ≤ <a
+ href="#sec-tointeger">ToInteger</a>(<i>y</i>) ≤ 99, let <i>yr</i> be 1900+<a
+ href="#sec-tointeger">ToInteger</a>(<i>y</i>); otherwise, let <i>yr</i> be <i>y</i>.</li>
+ <li>Return <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-makeday">MakeDay</a>(<i>yr</i>, <i>m</i>, <i>dt</i>), <a href="#sec-maketime">MakeTime</a>(<i>h</i>,
+ <i>min</i>, <i>s</i>, <i>milli</i>))).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>UTC</code> function is <b>7</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>UTC</code> function differs from the <code>Date</code> constructor in two
+ ways: it returns a <a href="#sec-time-values-and-time-range">time value</a> as a Number, rather than creating a Date
+ object, and it interprets the arguments in UTC rather than as local time.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-date-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.3.4"><a href="#sec-properties-of-the-date-prototype-object"
+ title="link to this section">20.3.4</a></span> Properties of the Date Prototype Object</h1>
+
+ <p>The Date prototype object is the intrinsic object %DatePrototype%. The Date prototype object is itself an ordinary
+ object. It is not a Date instance and does not have a [[DateValue]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Date
+ prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-date-prototype-object">20.3.4</a>).</p>
+
+ <p>Unless explicitly defined otherwise, the methods of the Date prototype object defined below are not generic and the
+ <b>this</b> value passed to them must be an object that has a [[DateValue]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> that has been initialized to a <a
+ href="#sec-time-values-and-time-range">time value</a>.</p>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">thisTimeValue(<i>value</i>)</span> performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object and <i>value</i> has a
+ [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li>Return the value of <i>value’s</i> [[DateValue]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+
+ <p>In following descriptions of functions that are properties of the Date prototype object, the phrase “this Date
+ object” refers to the object that is the <b>this</b> value for the invocation of the function. If the Type of the
+ <b>this</b> value is not Object, a <span class="value">TypeError</span> exception is thrown. The phrase “this <a
+ href="#sec-time-values-and-time-range">time value</a>” within the specification of a method refers to the result
+ returned by calling the abstract operation thisTimeValue with the <b>this</b> value of the method invocation passed as
+ the argument.</p>
+ </div>
+
+ <section id="sec-date.prototype.constructor">
+ <h1><span class="secnum" id="sec-20.3.4.1"><a href="#sec-date.prototype.constructor"
+ title="link to this section">20.3.4.1</a></span> Date.prototype.constructor</h1>
+
+ <p>The initial value of <code>Date.prototype.constructor</code> is the intrinsic object %Date%.</p>
+ </section>
+
+ <section id="sec-date.prototype.getdate">
+ <h1><span class="secnum" id="sec-20.3.4.2"><a href="#sec-date.prototype.getdate"
+ title="link to this section">20.3.4.2</a></span> Date.prototype.getDate ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-date-number">DateFromTime</a>(<a href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getday">
+ <h1><span class="secnum" id="sec-20.3.4.3"><a href="#sec-date.prototype.getday"
+ title="link to this section">20.3.4.3</a></span> Date.prototype.getDay ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-week-day">WeekDay</a>(<a href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getfullyear">
+ <h1><span class="secnum" id="sec-20.3.4.4"><a href="#sec-date.prototype.getfullyear"
+ title="link to this section">20.3.4.4</a></span> Date.prototype.getFullYear ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-year-number">YearFromTime</a>(<a href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.gethours">
+ <h1><span class="secnum" id="sec-20.3.4.5"><a href="#sec-date.prototype.gethours"
+ title="link to this section">20.3.4.5</a></span> Date.prototype.getHours ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<a
+ href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getmilliseconds">
+ <h1><span class="secnum" id="sec-20.3.4.6"><a href="#sec-date.prototype.getmilliseconds"
+ title="link to this section">20.3.4.6</a></span> Date.prototype.getMilliseconds ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<a
+ href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getminutes">
+ <h1><span class="secnum" id="sec-20.3.4.7"><a href="#sec-date.prototype.getminutes"
+ title="link to this section">20.3.4.7</a></span> Date.prototype.getMinutes ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<a
+ href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getmonth">
+ <h1><span class="secnum" id="sec-20.3.4.8"><a href="#sec-date.prototype.getmonth"
+ title="link to this section">20.3.4.8</a></span> Date.prototype.getMonth ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-month-number">MonthFromTime</a>(<a href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getseconds">
+ <h1><span class="secnum" id="sec-20.3.4.9"><a href="#sec-date.prototype.getseconds"
+ title="link to this section">20.3.4.9</a></span> Date.prototype.getSeconds ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<a
+ href="#sec-local-time">LocalTime</a>(<i>t</i>)).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.gettime">
+ <h1><span class="secnum" id="sec-20.3.4.10"><a href="#sec-date.prototype.gettime"
+ title="link to this section">20.3.4.10</a></span> Date.prototype.getTime ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.gettimezoneoffset">
+ <h1><span class="secnum" id="sec-20.3.4.11"><a href="#sec-date.prototype.gettimezoneoffset"
+ title="link to this section">20.3.4.11</a></span> Date.prototype.getTimezoneOffset ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return (<i>t</i> − <a href="#sec-local-time">LocalTime</a>(<i>t</i>)) / <a
+ href="#sec-hours-minutes-second-and-milliseconds">msPerMinute</a>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutcdate">
+ <h1><span class="secnum" id="sec-20.3.4.12"><a href="#sec-date.prototype.getutcdate"
+ title="link to this section">20.3.4.12</a></span> Date.prototype.getUTCDate ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-date-number">DateFromTime</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutcday">
+ <h1><span class="secnum" id="sec-20.3.4.13"><a href="#sec-date.prototype.getutcday"
+ title="link to this section">20.3.4.13</a></span> Date.prototype.getUTCDay ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-week-day">WeekDay</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutcfullyear">
+ <h1><span class="secnum" id="sec-20.3.4.14"><a href="#sec-date.prototype.getutcfullyear"
+ title="link to this section">20.3.4.14</a></span> Date.prototype.getUTCFullYear ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-year-number">YearFromTime</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutchours">
+ <h1><span class="secnum" id="sec-20.3.4.15"><a href="#sec-date.prototype.getutchours"
+ title="link to this section">20.3.4.15</a></span> Date.prototype.getUTCHours ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutcmilliseconds">
+ <h1><span class="secnum" id="sec-20.3.4.16"><a href="#sec-date.prototype.getutcmilliseconds"
+ title="link to this section">20.3.4.16</a></span> Date.prototype.getUTCMilliseconds ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutcminutes">
+ <h1><span class="secnum" id="sec-20.3.4.17"><a href="#sec-date.prototype.getutcminutes"
+ title="link to this section">20.3.4.17</a></span> Date.prototype.getUTCMinutes ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutcmonth">
+ <h1><span class="secnum" id="sec-20.3.4.18"><a href="#sec-date.prototype.getutcmonth"
+ title="link to this section">20.3.4.18</a></span> Date.prototype.getUTCMonth ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.getutcseconds">
+ <h1><span class="secnum" id="sec-20.3.4.19"><a href="#sec-date.prototype.getutcseconds"
+ title="link to this section">20.3.4.19</a></span> Date.prototype.getUTCSeconds ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<i>t</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.setdate">
+ <h1><span class="secnum" id="sec-20.3.4.20"><a href="#sec-date.prototype.setdate"
+ title="link to this section">20.3.4.20</a></span> Date.prototype.setDate ( date )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-local-time">LocalTime</a>(<a href="#sec-properties-of-the-date-prototype-object">this
+ time value</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dt</i>).</li>
+ <li>Let <i>newDate</i> be <a href="#sec-makedate">MakeDate</a>(<a href="#sec-makeday">MakeDay</a>(<a
+ href="#sec-year-number">YearFromTime</a>(<i>t</i>), <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>),
+ <i>dt</i>), <a href="#sec-day-number-and-time-within-day">TimeWithinDay</a>(<i>t</i>)).</li>
+ <li>Let <i>u</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<i>newDate</i>)).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>u</i>.</li>
+ <li>Return <i>u</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.setfullyear">
+ <h1><span class="secnum" id="sec-20.3.4.21"><a href="#sec-date.prototype.setfullyear"
+ title="link to this section">20.3.4.21</a></span> Date.prototype.setFullYear ( year [ , month [ , date ] ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, let <i>t</i> be <b>+0</b>; otherwise, let <i>t</i> be <a
+ href="#sec-local-time">LocalTime</a>(<i>t</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>y</i> be <a href="#sec-tonumber">ToNumber</a>(<i>year</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>If <i>month</i> is not specified, let <i>m</i> be <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>);
+ otherwise, let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>month</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>date</i> is not specified, let <i>dt</i> be <a href="#sec-date-number">DateFromTime</a>(<i>t</i>); otherwise,
+ let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dt</i>).</li>
+ <li>Let <i>newDate</i> be <a href="#sec-makedate">MakeDate</a>(<a href="#sec-makeday">MakeDay</a>(<i>y</i>, <i>m</i>,
+ <i>dt</i>), <a href="#sec-day-number-and-time-within-day">TimeWithinDay</a>(<i>t</i>)).</li>
+ <li>Let <i>u</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<i>newDate</i>)).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>u</i>.</li>
+ <li>Return <i>u</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setFullYear</code> method is <b>3</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>month</i> is not specified, this method behaves as if <i>month</i> were specified
+ with the value <code>getMonth()</code>. If <i>date</i> is not specified, it behaves as if <i>date</i> were specified
+ with the value <code>getDate()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.sethours">
+ <h1><span class="secnum" id="sec-20.3.4.22"><a href="#sec-date.prototype.sethours"
+ title="link to this section">20.3.4.22</a></span> Date.prototype.setHours ( hour [ , min [ , sec [ , ms ] ] ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-local-time">LocalTime</a>(<a href="#sec-properties-of-the-date-prototype-object">this
+ time value</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>h</i> be <a href="#sec-tonumber">ToNumber</a>(<i>hour</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>h</i>).</li>
+ <li>If <i>min</i> is not specified, let <i>m</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<i>t</i>); otherwise, let <i>m</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>min</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>sec</i> is not specified, let <i>s</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<i>t</i>); otherwise, let <i>s</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>sec</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>s</i>).</li>
+ <li>If <i>ms</i> is not specified, let <i>milli</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<i>t</i>); otherwise, let <i>milli</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>milli</i>).</li>
+ <li>Let <i>date</i> be <a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>), <a href="#sec-maketime">MakeTime</a>(<i>h</i>,
+ <i>m</i>, <i>s</i>, <i>milli</i>)).</li>
+ <li>Let <i>u</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<i>date</i>)).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>u</i>.</li>
+ <li>Return <i>u</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setHours</code> method is <b>4</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>min</i> is not specified, this method behaves as if <i>min</i> were specified with
+ the value <code>getMinutes()</code>. If <i>sec</i> is not specified, it behaves as if <i>sec</i> were specified with the
+ value <code>getSeconds()</code>. If <i>ms</i> is not specified, it behaves as if <i>ms</i> were specified with the value
+ <code>getMilliseconds()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.setmilliseconds">
+ <h1><span class="secnum" id="sec-20.3.4.23"><a href="#sec-date.prototype.setmilliseconds"
+ title="link to this section">20.3.4.23</a></span> Date.prototype.setMilliseconds ( ms )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-local-time">LocalTime</a>(<a href="#sec-properties-of-the-date-prototype-object">this
+ time value</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>ms</i> be <a href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ms</i>).</li>
+ <li>Let <i>time</i> be <a href="#sec-maketime">MakeTime</a>(<a
+ href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<i>t</i>), <a
+ href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<i>t</i>), <a
+ href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<i>t</i>), <i>ms</i>).</li>
+ <li>Let <i>u</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<a
+ href="#sec-makedate">MakeDate</a>(<a href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>),
+ <i>time</i>))).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>u</i>.</li>
+ <li>Return <i>u</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.setminutes">
+ <h1><span class="secnum" id="sec-20.3.4.24"><a href="#sec-date.prototype.setminutes"
+ title="link to this section">20.3.4.24</a></span> Date.prototype.setMinutes ( min [ , sec [ , ms ] ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-local-time">LocalTime</a>(<a href="#sec-properties-of-the-date-prototype-object">this
+ time value</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>min</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>sec</i> is not specified, let <i>s</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<i>t</i>); otherwise, let <i>s</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>sec</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>s</i>).</li>
+ <li>If <i>ms</i> is not specified, let <i>milli</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<i>t</i>); otherwise, let <i>milli</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>milli</i>).</li>
+ <li>Let <i>date</i> be <a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>), <a href="#sec-maketime">MakeTime</a>(<a
+ href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<i>t</i>), <i>m</i>, <i>s</i>,
+ <i>milli</i>)).</li>
+ <li>Let <i>u</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<i>date</i>)).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>u</i>.</li>
+ <li>Return <i>u</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setMinutes</code> method is <b>3</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>sec</i> is not specified, this method behaves as if <i>sec</i> were specified with
+ the value <code>getSeconds()</code>. If <i>ms</i> is not specified, this behaves as if <i>ms</i> were specified with the
+ value <code>getMilliseconds()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.setmonth">
+ <h1><span class="secnum" id="sec-20.3.4.25"><a href="#sec-date.prototype.setmonth"
+ title="link to this section">20.3.4.25</a></span> Date.prototype.setMonth ( month [ , date ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-local-time">LocalTime</a>(<a href="#sec-properties-of-the-date-prototype-object">this
+ time value</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>month</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>date</i> is not specified, let <i>dt</i> be <a href="#sec-date-number">DateFromTime</a>(<i>t</i>); otherwise,
+ let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dt</i>).</li>
+ <li>Let <i>newDate</i> be <a href="#sec-makedate">MakeDate</a>(<a href="#sec-makeday">MakeDay</a>(<a
+ href="#sec-year-number">YearFromTime</a>(<i>t</i>), <i>m</i>, <i>dt</i>), <a
+ href="#sec-day-number-and-time-within-day">TimeWithinDay</a>(<i>t</i>)).</li>
+ <li>Let <i>u</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<i>newDate</i>)).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>u</i>.</li>
+ <li>Return <i>u</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setMonth</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>date</i> is not specified, this method behaves as if <i>date</i> were specified
+ with the value <code>getDate()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.setseconds">
+ <h1><span class="secnum" id="sec-20.3.4.26"><a href="#sec-date.prototype.setseconds"
+ title="link to this section">20.3.4.26</a></span> Date.prototype.setSeconds ( sec [ , ms ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-local-time">LocalTime</a>(<a href="#sec-properties-of-the-date-prototype-object">this
+ time value</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>s</i> be <a href="#sec-tonumber">ToNumber</a>(<i>sec</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>s</i>).</li>
+ <li>If <i>ms</i> is not specified, let <i>milli</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<i>t</i>); otherwise, let <i>milli</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>milli</i>).</li>
+ <li>Let <i>date</i> be <a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>), <a href="#sec-maketime">MakeTime</a>(<a
+ href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<i>t</i>), <a
+ href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<i>t</i>), <i>s</i>, <i>milli</i>)).</li>
+ <li>Let <i>u</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-local-time">UTC</a>(<i>date</i>)).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>u</i>.</li>
+ <li>Return <i>u</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setSeconds</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>ms</i> is not specified, this method behaves as if <i>ms</i> were specified with
+ the value <code>getMilliseconds()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.settime">
+ <h1><span class="secnum" id="sec-20.3.4.27"><a href="#sec-date.prototype.settime"
+ title="link to this section">20.3.4.27</a></span> Date.prototype.setTime ( time )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object or <i>O</i> does not have a
+ [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, throw a <b>TypeError</b>
+ exeption.</li>
+ <li>Let <i>t</i> be <a href="#sec-tonumber">ToNumber</a>(<i>time</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<i>t</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i> to
+ <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.setutcdate">
+ <h1><span class="secnum" id="sec-20.3.4.28"><a href="#sec-date.prototype.setutcdate"
+ title="link to this section">20.3.4.28</a></span> Date.prototype.setUTCDate ( date )</h1>
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dt</i>).</li>
+ <li>Let <i>newDate</i> be <a href="#sec-makedate">MakeDate</a>(<a href="#sec-makeday">MakeDay</a>(<a
+ href="#sec-year-number">YearFromTime</a>(<i>t</i>), <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>),
+ <i>dt</i>), <a href="#sec-day-number-and-time-within-day">TimeWithinDay</a>(<i>t</i>)).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<i>newDate</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.setutcfullyear">
+ <h1><span class="secnum" id="sec-20.3.4.29"><a href="#sec-date.prototype.setutcfullyear"
+ title="link to this section">20.3.4.29</a></span> Date.prototype.setUTCFullYear ( year [ , month [ , date ] ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, let <i>t</i> be <b>+0</b>.</li>
+ <li>Let <i>y</i> be <a href="#sec-tonumber">ToNumber</a>(<i>year</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>If <i>month</i> is not specified, let <i>m</i> be <a href="#sec-month-number">MonthFromTime</a>(<i>t</i>);
+ otherwise, let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>month</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>date</i> is not specified, let <i>dt</i> be <a href="#sec-date-number">DateFromTime</a>(<i>t</i>); otherwise,
+ let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dt</i>).</li>
+ <li>Let <i>newDate</i> be <a href="#sec-makedate">MakeDate</a>(<a href="#sec-makeday">MakeDay</a>(<i>y</i>, <i>m</i>,
+ <i>dt</i>), <a href="#sec-day-number-and-time-within-day">TimeWithinDay</a>(<i>t</i>)).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<i>newDate</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setUTCFullYear</code> method is <b>3</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>month</i> is not specified, this method behaves as if <i>month</i> were specified
+ with the value <code>getUTCMonth()</code>. If <i>date</i> is not specified, it behaves as if <i>date</i> were specified
+ with the value <code>getUTCDate()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.setutchours">
+ <h1><span class="secnum" id="sec-20.3.4.30"><a href="#sec-date.prototype.setutchours"
+ title="link to this section">20.3.4.30</a></span> Date.prototype.setUTCHours ( hour [ , min [ , sec [ , ms ] ] ]
+ )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>h</i> be <a href="#sec-tonumber">ToNumber</a>(<i>hour</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>h</i>).</li>
+ <li>If <i>min</i> is not specified, let <i>m</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<i>t</i>); otherwise, let <i>m</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>min</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>m</i>).</li>
+ <li>If <i>sec</i> is not specified, let <i>s</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<i>t</i>); otherwise, let <i>s</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>sec</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>s</i>).</li>
+ <li>If <i>ms</i> is not specified, let <i>milli</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<i>t</i>); otherwise, let <i>milli</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>milli</i>).</li>
+ <li>Let <i>newDate</i> be <a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>), <a href="#sec-maketime">MakeTime</a>(<i>h</i>,
+ <i>m</i>, <i>s</i>, <i>milli</i>)).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<i>newDate</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setUTCHours</code> method is <b>4</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>min</i> is not specified, this method behaves as if <i>min</i> were specified with
+ the value <code>getUTCMinutes()</code>. If <i>sec</i> is not specified, it behaves as if <i>sec</i> were specified with
+ the value <code>getUTCSeconds()</code>. If <i>ms</i> is not specified, it behaves as if <i>ms</i> were specified with
+ the value <code>getUTCMilliseconds()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.setutcmilliseconds">
+ <h1><span class="secnum" id="sec-20.3.4.31"><a href="#sec-date.prototype.setutcmilliseconds"
+ title="link to this section">20.3.4.31</a></span> Date.prototype.setUTCMilliseconds ( ms )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>milli</i> be <a href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>milli</i>).</li>
+ <li>Let <i>time</i> be <a href="#sec-maketime">MakeTime</a>(<a
+ href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<i>t</i>), <a
+ href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<i>t</i>), <a
+ href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<i>t</i>), <i>milli</i>).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>), <i>time</i>)).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.setutcminutes">
+ <h1><span class="secnum" id="sec-20.3.4.32"><a href="#sec-date.prototype.setutcminutes"
+ title="link to this section">20.3.4.32</a></span> Date.prototype.setUTCMinutes ( min [ , sec [, ms ] ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>min</i>).</li>
+ <li>If <i>sec</i> is not specified, let <i>s</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">SecFromTime</a>(<i>t</i>); otherwise, let <i>s</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>sec</i>).</li>
+ <li>If <i>ms</i> is not specified, let <i>milli</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<i>t</i>); otherwise, let <i>milli</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li>Let <i>date</i> be <a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>), <a href="#sec-maketime">MakeTime</a>(<a
+ href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<i>t</i>), <i>m</i>, <i>s</i>,
+ <i>milli</i>)).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<i>date</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setUTCMinutes</code> method is <b>3</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>sec</i> is not specified, this method behaves as if <i>sec</i> were specified with
+ the value <code>getUTCSeconds()</code>. If <i>ms</i> is not specified, it function behaves as if <i>ms</i> were
+ specified with the value return by <code>getUTCMilliseconds()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.setutcmonth">
+ <h1><span class="secnum" id="sec-20.3.4.33"><a href="#sec-date.prototype.setutcmonth"
+ title="link to this section">20.3.4.33</a></span> Date.prototype.setUTCMonth ( month [ , date ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>m</i> be <a href="#sec-tonumber">ToNumber</a>(<i>month</i>).</li>
+ <li>If <i>date</i> is not specified, let <i>dt</i> be <a href="#sec-date-number">DateFromTime</a>(<i>t</i>); otherwise,
+ let <i>dt</i> be <a href="#sec-tonumber">ToNumber</a>(<i>date</i>).</li>
+ <li>Let <i>newDate</i> be <a href="#sec-makedate">MakeDate</a>(<a href="#sec-makeday">MakeDay</a>(<a
+ href="#sec-year-number">YearFromTime</a>(<i>t</i>), <i>m</i>, <i>dt</i>), <a
+ href="#sec-day-number-and-time-within-day">TimeWithinDay</a>(<i>t</i>)).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<i>newDate</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setUTCMonth</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>date</i> is not specified, this method behaves as if <i>date</i> were specified
+ with the value <code>getUTCDate()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.setutcseconds">
+ <h1><span class="secnum" id="sec-20.3.4.34"><a href="#sec-date.prototype.setutcseconds"
+ title="link to this section">20.3.4.34</a></span> Date.prototype.setUTCSeconds ( sec [ , ms ] )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>Let <i>s</i> be <a href="#sec-tonumber">ToNumber</a>(<i>sec</i>).</li>
+ <li>If <i>ms</i> is not specified, let <i>milli</i> be <a
+ href="#sec-hours-minutes-second-and-milliseconds">msFromTime</a>(<i>t</i>); otherwise, let <i>milli</i> be <a
+ href="#sec-tonumber">ToNumber</a>(<i>ms</i>).</li>
+ <li>Let <i>date</i> be <a href="#sec-makedate">MakeDate</a>(<a
+ href="#sec-day-number-and-time-within-day">Day</a>(<i>t</i>), <a href="#sec-maketime">MakeTime</a>(<a
+ href="#sec-hours-minutes-second-and-milliseconds">HourFromTime</a>(<i>t</i>), <a
+ href="#sec-hours-minutes-second-and-milliseconds">MinFromTime</a>(<i>t</i>), <i>s</i>, <i>milli</i>)).</li>
+ <li>Let <i>v</i> be <a href="#sec-timeclip">TimeClip</a>(<i>date</i>).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <i>v</i>.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>setUTCSeconds</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>ms</i> is not specified, this method behaves as if <i>ms</i> were specified with
+ the value <code>getUTCMilliseconds()</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.todatestring">
+ <h1><span class="secnum" id="sec-20.3.4.35"><a href="#sec-date.prototype.todatestring"
+ title="link to this section">20.3.4.35</a></span> Date.prototype.toDateString ( )</h1>
+
+ <p>This function returns a String value. The contents of the String are implementation-dependent, but are intended to
+ represent the “date” portion of the Date in the current time zone in a convenient, human-readable form.</p>
+ </section>
+
+ <section id="sec-date.prototype.toisostring">
+ <h1><span class="secnum" id="sec-20.3.4.36"><a href="#sec-date.prototype.toisostring"
+ title="link to this section">20.3.4.36</a></span> Date.prototype.toISOString ( )</h1>
+
+ <p>This function returns a String value representing the instance in time corresponding to <a
+ href="#sec-properties-of-the-date-prototype-object">this time value</a>. The format of the String is the Date Time string
+ format defined in <a href="#sec-date-time-string-format">20.3.1.15</a>. All fields are present in the String. The time
+ zone is always UTC, denoted by the suffix Z. If <a href="#sec-properties-of-the-date-prototype-object">this time value</a>
+ is not a finite Number or if the year is not a value that can be represented in that format (if necessary using extended
+ year format), a <b>RangeError</b> exception is thrown.</p>
+ </section>
+
+ <section id="sec-date.prototype.tojson">
+ <h1><span class="secnum" id="sec-20.3.4.37"><a href="#sec-date.prototype.tojson"
+ title="link to this section">20.3.4.37</a></span> Date.prototype.toJSON ( key )</h1>
+
+ <p>This function provides a String representation of a Date object for use by <code><a
+ href="#sec-json.stringify">JSON.stringify</a></code> (<a href="#sec-json.stringify">24.3.2</a>).</p>
+
+ <p>When the <code>toJSON</code> method is called with argument <var>key</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li>Let <i>tv</i> be <a href="#sec-toprimitive">ToPrimitive</a>(<i>O</i>, hint Number).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>tv</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>tv</i>) is Number and <i>tv</i> is not finite, return
+ <b>null</b>.</li>
+ <li>Return <a href="#sec-invoke">Invoke</a>(<i>O</i>, <code>"toISOString"</code>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The argument is ignored.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>toJSON</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a Date object. Therefore, it can be transferred to other kinds of objects for use as a method.
+ However, it does require that any such object have a <code>toISOString</code> method.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.tolocaledatestring">
+ <h1><span class="secnum" id="sec-20.3.4.38"><a href="#sec-date.prototype.tolocaledatestring"
+ title="link to this section">20.3.4.38</a></span> Date.prototype.toLocaleDateString ( [ reserved1 [ , reserved2 ] ]
+ )</h1>
+
+ <p>An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the
+ <code>Date.prototype.toLocaleDateString</code> method as specified in the ECMA-402 specification. If an ECMAScript
+ implementation does not include the ECMA-402 API the following specification of the <code>toLocaleDateString</code>
+ method is used.</p>
+
+ <p>This function returns a String value. The contents of the String are implementation-dependent, but are intended to
+ represent the “date” portion of the Date in the current time zone in a convenient, human-readable form that
+ corresponds to the conventions of the host environment’s current locale.</p>
+
+ <p>The meaning of the optional parameters to this method are defined in the ECMA-402 specification; implementations that
+ do not include ECMA-402 support must not use those parameter positions for anything else.</p>
+
+ <p>The <code>length</code> property of the <code>toLocaleDateString</code> method is <b>0</b>.</p>
+ </section>
+
+ <section id="sec-date.prototype.tolocalestring">
+ <h1><span class="secnum" id="sec-20.3.4.39"><a href="#sec-date.prototype.tolocalestring"
+ title="link to this section">20.3.4.39</a></span> Date.prototype.toLocaleString ( [ reserved1 [ , reserved2 ] ] )</h1>
+
+ <p>An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the
+ <code>Date.prototype.toLocaleString</code> method as specified in the ECMA-402 specification. If an ECMAScript
+ implementation does not include the ECMA-402 API the following specification of the <code>toLocaleString</code> method is
+ used.</p>
+
+ <p>This function returns a String value. The contents of the String are implementation-dependent, but are intended to
+ represent the Date in the current time zone in a convenient, human-readable form that corresponds to the conventions of
+ the host environment’s current locale.</p>
+
+ <p>The meaning of the optional parameters to this method are defined in the ECMA-402 specification; implementations that
+ do not include ECMA-402 support must not use those parameter positions for anything else.</p>
+
+ <p>The <code>length</code> property of the <code>toLocaleString</code> method is <b>0</b>.</p>
+ </section>
+
+ <section id="sec-date.prototype.tolocaletimestring">
+ <h1><span class="secnum" id="sec-20.3.4.40"><a href="#sec-date.prototype.tolocaletimestring"
+ title="link to this section">20.3.4.40</a></span> Date.prototype.toLocaleTimeString ( [ reserved1 [ , reserved2 ] ]
+ )</h1>
+
+ <p>An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the
+ <code>Date.prototype.toLocaleTimeString</code> method as specified in the ECMA-402 specification. If an ECMAScript
+ implementation does not include the ECMA-402 API the following specification of the <code>toLocaleString</code> method is
+ used.</p>
+
+ <p>This function returns a String value. The contents of the String are implementation-dependent, but are intended to
+ represent the “time” portion of the Date in the current time zone in a convenient, human-readable form that
+ corresponds to the conventions of the host environment’s current locale.</p>
+
+ <p>The meaning of the optional parameters to this method are defined in the ECMA-402 specification; implementations that
+ do not include ECMA-402 support must not use those parameter positions for anything else.</p>
+
+ <p>The <code>length</code> property of the <code>toLocaleTimeString</code> method is <b>0</b>.</p>
+ </section>
+
+ <section id="sec-date.prototype.tostring">
+ <div class="front">
+ <h1><span class="secnum" id="sec-20.3.4.41"><a href="#sec-date.prototype.tostring"
+ title="link to this section">20.3.4.41</a></span> Date.prototype.toString ( )</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be this Date object.</li>
+ <li>If <i>O</i> does not have a [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, then
+ <ol class="block">
+ <li>Let <i>tv</i> be NaN.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>tv</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-todatestring">ToDateString</a>(<i>tv</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For any Date object <span style="font-family: monospace"><i>d</i></span> whose
+ milliseconds amount is zero, the result of <code><a href="#sec-date.parse">Date.parse</a>(<i>d</i>.toString())</code>
+ is equal to <code><i>d</i>.valueOf()</code>. See <a href="#sec-date.parse">20.3.3.2</a>.</p>
+ </div>
+ </div>
+
+ <section id="sec-todatestring">
+ <h1><span class="secnum" id="sec-20.3.4.41.1"><a href="#sec-todatestring"
+ title="link to this section">20.3.4.41.1</a></span> Runtime Semantics: ToDateString(tv)</h1>
+
+ <p>The following steps are performed:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>tv</i>) is Number.</li>
+ <li>If <i>tv</i> is NaN, return <code>"Invalid Date"</code>.</li>
+ <li>Return an implementation-dependent String value that represents <i>tv</i> as a date and time in the current time
+ zone using a convenient, human-readable form.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-date.prototype.totimestring">
+ <h1><span class="secnum" id="sec-20.3.4.42"><a href="#sec-date.prototype.totimestring"
+ title="link to this section">20.3.4.42</a></span> Date.prototype.toTimeString ( )</h1>
+
+ <p>This function returns a String value. The contents of the String are implementation-dependent, but are intended to
+ represent the “time” portion of the Date in the current time zone in a convenient, human-readable form.</p>
+ </section>
+
+ <section id="sec-date.prototype.toutcstring">
+ <h1><span class="secnum" id="sec-20.3.4.43"><a href="#sec-date.prototype.toutcstring"
+ title="link to this section">20.3.4.43</a></span> Date.prototype.toUTCString ( )</h1>
+
+ <p>This function returns a String value. The contents of the String are implementation-dependent, but are intended to
+ represent <a href="#sec-properties-of-the-date-prototype-object">this time value</a> in a convenient, human-readable form
+ in UTC.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The intent is to produce a String representation of a date that is more readable than
+ the format specified in <a href="#sec-date-time-string-format">20.3.1.15</a>. It is not essential that the chosen format
+ be unambiguous or easily machine parsable. If an implementation does not have a preferred human-readable format it is
+ recommended to use the format defined in <a href="#sec-date-time-string-format">20.3.1.15</a> but with a space rather
+ than a “<code>T</code>” used to separate the date and time elements.</p>
+ </div>
+ </section>
+
+ <section id="sec-date.prototype.valueof">
+ <h1><span class="secnum" id="sec-20.3.4.44"><a href="#sec-date.prototype.valueof"
+ title="link to this section">20.3.4.44</a></span> Date.prototype.valueOf ( )</h1>
+
+ <p>The <code>valueOf</code> function returns a Number, which is <a
+ href="#sec-properties-of-the-date-prototype-object">this time value</a>.</p>
+ </section>
+
+ <section id="sec-date.prototype-@@toprimitive">
+ <h1><span class="secnum" id="sec-20.3.4.45"><a href="#sec-date.prototype-@@toprimitive"
+ title="link to this section">20.3.4.45</a></span> Date.prototype [ @@toPrimitive ] ( hint )</h1>
+
+ <p>This function is called by ECMAScript language operators to convert an object to a primitive value. The allowed values
+ for <var>hint</var> are "<code>default</code>", "<code>number</code>", and "<code>string</code>". Date objects, are
+ unique among built-in ECMAScript object in that they treat "<code>default</code>" as being equivalent to
+ "<code>string</code>", All other built-in ECMAScript objects treat "<code>default</code>" as being equivalent to
+ "<code>number</code>".</p>
+
+ <p>When the <code>@@toPrimitive</code> method is called with argument <var>hint</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value<b>.</b></li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>hint</i> is the string value "<code>string</code>" or the string value "<code>default</code>" , then
+ <ol class="block">
+ <li>Let <i>tryFirst</i> be "<code>string</code>".</li>
+ </ol>
+ </li>
+ <li>Else if <i>hint</i> is the string value "<code>number</code>", then
+ <ol class="block">
+ <li>Let <i>tryFirst</i> be "<code>number</code>".</li>
+ </ol>
+ </li>
+ <li>Else, throw a <b>TypeError</b> exception.</li>
+ <li>Return OrdinaryToPrimitive(<i>O</i>, <i>tryFirst</i>).</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.toPrimitive]"</code>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-date-instances">
+ <h1><span class="secnum" id="sec-20.3.5"><a href="#sec-properties-of-date-instances"
+ title="link to this section">20.3.5</a></span> Properties of Date Instances</h1>
+
+ <p>Date instances are ordinary objects that inherit properties from the Date prototype object. Date instances also have a
+ [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>. The [[DateValue]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the <a
+ href="#sec-time-values-and-time-range">time value</a> represented by this Date object.</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-text-processing">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21"><a href="#sec-text-processing" title="link to this section">21</a></span> Text
+ Processing</h1>
+ </div>
+
+ <section id="sec-string-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1"><a href="#sec-string-objects" title="link to this section">21.1</a></span> String
+ Objects</h1>
+ </div>
+
+ <section id="sec-string-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.1"><a href="#sec-string-constructor" title="link to this section">21.1.1</a></span>
+ The String Constructor</h1>
+
+ <p>The String constructor is the %String% intrinsic object and the initial value of the <code>String</code> property of
+ the global object. When called as a constructor it creates and initializes a new String object. When <code>String</code>
+ is called as a function rather than as a constructor, it performs a type conversion.</p>
+
+ <p>The <code>String</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>String</code> behaviour must include a <code>super</code> call to the <code>String</code> constructor to create and
+ initialize the subclass instance with a [[StringData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </div>
+
+ <section id="sec-string-constructor-string-value">
+ <h1><span class="secnum" id="sec-21.1.1.1"><a href="#sec-string-constructor-string-value"
+ title="link to this section">21.1.1.1</a></span> String ( value )</h1>
+
+ <p>When <code>String</code> is called with argument <var>value</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If no arguments were passed to this function invocation, let <i>s</i> be <code>""</code>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>If NewTarget is <b>undefined</b> and <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is
+ Symbol, return <a href="#sec-symboldescriptivestring">SymbolDescriptiveString</a>(<i>value</i>).</li>
+ <li>Let <i>s</i> be <a href="#sec-tostring">ToString</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>s</i>).</li>
+ <li>If NewTarget is <b>undefined</b><i>,</i> return <i>s</i>.</li>
+ <li>Return <a href="#sec-stringcreate">StringCreate</a>(<i>s</i>, <a
+ href="#sec-getprototypefromconstructor">GetPrototypeFromConstructor</a>(NewTarget,
+ <code>"%StringPrototype%"</code>)).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>String</code> function is <b>1</b>.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-string-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.2"><a href="#sec-properties-of-the-string-constructor"
+ title="link to this section">21.1.2</a></span> Properties of the String Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ String constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>1</b>), the String constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-string.fromcharcode">
+ <h1><span class="secnum" id="sec-21.1.2.1"><a href="#sec-string.fromcharcode"
+ title="link to this section">21.1.2.1</a></span> String.fromCharCode ( ...codeUnits )</h1>
+
+ <p>The <code>String.fromCharCode</code> function may be called with any number of arguments which form the rest parameter
+ <var>codeUnits</var>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>codeUnits</i> be a <a href="#sec-list-and-record-specification-type">List</a> containing the arguments passed
+ to this function.</li>
+ <li>Let <i>length</i> be the number of elements in <i>codeUnits</i><b>.</b></li>
+ <li>Let <i>elements</i> be a new <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>nextIndex</i> be 0.</li>
+ <li>Repeat while <i>nextIndex</i> < <i>length</i>
+ <ol class="block">
+ <li>Let <i>next</i> be <i>codeUnits</i>[<i>nextIndex</i>].</li>
+ <li>Let <i>nextCU</i> be <a href="#sec-touint16">ToUint16</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextCU</i>).</li>
+ <li>Append <i>nextCU</i> to the end of <i>elements</i>.</li>
+ <li>Let <i>nextIndex</i> be <i>nextIndex</i> + 1.</li>
+ </ol>
+ </li>
+ <li>Return the String value whose elements are, in order, the elements in the <a
+ href="#sec-list-and-record-specification-type">List</a> <i>elements</i>. If <i>length</i> is 0, the empty string is
+ returned.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>fromCharCode</code> function is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-string.fromcodepoint">
+ <h1><span class="secnum" id="sec-21.1.2.2"><a href="#sec-string.fromcodepoint"
+ title="link to this section">21.1.2.2</a></span> String.fromCodePoint ( ...codePoints )</h1>
+
+ <p>The <code>String.fromCodePoint</code> function may be called with any number of arguments which form the rest parameter
+ <var>codePoints</var>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>codePoints</i> be a <a href="#sec-list-and-record-specification-type">List</a> containing the arguments
+ passed to this function.</li>
+ <li>Let <i>length</i> be the number of elements in <i>codePoints</i><code>.</code></li>
+ <li>Let <i>elements</i> be a new <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>nextIndex</i> be 0.</li>
+ <li>Repeat while <i>nextIndex</i> < <i>length</i>
+ <ol class="block">
+ <li>Let <i>next</i> be <i>codePoints</i>[<i>nextIndex</i>].</li>
+ <li>Let <i>nextCP</i> be <a href="#sec-tonumber">ToNumber</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextCP</i>).</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>nextCP</i>, <a href="#sec-tointeger">ToInteger</a>(<i>nextCP</i>))
+ is <b>false</b>, throw a <b>RangeError</b> exception.</li>
+ <li>If <i>nextCP</i> < 0 or <i>nextCP</i> > 0x10FFFF, throw a <b>RangeError</b> exception.</li>
+ <li>Append the elements of the <a href="#sec-utf16encoding">UTF16Encoding</a> (<a
+ href="#sec-utf16encoding">10.1.1</a>) of <i>nextCP</i> to the end of <i>elements</i>.</li>
+ <li>Let <i>nextIndex</i> be <i>nextIndex</i> + 1.</li>
+ </ol>
+ </li>
+ <li>Return the String value whose elements are, in order, the elements in the <a
+ href="#sec-list-and-record-specification-type">List</a> <i>elements</i>. If <i>length</i> is 0, the empty string is
+ returned.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>fromCodePoint</code> function is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-string.prototype">
+ <h1><span class="secnum" id="sec-21.1.2.3"><a href="#sec-string.prototype"
+ title="link to this section">21.1.2.3</a></span> String.prototype</h1>
+
+ <p>The initial value of <code>String.prototype</code> is the intrinsic object %StringPrototype% (<a
+ href="#sec-properties-of-the-string-prototype-object">21.1.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-string.raw">
+ <h1><span class="secnum" id="sec-21.1.2.4"><a href="#sec-string.raw" title="link to this section">21.1.2.4</a></span>
+ String.raw ( template , ...substitutions )</h1>
+
+ <p>The <code>String.raw</code> function may be called with a variable number of arguments. The first argument is
+ <var>template</var> and the remainder of the arguments form the <a href="#sec-list-and-record-specification-type">List</a>
+ <var>substitutions</var>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>substitutions</i> be a <a href="#sec-list-and-record-specification-type">List</a> consisting of all of the
+ arguments passed to this function, starting with the second argument. If fewer than two arguments were passed, the
+ <a href="#sec-list-and-record-specification-type">List</a> is empty.</li>
+ <li>Let <i>numberOfSubstitutions</i> be the number of elements in <i>substitutions</i>.</li>
+ <li>Let <i>cooked</i> be <a href="#sec-toobject">ToObject</a>(<i>template</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>cooked</i>).</li>
+ <li>Let <i>rawValue</i> be <a href="#sec-get-o-p">Get</a>(<i>cooked</i>, <code>"raw"</code>)<code>.</code></li>
+ <li>Let <i>raw</i> be <a href="#sec-toobject">ToObject</a>(<i>rawValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>raw</i>).</li>
+ <li>Let <i>literalSegments</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>raw</i>,
+ <code>"length"</code>))<code>.</code></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>literalSegments</i>).</li>
+ <li>If <i>literalSegments</i> ≤ 0, return the empty string.</li>
+ <li>Let <i>stringElements</i> be a new <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>nextIndex</i> be 0.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>nextKey</i> be <a href="#sec-tostring">ToString</a>(<i>nextIndex</i>).</li>
+ <li>Let <i>next</i> be <a href="#sec-get-o-p">Get</a>(<i>raw</i>, <i>nextKey</i>).</li>
+ <li>Let <i>nextSeg</i> be <a href="#sec-tostring">ToString</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextSeg</i>).</li>
+ <li>Append in order the code unit elements of <i>nextSeg</i> to the end of <i>stringElements</i>.</li>
+ <li>If <i>nextIndex</i> + 1 = <i>literalSegments</i>, then
+ <ol class="block">
+ <li>Return the string value whose code units are, in order, the elements in the <a
+ href="#sec-list-and-record-specification-type">List</a> <i>stringElements</i>. If <i>stringElements</i> has
+ no elements, the empty string is returned.</li>
+ </ol>
+ </li>
+ <li>If <i>nextIndex</i> <i>< numberOfSubstitutions</i>, let <i>next</i> be
+ <i>substitutions</i>[<i>nextIndex</i>].</li>
+ <li>Else, let <i>next</i> be the empty String.</li>
+ <li>Let <i>nextSub</i> be <a href="#sec-tostring">ToString</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextSub</i>).</li>
+ <li>Append in order the code unit elements of <i>nextSub</i> to the end of <i>stringElements</i>.</li>
+ <li>Let <i>nextIndex</i> be <i>nextIndex</i> + 1.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>raw</code> function is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> String.raw is intended for use as a tag function of a Tagged Template (<a
+ href="#sec-tagged-templates">12.3.7</a>). When called as such, the first argument will be a well formed template object
+ and the rest parameter will contain the substitution values.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-string-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.3"><a href="#sec-properties-of-the-string-prototype-object"
+ title="link to this section">21.1.3</a></span> Properties of the String Prototype Object</h1>
+
+ <p>The String prototype object is the intrinsic object %StringPrototype%. The String prototype object is itself an
+ ordinary object. It is not a String instance and does not have a [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ String prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+
+ <p>Unless explicitly stated otherwise, the methods of the String prototype object defined below are not generic and the
+ <b>this</b> value passed to them must be either a String value or an object that has a [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> that has been initialized to a String value.</p>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">thisStringValue(<i>value</i>)</span> performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is String, return <i>value</i>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object and <i>value</i> has a
+ [[StringData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>value</i>’s [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is a String value.</li>
+ <li>Return the value of <i>value’s</i> [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+
+ <p>The phrase “this String value” within the specification of a method refers to the result returned by
+ calling the abstract operation <span style="font-family: Times New Roman">thisStringValue</span> with the <b>this</b>
+ value of the method invocation passed as the argument.</p>
+ </div>
+
+ <section id="sec-string.prototype.charat">
+ <h1><span class="secnum" id="sec-21.1.3.1"><a href="#sec-string.prototype.charat"
+ title="link to this section">21.1.3.1</a></span> String.prototype.charAt ( pos )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Returns a single element String containing the code unit at index <i>pos</i> in the
+ String value resulting from converting this object to a String. If there is no element at that index, the result is the
+ empty String. The result is a String value, not a String object.</p>
+
+ <p>If <i>pos</i> is a value of Number type that is an integer, then the result of
+ <code>x.charAt(</code><i>pos</i><code>)</code> is equal to the result of
+ <code>x.substring(</code><i>pos</i><code>,</code> <i>pos</i><code>+1)</code>.</p>
+ </div>
+
+ <p>When the <code>charAt</code> method is called with one argument <var>pos</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>position</i> be <a href="#sec-tointeger">ToInteger</a>(<i>pos</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>position</i>).</li>
+ <li>Let <i>size</i> be the number of elements in <i>S</i>.</li>
+ <li>If <i>position</i> < 0 or <i>position</i> ≥ <i>size</i>, return the empty String.</li>
+ <li>Return a String of length 1, containing one code unit from <i>S</i>, namely the code unit at index
+ <i>position</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>charAt</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.charcodeat">
+ <h1><span class="secnum" id="sec-21.1.3.2"><a href="#sec-string.prototype.charcodeat"
+ title="link to this section">21.1.3.2</a></span> String.prototype.charCodeAt ( pos )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Returns a Number (a nonnegative integer less than 2<sup>16</sup>) that is the code unit
+ value of the string element at index <i>pos</i> in the String resulting from converting this object to a String. If
+ there is no element at that index, the result is <b>NaN</b>.</p>
+ </div>
+
+ <p>When the <code>charCodeAt</code> method is called with one argument <var>pos</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>position</i> be <a href="#sec-tointeger">ToInteger</a>(<i>pos</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>position</i>).</li>
+ <li>Let <i>size</i> be the number of elements in <i>S</i>.</li>
+ <li>If <i>position</i> < 0 or <i>position</i> ≥ <i>size</i>, return <b>NaN</b>.</li>
+ <li>Return a value of Number type, whose value is the code unit value of the element at index <i>position</i> in the
+ String <i>S</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>charCodeAt</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.codepointat">
+ <h1><span class="secnum" id="sec-21.1.3.3"><a href="#sec-string.prototype.codepointat"
+ title="link to this section">21.1.3.3</a></span> String.prototype.codePointAt ( pos )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Returns a nonnegative integer Number less than 1114112 (0x110000) that is the code point
+ value of the UTF-16 encoded code point (<a href="#sec-ecmascript-language-types-string-type">6.1.4</a>) starting at the
+ string element at index <i>pos</i> in the String resulting from converting this object to a String. If there is no
+ element at that index, the result is <b>undefined</b>. If a valid UTF-16 surrogate pair does not begin at <i>pos</i>,
+ the result is the code unit at <i>pos</i>.</p>
+ </div>
+
+ <p>When the <code>codePointAt</code> method is called with one argument <var>pos</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>position</i> be <a href="#sec-tointeger">ToInteger</a>(<i>pos</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>position</i>).</li>
+ <li>Let <i>size</i> be the number of elements in <i>S</i>.</li>
+ <li>If <i>position</i> < 0 or <i>position</i> ≥ <i>size</i>, return <b>undefined</b>.</li>
+ <li>Let <i>first</i> be the code unit value of the element at index <i>position</i> in the String <i>S</i>.</li>
+ <li>If <i>first</i> < 0xD800 or <i>first</i> > 0xDBFF or <i>position</i>+1 = <i>size</i>, return
+ <i>first</i>.</li>
+ <li>Let <i>second</i> be the code unit value of the element at index <i>position</i>+1 in the String <i>S</i>.</li>
+ <li>If <i>second</i> < 0xDC00 or <i>second</i> > 0xDFFF, return <i>first</i>.</li>
+ <li>Return ((<i>first</i> – 0xD800) × 1024) + (<i>second</i> – 0xDC00) + 0x10000.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>codePointAt</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.concat">
+ <h1><span class="secnum" id="sec-21.1.3.4"><a href="#sec-string.prototype.concat"
+ title="link to this section">21.1.3.4</a></span> String.prototype.concat ( ...args )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> When the <code>concat</code> method is called it returns a String consisting of the code
+ units of the <code>this</code> object (converted to a String) followed by the code units of each of the arguments
+ converted to a String. The result is a String value, not a String object.</p>
+ </div>
+
+ <p>When the <code>concat</code> method is called with zero or more arguments the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>args</i> be a <a href="#sec-list-and-record-specification-type">List</a> whose elements are the arguments
+ passed to this function.</li>
+ <li>Let <i>R</i> be <i>S</i>.</li>
+ <li>Repeat, while <i>args</i> is not empty
+ <ol class="block">
+ <li>Remove the first element from <i>args</i> and let <i>next</i> be the value of that element.</li>
+ <li>Let <i>nextString</i> be <a href="#sec-tostring">ToString</a>(<i>next</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextString</i>).</li>
+ <li>Let <i>R</i> be the String value consisting of the code units of the previous value of <i>R</i> followed by the
+ code units of <i>nextString</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>R</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>concat</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>concat</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.constructor">
+ <h1><span class="secnum" id="sec-21.1.3.5"><a href="#sec-string.prototype.constructor"
+ title="link to this section">21.1.3.5</a></span> String.prototype.constructor</h1>
+
+ <p>The initial value of <code>String.prototype.constructor</code> is the intrinsic object %String%.</p>
+ </section>
+
+ <section id="sec-string.prototype.endswith">
+ <h1><span class="secnum" id="sec-21.1.3.6"><a href="#sec-string.prototype.endswith"
+ title="link to this section">21.1.3.6</a></span> String.prototype.endsWith ( searchString [ , endPosition] )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>isRegExp</i> be <a href="#sec-isregexp">IsRegExp</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isRegExp</i>).</li>
+ <li>If <i>isRegExp</i> is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>searchStr</i> be <a href="#sec-tostring">ToString</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>searchStr</i>).</li>
+ <li>Let <i>len</i> be the number of elements in <i>S</i>.</li>
+ <li>If <i>endPosition</i> is <b>undefined</b>, let <i>pos</i> be <i>len</i>, else let <i>pos</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>endPosition</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>pos</i>).</li>
+ <li>Let <i>end</i> be min(max(<i>pos</i>, 0), <i>len</i>).</li>
+ <li>Let <i>searchLength</i> be the number of elements in <i>searchStr</i>.</li>
+ <li>Let <i>start</i> be <i>end</i> - <i>searchLength</i>.</li>
+ <li>If <i>start</i> is less than 0, return <b>false</b><i>.</i></li>
+ <li>If the sequence of elements of <i>S</i> starting at <i>start</i> of length <i>searchLength</i> is the same as the
+ full element sequence of <i>searchStr</i>, return <b>true</b>.</li>
+ <li>Otherwise, return <b>false</b>.</li>
+ </ol>
+
+ <p>The <b>length</b> property of the <b>endsWith</b> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> Returns <b>true</b> if the sequence of elements of <i>searchString</i> converted to a
+ String is the same as the corresponding elements of this object (converted to a String) starting at <i>endPosition</i>
+ – length(this). Otherwise returns <b>false</b>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Throwing an exception if the first argument is a RegExp is specified in order to allow
+ future editions to define extends that allow such argument values.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> The <b>endsWith</b> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.includes">
+ <h1><span class="secnum" id="sec-21.1.3.7"><a href="#sec-string.prototype.includes"
+ title="link to this section">21.1.3.7</a></span> String.prototype.includes ( searchString [ , position ] )</h1>
+
+ <p>The <code>includes</code> method takes two arguments, <i>searchString</i> and <i>position</i>, and performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>isRegExp</i> be <a href="#sec-isregexp">IsRegExp</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isRegExp</i>).</li>
+ <li>If <i>isRegExp</i> is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>searchStr</i> be <a href="#sec-tostring">ToString</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>searchStr</i>).</li>
+ <li>Let <i>pos</i> be <a href="#sec-tointeger">ToInteger</a>(<i>position</i>). (If <i>position</i> is <b>undefined</b>,
+ this step produces the value <b>0</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>pos</i>).</li>
+ <li>Let <i>len</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>start</i> be min(max(<i>pos</i>, 0), <i>len</i>).</li>
+ <li>Let <i>searchLen</i> be the number of elements in <i>searchStr</i>.</li>
+ <li>If there exists any integer <i>k</i> not smaller than <i>start</i> such that <i>k</i> + <i>searchLen</i> is not
+ greater than <i>len</i>, and for all nonnegative integers <i>j</i> less than <i>searchLen</i>, the code unit at
+ index <i>k</i>+<i>j</i> of <i>S</i> is the same as the code unit at index <i>j</i> of <i>searchStr,</i> return
+ <b>true</b>; but if there is no such integer <i>k</i>, return <b>false</b>.</li>
+ </ol>
+
+ <p>The <b>length</b> property of the <code>includes</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> If <i>searchString</i> appears as a substring of the result of converting this object
+ to a String, at one or more indices that are greater than or equal to <i>position</i>, return <b>true</b>; otherwise,
+ returns <b>false</b>. If <i>position</i> is <b>undefined</b>, 0 is assumed, so as to search all of the String.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Throwing an exception if the first argument is a RegExp is specified in order to allow
+ future editions to define extensions that allow such argument values.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> The <code>includes</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.indexof">
+ <h1><span class="secnum" id="sec-21.1.3.8"><a href="#sec-string.prototype.indexof"
+ title="link to this section">21.1.3.8</a></span> String.prototype.indexOf ( searchString [ , position ] )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>searchString</i> appears as a substring of the result of converting this object to
+ a String, at one or more indices that are greater than or equal to <i>position</i>, then the smallest such index is
+ returned; otherwise, <code>‑1</code> is returned. If <i>position</i> is <b>undefined</b>, 0 is assumed, so as to
+ search all of the String.</p>
+ </div>
+
+ <p>The <code>indexOf</code> method takes two arguments, <var>searchString</var> and <var>position</var>, and performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>searchStr</i> be <a href="#sec-tostring">ToString</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>searchStr</i>).</li>
+ <li>Let <i>pos</i> be <a href="#sec-tointeger">ToInteger</a>(<i>position</i>). (If <i>position</i> is <b>undefined</b>,
+ this step produces the value <code>0</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>pos</i>).</li>
+ <li>Let <i>len</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>start</i> be min(max(<i>pos</i>, 0), <i>len</i>).</li>
+ <li>Let <i>searchLen</i> be the number of elements in <i>searchStr</i>.</li>
+ <li>Return the smallest possible integer <i>k</i> not smaller than <i>start</i> such that <i>k</i>+ <i>searchLen</i> is
+ not greater than <i>len</i>, and for all nonnegative integers <i>j</i> less than <i>searchLen</i>, the code unit at
+ index <i>k</i>+<i>j</i> of <i>S</i> is the same as the code unit at index <i>j</i> of <i>searchStr</i>; but if there
+ is no such integer <i>k</i>, return the value <code>-1</code><span style="font-family: sans-serif">.</span></li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>indexOf</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>indexOf</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.lastindexof">
+ <h1><span class="secnum" id="sec-21.1.3.9"><a href="#sec-string.prototype.lastindexof"
+ title="link to this section">21.1.3.9</a></span> String.prototype.lastIndexOf ( searchString [ , position ] )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <i>searchString</i> appears as a substring of the result of converting this object to
+ a String at one or more indices that are smaller than or equal to <i>position</i>, then the greatest such index is
+ returned; otherwise, <code>‑1</code> is returned. If <i>position</i> is <b>undefined</b>, the length of the
+ String value is assumed, so as to search all of the String.</p>
+ </div>
+
+ <p>The <code>lastIndexOf</code> method takes two arguments, <var>searchString</var> and <var>position</var>, and performs
+ the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>searchStr</i> be <a href="#sec-tostring">ToString</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>searchString</i>).</li>
+ <li>Let <i>numPos</i> be <a href="#sec-tonumber">ToNumber</a>(<i>position</i>). (If <i>position</i> is <b>undefined</b>,
+ this step produces the value <b>NaN</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>numPos</i>).</li>
+ <li>If <i>numPos</i> is <b>NaN</b>, let <i>pos</i> be <b>+∞</b>; otherwise, let <i>pos</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>numPos</i>).</li>
+ <li>Let <i>len</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>start</i> be min(max(<i>pos</i>, 0), <i>len</i>).</li>
+ <li>Let <i>searchLen</i> be the number of elements in <i>searchStr</i>.</li>
+ <li>Return the largest possible nonnegative integer <i>k</i> not larger than <i>start</i> such that <i>k</i>+
+ <i>searchLen</i> is not greater than <i>len</i>, and for all nonnegative integers <i>j</i> less than
+ <i>searchLen</i>, the code unit at index <i>k</i>+<i>j</i> of <i>S</i> is the same as the code unit at index
+ <i>j</i> of <i>searchStr</i>; but if there is no such integer <i>k</i>, return the value <code>-1</code>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>lastIndexOf</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>lastIndexOf</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.localecompare">
+ <h1><span class="secnum" id="sec-21.1.3.10"><a href="#sec-string.prototype.localecompare"
+ title="link to this section">21.1.3.10</a></span> String.prototype.localeCompare ( that [, reserved1 [ , reserved2 ] ]
+ )</h1>
+
+ <p>An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the
+ <code>localeCompare</code> method as specified in the ECMA-402 specification. If an ECMAScript implementation does not
+ include the ECMA-402 API the following specification of the <code>localeCompare</code> method is used.</p>
+
+ <p>When the <code>localeCompare</code> method is called with argument <var>that</var>, it returns a Number other than
+ <b>NaN</b> that represents the result of a locale-sensitive String comparison of the <b>this</b> value (converted to a
+ String) with <var>that</var> (converted to a String). The two Strings are <var>S</var> and <span class="nt">That</span>.
+ The two Strings are compared in an implementation-defined fashion. The result is intended to order String values in the
+ sort order specified by a host default locale, and will be negative, zero, or positive, depending on whether <var>S</var>
+ comes before <span class="nt">That</span> in the sort order, the Strings are equal, or <var>S</var> comes after <span
+ class="nt">That</span> in the sort order, respectively.</p>
+
+ <p>Before performing the comparisons, the following steps are performed to prepare the Strings:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>That</i> be <a href="#sec-tostring">ToString</a>(<i>that</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>That</i>).</li>
+ </ol>
+
+ <p>The meaning of the optional second and third parameters to this method are defined in the ECMA-402 specification;
+ implementations that do not include ECMA-402 support must not assign any other interpretation to those parameter
+ positions.</p>
+
+ <p>The <code>localeCompare</code> method, if considered as a function of two arguments <b>this</b> and <var>that</var>, is
+ a consistent comparison function (as defined in <a href="#sec-array.prototype.sort">22.1.3.24</a>) on the set of all
+ Strings.</p>
+
+ <p>The actual return values are implementation-defined to permit implementers to encode additional information in the
+ value, but the function is required to define a total ordering on all Strings. This function must treat Strings that are
+ canonically equivalent according to the Unicode standard as identical and must return <code>0</code> when comparing
+ Strings that are considered canonically equivalent.</p>
+
+ <p>The <code>length</code> property of the <code>localeCompare</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The <code>localeCompare</code> method itself is not directly suitable as an argument
+ to <code><a href="#sec-array.prototype.sort">Array.prototype.sort</a></code> because the latter requires a function of
+ two arguments.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> This function is intended to rely on whatever language-sensitive comparison
+ functionality is available to the ECMAScript environment from the host environment, and to compare according to the
+ rules of the host environment’s current locale. However, regardless of the host provided comparison capabilities,
+ this function must treat Strings that are canonically equivalent according to the Unicode standard as identical. It is
+ recommended that this function not honour Unicode compatibility equivalences or decompositions. For a definition and
+ discussion of canonical equivalence see the Unicode Standard, chapters 2 and 3, as well as Unicode Standard Annex #15,
+ Unicode Normalization Forms (<a href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a>)
+ and Unicode Technical Note #5, Canonical Equivalence in Applications (<a
+ href="http://www.unicode.org/notes/tn5/">http://www.unicode.org/notes/tn5/</a>). Also see Unicode Technical Standard
+ #10, Unicode Collation Algorithm (<a
+ href="http://www.unicode.org/reports/tr10/">http://www.unicode.org/reports/tr10/</a>).</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> The <code>localeCompare</code> function is intentionally generic; it does not require
+ that its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.match">
+ <h1><span class="secnum" id="sec-21.1.3.11"><a href="#sec-string.prototype.match"
+ title="link to this section">21.1.3.11</a></span> String.prototype.match ( regexp )</h1>
+
+ <p>When the <code>match</code> method is called with argument <var>regexp</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <i>regexp</i> is not <b>undefined<i>,</i></b> then
+ <ol class="block">
+ <li>Let <i>matcher</i> be <a href="#sec-getmethod">GetMethod</a>(<i>regexp</i>, @@match).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>matcher</i>).</li>
+ <li>If <i>matcher</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-call">Call</a>(<i>matcher</i>, <i>regexp</i>, «‍<i>O</i>»).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>rx</i> be <a href="#sec-regexpcreate">RegExpCreate</a>(<i>regexp</i>, <b>undefined</b>) (<a
+ href="#sec-regexpcreate">see 21.2.3.2.3</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rx</i>).</li>
+ <li>Return <a href="#sec-invoke">Invoke</a>(<i>rx</i>, @@match, «‍<i>S</i>»).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>match</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.normalize">
+ <h1><span class="secnum" id="sec-21.1.3.12"><a href="#sec-string.prototype.normalize"
+ title="link to this section">21.1.3.12</a></span> String.prototype.normalize ( [ form ] )</h1>
+
+ <p>When the <code>normalize</code> method is called with one argument <var>form</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>If <i>form</i> is not provided or <i>form</i> is <b>undefined</b> let <i>form</i> be
+ <code><b>"</b>NFC<b>"</b></code>.</li>
+ <li>Let <i>f</i> be <a href="#sec-tostring">ToString</a>(<i>form</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>f</i>).</li>
+ <li>If <i>f</i> is not one of <code><b>"</b>NFC<b>"</b></code>, <code><b>"</b>NFD<b>"</b></code>,
+ <code><b>"</b>NFKC<b>"</b></code>, or <code><b>"</b>NFKD<b>"</b></code>, throw a <b>RangeError</b> Exception.</li>
+ <li>Let <i>ns</i> be the String value that is the result of normalizing <i>S</i> into the normalization form named by
+ <i>f</i> as specified in <i>Unicode Standard Annex #15, Unicode</i> <i>Normalization Forms</i>.</li>
+ <li>Return <i>ns</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>normalize</code> method is <b>0</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>normalize</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.repeat">
+ <h1><span class="secnum" id="sec-21.1.3.13"><a href="#sec-string.prototype.repeat"
+ title="link to this section">21.1.3.13</a></span> String.prototype.repeat ( count )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>n</i> be <a href="#sec-tointeger">ToInteger</a>(<i>count</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>n</i>).</li>
+ <li>If <i>n</i> < 0, throw a <b>RangeError</b> exception.</li>
+ <li>If <i>n</i> is +∞, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>T</i> be a String value that is made from <i>n</i> copies of <i>S</i> appended together. If <i>n</i> is 0,
+ <i>T</i> is the empty String.</li>
+ <li>Return <i>T</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> This method creates a String consisting of the code units of the <code>this</code>
+ object (converted to String) repeated <i>count</i> times.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>repeat</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.replace">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.3.14"><a href="#sec-string.prototype.replace"
+ title="link to this section">21.1.3.14</a></span> String.prototype.replace (searchValue, replaceValue )</h1>
+
+ <p>When the <code>replace</code> method is called with arguments <var>searchValue</var> and <var>replaceValue</var> the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <i>searchValue</i> is not <b>undefined<i>,</i></b> then
+ <ol class="block">
+ <li>Let <i>replacer</i> be <a href="#sec-getmethod">GetMethod</a>(<i>searchValue</i>, @@replace).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>replacer</i>).</li>
+ <li>If <i>replacer</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-call">Call</a>(<i>replacer</i>, <i>searchValue</i>, «<i>O</i>,
+ <i>replaceValue</i>»).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>string</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>string</i>).</li>
+ <li>Let <i>searchString</i> be <a href="#sec-tostring">ToString</a>(<i>searchValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>searchString</i>).</li>
+ <li>Let <i>functionalReplace</i> be <a href="#sec-iscallable">IsCallable</a>(<i>replaceValue</i>).</li>
+ <li>If <i>functionalReplace</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>replaceValue</i> be <a href="#sec-tostring">ToString</a>(<i>replaceValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>replaceValue</i>).</li>
+ </ol>
+ </li>
+ <li>Search <i>string</i> for the first occurrence of <i>searchString</i> and let <i>pos</i> be the index within
+ <i>string</i> of the first code unit of the matched substring and let <i>matched</i> be <i>searchString</i>. If no
+ occurrences of <i>searchString</i> were found, return <i>string</i>.</li>
+ <li>If <i>functionalReplace</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>replValue</i> be <a href="#sec-call">Call</a>(<i>replaceValue</i>,
+ <b>undefined</b>,«<i>matched</i>, <i>pos</i>, and <i>string</i>»).</li>
+ <li>Let <i>replStr</i> be <a href="#sec-tostring">ToString</a>(<i>replValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>replStr</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>captures</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>replStr</i> be <a href="#sec-getreplacesubstitution">GetReplaceSubstitution</a>(<i>matched</i>,
+ <i>string</i>, <i>pos</i>, <i>captures</i>, <i>replaceValue</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>tailPos</i> be <i>pos</i> + the number of code units in <i>matched</i>.</li>
+ <li>Let <i>newString</i> be the String formed by concatenating the first <i>pos</i> code units of <i>string</i>,
+ <i>replStr</i>, and the trailing substring of <i>string</i> starting at index <i>tailPos</i>. If <i>pos</i> is 0,
+ the first element of the concatenation will be the empty String.</li>
+ <li>Return <i>newString</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>replace</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </div>
+
+ <section id="sec-getreplacesubstitution">
+ <h1><span class="secnum" id="sec-21.1.3.14.1"><a href="#sec-getreplacesubstitution"
+ title="link to this section">21.1.3.14.1</a></span> Runtime Semantics: GetReplaceSubstitution Abstract
+ Operation</h1>
+
+ <p>The abstract operation GetReplaceSubstitution(<var>matched</var>, <var>string</var>, <var>position</var>, <span
+ style="font-family: Times New Roman"><i>captures</i>, <i>replacement</i></span>) performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>matched</i>) is String.</li>
+ <li>Let <i>matchLength</i> be the number of code units in <i>matched</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>string</i>) is String.</li>
+ <li>Let <i>stringLength</i> be the number of code units in <i>string</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>position</i> is a nonnegative integer.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>position</i> ≤ <i>stringLength</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>captures</i> is a possibly empty <a
+ href="#sec-list-and-record-specification-type">List</a> of Strings.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ecmascript-data-types-and-values">Type</a>(
+ <i>replacement</i>) is String</li>
+ <li>Let <i>tailPos</i> be <i>position</i> + <i>matchLength</i>.</li>
+ <li>Let <i>m</i> be the number of elements in <i>captures</i>.</li>
+ <li>Let <i>result</i> be a String value derived from <i>replacement</i> by copying code unit elements from
+ <i>replacement</i> to <i>result</i> while performing replacements as specified in <a href="#table-45">Table
+ 45</a>. These <code>$</code> replacements are done left-to-right, and, once such a replacement is performed, the
+ new replacement text is not subject to further replacements.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+
+ <figure>
+ <figcaption><span id="table-45">Table 45</span> — Replacement Text Symbol Substitutions</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Code units</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Unicode Characters</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Replacement text</th>
+ </tr>
+ <tr>
+ <td>0x0024, 0x0024</td>
+ <td><code>$$</code></td>
+ <td><code>$</code></td>
+ </tr>
+ <tr>
+ <td>0x0024, 0x0026</td>
+ <td><code>$&</code></td>
+ <td><i>matched</i></td>
+ </tr>
+ <tr>
+ <td>0x0024, 0x0060</td>
+ <td><code>$`</code></td>
+ <td>If <i>position</i> is 0, the replacement is the empty String. Otherwise the replacement is the substring of <i>string</i> that starts at index 0 and whose last code unit is at index <i>position</i> -1.</td>
+ </tr>
+ <tr>
+ <td>0x0024, 0x0027</td>
+ <td><code>$'</code></td>
+ <td>If <i>tailPos</i> ≥ <i>stringLength</i>, the replacement is the empty String. Otherwise the replacement is the substring of <i>string</i> that starts at index <i>tailPos</i> and continues to the end of <i>string</i>.</td>
+ </tr>
+ <tr>
+ <td>0x0024, N, where<br>0x0031 ≤ N ≤ 0x0039</td>
+ <td><code>$n</code> <span style="font-family: Times New Roman">where</span> <code><br>n</code> <span style="font-family: Times New Roman">is one of</span> <code>1 2 3 4 5 6 7 8 9</code> <span style="font-family: Times New Roman">and</span> <code>$n</code> <span style="font-family: Times New Roman">is not followed by a decimal digit</span></td>
+ <td>The <i>n</i><sup>th</sup> element of <i>captures</i>, where <i>n</i> is a single digit in the range 1 to 9. If <i>n</i>≤<i>m</i> and the <i>n</i>th element of <i>captures</i> is <b>undefined</b>, use the empty String instead. If <i>n</i>><i>m</i>, the result is implementation-defined.</td>
+ </tr>
+ <tr>
+ <td>0x0024, N, N where<br>0x0030 ≤ N ≤ 0x0039</td>
+ <td><code>$nn</code> <span style="font-family: Times New Roman">where</span> <code><br>n</code> <span style="font-family: Times New Roman">is one of</span> <code>0 1 2 3 4 5 6 7 8 9</code></td>
+ <td>The <i>nn</i><sup>th</sup> element of <i>captures</i>, where <i>nn</i> is a two-digit decimal number in the range 01 to 99. If <i>nn</i>≤<i>m</i> and the <i>nn</i><sup>th</sup> element of <i>captures</i> is <b>undefined</b>, use the empty String instead. If <i>nn</i> is 00 or <i>nn</i>><i>m</i>, the result is implementation-defined.</td>
+ </tr>
+ <tr>
+ <td>0x0024</td>
+ <td><code>$</code> <span style="font-family: Times New Roman">in any context that does not match any of the above.</span></td>
+ <td><code>$</code></td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+
+ <section id="sec-string.prototype.search">
+ <h1><span class="secnum" id="sec-21.1.3.15"><a href="#sec-string.prototype.search"
+ title="link to this section">21.1.3.15</a></span> String.prototype.search ( regexp )</h1>
+
+ <p>When the search method is called with argument <var>regexp</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <i>regexp</i> is not <b>undefined<i>,</i></b> then
+ <ol class="block">
+ <li>Let <i>searcher</i> be <a href="#sec-getmethod">GetMethod</a>(<i>regexp</i>, @@search).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>searcher</i>).</li>
+ <li>If <i>searcher</i> is not <b>undefined</b> , then
+ <ol class="block">
+ <li>Return <a href="#sec-call">Call</a>(<i>searcher</i>, <i>regexp</i>, «<i>O</i>»)</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>string</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>string</i>).</li>
+ <li>Let <i>rx</i> be <a href="#sec-regexpcreate">RegExpCreate</a>(<i>regexp</i>, <b>undefined)</b> (<a
+ href="#sec-regexpcreate">see 21.2.3.2.3</a>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rx</i>).</li>
+ <li>Return <a href="#sec-invoke">Invoke</a>(<i>rx</i>, @@search, «‍<i>string</i>»).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>search</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.slice">
+ <h1><span class="secnum" id="sec-21.1.3.16"><a href="#sec-string.prototype.slice"
+ title="link to this section">21.1.3.16</a></span> String.prototype.slice ( start, end )</h1>
+
+ <p>The <code>slice</code> method takes two arguments, <var>start</var> and <var>end</var>, and returns a substring of the
+ result of converting this object to a String, starting from index <var>start</var> and running to, but not including,
+ index <var>end</var> (or through the end of the String if <var>end</var> is <b>undefined</b>). If <var>start</var> is
+ negative, it is treated as <span style="font-family: Times New Roman"><i>sourceLength</i>+<i>start</i></span> where
+ <var>sourceLength</var> is the length of the String. If <var>end</var> is negative, it is treated as <span
+ style="font-family: Times New Roman"><i>sourceLength</i>+<i>end</i></span> where <var>sourceLength</var> is the length of
+ the String. The result is a String value, not a String object. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>len</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>intStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>intStart</i>).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>intEnd</i> be <i>len</i>; else let <i>intEnd</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>intEnd</i>).</li>
+ <li>If <i>intStart</i> < 0, let <i>from</i> be max(<i>len</i> + <i>intStart</i>,0); otherwise let <i>from</i> be
+ min(<i>intStart</i>, <i>len</i>).</li>
+ <li>If <i>intEnd</i> < 0, let <i>to</i> be max(<i>len</i> + <i>intEnd</i>,0); otherwise let <i>to</i> be
+ min(<i>intEnd</i>, <i>len</i>).</li>
+ <li>Let <i>span</i> be max(<i>to</i> – <i>from</i>,0).</li>
+ <li>Return a String value containing <i>span</i> consecutive elements from <i>S</i> beginning with the element at index
+ <i>from</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>slice</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>slice</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.split">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.3.17"><a href="#sec-string.prototype.split"
+ title="link to this section">21.1.3.17</a></span> String.prototype.split ( separator, limit )</h1>
+
+ <p>Returns an Array object into which substrings of the result of converting this object to a String have been stored.
+ The substrings are determined by searching from left to right for occurrences of <var>separator</var>; these occurrences
+ are not part of any substring in the returned array, but serve to divide up the String value. The value of
+ <var>separator</var> may be a String of any length or it may be a RegExp object.</p>
+
+ <p>When the <code>split</code> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <i>separator</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>splitter</i> be <a href="#sec-getmethod">GetMethod</a>(<i>separator</i>, @@split).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>splitter</i>).</li>
+ <li>If <i>splitter</i> is not <b>undefined</b> , then
+ <ol class="block">
+ <li>Return <a href="#sec-call">Call</a>(<i>splitter</i>, <i>separator</i>, «‍<i>O</i>,
+ <i>limit</i>»).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>lengthA</i> be 0.</li>
+ <li>If <i>limit</i> is <b>undefined</b>, let <i>lim</i> = 2<sup>53</sup>–1; else let <i>lim</i> = <a
+ href="#sec-tolength">ToLength</a>(<i>limit</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lim</i>).</li>
+ <li>Let <i>s</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>p</i> = 0.</li>
+ <li>Let <i>R</i> be <a href="#sec-tostring">ToString</a>(<i>separator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>R</i>).</li>
+ <li>If <i>lim</i> = 0, return <i>A</i>.</li>
+ <li>If <i>separator</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>,
+ <code>"<b>0</b>"</code>, <i>S</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above call will never result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>s</i> = 0, then
+ <ol class="block">
+ <li>Let <i>z</i> be <a href="#sec-splitmatch">SplitMatch</a>(<i>S</i>, 0, <i>R</i>).</li>
+ <li>If <i>z</i> is not <b>false</b>, return <i>A</i>.</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>,
+ <code>"<b>0</b>"</code>, <i>S</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above call will never result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>q</i> = <i>p</i>.</li>
+ <li>Repeat, while <i>q</i> ≠ <i>s</i>
+ <ol class="block">
+ <li>Let <i>e</i> be <a href="#sec-splitmatch">SplitMatch</a>(<i>S, q, R</i>).</li>
+ <li>If <i>e</i> is <b>false</b>, let <i>q</i> = <i>q</i>+1.</li>
+ <li>Else <i>e</i> is an integer index into <i>S</i>,
+ <ol class="block">
+ <li>If <i>e</i> = <i>p</i>, let <i>q</i> = <i>q</i>+1.</li>
+ <li>Else <i>e</i> ≠ <i>p</i>,
+ <ol class="block">
+ <li>Let <i>T</i> be a String value equal to the substring of <i>S</i> consisting of the code units at
+ indices <i>p</i> (inclusive) through <i>q</i> (exclusive).</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>lengthA</i>), <i>T</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above call will never result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Increment <i>lengthA</i> by 1.</li>
+ <li>If <i>lengthA</i> = <i>lim</i>, return <i>A</i>.</li>
+ <li>Let <i>p</i> = <i>e</i>.</li>
+ <li>Let <i>q</i> = <i>p</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>T</i> be a String value equal to the substring of <i>S</i> consisting of the code units at indices <i>p</i>
+ (inclusive) through <i>s</i> (exclusive).</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>lengthA</i>), <i>T</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The above call will never result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>split</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The value of <i>separator</i> may be an empty String, an empty regular expression,
+ or a regular expression that can match an empty String. In this case, <i>separator</i> does not match the empty
+ substring at the beginning or end of the input String, nor does it match the empty substring at the end of the
+ previous separator match. (For example, if <i>separator</i> is the empty String, the String is split up into
+ individual code unit elements; the length of the result array equals the length of the String, and each substring
+ contains one code unit.) If <i>separator</i> is a regular expression, only the first match at a given index of the
+ <b>this</b> String is considered, even if backtracking could yield a non-empty-substring match at that index. (For
+ example, <code>"ab".split(/a*?/)</code> evaluates to the array <code>["a","b"]</code>, while
+ <code>"ab".split(/a*/)</code> evaluates to the array<code>["","b"]</code>.)</p>
+
+ <p>If the <b>this</b> object is (or converts to) the empty String, the result depends on whether <i>separator</i> can
+ match the empty String. If it can, the result array contains no elements. Otherwise, the result array contains one
+ element, which is the empty String.</p>
+
+ <p>If <i>separator</i> is a regular expression that contains capturing parentheses, then each time <i>separator</i> is
+ matched the results (including any <b>undefined</b> results) of the capturing parentheses are spliced into the output
+ array. For example,</p>
+
+ <pre>"A<B>bold</B>and<CODE>coded</CODE>".split(/<(\/)?([^<>]+)>/)</pre>
+
+ <p>evaluates to the array</p>
+
+ <pre>["A", undefined, "B", "bold", "/", "B", "and", undefined,<br> "CODE", "coded", "/", "CODE", ""]</pre>
+
+ <p>If <i>separator</i> is <b>undefined</b>, then the result array contains just one String, which is the <b>this</b>
+ value (converted to a String). If <i>limit</i> is not <b>undefined</b>, then the output array is truncated so that it
+ contains no more than <i>limit</i> elements.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>split</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </div>
+
+ <section id="sec-splitmatch">
+ <h1><span class="secnum" id="sec-21.1.3.17.1"><a href="#sec-splitmatch"
+ title="link to this section">21.1.3.17.1</a></span> Runtime Semantics: SplitMatch Abstract Operation</h1>
+
+ <p>The abstract operation SplitMatch takes three parameters, a String <var>S</var>, an integer <var>q</var>, and a
+ String <var>R</var>, and performs the following in order to return either <b>false</b> or the end index of a match:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is String.</li>
+ <li>Let <i>r</i> be the number of code units in <i>R</i>.</li>
+ <li>Let <i>s</i> be the number of code units in <i>S</i>.</li>
+ <li>If <i>q</i>+<i>r</i> > <i>s</i>, return <b>false</b>.</li>
+ <li>If there exists an integer <i>i</i> between 0 (inclusive) and <i>r</i> (exclusive) such that the code unit at
+ index <i>q</i>+<i>i</i> of <i>S</i> is different from the code unit at index <i>i</i> of <i>R</i>, return
+ <b>false</b>.</li>
+ <li>Return <i>q</i>+<i>r</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-string.prototype.startswith">
+ <h1><span class="secnum" id="sec-21.1.3.18"><a href="#sec-string.prototype.startswith"
+ title="link to this section">21.1.3.18</a></span> String.prototype.startsWith ( searchString [, position ] )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>isRegExp</i> be <a href="#sec-isregexp">IsRegExp</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isRegExp</i>).</li>
+ <li>If <i>isRegExp</i> is <b>true</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>searchStr</i> be <a href="#sec-tostring">ToString</a>(<i>searchString</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>searchString</i>).</li>
+ <li>Let <i>pos</i> be <a href="#sec-tointeger">ToInteger</a>(<i>position</i>). (If <i>position</i> is <b>undefined</b>,
+ this step produces the value <b>0</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>pos</i>).</li>
+ <li>Let <i>len</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>start</i> be min(max(<i>pos</i>, 0), <i>len</i>).</li>
+ <li>Let <i>searchLength</i> be the number of elements in <i>searchStr</i>.</li>
+ <li>If <i>searchLength+start</i> is greater than <i>len</i>, return <b>false</b><i>.</i></li>
+ <li>If the sequence of elements of <i>S</i> starting at <i>start</i> of length <i>searchLength</i> is the same as the
+ full element sequence of <i>searchStr</i>, return <b>true</b>.</li>
+ <li>Otherwise, return <b>false</b>.</li>
+ </ol>
+
+ <p>The <b>length</b> property of the <b>startsWith</b> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> This method returns <b>true</b> if the sequence of elements of <i>searchString</i>
+ converted to a String is the same as the corresponding elements of this object (converted to a String) starting at index
+ <i>position</i>. Otherwise returns <b>false</b>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Throwing an exception if the first argument is a RegExp is specified in order to allow
+ future editions to define extends that allow such argument values.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> The <b>startsWith</b> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.substring">
+ <h1><span class="secnum" id="sec-21.1.3.19"><a href="#sec-string.prototype.substring"
+ title="link to this section">21.1.3.19</a></span> String.prototype.substring ( start, end )</h1>
+
+ <p>The <b>substring</b> method takes two arguments, <var>start</var> and <var>end</var>, and returns a substring of the
+ result of converting this object to a String, starting from index <var>start</var> and running to, but not including,
+ index <var>end</var> of the String (or through the end of the String is <var>end</var> is <b>undefined</b>). The result is
+ a String value, not a String object.</p>
+
+ <p>If either argument is <b>NaN</b> or negative, it is replaced with zero; if either argument is larger than the length of
+ the String, it is replaced with the length of the String.</p>
+
+ <p>If <var>start</var> is larger than <var>end</var>, they are swapped.</p>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>len</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>intStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>intStart</i>).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>intEnd</i> be <i>len</i>; else let <i>intEnd</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>intEnd</i>).</li>
+ <li>Let <i>finalStart</i> be min(max(<i>intStart</i>, 0), <i>len</i>).</li>
+ <li>Let <i>finalEnd</i> be min(max(<i>intEnd</i>, 0), <i>len</i>).</li>
+ <li>Let <i>from</i> be min(<i>finalStart</i>, <i>finalEnd</i>).</li>
+ <li>Let <i>to</i> be max(<i>finalStart</i>, <i>finalEnd</i>).</li>
+ <li>Return a String whose length is <i>to</i> - <i>from</i>, containing code units from <i>S</i>, namely the code units
+ with indices <i>from</i> through <i>to</i> −1, in ascending order.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>substring</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>substring</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.tolocalelowercase">
+ <h1><span class="secnum" id="sec-21.1.3.20"><a href="#sec-string.prototype.tolocalelowercase"
+ title="link to this section">21.1.3.20</a></span> String.prototype.toLocaleLowerCase ( [ reserved1 [ , reserved2 ] ]
+ )</h1>
+
+ <p>This function interprets a string value as a sequence of UTF-16 encoded code points, as described in <a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>.</p>
+
+ <p>This function works exactly the same as <code>toLowerCase</code> except that its result is intended to yield the
+ correct result for the host environment’s current locale, rather than a locale-independent result. There will only
+ be a difference in the few cases (such as Turkish) where the rules for that language conflict with the regular Unicode
+ case mappings.</p>
+
+ <p>The <b>length</b> property of the <b>toLocaleLowerCase</b> method is <b>0</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The meaning of the optional first and second parameters to this method is reserved for
+ use by the ECMA-402 specification; it is recommended that implementations do not use those parameter positions for
+ anything else.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>toLocaleLowerCase</code> function is intentionally generic; it does not
+ require that its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for
+ use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.tolocaleuppercase">
+ <h1><span class="secnum" id="sec-21.1.3.21"><a href="#sec-string.prototype.tolocaleuppercase"
+ title="link to this section">21.1.3.21</a></span> String.prototype.toLocaleUpperCase ([ reserved1 [ , reserved2 ] ]
+ )</h1>
+
+ <p>This function interprets a string value as a sequence of UTF-16 encoded code points, as described in <a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>.</p>
+
+ <p>This function works exactly the same as <code>toUpperCase</code> except that its result is intended to yield the
+ correct result for the host environment’s current locale, rather than a locale-independent result. There will only
+ be a difference in the few cases (such as Turkish) where the rules for that language conflict with the regular Unicode
+ case mappings.</p>
+
+ <p>The <b>length</b> property of the <b>toLocaleUpperCase</b> method is <b>0</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The meaning of the optional first and second parameters to this method is reserved for
+ use by the ECMA-402 specification; it is recommended that implementations do not use those parameter positions for
+ anything else.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>toLocaleUpperCase</code> function is intentionally generic; it does not
+ require that its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for
+ use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.tolowercase">
+ <h1><span class="secnum" id="sec-21.1.3.22"><a href="#sec-string.prototype.tolowercase"
+ title="link to this section">21.1.3.22</a></span> String.prototype.toLowerCase ( )</h1>
+
+ <p>This function interprets a string value as a sequence of UTF-16 encoded code points, as described in <a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>cpList</i> be a <a href="#sec-list-and-record-specification-type">List</a> containing in order the code
+ points as defined in <a href="#sec-ecmascript-language-types-string-type">6.1.4</a> of <i>S</i>, starting at the
+ first element of <i>S</i>.</li>
+ <li>For each code point <i>c</i> in <i>cpList</i>, if the Unicode Character Database provides a language insensitive
+ lower case equivalent of <i>c</i> then replace <i>c</i> in <i>cpList</i> with that equivalent code point(s).</li>
+ <li>Let <i>cuList</i> be a new <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each code point <i>c</i> in <i>cpList</i>, in order, append to <i>cuList</i> the elements of the <a
+ href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of <i>c</i>.</li>
+ <li>Let <i>L</i> be a String whose elements are, in order, the elements of <i>cuList</i> .</li>
+ <li>Return <i>L</i>.</li>
+ </ol>
+
+ <p class="Note">The result must be derived according to the locale-insensitive case mappings in the Unicode Character
+ Database (this explicitly includes not only the UnicodeData.txt file, but also all locale-insensitive mappings in the
+ SpecialCasings.txt file that accompanies it).</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The case mapping of some code points may produce multiple code points . In this case
+ the result String may not be the same length as the source String. Because both <code>toUpperCase</code> and
+ <code>toLowerCase</code> have context-sensitive behaviour, the functions are not symmetrical. In other words,
+ <code>s.toUpperCase().toLowerCase()</code> is not necessarily equal to <code>s.toLowerCase()</code>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>toLowerCase</code> function is intentionally generic; it does not require
+ that its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.tostring">
+ <h1><span class="secnum" id="sec-21.1.3.23"><a href="#sec-string.prototype.tostring"
+ title="link to this section">21.1.3.23</a></span> String.prototype.toString ( )</h1>
+
+ <p>When the <code>toString</code> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>s</i> be thisStringValue(<b>this</b> value).</li>
+ <li>Return <i>s</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For a String object, the <code>toString</code> method happens to return the same thing
+ as the <code>valueOf</code> method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.touppercase">
+ <h1><span class="secnum" id="sec-21.1.3.24"><a href="#sec-string.prototype.touppercase"
+ title="link to this section">21.1.3.24</a></span> String.prototype.toUpperCase ( )</h1>
+
+ <p>This function interprets a string value as a sequence of UTF-16 encoded code points, as described in <a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>.</p>
+
+ <p>This function behaves in exactly the same way as <code><a
+ href="#sec-string.prototype.tolowercase">String.prototype.toLowerCase</a></code>, except that code points are mapped to
+ their <var>uppercase</var> equivalents as specified in the Unicode Character Database.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>toUpperCase</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.trim">
+ <h1><span class="secnum" id="sec-21.1.3.25"><a href="#sec-string.prototype.trim"
+ title="link to this section">21.1.3.25</a></span> String.prototype.trim ( )</h1>
+
+ <p>This function interprets a string value as a sequence of UTF-16 encoded code points, as described in <a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>.</p>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>T</i> be a String value that is a copy of <i>S</i> with both leading and trailing white space removed. The
+ definition of white space is the union of <i>WhiteSpace</i> and <i>LineTerminator</i>. When determining whether a
+ Unicode code point is in Unicode general category “Zs”, code unit sequences are interpreted as UTF-16
+ encoded code point sequences as specified in <a href="#sec-ecmascript-language-types-string-type">6.1.4</a>.</li>
+ <li>Return <i>T</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>trim</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.valueof">
+ <h1><span class="secnum" id="sec-21.1.3.26"><a href="#sec-string.prototype.valueof"
+ title="link to this section">21.1.3.26</a></span> String.prototype.valueOf ( )</h1>
+
+ <p>When the <code>valueOf</code> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>s</i> be thisStringValue(<b>this</b> value).</li>
+ <li>Return <i>s</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype-@@iterator">
+ <h1><span class="secnum" id="sec-21.1.3.27"><a href="#sec-string.prototype-@@iterator"
+ title="link to this section">21.1.3.27</a></span> String.prototype [ @@iterator ]( )</h1>
+
+ <p>When the @@iterator method is called it returns an Iterator object (<a href="#sec-iterator-interface">25.1.1.2</a>)
+ that iterates over the code points of a String value, returning each code point as a String value. The following steps are
+ taken:</p>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Return <a href="#sec-createstringiterator">CreateStringIterator</a>(<i>S</i>).</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.iterator]"</code>.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-string-instances">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.4"><a href="#sec-properties-of-string-instances"
+ title="link to this section">21.1.4</a></span> Properties of String Instances</h1>
+
+ <p>String instances are String exotic objects and have the internal methods specified for such objects. String instances
+ inherit properties from the String prototype object. String instances also have a [[StringData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>String instances have a <code>length</code> property, and a set of enumerable properties with integer indexed
+ names.</p>
+ </div>
+
+ <section id="sec-properties-of-string-instances-length">
+ <h1><span class="secnum" id="sec-21.1.4.1"><a href="#sec-properties-of-string-instances-length"
+ title="link to this section">21.1.4.1</a></span> length</h1>
+
+ <p>The number of elements in the String value represented by this String object.</p>
+
+ <p>Once a String object is initialized, this property is unchanging. It has the attributes { [[Writable]]: <b>false</b>,
+ [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-string-iterator-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.5"><a href="#sec-string-iterator-objects"
+ title="link to this section">21.1.5</a></span> String Iterator Objects</h1>
+
+ <p>An String Iterator is an object, that represents a specific iteration over some specific String instance object. There
+ is not a named constructor for String Iterator objects. Instead, String iterator objects are created by calling certain
+ methods of String instance objects.</p>
+ </div>
+
+ <section id="sec-createstringiterator">
+ <h1><span class="secnum" id="sec-21.1.5.1"><a href="#sec-createstringiterator"
+ title="link to this section">21.1.5.1</a></span> CreateStringIterator Abstract Operation</h1>
+
+ <p>Several methods of String objects return Iterator objects. The abstract operation CreateStringIterator with argument
+ <var>string</var> is used to create such iterator objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>string</i>) is String.</li>
+ <li>Let <i>iterator</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%StringIteratorPrototype%,
+ «[[IteratedString]], [[StringIteratorNextIndex]] »).</li>
+ <li>Set <i>iterator’s</i> [[IteratedString]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>string</i>.</li>
+ <li>Set <i>iterator’s</i> [[StringIteratorNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to 0.</li>
+ <li>Return <i>iterator</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%stringiteratorprototype%-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.1.5.2"><a href="#sec-%stringiteratorprototype%-object"
+ title="link to this section">21.1.5.2</a></span> The %StringIteratorPrototype% Object</h1>
+
+ <p>All String Iterator Objects inherit properties from the %StringIteratorPrototype% intrinsic object. The
+ %StringIteratorPrototype% object is an ordinary object and its [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the %IteratorPrototype% intrinsic object (<a
+ href="#sec-%iteratorprototype%-object">25.1.2</a>). In addition, %StringIteratorPrototype% has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-%stringiteratorprototype%.next">
+ <h1><span class="secnum" id="sec-21.1.5.2.1"><a href="#sec-%stringiteratorprototype%.next"
+ title="link to this section">21.1.5.2.1</a></span> %StringIteratorPrototype%.next ( )</h1>
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have all of the internal slots of an String Iterator Instance (<a
+ href="#sec-properties-of-string-iterator-instances">21.1.5.3</a>), throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>s</i> be the value of the [[IteratedString]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>s</i> is <b>undefined</b>, return <a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ <li>Let <i>position</i> be the value of the [[StringIteratorNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>len</i> be the number of elements in <i>s</i>.</li>
+ <li>If <i>position</i> ≥ <i>len</i>, then
+ <ol class="block">
+ <li>Set the value of the [[IteratedString]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of <i>O</i> to <b>undefined</b>.</li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Let <i>first</i> be the code unit value at index <i>position</i> in <i>s</i>.</li>
+ <li>If <i>first</i> < 0xD800 or <i>first</i> > 0xDBFF or <i>position</i>+1 = <i>len</i>, let <i>resultString</i>
+ be the string consisting of the single code unit <i>first</i>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>second</i> be the code unit value at index <i>position</i>+1 in the String <i>S</i>.</li>
+ <li>If <i>second</i> < 0xDC00 or <i>second</i> > 0xDFFF, let <i>resultString</i> be the string consisting of
+ the single code unit <i>first</i>.</li>
+ <li>Else, let <i>resultString</i> be the string consisting of the code unit <i>first</i> followed by the code unit
+ <i>second</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>resultSize</i> be the number of code units in <i>resultString</i>.</li>
+ <li>Set the value of the [[StringIteratorNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i> to <i>position</i>+
+ <i>resultSize</i>.</li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>resultString</i>, <b>false</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%stringiteratorprototype%-@@tostringtag">
+ <h1><span class="secnum" id="sec-21.1.5.2.2"><a href="#sec-%stringiteratorprototype%-@@tostringtag"
+ title="link to this section">21.1.5.2.2</a></span> %StringIteratorPrototype% [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>String Iterator</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-string-iterator-instances">
+ <h1><span class="secnum" id="sec-21.1.5.3"><a href="#sec-properties-of-string-iterator-instances"
+ title="link to this section">21.1.5.3</a></span> Properties of String Iterator Instances</h1>
+
+ <p>String Iterator instances are ordinary objects that inherit properties from the %StringIteratorPrototype% intrinsic
+ object. String Iterator instances are initially created with the internal slots listed in <a href="#table-46">Table
+ 46</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-46">Table 46</span> — Internal Slots of String Iterator Instances</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[IteratedString]]</td>
+ <td>The String value whose elements are being iterated.</td>
+ </tr>
+ <tr>
+ <td>[[StringIteratorNextIndex]]</td>
+ <td>The integer index of the next string index to be examined by this iteration.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-regexp-regular-expression-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2"><a href="#sec-regexp-regular-expression-objects"
+ title="link to this section">21.2</a></span> RegExp (Regular Expression) Objects</h1>
+
+ <p>A RegExp object contains a regular expression and the associated flags.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The form and functionality of regular expressions is modelled after the regular expression
+ facility in the Perl 5 programming language.</p>
+ </div>
+ </div>
+
+ <section id="sec-patterns">
+ <h1><span class="secnum" id="sec-21.2.1"><a href="#sec-patterns" title="link to this section">21.2.1</a></span>
+ Patterns</h1>
+
+ <p>The <code>RegExp</code> constructor applies the following grammar to the input pattern String. An error occurs if the
+ grammar cannot interpret the String as an expansion of <span class="nt">Pattern</span>.</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Pattern</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">Disjunction</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Disjunction</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">Alternative</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">Alternative</span><sub>[?U]</sub> <code class="t">|</code> <span class="nt">Disjunction</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Alternative</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">Alternative</span><sub>[?U]</sub> <span class="nt">Term</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Term</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">Assertion</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">Atom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">Atom</span><sub>[?U]</sub> <span class="nt">Quantifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Assertion</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">^</code></div>
+ <div class="rhs"><code class="t">$</code></div>
+ <div class="rhs"><code class="t">\</code> <code class="t">b</code></div>
+ <div class="rhs"><code class="t">\</code> <code class="t">B</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">=</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">!</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Quantifier</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">QuantifierPrefix</span></div>
+ <div class="rhs"><span class="nt">QuantifierPrefix</span> <code class="t">?</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">*</code></div>
+ <div class="rhs"><code class="t">+</code></div>
+ <div class="rhs"><code class="t">?</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">,</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">,</code> <span class="nt">DecimalDigits</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Atom</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">PatternCharacter</span></div>
+ <div class="rhs"><code class="t">.</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">AtomEscape</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">CharacterClass</span><sub>[?U]</sub></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">:</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SyntaxCharacter</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">^</code> <code class="t">$</code> <code class="t">\</code> <code class="t">.</code> <code class="t">*</code> <code class="t">+</code> <code class="t">?</code> <code class="t">(</code> <code class="t">)</code> <code class="t">[</code> <code class="t">]</code> <code class="t">{</code> <code class="t">}</code> <code class="t">|</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PatternCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">SyntaxCharacter</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AtomEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalEscape</span></div>
+ <div class="rhs"><span class="nt">CharacterEscape</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">CharacterClassEscape</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CharacterEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">ControlEscape</span></div>
+ <div class="rhs"><code class="t">c</code> <span class="nt">ControlLetter</span></div>
+ <div class="rhs"><span class="nt">HexEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">RegExpUnicodeEscapeSequence</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">IdentityEscape</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ControlEscape</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">f</code> <code class="t">n</code> <code class="t">r</code> <code class="t">t</code> <code class="t">v</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ControlLetter</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">a</code> <code class="t">b</code> <code class="t">c</code> <code class="t">d</code> <code class="t">e</code> <code class="t">f</code> <code class="t">g</code> <code class="t">h</code> <code class="t">i</code> <code class="t">j</code> <code class="t">k</code> <code class="t">l</code> <code class="t">m</code> <code class="t">n</code> <code class="t">o</code> <code class="t">p</code> <code class="t">q</code> <code class="t">r</code> <code class="t">s</code> <code class="t">t</code> <code class="t">u</code> <code class="t">v</code> <code class="t">w</code> <code class="t">x</code> <code class="t">y</code> <code class="t">z</code></div>
+ <div class="rhs"><code class="t">A</code> <code class="t">B</code> <code class="t">C</code> <code class="t">D</code> <code class="t">E</code> <code class="t">F</code> <code class="t">G</code> <code class="t">H</code> <code class="t">I</code> <code class="t">J</code> <code class="t">K</code> <code class="t">L</code> <code class="t">M</code> <code class="t">N</code> <code class="t">O</code> <code class="t">P</code> <code class="t">Q</code> <code class="t">R</code> <code class="t">S</code> <code class="t">T</code> <code class="t">U</code> <code class="t">V</code> <code class="t">W</code> <code class="t">X</code> <code class="t">Y</code> <code class="t">Z</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">RegExpUnicodeEscapeSequence</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">u</code> <span class="nt">LeadSurrogate</span> <code class="t">\u</code> <span class="nt">TrailSurrogate</span></div>
+ <div class="rhs"><code class="t">u</code> <span class="nt">Hex4Digits</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></div>
+ </div>
+
+ <ul>
+ <li>It is a Syntax Error if the MV of <span class="nt">HexDigits</span> > <span style="font-family: Times New
+ Roman">1114111<i>.</i></span></li>
+ </ul>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LeadSurrogate</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">Hex4Digits</span> <span class="grhsannot">[match only if the SV of <span class="nt">Hex4Digits</span> is in the inclusive range 0xD800 to 0xDBFF]</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">TrailSurrogate</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">Hex4Digits</span> <span class="grhsannot">[match only if the SV of <span class="nt">Hex4Digits</span> is in the inclusive range 0xDC00 to 0xDFFF]</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IdentityEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">SyntaxCharacter</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">UnicodeIDContinue</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalEscape</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalIntegerLiteral</span> <span class="grhsannot">[lookahead ∉ <span class="nt">DecimalDigit</span>]</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">d</code> <code class="t">D</code> <code class="t">s</code> <code class="t">S</code> <code class="t">w</code> <code class="t">W</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CharacterClass</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">[</code> <span class="grhsannot">[lookahead ∉ {<code class="t">^</code>}]</span> <span class="nt">ClassRanges</span><sub>[?U]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <code class="t">^</code> <span class="nt">ClassRanges</span><sub>[?U]</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassRanges</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">NonemptyClassRanges</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonemptyClassRanges</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub> <span class="nt">NonemptyClassRangesNoDash</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub> <code class="t">-</code> <span class="nt">ClassAtom</span><sub>[?U]</sub> <span class="nt">ClassRanges</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonemptyClassRangesNoDash</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub> <span class="nt">NonemptyClassRangesNoDash</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub> <code class="t">-</code> <span class="nt">ClassAtom</span><sub>[?U]</sub> <span class="nt">ClassRanges</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassAtom</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">-</code></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassAtomNoDash</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">-</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">ClassEscape</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalEscape</span></div>
+ <div class="rhs"><code class="t">b</code></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">-</code></div>
+ <div class="rhs"><span class="nt">CharacterEscape</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">CharacterClassEscape</span></div>
+ </div>
+ </section>
+
+ <section id="sec-pattern-semantics">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.2"><a href="#sec-pattern-semantics" title="link to this section">21.2.2</a></span>
+ Pattern Semantics</h1>
+
+ <p>A regular expression pattern is converted into an internal procedure using the process described below. An
+ implementation is encouraged to use more efficient algorithms than the ones listed below, as long as the results are the
+ same. The internal procedure is used as the value of a RegExp object’s [[RegExpMatcher]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>A <span class="nt">Pattern</span> is either a BMP pattern or a Unicode pattern depending upon whether or not its
+ associated flags contain an <code>"u"</code>. A BMP pattern matches against a String interpreted as consisting of a
+ sequence of 16-bit values that are Unicode code points in the range of the Basic Multilingual Plane. A Unicode pattern
+ matches against a String interpreted as consisting of Unicode code points encoded using UTF-16. In the context of
+ describing the behaviour of a BMP pattern “character” means a single 16-bit Unicode BMP code point. In the
+ context of describing the behaviour of a Unicode pattern “character” means a UTF-16 encoded code point (<a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>). In either context, “character value” means the
+ numeric value of the code unit or code point.</p>
+
+ <p>The semantics of <span class="nt">Pattern</span> is defined as if a <span class="nt">Pattern</span> was a <a
+ href="#sec-list-and-record-specification-type">List</a> of <span class="nt">SourceCharacter</span> values where each <span
+ class="nt">SourceCharacter</span> corresponds to a Unicode code point. If a BMP pattern contains a non-BMP <span
+ class="nt">SourceCharacter</span> the entire pattern is encoded using UTF-16 and the individual code units of that
+ encoding are used as the elements of the <a href="#sec-list-and-record-specification-type">List</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For example, consider a pattern expressed in source text as the single non-BMP character
+ <span style="font-family: sans-serif">U+1D11E (MUSICAL SYMBOL G CLEF). Interpreted as a Unicode pattern, it would be a
+ single element (character) <a href="#sec-list-and-record-specification-type">List</a> consisting of the single code
+ point 0x1D11E. However, interpreted as a BMP pattern, it is first UTF-16 encoded to produce a two element <a
+ href="#sec-list-and-record-specification-type">List</a> consisting of the code units 0xD834 and 0xDD1E.</span></p>
+
+ <p>Patterns are passed to the RegExp constructor as ECMAScript string values in which non-BMP characters are UTF-16
+ encoded. For example, the single character MUSICAL SYMBOL G CLEF pattern, expressed as a string value, is a String of
+ length 2 whose elements were the code units 0xD834 and 0xDD1E. So no further translation of the string would be
+ necessary to process it as a BMP pattern consisting of two pattern characters. However, to process it as a Unicode
+ pattern the string value must treated as if it was UTF-16 decoded into a <a
+ href="#sec-list-and-record-specification-type">List</a> consisting of a single pattern character, the code point
+ U+1D11E.</p>
+
+ <p>An implementation may not actually perform such translations to or from UTF-16, but the semantics of this
+ specification requires that the result of pattern matching be as if such translations were performed.</p>
+ </div>
+ </div>
+
+ <section id="sec-notation">
+ <h1><span class="secnum" id="sec-21.2.2.1"><a href="#sec-notation" title="link to this section">21.2.2.1</a></span>
+ Notation</h1>
+
+ <p>The descriptions below use the following variables:</p>
+
+ <ul>
+ <li>
+ <p><span class="nt">Input</span> is a <a href="#sec-list-and-record-specification-type">List</a> consisting of all of
+ the characters, in order, of the String being matched by the regular expression pattern. Each character is either a
+ code unit or a code point, depending upon the kind of pattern involved. The notation <span style="font-family: Times
+ New Roman"><i>input</i>[<i>n</i>]</span> means the <span style="font-family: Times New
+ Roman"><i>n<sup>th</sup></i></span> character of <var>input</var>, where <var>n</var> can range between 0 (inclusive)
+ and <span class="nt">InputLength</span> (exclusive).</p>
+ </li>
+
+ <li>
+ <p><span class="nt">InputLength</span> is the number of characters in <span class="nt">Input</span>.</p>
+ </li>
+
+ <li>
+ <p><span class="nt">NcapturingParens</span> is the total number of left capturing parentheses (i.e. the total number
+ of times the <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code class="t">(</code>
+ <span class="nt">Disjunction</span> <code class="t">)</code></span> production is expanded) in the pattern. A left
+ capturing parenthesis is any <code>(</code> pattern character that is matched by the <code>(</code> terminal of the
+ <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code class="t">(</code> <span
+ class="nt">Disjunction</span> <code class="t">)</code></span> production.</p>
+ </li>
+
+ <li>
+ <p><span class="nt">IgnoreCase</span> is <b>true</b> if the RegExp object's [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> contains <code>"i"</code> and otherwise is
+ <b>false</b>.</p>
+ </li>
+
+ <li>
+ <p><span class="nt">Multiline</span> is <b>true</b> if the RegExp object’s [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> contains <code>"m"</code> and otherwise is
+ <b>false</b>.</p>
+ </li>
+
+ <li>
+ <p><span class="nt">Unicode</span> is <b>true</b> if the RegExp object’s [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> contains <code>"u"</code> and otherwise is
+ <b>false</b>.</p>
+ </li>
+ </ul>
+
+ <p>Furthermore, the descriptions below use the following internal data structures:</p>
+
+ <ul>
+ <li>
+ <p>A <span class="nt">CharSet</span> is a mathematical set of characters, either code units or code points depending
+ up the state of the <span class="nt">Unicode</span> flag. “All characters” means either all code unit
+ values or all code point values also depending upon the state if <span class="nt">Unicode</span>.</p>
+ </li>
+
+ <li>
+ <p>A <span class="nt">State</span> is an ordered pair <span style="font-family: Times New Roman">(<i>endIndex</i>,
+ <i>captures</i>)</span> where <var>endIndex</var> is an integer and <var>captures</var> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of <span class="nt">NcapturingParens</span> values. <span
+ class="nt">States</span> are used to represent partial match states in the regular expression matching algorithms. The
+ <var>endIndex</var> is one plus the index of the last input character matched so far by the pattern, while
+ <var>captures</var> holds the results of capturing parentheses. The <span style="font-family: Times New
+ Roman"><i>n<sup>th</sup></i></span> element of <var>captures</var> is either a <a
+ href="#sec-list-and-record-specification-type">List</a> that represents the value obtained by the <span
+ style="font-family: Times New Roman"><i>n<sup>th</sup></i></span> set of capturing parentheses or <b>undefined</b> if
+ the <span style="font-family: Times New Roman"><i>n<sup>th</sup></i></span> set of capturing parentheses hasn’t
+ been reached yet. Due to backtracking, many <span class="nt">States</span> may be in use at any time during the
+ matching process.</p>
+ </li>
+
+ <li>
+ <p>A <span class="nt">MatchResult</span> is either a <span class="nt">State</span> or the special token <b>failure</b>
+ that indicates that the match failed.</p>
+ </li>
+
+ <li>
+ <p>A <span class="nt">Continuation</span> procedure is an internal closure (i.e. an internal procedure with some
+ arguments already bound to values) that takes one <span class="nt">State</span> argument and returns a <span
+ class="nt">MatchResult</span> result. If an internal closure references variables which are bound in the function that
+ creates the closure, the closure uses the values that these variables had at the time the closure was created. The
+ <span class="nt">Continuation</span> attempts to match the remaining portion (specified by the closure's already-bound
+ arguments) of the pattern against <span class="nt">Input</span>, starting at the intermediate state given by its <span
+ class="nt">State</span> argument. If the match succeeds, the <span class="nt">Continuation</span> returns the final
+ <span class="nt">State</span> that it reached; if the match fails, the <span class="nt">Continuation</span> returns
+ <b>failure</b>.</p>
+ </li>
+
+ <li>
+ <p>A <span class="nt">Matcher</span> procedure is an internal closure that takes two arguments — a <span
+ class="nt">State</span> and a <span class="nt">Continuation</span> — and returns a <span
+ class="nt">MatchResult</span> result. A <span class="nt">Matcher</span> attempts to match a middle subpattern
+ (specified by the closure's already-bound arguments) of the pattern against <span class="nt">Input</span>, starting at
+ the intermediate state given by its <span class="nt">State</span> argument. The <span class="nt">Continuation</span>
+ argument should be a closure that matches the rest of the pattern. After matching the subpattern of a pattern to
+ obtain a new <span class="nt">State</span>, the <span class="nt">Matcher</span> then calls <span
+ class="nt">Continuation</span> on that new <span class="nt">State</span> to test if the rest of the pattern can match
+ as well. If it can, the <i>Matcher</i> returns the <span class="nt">State</span> returned by <span
+ class="nt">Continuation</span>; if not, the <span class="nt">Matcher</span> may try different choices at its choice
+ points, repeatedly calling <span class="nt">Continuation</span> until it either succeeds or all possibilities have
+ been exhausted.</p>
+ </li>
+
+ <li>
+ <p>An <span class="nt">AssertionTester</span> procedure is an internal closure that takes a <span
+ class="nt">State</span> argument and returns a Boolean result. The assertion tester tests a specific condition
+ (specified by the closure's already-bound arguments) against the current place in <span class="nt">Input</span> and
+ returns <b>true</b> if the condition matched or <b>false</b> if not.</p>
+ </li>
+
+ <li>
+ <p>An <span class="nt">EscapeValue</span> is either a character or an integer. An <span class="nt">EscapeValue</span>
+ is used to denote the interpretation of a <span class="nt">DecimalEscape</span> escape sequence: a character
+ <var>ch</var> means that the escape sequence is interpreted as the character <var>ch</var>, while an integer
+ <var>n</var> means that the escape sequence is interpreted as a backreference to the <span style="font-family: Times
+ New Roman"><i>n</i><sup>th</sup></span> set of capturing parentheses.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-pattern">
+ <h1><span class="secnum" id="sec-21.2.2.2"><a href="#sec-pattern" title="link to this section">21.2.2.2</a></span>
+ Pattern</h1>
+
+ <p>The production <span class="prod"><span class="nt">Pattern</span> <span class="geq">::</span> <span
+ class="nt">Disjunction</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Disjunction</i> to obtain a Matcher <i>m</i>.</li>
+ <li>Return an internal closure that takes two arguments, a String <i>str</i> and an integer <i>index</i>, and performs
+ the following:
+ <ol class="nested proc">
+ <li>If <i>Unicode</i> is <b>true</b>, let <i>Input</i> be a <a
+ href="#sec-list-and-record-specification-type">List</a> consisting of the sequence of code points of <i>str</i>
+ interpreted as a UTF-16 encoded (<a href="#sec-ecmascript-language-types-string-type">6.1.4</a>) Unicode string.
+ Otherwise, let <i>Input</i> be a <a href="#sec-list-and-record-specification-type">List</a> consisting of the
+ sequence of code units that are the elements of <i>str</i>. <i>Input</i> will be used throughout the algorithms
+ in <a href="#sec-pattern-semantics">21.2.2</a>. Each element of <i>Input</i> is considered to be a
+ character.</li>
+ <li>Let <i>listIndex</i> be the index into <i>Input</i> of the character that was obtained from element <i>index</i>
+ of <i>str</i>.</li>
+ <li>Let <i>InputLength</i> be the number of characters contained in <i>Input</i>. This variable will be used
+ throughout the algorithms in <a href="#sec-pattern-semantics">21.2.2</a>.</li>
+ <li>Let <i>c</i> be a Continuation that always returns its State argument as a successful MatchResult.</li>
+ <li>Let <i>cap</i> be a <a href="#sec-list-and-record-specification-type">List</a> of <i>NcapturingParens</i>
+ <b>undefined</b> values, indexed 1 through <i>NcapturingParens</i>.</li>
+ <li>Let <i>x</i> be the State (<i>listIndex</i>, <i>cap</i>).</li>
+ <li><a href="#sec-call">Call</a> <i>m</i>(<i>x</i>, <i>c</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A Pattern evaluates ("compiles") to an internal procedure value. <code><a
+ href="#sec-regexp.prototype.exec">RegExp.prototype.exec</a></code> and other methods can then apply this procedure to a
+ String and an offset within the String to determine whether the pattern would match starting at exactly that offset
+ within the String, and, if it does match, what the values of the capturing parentheses would be. The algorithms in <a
+ href="#sec-pattern-semantics">21.2.2</a> are designed so that compiling a pattern may throw a <b>SyntaxError</b>
+ exception; on the other hand, once the pattern is successfully compiled, applying its result internal procedure to find
+ a match in a String cannot throw an exception (except for any host-defined exceptions that can occur anywhere such as
+ out-of-memory).</p>
+ </div>
+ </section>
+
+ <section id="sec-disjunction">
+ <h1><span class="secnum" id="sec-21.2.2.3"><a href="#sec-disjunction" title="link to this section">21.2.2.3</a></span>
+ Disjunction</h1>
+
+ <p>The production <span class="prod"><span class="nt">Disjunction</span> <span class="geq">::</span> <span
+ class="nt">Alternative</span></span> evaluates by evaluating <span class="nt">Alternative</span> to obtain a <span
+ style="font-family: Times New Roman">Matcher</span> and returning that <span style="font-family: Times New
+ Roman">Matcher</span>.</p>
+
+ <p>The production <span class="prod"><span class="nt">Disjunction</span> <span class="geq">::</span> <span
+ class="nt">Alternative</span> <code class="t">|</code> <span class="nt">Disjunction</span></span> evaluates as
+ follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Alternative</i> to obtain a Matcher <i>m1</i>.</li>
+ <li>Evaluate <i>Disjunction</i> to obtain a Matcher <i>m2</i>.</li>
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps when evaluated:
+ <ol class="nested proc">
+ <li><a href="#sec-call">Call</a> <i>m1</i>(<i>x</i>, <i>c</i>) and let <i>r</i> be its result.</li>
+ <li>If <i>r</i> isn't <b>failure</b>, return <i>r</i>.</li>
+ <li><a href="#sec-call">Call</a> <i>m2</i>(<i>x</i>, <i>c</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>|</code> regular expression operator separates two alternatives. The pattern
+ first tries to match the left <i>Alternative</i> (followed by the sequel of the regular expression); if it fails, it
+ tries to match the right <i>Disjunction</i> (followed by the sequel of the regular expression). If the left
+ <i>Alternative</i>, the right <i>Disjunction</i>, and the sequel all have choice points, all choices in the sequel are
+ tried before moving on to the next choice in the left <i>Alternative</i>. If choices in the left <i>Alternative</i> are
+ exhausted, the right <i>Disjunction</i> is tried instead of the left <i>Alternative</i>. Any capturing parentheses
+ inside a portion of the pattern skipped by <code>|</code> produce <b>undefined</b> values instead of Strings. Thus, for
+ example,</p>
+
+ <pre>/a|ab/.exec("abc")</pre>
+
+ <p>returns the result <code>"a"</code> and not <code>"ab"</code>. Moreover,</p>
+
+ <pre>/((a)|(ab))((c)|(bc))/.exec("abc")</pre>
+
+ <p>returns the array</p>
+
+ <pre>["abc", "a", "a", undefined, "bc", undefined, "bc"]</pre>
+
+ <p>and not</p>
+
+ <pre>["abc", "ab", undefined, "ab", "c", "c", undefined]</pre>
+ </div>
+ </section>
+
+ <section id="sec-alternative">
+ <h1><span class="secnum" id="sec-21.2.2.4"><a href="#sec-alternative" title="link to this section">21.2.2.4</a></span>
+ Alternative</h1>
+
+ <p>The production <span class="prod"><span class="nt">Alternative</span> <span class="geq">::</span> <span
+ class="grhsannot">[empty]</span></span> evaluates by returning a Matcher that takes two arguments, a State <var>x</var>
+ and a Continuation <var>c</var>, and returns the result of calling <var>c</var>(<var>x</var>).</p>
+
+ <p>The production <span class="prod"><span class="nt">Alternative</span> <span class="geq">::</span> <span
+ class="nt">Alternative</span> <span class="nt">Term</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Alternative</i> to obtain a Matcher <i>m1</i>.</li>
+ <li>Evaluate <i>Term</i> to obtain a Matcher <i>m2</i>.</li>
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps when evaluated:
+ <ol class="nested proc">
+ <li>Create a Continuation <i>d</i> that takes a State argument <i>y</i> and returns the result of calling
+ <i>m2</i>(<i>y</i>, <i>c</i>).</li>
+ <li><a href="#sec-call">Call</a> <i>m1</i>(<i>x</i>, <i>d</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Consecutive <i>Terms</i> try to simultaneously match consecutive portions of
+ <i>Input</i>. If the left <i>Alternative</i>, the right <i>Term</i>, and the sequel of the regular expression all have
+ choice points, all choices in the sequel are tried before moving on to the next choice in the right <i>Term</i>, and all
+ choices in the right <i>Term</i> are tried before moving on to the next choice in the left <i>Alternative</i>.</p>
+ </div>
+ </section>
+
+ <section id="sec-term">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.2.5"><a href="#sec-term" title="link to this section">21.2.2.5</a></span>
+ Term</h1>
+
+ <p>The production <span class="prod"><span class="nt">Term</span> <span class="geq">::</span> <span
+ class="nt">Assertion</span></span> evaluates by returning an internal Matcher closure that takes two arguments, a State
+ <var>x</var> and a Continuation <var>c</var>, and performs the following steps when evaluated:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Assertion</i> to obtain an AssertionTester <i>t</i>.</li>
+ <li><a href="#sec-call">Call</a> <i>t</i>(<i>x</i>) and let <i>r</i> be the resulting Boolean value.</li>
+ <li>If <i>r</i> is <b>false</b>, return <b>failure</b>.</li>
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>x</i>) and return its result.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Term</span> <span class="geq">::</span> <span
+ class="nt">Atom</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the Matcher that is the result of evaluating <i>Atom</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Term</span> <span class="geq">::</span> <span
+ class="nt">Atom</span> <span class="nt">Quantifier</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Atom</i> to obtain a Matcher <i>m</i>.</li>
+ <li>Evaluate <i>Quantifier</i> to obtain the three results: an integer <i>min</i>, an integer (or ∞) <i>max</i>,
+ and Boolean <i>greedy</i>.</li>
+ <li>If <i>max</i> is finite and less than <i>min</i>, throw a <b>SyntaxError</b> exception.</li>
+ <li>Let <i>parenIndex</i> be the number of left capturing parentheses in the entire regular expression that occur to
+ the left of this production expansion's <i>Term</i>. This is the total number of times the <span
+ class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code class="t">(</code> <span
+ class="nt">Disjunction</span> <code class="t">)</code></span> production is expanded prior to this production's
+ <i>Term</i> plus the total number of <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span>
+ <code class="t">(</code> <span class="nt">Disjunction</span> <code class="t">)</code></span> productions enclosing
+ this <i>Term</i>.</li>
+ <li>Let <i>parenCount</i> be the number of left capturing parentheses in the expansion of this production's
+ <i>Atom</i>. This is the total number of <span class="prod"><span class="nt">Atom</span> <span
+ class="geq">::</span> <code class="t">(</code> <span class="nt">Disjunction</span> <code class="t">)</code></span>
+ productions enclosed by this production's <i>Atom</i>.</li>
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps when evaluated:
+ <ol class="nested proc">
+ <li><a href="#sec-call">Call</a> RepeatMatcher(<i>m</i>, <i>min</i>, <i>max</i>, <i>greedy</i>, <i>x</i>,
+ <i>c</i>, <i>parenIndex</i>, <i>parenCount</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+ </div>
+
+ <section id="sec-runtime-semantics-repeatmatcher-abstract-operation">
+ <h1><span class="secnum" id="sec-21.2.2.5.1"><a href="#sec-runtime-semantics-repeatmatcher-abstract-operation"
+ title="link to this section">21.2.2.5.1</a></span> Runtime Semantics: RepeatMatcher Abstract Operation</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">RepeatMatcher</span> takes eight parameters, a
+ Matcher <var>m</var>, an integer <var>min</var>, an integer (or ∞) <var>max</var>, a Boolean <var>greedy</var>, a
+ State <var>x</var>, a Continuation <var>c</var>, an integer <var>parenIndex</var>, and an integer <var>parenCount</var>,
+ and performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>max</i> is zero, return <i>c</i>(<i>x</i>).</li>
+ <li>Create an internal Continuation closure <i>d</i> that takes one State argument <i>y</i> and performs the following
+ steps when evaluated:
+ <ol class="nested proc">
+ <li>If <i>min</i> is zero and <i>y</i>'s <i>endIndex</i> is equal to <i>x</i>'s <i>endIndex</i>, return
+ <b>failure</b>.</li>
+ <li>If <i>min</i> is zero, let <i>min2</i> be zero; otherwise let <i>min2</i> be <i>min</i>–1.</li>
+ <li>If <i>max</i> is ∞, let <i>max2</i> be ∞; otherwise let <i>max2</i> be <i>max</i>–1.</li>
+ <li><a href="#sec-call">Call</a> RepeatMatcher(<i>m</i>, <i>min2</i>, <i>max2</i>, <i>greedy</i>, <i>y</i>,
+ <i>c</i>, <i>parenIndex</i>, <i>parenCount</i>) and return its result.</li>
+ </ol>
+ </li>
+ <li>Let <i>cap</i> be a fresh copy of <i>x</i>'s <i>captures</i> <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For every integer <i>k</i> that satisfies <i>parenIndex</i> < <i>k</i> and <i>k</i> ≤
+ <i>parenIndex</i>+<i>parenCount</i>, set <i>cap</i>[<i>k</i>] to <b>undefined</b>.</li>
+ <li>Let <i>e</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li>Let <i>xr</i> be the State (<i>e</i>, <i>cap</i>).</li>
+ <li>If <i>min</i> is not zero, return <i>m</i>(<i>xr</i>, <i>d</i>).</li>
+ <li>If <i>greedy</i> is <b>false</b>, then
+ <ol class="block">
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>x</i>) and let <i>z</i> be its result.</li>
+ <li>If <i>z</i> is not <b>failure</b>, return <i>z</i>.</li>
+ <li><a href="#sec-call">Call</a> <i>m</i>(<i>xr</i>, <i>d</i>) and return its result.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-call">Call</a> <i>m</i>(<i>xr</i>, <i>d</i>) and let <i>z</i> be its result.</li>
+ <li>If <i>z</i> is not <b>failure</b>, return <i>z</i>.</li>
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>x</i>) and return its result.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> An <i>Atom</i> followed by a <i>Quantifier</i> is repeated the number of times
+ specified by the <i>Quantifier</i>. A <i>Quantifier</i> can be non-greedy, in which case the <i>Atom</i> pattern is
+ repeated as few times as possible while still matching the sequel, or it can be greedy, in which case the <i>Atom</i>
+ pattern is repeated as many times as possible while still matching the sequel. The <i>Atom</i> pattern is repeated
+ rather than the input character sequence that it matches, so different repetitions of the <i>Atom</i> can match
+ different input substrings.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> If the <i>Atom</i> and the sequel of the regular expression all have choice points,
+ the <i>Atom</i> is first matched as many (or as few, if non-greedy) times as possible. All choices in the sequel are
+ tried before moving on to the next choice in the last repetition of <i>Atom</i>. All choices in the last
+ (n<sup>th</sup>) repetition of <i>Atom</i> are tried before moving on to the next choice in the next-to-last
+ (n–1)<sup>st</sup> repetition of <i>Atom</i>; at which point it may turn out that more or fewer repetitions of
+ <i>Atom</i> are now possible; these are exhausted (again, starting with either as few or as many as possible) before
+ moving on to the next choice in the (n-1)<sup>st</sup> repetition of <i>Atom</i> and so on.</p>
+
+ <p>Compare</p>
+
+ <pre>/a[a-z]{2,4}/.exec("abcdefghi")</pre>
+
+ <p>which returns <code>"abcde"</code> with</p>
+
+ <pre>/a[a-z]{2,4}?/.exec("abcdefghi")</pre>
+
+ <p>which returns <code>"abc"</code>.</p>
+
+ <p>Consider also</p>
+
+ <pre>/(aa|aabaac|ba|b|c)*/.exec("aabaac")</pre>
+
+ <p>which, by the choice point ordering above, returns the array</p>
+
+ <pre>["aaba", "ba"]</pre>
+
+ <p>and not any of:</p>
+
+ <pre>["aabaac", "aabaac"]</pre>
+ <pre>["aabaac", "c"]</pre>
+
+ <p>The above ordering of choice points can be used to write a regular expression that calculates the greatest common
+ divisor of two numbers (represented in unary notation). The following example calculates the gcd of 10 and 15:</p>
+
+ <pre>"aaaaaaaaaa,aaaaaaaaaaaaaaa".replace(/^(a+)\1*,\1+$/,"$1")</pre>
+
+ <p>which returns the gcd in unary notation <code>"aaaaa"</code>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> Step 5 of the RepeatMatcher clears <i>Atom's</i> captures each time <i>Atom</i> is
+ repeated. We can see its behaviour in the regular expression</p>
+
+ <pre>/(z)((a+)?(b+)?(c))*/.exec("zaacbbbcac")</pre>
+
+ <p>which returns the array</p>
+
+ <pre>["zaacbbbcac", "z", "ac", "a", undefined, "c"]</pre>
+
+ <p>and not</p>
+
+ <pre>["zaacbbbcac", "z", "ac", "a", "bbb", "c"]</pre>
+
+ <p>because each iteration of the outermost <code>*</code> clears all captured Strings contained in the quantified
+ <span class="nt">Atom</span>, which in this case includes capture Strings numbered 2, 3, 4, and 5.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 4</span> Step 1 of the RepeatMatcher's <i>d</i> closure states that, once the minimum number
+ of repetitions has been satisfied, any more expansions of <i>Atom</i> that match the empty character sequence are not
+ considered for further repetitions. This prevents the regular expression engine from falling into an infinite loop on
+ patterns such as:</p>
+
+ <pre>/(a*)*/.exec("b")</pre>
+
+ <p>or the slightly more complicated:</p>
+
+ <pre>/(a*)b\1+/.exec("baaaac")</pre>
+
+ <p>which returns the array</p>
+
+ <pre>["b", ""]</pre>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-assertion">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.2.6"><a href="#sec-assertion" title="link to this section">21.2.2.6</a></span>
+ Assertion</h1>
+
+ <p>The production <span class="prod"><span class="nt">Assertion</span> <span class="geq">::</span> <code
+ class="t">^</code></span> evaluates by returning an internal AssertionTester closure that takes a State argument
+ <var>x</var> and performs the following steps when evaluated:</p>
+
+ <ol class="proc">
+ <li>Let <i>e</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li>If <i>e</i> is zero, return <b>true</b>.</li>
+ <li>If <i>Multiline</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>If the character <i>Input</i>[<i>e</i>–1] is one of <i>LineTerminator</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Even when the <code>y</code> flag is used with a pattern, <code>^</code> always
+ matches only at the beginning of <i>Input</i>, or (if <i>Multiline</i> is <b>true</b>) at the beginning of a line.</p>
+ </div>
+
+ <p>The production <span class="prod"><span class="nt">Assertion</span> <span class="geq">::</span> <code
+ class="t">$</code></span> evaluates by returning an internal AssertionTester closure that takes a State argument
+ <var>x</var> and performs the following steps when evaluated:</p>
+
+ <ol class="proc">
+ <li>Let <i>e</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li>If <i>e</i> is equal to <i>InputLength</i>, return <b>true</b>.</li>
+ <li>If <i>Multiline</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>If the character <i>Input</i>[<i>e</i>] is one of <i>LineTerminator</i>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Assertion</span> <span class="geq">::</span> <code
+ class="t">\</code> <code class="t">b</code></span> evaluates by returning an internal AssertionTester closure that takes
+ a State argument <var>x</var> and performs the following steps when evaluated:</p>
+
+ <ol class="proc">
+ <li>Let <i>e</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li><a href="#sec-call">Call</a> IsWordChar(<i>e</i>–1) and let <i>a</i> be the Boolean result.</li>
+ <li><a href="#sec-call">Call</a> IsWordChar(<i>e</i>) and let <i>b</i> be the Boolean result.</li>
+ <li>If <i>a</i> is <b>true</b> and <i>b</i> is <b>false</b>, return <b>true</b>.</li>
+ <li>If <i>a</i> is <b>false</b> and <i>b</i> is <b>true</b>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Assertion</span> <span class="geq">::</span> <code
+ class="t">\</code> <code class="t">B</code></span> evaluates by returning an internal AssertionTester closure that takes
+ a State argument <var>x</var> and performs the following steps when evaluated:</p>
+
+ <ol class="proc">
+ <li>Let <i>e</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li><a href="#sec-call">Call</a> IsWordChar(<i>e</i>–1) and let <i>a</i> be the Boolean result.</li>
+ <li><a href="#sec-call">Call</a> IsWordChar(<i>e</i>) and let <i>b</i> be the Boolean result.</li>
+ <li>If <i>a</i> is <b>true</b> and <i>b</i> is <b>false</b>, return <b>false</b>.</li>
+ <li>If <i>a</i> is <b>false</b> and <i>b</i> is <b>true</b>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Assertion</span> <span class="geq">::</span> <code
+ class="t">(</code> <code class="t">?</code> <code class="t">=</code> <span class="nt">Disjunction</span> <code
+ class="t">)</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Disjunction</i> to obtain a Matcher <i>m</i>.</li>
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps:
+ <ol class="nested proc">
+ <li>Let <i>d</i> be a Continuation that always returns its State argument as a successful MatchResult.</li>
+ <li><a href="#sec-call">Call</a> <i>m</i>(<i>x</i>, <i>d</i>) and let <i>r</i> be its result.</li>
+ <li>If <i>r</i> is <b>failure</b>, return <b>failure</b>.</li>
+ <li>Let <i>y</i> be <i>r</i>'s State.</li>
+ <li>Let <i>cap</i> be <i>y</i>'s <i>captures</i> <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>xe</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li>Let <i>z</i> be the State (<i>xe</i>, <i>cap</i>).</li>
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>z</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Assertion</span> <span class="geq">::</span> <code
+ class="t">(</code> <code class="t">?</code> <code class="t">!</code> <span class="nt">Disjunction</span> <code
+ class="t">)</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Disjunction</i> to obtain a Matcher <i>m</i>.</li>
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps:
+ <ol class="nested proc">
+ <li>Let <i>d</i> be a Continuation that always returns its State argument as a successful MatchResult.</li>
+ <li><a href="#sec-call">Call</a> <i>m</i>(<i>x</i>, <i>d</i>) and let <i>r</i> be its result.</li>
+ <li>If <i>r</i> isn't <b>failure</b>, return <b>failure</b>.</li>
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>x</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+ </div>
+
+ <section id="sec-runtime-semantics-iswordchar-abstract-operation">
+ <h1><span class="secnum" id="sec-21.2.2.6.1"><a href="#sec-runtime-semantics-iswordchar-abstract-operation"
+ title="link to this section">21.2.2.6.1</a></span> Runtime Semantics: IsWordChar Abstract Operation</h1>
+
+ <p>The abstract operation IsWordChar takes an integer parameter <var>e</var> and performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>e</i> is –1 or <i>e</i> is <i>InputLength</i>, return <b>false</b>.</li>
+ <li>Let <i>c</i> be the character <i>Input</i>[<i>e</i>].</li>
+ <li>If <i>c</i> is one of the sixty-three characters below, return <b>true</b>.
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>a</code></td>
+ <td><code>b</code></td>
+ <td><code>c</code></td>
+ <td><code>d</code></td>
+ <td><code>e</code></td>
+ <td><code>f</code></td>
+ <td><code>g</code></td>
+ <td><code>h</code></td>
+ <td><code>i</code></td>
+ <td><code>j</code></td>
+ <td><code>k</code></td>
+ <td><code>l</code></td>
+ <td><code>m</code></td>
+ <td><code>n</code></td>
+ <td><code>o</code></td>
+ <td><code>p</code></td>
+ <td><code>q</code></td>
+ <td><code>r</code></td>
+ <td><code>s</code></td>
+ <td><code>t</code></td>
+ <td><code>u</code></td>
+ <td><code>v</code></td>
+ <td><code>w</code></td>
+ <td><code>x</code></td>
+ <td><code>y</code></td>
+ <td><code>z</code></td>
+ </tr>
+ <tr>
+ <td><code>A</code></td>
+ <td><code>B</code></td>
+ <td><code>C</code></td>
+ <td><code>D</code></td>
+ <td><code>E</code></td>
+ <td><code>F</code></td>
+ <td><code>G</code></td>
+ <td><code>H</code></td>
+ <td><code>I</code></td>
+ <td><code>J</code></td>
+ <td><code>K</code></td>
+ <td><code>L</code></td>
+ <td><code>M</code></td>
+ <td><code>N</code></td>
+ <td><code>O</code></td>
+ <td><code>P</code></td>
+ <td><code>Q</code></td>
+ <td><code>R</code></td>
+ <td><code>S</code></td>
+ <td><code>T</code></td>
+ <td><code>U</code></td>
+ <td><code>V</code></td>
+ <td><code>W</code></td>
+ <td><code>X</code></td>
+ <td><code>Y</code></td>
+ <td><code>Z</code></td>
+ </tr>
+ <tr>
+ <td><code>0</code></td>
+ <td><code>1</code></td>
+ <td><code>2</code></td>
+ <td><code>3</code></td>
+ <td><code>4</code></td>
+ <td><code>5</code></td>
+ <td><code>6</code></td>
+ <td><code>7</code></td>
+ <td><code>8</code></td>
+ <td><code>9</code></td>
+ <td><code>_</code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-quantifier">
+ <h1><span class="secnum" id="sec-21.2.2.7"><a href="#sec-quantifier" title="link to this section">21.2.2.7</a></span>
+ Quantifier</h1>
+
+ <p>The production <span class="prod"><span class="nt">Quantifier</span> <span class="geq">::</span> <span
+ class="nt">QuantifierPrefix</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>QuantifierPrefix</i> to obtain the two results: an integer <i>min</i> and an integer (or ∞)
+ <i>max</i>.</li>
+ <li>Return the three results <i>min</i>, <i>max</i>, and <b>true</b>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Quantifier</span> <span class="geq">::</span> <span
+ class="nt">QuantifierPrefix</span> <code class="t">?</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>QuantifierPrefix</i> to obtain the two results: an integer <i>min</i> and an integer (or ∞)
+ <i>max</i>.</li>
+ <li>Return the three results <i>min</i>, <i>max</i>, and <b>false</b>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span> <code
+ class="t">*</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the two results 0 and ∞.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span> <code
+ class="t">+</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the two results 1 and ∞.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span> <code
+ class="t">?</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the two results 0 and 1.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span> <code
+ class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">}</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>i</i> be the MV of <i>DecimalDigits</i> (<a href="#sec-literals-numeric-literals">see 11.8.3</a>).</li>
+ <li>Return the two results <i>i</i> and <i>i</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span> <code
+ class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">,</code> <code class="t">}</code></span>
+ evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>i</i> be the MV of <i>DecimalDigits</i>.</li>
+ <li>Return the two results <i>i</i> and ∞.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span> <code
+ class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">,</code> <span class="nt">DecimalDigits</span>
+ <code class="t">}</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>i</i> be the MV of the first <i>DecimalDigits</i>.</li>
+ <li>Let <i>j</i> be the MV of the second <i>DecimalDigits</i>.</li>
+ <li>Return the two results <i>i</i> and <i>j</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-atom">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.2.8"><a href="#sec-atom" title="link to this section">21.2.2.8</a></span>
+ Atom</h1>
+
+ <p>The production <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <span
+ class="nt">PatternCharacter</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>ch</i> be the character matched by <i>PatternCharacter</i>.</li>
+ <li>Let <i>A</i> be a one-element CharSet containing the character <i>ch</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterSetMatcher(<i>A</i>, <b>false</b>) and return its Matcher result.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code
+ class="t">.</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>A</i> be the set of all characters except <i>LineTerminator</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterSetMatcher(<i>A</i>, <b>false</b>) and return its Matcher result.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code class="t">\</code>
+ <span class="nt">AtomEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the Matcher that is the result of evaluating <i>AtomEscape</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <span
+ class="nt">CharacterClass</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>CharacterClass</i> to obtain a CharSet <i>A</i> and a Boolean <i>invert</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterSetMatcher(<i>A</i>, <i>invert</i>) and return its Matcher result.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code class="t">(</code>
+ <span class="nt">Disjunction</span> <code class="t">)</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>Disjunction</i> to obtain a Matcher <i>m</i>.</li>
+ <li>Let <i>parenIndex</i> be the number of left capturing parentheses in the entire regular expression that occur to
+ the left of this production expansion's initial left parenthesis. This is the total number of times the <span
+ class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code class="t">(</code> <span
+ class="nt">Disjunction</span> <code class="t">)</code></span> production is expanded prior to this production's
+ <i>Atom</i> plus the total number of <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span>
+ <code class="t">(</code> <span class="nt">Disjunction</span> <code class="t">)</code></span> productions enclosing
+ this <i>Atom</i>.</li>
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps:
+ <ol class="nested proc">
+ <li>Create an internal Continuation closure <i>d</i> that takes one State argument <i>y</i> and performs the
+ following steps:
+ <ol class="nested proc">
+ <li>Let <i>cap</i> be a fresh copy of <i>y</i>'s <i>captures</i> <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>xe</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li>Let <i>ye</i> be <i>y</i>'s <i>endIndex</i>.</li>
+ <li>Let <i>s</i> be a fresh <a href="#sec-list-and-record-specification-type">List</a> whose characters are
+ the characters of <i>Input</i> at indices <i>xe</i> (inclusive) through <i>ye</i> (exclusive).</li>
+ <li>Set <i>cap</i>[<i>parenIndex</i>+1] to <i>s</i>.</li>
+ <li>Let <i>z</i> be the State (<i>ye</i>, <i>cap</i>).</li>
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>z</i>) and return its result.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-call">Call</a> <i>m</i>(<i>x</i>, <i>d</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code class="t">(</code>
+ <code class="t">?</code> <code class="t">:</code> <span class="nt">Disjunction</span> <code class="t">)</code></span>
+ evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the Matcher that is the result of evaluating <i>Disjunction</i>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-runtime-semantics-charactersetmatcher-abstract-operation">
+ <h1><span class="secnum" id="sec-21.2.2.8.1"><a href="#sec-runtime-semantics-charactersetmatcher-abstract-operation"
+ title="link to this section">21.2.2.8.1</a></span> Runtime Semantics: CharacterSetMatcher Abstract Operation</h1>
+
+ <p>The abstract operation CharacterSetMatcher takes two arguments, a CharSet <var>A</var> and a Boolean flag
+ <var>invert</var>, and performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps when evaluated:
+ <ol class="nested proc">
+ <li>Let <i>e</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li>If <i>e</i> is <i>InputLength</i>, return <b>failure</b>.</li>
+ <li>Let <i>ch</i> be the character <i>Input</i>[<i>e</i>].</li>
+ <li>Let <i>cc</i> be Canonicalize(<i>ch</i>).</li>
+ <li>If <i>invert</i> is <b>false</b>, then
+ <ol class="block">
+ <li>If there does not exist a member <i>a</i> of set <i>A</i> such that Canonicalize(<i>a</i>) is <i>cc</i>,
+ return <b>failure</b>.</li>
+ </ol>
+ </li>
+ <li>Else <i>invert</i> is <b>true</b>,
+ <ol class="block">
+ <li>If there exists a member <i>a</i> of set <i>A</i> such that Canonicalize(<i>a</i>) is <i>cc</i>, return
+ <b>failure.</b></li>
+ </ol>
+ </li>
+ <li>Let <i>cap</i> be <i>x</i>'s <i>captures</i> <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>y</i> be the State (<i>e</i>+1, <i>cap</i>).</li>
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>y</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-runtime-semantics-canonicalize-abstract-operation">
+ <h1><span class="secnum" id="sec-21.2.2.8.2"><a href="#sec-runtime-semantics-canonicalize-abstract-operation"
+ title="link to this section">21.2.2.8.2</a></span> Runtime Semantics: Canonicalize Abstract Operation</h1>
+
+ <p>The abstract operation Canonicalize takes a character parameter <var>ch</var> and performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>IgnoreCase</i> is <b>false</b>, return <i>ch</i>.</li>
+ <li>If <i>Unicode</i> is <b>true</b>,
+ <ol class="block">
+ <li>If the file CaseFolding.txt of the Unicode Character Database provides a simple or common case folding mapping
+ for <i>ch</i>, return the result of applying that mapping to <i>ch</i>.</li>
+ <li>Else, return <i>ch.</i></li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>ch</i> is a UTF-16 code unit.</li>
+ <li>Let <i>s</i> be the ECMAScript String value consisting of the single code unit <i>ch</i>.</li>
+ <li>Let <i>u</i> be the same result produced as if by performing the algorithm for <code><a
+ href="#sec-string.prototype.touppercase">String.prototype.toUpperCase</a></code> using <i>s</i> as the
+ <b>this</b> value.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>u</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>u</i> is a String value.</li>
+ <li>If <i>u</i> does not consist of a single code unit, return <i>ch</i>.</li>
+ <li>Let <i>cu</i> be <i>u</i>’s single code unit element.</li>
+ <li>If <i>ch</i>'s code unit value ≥ 128 and <i>cu</i>'s code unit value < 128, return <i>ch</i>.</li>
+ <li>Return <i>cu</i>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> Parentheses of the form <code>(</code> <i>Disjunction</i> <code>)</code> serve both
+ to group the components of the <i>Disjunction</i> pattern together and to save the result of the match. The result can
+ be used either in a backreference (<code>\</code> followed by a nonzero decimal number), referenced in a replace
+ String, or returned as part of an array from the regular expression matching internal procedure. To inhibit the
+ capturing behaviour of parentheses, use the form <code>(?:</code> <i>Disjunction</i> <code>)</code> instead.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The form <code>(?=</code> <i>Disjunction</i> <code>)</code> specifies a zero-width
+ positive lookahead. In order for it to succeed, the pattern inside <i>Disjunction</i> must match at the current
+ position, but the current position is not advanced before matching the sequel. If <i>Disjunction</i> can match at the
+ current position in several ways, only the first one is tried. Unlike other regular expression operators, there is no
+ backtracking into a <code>(?=</code> form (this unusual behaviour is inherited from Perl). This only matters when the
+ <i>Disjunction</i> contains capturing parentheses and the sequel of the pattern contains backreferences to those
+ captures.</p>
+
+ <p>For example,</p>
+
+ <pre>/(?=(a+))/.exec("baaabac")</pre>
+
+ <p>matches the empty String immediately after the first <code>b</code> and therefore returns the array:</p>
+
+ <pre>["", "aaa"]</pre>
+
+ <p>To illustrate the lack of backtracking into the lookahead, consider:</p>
+
+ <pre>/(?=(a+))a*b\1/.exec("baaabac")</pre>
+
+ <p>This expression returns</p>
+
+ <pre>["aba", "a"]</pre>
+
+ <p>and not:</p>
+
+ <pre>["aaaba", "a"]</pre>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> The form <code>(?!</code> <i>Disjunction</i> <code>)</code> specifies a zero-width
+ negative lookahead. In order for it to succeed, the pattern inside <i>Disjunction</i> must fail to match at the
+ current position. The current position is not advanced before matching the sequel. <i>Disjunction</i> can contain
+ capturing parentheses, but backreferences to them only make sense from within <i>Disjunction</i> itself.
+ Backreferences to these capturing parentheses from elsewhere in the pattern always return <b>undefined</b> because the
+ negative lookahead must fail for the pattern to succeed. For example,</p>
+
+ <pre>/(.*?)a(?!(a+)b\2c)\2(.*)/.exec("baaabaac")</pre>
+
+ <p>looks for an <code>a</code> not immediately followed by some positive number n of <code>a</code>'s, a
+ <code>b</code>, another n <code>a</code>'s (specified by the first <code>\2</code>) and a <code>c</code>. The second
+ <code>\2</code> is outside the negative lookahead, so it matches against <b>undefined</b> and therefore always
+ succeeds. The whole expression returns the array:</p>
+
+ <pre>["baaabaac", "ba", undefined, "abaac"]</pre>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 4</span> In case-insignificant matches when <i>Unicode</i> is <b>true</b>, all characters are
+ implicitly case-folded using the simple mapping provided by the Unicode standard immediately before they are compared.
+ The simple mapping always maps to a single code point, so it does not map, for example, <code>"ß"</code>
+ (U+00DF) to <code>"SS"</code>. It may however map a code point outside the Basic Latin range to a character within,
+ for example, “<span style="font-family: sans-serif">ſ</span>” (U+017F) to “s”. Such
+ characters are not mapped if <i>Unicode</i> is <b>false</b>. This prevents Unicode code points such as U+017F and
+ U+212A from matching regular expressions such as <code>/[a‑z]/i</code>, but they will match
+ <code>/[a‑z]/ui</code>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-atomescape">
+ <h1><span class="secnum" id="sec-21.2.2.9"><a href="#sec-atomescape" title="link to this section">21.2.2.9</a></span>
+ AtomEscape</h1>
+
+ <p>The production <span class="prod"><span class="nt">AtomEscape</span> <span class="geq">::</span> <span
+ class="nt">DecimalEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>DecimalEscape</i> to obtain an EscapeValue <i>E</i>.</li>
+ <li>If <i>E</i> is a character, then
+ <ol class="block">
+ <li>Let <i>ch</i> be <i>E</i>'s character.</li>
+ <li>Let <i>A</i> be a one-element CharSet containing the character <i>ch</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterSetMatcher(<i>A</i>, <b>false</b>) and return its Matcher result.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>E</i> must be an integer.</li>
+ <li>Let <i>n</i> be that integer.</li>
+ <li>If <i>n</i>=0 or <i>n</i>><i>NcapturingParens</i>, throw a <b>SyntaxError</b> exception.</li>
+ <li>Return an internal Matcher closure that takes two arguments, a State <i>x</i> and a Continuation <i>c</i>, and
+ performs the following steps:
+ <ol class="nested proc">
+ <li>Let <i>cap</i> be <i>x</i>'s <i>captures</i> <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>s</i> be <i>cap</i>[<i>n</i>].</li>
+ <li>If <i>s</i> is <b>undefined</b>, return <i>c</i>(<i>x</i>).</li>
+ <li>Let <i>e</i> be <i>x</i>'s <i>endIndex</i>.</li>
+ <li>Let <i>len</i> be <i>s</i>'s length.</li>
+ <li>Let <i>f</i> be <i>e</i>+<i>len</i>.</li>
+ <li>If <i>f</i>><i>InputLength</i>, return <b>failure</b>.</li>
+ <li>If there exists an integer <i>i</i> between 0 (inclusive) and <i>len</i> (exclusive) such that
+ Canonicalize(<i>s</i>[<i>i</i>]) is not the same character value as Canonicalize(<i>Input</i>
+ [<i>e</i>+<i>i</i>]), return <b>failure</b>.</li>
+ <li>Let <i>y</i> be the State (<i>f</i>, <i>cap</i>).</li>
+ <li><a href="#sec-call">Call</a> <i>c</i>(<i>y</i>) and return its result.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">AtomEscape</span> <span class="geq">::</span> <span
+ class="nt">CharacterEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>CharacterEscape</i> to obtain a character <i>ch</i>.</li>
+ <li>Let <i>A</i> be a one-element CharSet containing the character <i>ch</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterSetMatcher(<i>A</i>, <b>false</b>) and return its Matcher result.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">AtomEscape</span> <span class="geq">::</span> <span
+ class="nt">CharacterClassEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>CharacterClassEscape</i> to obtain a CharSet <i>A</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterSetMatcher(<i>A</i>, <b>false</b>) and return its Matcher result.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> An escape sequence of the form <code>\</code> followed by a nonzero decimal number
+ <i>n</i> matches the result of the <i>n</i>th set of capturing parentheses (<a href="#sec-decimalescape">see
+ 21.2.2.11</a>). It is an error if the regular expression has fewer than <i>n</i> capturing parentheses. If the regular
+ expression has <i>n</i> or more capturing parentheses but the <i>n</i>th one is <b>undefined</b> because it has not
+ captured anything, then the backreference always succeeds.</p>
+ </div>
+ </section>
+
+ <section id="sec-characterescape">
+ <h1><span class="secnum" id="sec-21.2.2.10"><a href="#sec-characterescape"
+ title="link to this section">21.2.2.10</a></span> CharacterEscape</h1>
+
+ <p>The production <span class="prod"><span class="nt">CharacterEscape</span> <span class="geq">::</span> <span
+ class="nt">ControlEscape</span></span> evaluates by returning the character according to <a href="#table-47">Table
+ 47</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-47">Table 47</span> — ControlEscape Character Values</figcaption>
+ <table class="real-table">
+ <tr>
+ <th>ControlEscape</th>
+ <th>Character Value</th>
+ <th>Code Point</th>
+ <th>Unicode Name</th>
+ <th>Symbol</th>
+ </tr>
+ <tr>
+ <td><code>t</code></td>
+ <td>9</td>
+ <td><code>U+0009</code></td>
+ <td>CHARACTER TABULATION</td>
+ <td><HT></td>
+ </tr>
+ <tr>
+ <td><code>n</code></td>
+ <td>10</td>
+ <td><code>U+000A</code></td>
+ <td>LINE FEED (LF)</td>
+ <td><LF></td>
+ </tr>
+ <tr>
+ <td><code>v</code></td>
+ <td>11</td>
+ <td><code>U+000B</code></td>
+ <td>LINE TABULATION</td>
+ <td><VT></td>
+ </tr>
+ <tr>
+ <td><code>f</code></td>
+ <td>12</td>
+ <td><code>U+000C</code></td>
+ <td>FORM FEED (FF)</td>
+ <td><FF></td>
+ </tr>
+ <tr>
+ <td><code>r</code></td>
+ <td>13</td>
+ <td><code>U+000D</code></td>
+ <td>CARRIAGE RETURN (CR)</td>
+ <td><CR></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The production <span class="prod"><span class="nt">CharacterEscape</span> <span class="geq">::</span> <code
+ class="t">c</code> <span class="nt">ControlLetter</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>ch</i> be the character matched by <i>ControlLetter</i>.</li>
+ <li>Let <i>i</i> be <i>ch</i>'s character value.</li>
+ <li>Let <i>j</i> be the remainder of dividing <i>i</i> by 32.</li>
+ <li>Return the character whose character value is <i>j</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">CharacterEscape</span> <span class="geq">::</span> <span
+ class="nt">HexEscapeSequence</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the character whose code is the SV of <i>HexEscapeSequence</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">CharacterEscape</span> <span class="geq">::</span> <span
+ class="nt">RegExpUnicodeEscapeSequence</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the result of evaluating <i>RegExpUnicodeEscapeSequence</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">CharacterEscape</span> <span class="geq">::</span> <span
+ class="nt">IdentityEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the character matched by <i>IdentityEscape</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">RegExpUnicodeEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">u</code> <span class="nt">LeadSurrogate</span> <code class="t">\u</code> <span
+ class="nt">TrailSurrogate</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>lead</i> be the result of evaluating <i>LeadSurrogate</i>.</li>
+ <li>Let <i>trail</i> be the result of evaluating <i>TrailSurrogate</i>.</li>
+ <li>Let <i>cp</i> be <a href="#sec-utf16decode">UTF16Decode</a>(<i>lead</i>, <i>trail</i>).</li>
+ <li>Return the character whose character value is <i>cp</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">RegExpUnicodeEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">u</code> <span class="nt">Hex4Digits</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the character whose code is the SV of <i>Hex4Digits</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">RegExpUnicodeEscapeSequence</span> <span class="geq">::</span> <code
+ class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the character whose code is the MV of <i>HexDigits</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">LeadSurrogate</span> <span class="geq">::</span> <span
+ class="nt">Hex4Digits</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the character whose code is the SV of <i>Hex4Digits</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">TrailSurrogate</span> <span class="geq">::</span> <span
+ class="nt">Hex4Digits</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the character whose code is the SV of <i>Hex4Digits</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-decimalescape">
+ <h1><span class="secnum" id="sec-21.2.2.11"><a href="#sec-decimalescape" title="link to this section">21.2.2.11</a></span>
+ DecimalEscape</h1>
+
+ <p>The production <span class="prod"><span class="nt">DecimalEscape</span> <span class="geq">::</span> <span
+ class="nt">DecimalIntegerLiteral</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>i</i> be the MV of <i>DecimalIntegerLiteral</i>.</li>
+ <li>If <i>i</i> is zero, return the EscapeValue consisting of the character U+0000 (NULL).</li>
+ <li>Return the EscapeValue consisting of the integer <i>i</i>.</li>
+ </ol>
+
+ <p>The definition of “the MV of <span class="nt">DecimalIntegerLiteral</span>” is in <a
+ href="#sec-literals-numeric-literals">11.8.3</a>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If <code>\</code> is followed by a decimal number <i>n</i> whose first digit is not
+ <code>0</code>, then the escape sequence is considered to be a backreference. It is an error if <i>n</i> is greater than
+ the total number of left capturing parentheses in the entire regular expression. <code>\0</code> represents the
+ <NUL> character and cannot be followed by a decimal digit.</p>
+ </div>
+ </section>
+
+ <section id="sec-characterclassescape">
+ <h1><span class="secnum" id="sec-21.2.2.12"><a href="#sec-characterclassescape"
+ title="link to this section">21.2.2.12</a></span> CharacterClassEscape</h1>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code
+ class="t">d</code></span> evaluates by returning the ten-element set of characters containing the characters
+ <code>0</code> through <code>9</code> inclusive.</p>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code
+ class="t">D</code></span> evaluates by returning the set of all characters not included in the set returned by <span
+ class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code class="t">d</code></span>
+ .</p>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code
+ class="t">s</code></span> evaluates by returning the set of characters containing the characters that are on the
+ right-hand side of the <span class="nt">WhiteSpace</span> (<a href="#sec-white-space">11.2</a>) or <span
+ class="nt">LineTerminator</span> (<a href="#sec-line-terminators">11.3</a>) productions.</p>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code
+ class="t">S</code></span> evaluates by returning the set of all characters not included in the set returned by <span
+ class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code class="t">s</code></span>
+ .</p>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code
+ class="t">w</code></span> evaluates by returning the set of characters containing the sixty-three characters:</p>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>a</code></td>
+ <td><code>b</code></td>
+ <td><code>c</code></td>
+ <td><code>d</code></td>
+ <td><code>e</code></td>
+ <td><code>f</code></td>
+ <td><code>g</code></td>
+ <td><code>h</code></td>
+ <td><code>i</code></td>
+ <td><code>j</code></td>
+ <td><code>k</code></td>
+ <td><code>l</code></td>
+ <td><code>m</code></td>
+ <td><code>n</code></td>
+ <td><code>o</code></td>
+ <td><code>p</code></td>
+ <td><code>q</code></td>
+ <td><code>r</code></td>
+ <td><code>s</code></td>
+ <td><code>t</code></td>
+ <td><code>u</code></td>
+ <td><code>v</code></td>
+ <td><code>w</code></td>
+ <td><code>x</code></td>
+ <td><code>y</code></td>
+ <td><code>z</code></td>
+ </tr>
+ <tr>
+ <td><code>A</code></td>
+ <td><code>B</code></td>
+ <td><code>C</code></td>
+ <td><code>D</code></td>
+ <td><code>E</code></td>
+ <td><code>F</code></td>
+ <td><code>G</code></td>
+ <td><code>H</code></td>
+ <td><code>I</code></td>
+ <td><code>J</code></td>
+ <td><code>K</code></td>
+ <td><code>L</code></td>
+ <td><code>M</code></td>
+ <td><code>N</code></td>
+ <td><code>O</code></td>
+ <td><code>P</code></td>
+ <td><code>Q</code></td>
+ <td><code>R</code></td>
+ <td><code>S</code></td>
+ <td><code>T</code></td>
+ <td><code>U</code></td>
+ <td><code>V</code></td>
+ <td><code>W</code></td>
+ <td><code>X</code></td>
+ <td><code>Y</code></td>
+ <td><code>Z</code></td>
+ </tr>
+ <tr>
+ <td><code>0</code></td>
+ <td><code>1</code></td>
+ <td><code>2</code></td>
+ <td><code>3</code></td>
+ <td><code>4</code></td>
+ <td><code>5</code></td>
+ <td><code>6</code></td>
+ <td><code>7</code></td>
+ <td><code>8</code></td>
+ <td><code>9</code></td>
+ <td><code>_</code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code
+ class="t">W</code></span> evaluates by returning the set of all characters not included in the set returned by <span
+ class="prod"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <code class="t">w</code></span>
+ .</p>
+ </section>
+
+ <section id="sec-characterclass">
+ <h1><span class="secnum" id="sec-21.2.2.13"><a href="#sec-characterclass"
+ title="link to this section">21.2.2.13</a></span> CharacterClass</h1>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClass</span> <span class="geq">::</span> <code
+ class="t">[</code> <span class="nt">ClassRanges</span> <code class="t">]</code></span> evaluates by evaluating <span
+ class="nt">ClassRanges</span> to obtain a CharSet and returning that CharSet and the Boolean <b>false</b>.</p>
+
+ <p>The production <span class="prod"><span class="nt">CharacterClass</span> <span class="geq">::</span> <code
+ class="t">[</code> <code class="t">^</code> <span class="nt">ClassRanges</span> <code class="t">]</code></span> evaluates
+ by evaluating <span class="nt">ClassRanges</span> to obtain a CharSet and returning that CharSet and the Boolean
+ <b>true</b>.</p>
+ </section>
+
+ <section id="sec-classranges">
+ <h1><span class="secnum" id="sec-21.2.2.14"><a href="#sec-classranges" title="link to this section">21.2.2.14</a></span>
+ ClassRanges</h1>
+
+ <p>The production <span class="prod"><span class="nt">ClassRanges</span> <span class="geq">::</span> <span
+ class="grhsannot">[empty]</span></span> evaluates by returning the empty CharSet.</p>
+
+ <p>The production <span class="prod"><span class="nt">ClassRanges</span> <span class="geq">::</span> <span
+ class="nt">NonemptyClassRanges</span></span> evaluates by evaluating <span class="nt">NonemptyClassRanges</span> to obtain
+ a CharSet and returning that CharSet.</p>
+ </section>
+
+ <section id="sec-nonemptyclassranges">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.2.15"><a href="#sec-nonemptyclassranges"
+ title="link to this section">21.2.2.15</a></span> NonemptyClassRanges</h1>
+
+ <p>The production <span class="prod"><span class="nt">NonemptyClassRanges</span> <span class="geq">::</span> <span
+ class="nt">ClassAtom</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet that is the result of evaluating <i>ClassAtom</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">NonemptyClassRanges</span> <span class="geq">::</span> <span
+ class="nt">ClassAtom</span> <span class="nt">NonemptyClassRangesNoDash</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>ClassAtom</i> to obtain a CharSet <i>A</i>.</li>
+ <li>Evaluate <i>NonemptyClassRangesNoDash</i> to obtain a CharSet <i>B</i>.</li>
+ <li>Return the union of CharSets <i>A</i> and <i>B</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">NonemptyClassRanges</span> <span class="geq">::</span> <span
+ class="nt">ClassAtom</span> <code class="t">-</code> <span class="nt">ClassAtom</span> <span
+ class="nt">ClassRanges</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate the first <i>ClassAtom</i> to obtain a CharSet <i>A</i>.</li>
+ <li>Evaluate the second <i>ClassAtom</i> to obtain a CharSet <i>B</i>.</li>
+ <li>Evaluate <i>ClassRanges</i> to obtain a CharSet <i>C</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterRange(<i>A</i>, <i>B</i>) and let <i>D</i> be the resulting CharSet.</li>
+ <li>Return the union of CharSets <i>D</i> and <i>C</i>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-runtime-semantics-characterrange-abstract-operation">
+ <h1><span class="secnum" id="sec-21.2.2.15.1"><a href="#sec-runtime-semantics-characterrange-abstract-operation"
+ title="link to this section">21.2.2.15.1</a></span> Runtime Semantics: CharacterRange Abstract Operation</h1>
+
+ <p>The abstract operation CharacterRange takes two CharSet parameters <var>A</var> and <var>B</var> and performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>If <i>A</i> does not contain exactly one character or <i>B</i> does not contain exactly one character, throw a
+ <b>SyntaxError</b> exception.</li>
+ <li>Let <i>a</i> be the one character in CharSet <i>A</i>.</li>
+ <li>Let <i>b</i> be the one character in CharSet <i>B</i>.</li>
+ <li>Let <i>i</i> be the character value of character <i>a</i>.</li>
+ <li>Let <i>j</i> be the character value of character <i>b</i>.</li>
+ <li>If <i>i</i> > <i>j</i>, throw a <b>SyntaxError</b> exception.</li>
+ <li>Return the set containing all characters numbered <i>i</i> through <i>j</i>, inclusive.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-nonemptyclassrangesnodash">
+ <h1><span class="secnum" id="sec-21.2.2.16"><a href="#sec-nonemptyclassrangesnodash"
+ title="link to this section">21.2.2.16</a></span> NonemptyClassRangesNoDash</h1>
+
+ <p>The production <span class="prod"><span class="nt">NonemptyClassRangesNoDash</span> <span class="geq">::</span> <span
+ class="nt">ClassAtom</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet that is the result of evaluating <i>ClassAtom</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">NonemptyClassRangesNoDash</span> <span class="geq">::</span> <span
+ class="nt">ClassAtomNoDash</span> <span class="nt">NonemptyClassRangesNoDash</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>ClassAtomNoDash</i> to obtain a CharSet <i>A</i>.</li>
+ <li>Evaluate <i>NonemptyClassRangesNoDash</i> to obtain a CharSet <i>B</i>.</li>
+ <li>Return the union of CharSets <i>A</i> and <i>B</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">NonemptyClassRangesNoDash</span> <span class="geq">::</span> <span
+ class="nt">ClassAtomNoDash</span> <code class="t">-</code> <span class="nt">ClassAtom</span> <span
+ class="nt">ClassRanges</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>ClassAtomNoDash</i> to obtain a CharSet <i>A</i>.</li>
+ <li>Evaluate <i>ClassAtom</i> to obtain a CharSet <i>B</i>.</li>
+ <li>Evaluate <i>ClassRanges</i> to obtain a CharSet <i>C</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterRange(<i>A</i>, <i>B</i>) and let <i>D</i> be the resulting CharSet.</li>
+ <li>Return the union of CharSets <i>D</i> and <i>C</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> <i>ClassRanges</i> can expand into single <i>ClassAtoms</i> and/or ranges of two
+ <i>ClassAtoms</i> separated by dashes. In the latter case the <i>ClassRanges</i> includes all characters between the
+ first <i>ClassAtom</i> and the second <i>ClassAtom</i>, inclusive; an error occurs if either <i>ClassAtom</i> does not
+ represent a single character (for example, if one is <code>\w</code>) or if the first <i>ClassAtom's</i> character value
+ is greater than the second <i>ClassAtom's</i> character value.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Even if the pattern ignores case, the case of the two ends of a range is significant
+ in determining which characters belong to the range. Thus, for example, the pattern <code>/[E-F]/i</code> matches only
+ the letters <code>E</code>, <code>F</code>, <code>e</code>, and <code>f</code>, while the pattern <code>/[E-f]/i</code>
+ matches all upper and lower-case letters in the Unicode Basic Latin block as well as the symbols <code>[</code>,
+ <code>\</code>, <code>]</code>, <code>^</code>, <code>_</code>, and <code>`</code>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> A <code>-</code> character can be treated literally or it can denote a range. It is
+ treated literally if it is the first or last character of <span class="nt">ClassRanges</span>, the beginning or end
+ limit of a range specification, or immediately follows a range specification.</p>
+ </div>
+ </section>
+
+ <section id="sec-classatom">
+ <h1><span class="secnum" id="sec-21.2.2.17"><a href="#sec-classatom" title="link to this section">21.2.2.17</a></span>
+ ClassAtom</h1>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtom</span> <span class="geq">::</span> <code
+ class="t">-</code></span> evaluates by returning the CharSet containing the one character <code>-</code>.</p>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtom</span> <span class="geq">::</span> <span
+ class="nt">ClassAtomNoDash</span></span> evaluates by evaluating <span class="nt">ClassAtomNoDash</span> to obtain a
+ CharSet and returning that CharSet.</p>
+ </section>
+
+ <section id="sec-classatomnodash">
+ <h1><span class="secnum" id="sec-21.2.2.18"><a href="#sec-classatomnodash"
+ title="link to this section">21.2.2.18</a></span> ClassAtomNoDash</h1>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtomNoDash</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span
+ class="grhsmod">or</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">-</code></span>
+ evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet containing the character matched by <i>SourceCharacter</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtomNoDash</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">ClassEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet that is the result of evaluating <i>ClassEscape</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-classescape">
+ <h1><span class="secnum" id="sec-21.2.2.19"><a href="#sec-classescape" title="link to this section">21.2.2.19</a></span>
+ ClassEscape</h1>
+
+ <p>The production <span class="prod"><span class="nt">ClassEscape</span> <span class="geq">::</span> <span
+ class="nt">DecimalEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Evaluate <i>DecimalEscape</i> to obtain an EscapeValue <i>E</i>.</li>
+ <li>If <i>E</i> is not a character, throw a <b>SyntaxError</b> exception.</li>
+ <li>Let <i>ch</i> be <i>E</i>'s character.</li>
+ <li>Return the one-element CharSet containing the character <i>ch</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">ClassEscape</span> <span class="geq">::</span> <code
+ class="t">b</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet containing the single character <BS> U+0008 (BACKSPACE).</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">ClassEscape</span> <span class="geq">::</span> <code
+ class="t">-</code></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet containing the single character - U+002D (HYPEN-MINUS).</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">ClassEscape</span> <span class="geq">::</span> <span
+ class="nt">CharacterEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet containing the single character that is the result of evaluating <i>CharacterEscape</i>.</li>
+ </ol>
+
+ <p>The production <span class="prod"><span class="nt">ClassEscape</span> <span class="geq">::</span> <span
+ class="nt">CharacterClassEscape</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Return the CharSet that is the result of evaluating <i>CharacterClassEscape</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> A <i>ClassAtom</i> can use any of the escape sequences that are allowed in the rest of
+ the regular expression except for <code>\b</code>, <code>\B</code>, and backreferences. Inside a <i>CharacterClass</i>,
+ <code>\b</code> means the backspace character, while <code>\B</code> and backreferences raise errors. Using a
+ backreference inside a <i>ClassAtom</i> causes an error.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-regexp-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.3"><a href="#sec-regexp-constructor" title="link to this section">21.2.3</a></span>
+ The RegExp Constructor</h1>
+
+ <p>The RegExp constructor is the %RegExp% intrinsic object and the initial value of the <code>RegExp</code> property of
+ the global object. When <code>RegExp</code> is called as a function rather than as a constructor, it creates and
+ initializes a new RegExp object. Thus the function call <code><b>RegExp(</b>…<b>)</b></code> is equivalent to the
+ object creation expression <code><b>new RegExp(</b>…<b>)</b></code> with the same arguments.</p>
+
+ <p>The <code>RegExp</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>RegExp</code> behaviour must include a <code>super</code> call to the <code>RegExp</code> constructor to create and
+ initialize subclass instances with the necessary internal slots.</p>
+ </div>
+
+ <section id="sec-regexp-pattern-flags">
+ <h1><span class="secnum" id="sec-21.2.3.1"><a href="#sec-regexp-pattern-flags"
+ title="link to this section">21.2.3.1</a></span> RegExp ( pattern, flags )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>patternIsRegExp</i> be <a href="#sec-isregexp">IsRegExp</a>(<i>pattern</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>patternIsRegExp</i>).</li>
+ <li>If NewTarget is not <b>undefined</b>, let <i>newTarget</i> be NewTarget.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>newTarget</i> be the active function object.</li>
+ <li>If <i>patternIsRegExp</i> is <b>true</b> and <i>flags</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>patternConstructor</i> be <a href="#sec-get-o-p">Get</a>(<i>pattern</i>,
+ <code>"constructor"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>patternConstructor</i>).</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>newTarget</i>, <i>patternConstructor</i>) is <b>true</b>,
+ return <i>pattern</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>pattern</i>) is Object and <i>pattern</i> has a
+ [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li>Let <i>P</i> be the value of <i>pattern’s</i> [[OriginalSource]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>flags</i> is <b>undefined</b>, let <i>F</i> be the value of <i>pattern’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Else, let <i>F</i> be <i>flags</i>.</li>
+ </ol>
+ </li>
+ <li>Else if <i>patternIsRegExp</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>P</i> be <a href="#sec-get-o-p">Get</a>(<i>pattern</i>, <code>"source"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>If <i>flags</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>F</i> be <a href="#sec-get-o-p">Get</a>(<i>pattern</i>, <code>"flags"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>F</i>).</li>
+ </ol>
+ </li>
+ <li>Else, let <i>F</i> be <i>flags</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>P</i> be <i>pattern</i>.</li>
+ <li>Let <i>F</i> be <i>flags</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>O</i> be <a href="#sec-regexpalloc">RegExpAlloc</a>(<i>newTarget</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Return <a href="#sec-regexpinitialize">RegExpInitialize</a>(<i>O,</i> <i>P</i>, <i>F</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If pattern is supplied using a <i>StringLiteral</i>, the usual escape sequence
+ substitutions are performed before the String is processed by RegExp. If pattern must contain an escape sequence to be
+ recognized by RegExp, any REVERSE SOLIDUS (<code>\)</code> code points must be escaped within the <i>StringLiteral</i>
+ to prevent them being removed when the contents of the <i>StringLiteral</i> are formed.</p>
+ </div>
+ </section>
+
+ <section id="sec-abstract-operations-for-the-regexp-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.3.2"><a href="#sec-abstract-operations-for-the-regexp-constructor"
+ title="link to this section">21.2.3.2</a></span> Abstract Operations for the RegExp Constructor</h1>
+ </div>
+
+ <section id="sec-regexpalloc">
+ <h1><span class="secnum" id="sec-21.2.3.2.1"><a href="#sec-regexpalloc"
+ title="link to this section">21.2.3.2.1</a></span> Runtime Semantics: RegExpAlloc ( newTarget )</h1>
+
+ <p>When the abstract operation RegExpAlloc with argument <var>newTarget</var> is called, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(<i>newTarget</i>,
+ <code>"%RegExpPrototype%"</code>, «‍[[RegExpMatcher]], [[OriginalSource]],
+ [[OriginalFlags]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-definepropertyorthrow">DefinePropertyOrThrow</a>(<i>obj</i>,
+ <code>"lastIndex"</code>, PropertyDescriptor {[[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>false</b>}).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-regexpinitialize">
+ <h1><span class="secnum" id="sec-21.2.3.2.2"><a href="#sec-regexpinitialize"
+ title="link to this section">21.2.3.2.2</a></span> Runtime Semantics: RegExpInitialize ( obj, pattern, flags )</h1>
+
+ <p>When the abstract operation RegExpInitialize with arguments <i><span style="font-family: Times New
+ Roman">obj</span>,</i> <var>pattern</var>, and <var>flags</var> is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>pattern</i> is <b>undefined</b>, let <i>P</i> be the empty String.</li>
+ <li>Else, let <i>P</i> be <a href="#sec-tostring">ToString</a>(<i>pattern</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>P</i>).</li>
+ <li>If <i>flags</i> is <b>undefined</b>, let <i>F</i> be the empty String.</li>
+ <li>Else, let <i>F</i> be <a href="#sec-tostring">ToString</a>(<i>flags</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>F</i>).</li>
+ <li>If <i>F</i> contains any code unit other than <code>"g"</code>, <code>"i"</code>, <code>"m"</code>,
+ <code>"u"</code>, or <code>"y"</code> or if it contains the same code unit more than once, throw a
+ <b>SyntaxError</b> exception.</li>
+ <li>If <i>F</i> contains <code>"u"</code>, let <i>BMP</i> be <b>false</b>; else let <i>BMP</i> be <b>true</b>.</li>
+ <li>If <i>BMP</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Parse <i>P</i> using the grammars in <a href="#sec-patterns">21.2.1</a> and interpreting each of its 16-bit
+ elements as a Unicode BMP code point. UTF-16 decoding is not applied to the elements. The goal symbol for the
+ parse is <i>Pattern</i>.Throw a <b>SyntaxError</b> exception if <i>P</i> did not conform to the grammar or if
+ any elements of <i>P</i> were not matched by the parse.</li>
+ <li>Let <i>patternCharacters</i> be a <a href="#sec-list-and-record-specification-type">List</a> whose elements
+ are the code unit elements of <i>P.</i></li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Parse <i>P</i> using the grammars in <a href="#sec-patterns">21.2.1</a> and interpreting <i>P</i> as UTF-16
+ encoded Unicode code points (<a href="#sec-ecmascript-language-types-string-type">6.1.4</a>). The goal symbol
+ for the parse is <i>Pattern</i><sub>[U]</sub>. Throw a <b>SyntaxError</b> exception if <i>P</i> did not
+ conform to the grammar or if any elements of <i>P</i> were not matched by the parse.</li>
+ <li>Let <i>patternCharacters</i> be a <a href="#sec-list-and-record-specification-type">List</a> whose elements
+ are the code points resulting from applying UTF-16 decoding to <i>P</i>’s sequence of elements.</li>
+ </ol>
+ </li>
+ <li>Set the value of <i>obj’s</i> [[OriginalSource]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <i>P</i>.</li>
+ <li>Set the value of <i>obj’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <i>F</i>.</li>
+ <li>Set <i>obj’s</i> [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to the internal procedure that evaluates the above parse of <i>P</i> by applying the semantics provided
+ in <a href="#sec-pattern-semantics">21.2.2</a> using <i>patternCharacters</i> as the pattern’s <a
+ href="#sec-list-and-record-specification-type">List</a> of <i>SourceCharacter</i> values and <i>F</i> as the flag
+ parameters.</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>obj</i>, <code>"lastIndex"</code>, 0,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-regexpcreate">
+ <h1><span class="secnum" id="sec-21.2.3.2.3"><a href="#sec-regexpcreate"
+ title="link to this section">21.2.3.2.3</a></span> Runtime Semantics: RegExpCreate ( P, F )</h1>
+
+ <p>When the abstract operation RegExpCreate with arguments <var>P</var> and <var>F</var> is called, the following steps
+ are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-regexpalloc">RegExpAlloc</a>(%RegExp%).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li>Return <a href="#sec-regexpinitialize">RegExpInitialize</a>(<i>obj,</i> <i>P</i>, <i>F</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-escaperegexppattern">
+ <h1><span class="secnum" id="sec-21.2.3.2.4"><a href="#sec-escaperegexppattern"
+ title="link to this section">21.2.3.2.4</a></span> Runtime Semantics: EscapeRegExpPattern ( P, F )</h1>
+
+ <p>When the abstract operation EscapeRegExpPattern with arguments <var>P</var> and <var>F</var> is called, the following
+ occurs:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be a String in the form of a <i>Pattern</i> (<i>Pattern</i><sub>[U]</sub> if <i>F</i> contains
+ <code>"u"</code><span style="font-family: sans-serif">)</span> equivalent to <i>P</i> interpreted as UTF-16
+ encoded Unicode code points (<a href="#sec-ecmascript-language-types-string-type">6.1.4</a>), in which certain
+ code points are escaped as described below. <i>S</i> may or may not be identical to <i>P</i>; however, the
+ internal procedure that would result from evaluating <i>S</i> as a <i>Pattern</i> (<i>Pattern</i><sub>[U]</sub> if
+ <i>F</i> contains <code>"u"</code><span style="font-family: sans-serif">)</span> must behave identically to the
+ internal procedure given by the constructed object's [[RegExpMatcher]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>. Multiple calls to this abstract
+ operation using the same values for <i>P</i> and <i>F</i> must produce identical results.</li>
+ <li>The code points <code>/</code> or any <i>LineTerminator</i> occurring in the pattern shall be escaped in <i>S</i>
+ as necessary to ensure that the String value formed by concatenating the Strings <code>"/"</code>, <i>S</i>,
+ <code>"/"</code>, and <i>F</i> can be parsed (in an appropriate lexical context) as a
+ <i>RegularExpressionLiteral</i> that behaves identically to the constructed regular expression. For example, if
+ <i>P</i> is <code>"/"</code>, then <i>S</i> could be <code>"\/"</code> or <code>"\u002F"</code>, among other
+ possibilities, but not <code>"/"</code>, because <code>///</code> followed by <i>F</i> would be parsed as a
+ <i>SingleLineComment</i> rather than a <i>RegularExpressionLiteral</i>. If <i>P</i> is the empty String, this
+ specification can be met by letting <i>S</i> be <code>"(?:)"</code>.</li>
+ <li>Return <i>S</i>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-regexp-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.4"><a href="#sec-properties-of-the-regexp-constructor"
+ title="link to this section">21.2.4</a></span> Properties of the RegExp Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ RegExp constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>2</b>), the RegExp constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-regexp.prototype">
+ <h1><span class="secnum" id="sec-21.2.4.1"><a href="#sec-regexp.prototype"
+ title="link to this section">21.2.4.1</a></span> RegExp.prototype</h1>
+
+ <p>The initial value of <code>RegExp.prototype</code> is the intrinsic object %RegExpPrototype% (<a
+ href="#sec-properties-of-the-regexp-prototype-object">21.2.5</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-get-regexp-@@species">
+ <h1><span class="secnum" id="sec-21.2.4.2"><a href="#sec-get-regexp-@@species"
+ title="link to this section">21.2.4.2</a></span> get RegExp [ @@species ]</h1>
+
+ <p><code>RegExp[@@species]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"get[Symbol.species]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> RegExp prototype methods normally use their <code>this</code> object’s constructor
+ to create a derived object. However, a subclass constructor may over-ride that default behaviour by redefining its
+ @@species property.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-regexp-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.5"><a href="#sec-properties-of-the-regexp-prototype-object"
+ title="link to this section">21.2.5</a></span> Properties of the RegExp Prototype Object</h1>
+
+ <p>The RegExp prototype object is the intrinsic object %RegExpPrototype%. The RegExp prototype object is an ordinary
+ object. It is not a RegExp instance and does not have a [[RegExpMatcher]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> or any of the other internal slots of RegExp
+ instance objects.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ RegExp prototype object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The RegExp prototype object does not have a <code>valueOf</code> property of its own;
+ however, it inherits the <code>valueOf</code> property from the Object prototype object.</p>
+ </div>
+ </div>
+
+ <section id="sec-regexp.prototype.constructor">
+ <h1><span class="secnum" id="sec-21.2.5.1"><a href="#sec-regexp.prototype.constructor"
+ title="link to this section">21.2.5.1</a></span> RegExp.prototype.constructor</h1>
+
+ <p>The initial value of <code>RegExp.prototype.constructor</code> is the intrinsic object %RegExp%.</p>
+ </section>
+
+ <section id="sec-regexp.prototype.exec">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.5.2"><a href="#sec-regexp.prototype.exec"
+ title="link to this section">21.2.5.2</a></span> RegExp.prototype.exec ( string )</h1>
+
+ <p>Performs a regular expression match of <var>string</var> against the regular expression and returns an Array object
+ containing the results of the match, or <b>null</b> if <var>string</var> did not match.</p>
+
+ <p>The String <span style="font-family: Times New Roman"><a href="#sec-tostring">ToString</a>(<i>string</i>)</span> is
+ searched for an occurrence of the regular expression pattern as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>R</i> is %RegExpPrototype%, then
+ <ol class="block">
+ <li>Let <i>R</i> be <a href="#sec-regexpcreate">RegExpCreate</a>(<code>""</code>, <code>""</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>R</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>R</i> does not have a [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Return <a href="#sec-regexpbuiltinexec">RegExpBuiltinExec</a>(<i>R</i>, <i>S</i><b>)</b>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-regexpexec">
+ <h1><span class="secnum" id="sec-21.2.5.2.1"><a href="#sec-regexpexec"
+ title="link to this section">21.2.5.2.1</a></span> Runtime Semantics: RegExpExec ( R, S )</h1>
+
+ <p>The abstract operation RegExpExec with arguments <var>R</var> and <var>S</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is Object.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is String.</li>
+ <li>Let <i>exec</i> be <a href="#sec-get-o-p">Get</a>(<i>R</i>, <code>"<b>exec"</b></code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exec</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>exec</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-call">Call</a>(<i>exec</i>, <i>R</i>, «<i>S</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>result</i>) is neither Object or Null, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>R</i> does not have a [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <a href="#sec-regexpbuiltinexec">RegExpBuiltinExec</a>(<i>R</i>, <i>S</i><b>)</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If a callable <code>exec</code> property is not found this algorithm falls back to
+ attempting to use the built-in RegExp matching algorithm. This provides compatible behaviour for code written for
+ prior editions where most built-in algorithms that use regular expressions did not perform a dynamic property lookup
+ of <code>exec</code>.</p>
+ </div>
+ </section>
+
+ <section id="sec-regexpbuiltinexec">
+ <h1><span class="secnum" id="sec-21.2.5.2.2"><a href="#sec-regexpbuiltinexec"
+ title="link to this section">21.2.5.2.2</a></span> Runtime Semantics: RegExpBuiltinExec ( R, S )</h1>
+
+ <p>The abstract operation RegExpBuiltinExec with arguments <var>R</var> and <var>S</var> performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>R</i> is an initialized RegExp instance.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is String.</li>
+ <li>Let <i>length</i> be the number of code units in <i>S</i>.</li>
+ <li>Let <i>lastIndex</i> be <a href="#sec-tolength">ToLength</a>(<a
+ href="#sec-get-o-p">Get</a>(<i>R</i>,<code>"<b>lastIndex</b>"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lastIndex</i>).</li>
+ <li>Let <i>global</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"<b>global"</b></code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>global</i>).</li>
+ <li>Let <i>sticky</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"<b>sticky"</b></code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>sticky</i>).</li>
+ <li>If <i>global</i> is <b>false</b> and <i>sticky</i> is <b>false</b>, let <i>i</i> = 0.</li>
+ <li>Let <i>matcher</i> be the value of <i>R’s</i> [[RegExpMatcher]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>flags</i> be the value of <i>R’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>flags</i> contains <code>"u"</code>, let <i>fullUnicode</i> be <b>true</b>, else let <i>fullUnicode</i> be
+ <b>false.</b></li>
+ <li>Let <i>matchSucceeded</i> be <b>false</b>.</li>
+ <li>Repeat, while <i>matchSucceeded</i> is <b>false</b>
+ <ol class="block">
+ <li>If <i>lastIndex</i> > <i>length</i>, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>R</i>, <code>"<b>lastIndex"</b></code>,
+ 0, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <b>null</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>r</i> be <i>matcher</i>(<i>S</i>, <i>lastIndex</i>).</li>
+ <li>If <i>r</i> is <b>failure</b>, then
+ <ol class="block">
+ <li>If <i>sticky</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>R</i>,
+ <code>"<b>lastIndex"</b></code>, 0, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <b>null</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>lastIndex</i> = <i>lastIndex</i>+1.</li>
+ </ol>
+ </li>
+ <li>else
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>r</i> is a State.</li>
+ <li>Set <i>matchSucceeded</i> to <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>e</i> be <i>r</i>'s <i>endIndex</i> value.</li>
+ <li>If <i>fullUnicode</i> is <b>true</b>, then
+ <ol class="block">
+ <li><i>e</i> is an index into the <i>Input</i> character list, derived from <i>S</i>, matched by <i>matcher</i>.
+ Let <i>eUTF</i> be the smallest index into <i>S</i> that corresponds to the character at element <i>e</i> of
+ <i>Input</i>. If <i>e</i> is greater than the length of <i>Input</i>, then <i>eUTF</i> is 1 + the number of
+ code units in <i>S.</i></li>
+ <li>Let <i>e</i> be <i>eUTF</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>global</i> is <b>true</b> or <i>sticky</i> is <b>true</b>,
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>R</i>, <code>"<b>lastIndex"</b></code>,
+ <i>e</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>n</i> be the length of <i>r</i>'s <i>captures</i> <a
+ href="#sec-list-and-record-specification-type">List</a>. (This is the same value as <a
+ href="#sec-notation">21.2.2.1</a>'s <i>NcapturingParens</i>.)</li>
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(<i>n</i> + 1).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The value of <i>A</i>’s <code>"<b>length"</b></code>
+ property is <i>n</i> + 1.</li>
+ <li>Let <i>matchIndex</i> be <i>lastIndex</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The following <a
+ href="#sec-createdataproperty">CreateDataProperty</a> calls will not result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <code>"<b>index"</b></code>,
+ <i>matchIndex</i>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <code>"<b>input"</b></code>,
+ <i>S</i>).</li>
+ <li>Let <i>matchedSubstr</i> be the matched substring (i.e. the portion of <i>S</i> between offset <i>lastIndex</i>
+ inclusive and offset <i>e</i> exclusive).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <code>"<b>0"</b></code>,
+ <i>matchedSubstr</i>).</li>
+ <li>For each integer <i>i</i> such that <i>i</i> > 0 and <i>i</i> ≤ <i>n</i>
+ <ol class="block">
+ <li>Let <i>captureI</i> be <i>i</i><sup>th</sup> element of <i>r</i>'s <i>captures</i> <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <i>captureI</i> is <b>undefined</b>, let <i>capturedValue</i> be <b>undefined</b>.</li>
+ <li>Else if <i>fullUnicode</i> is <b>true</b>,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>captureI</i> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of code points.</li>
+ <li>Let <i>capturedValue</i> be a string whose code units are the <a
+ href="#sec-utf16encoding">UTF16Encoding</a> <span style="font-family: sans-serif">(<a
+ href="#sec-utf16encoding">10.1.1</a>)</span> of the code points of <i>capture.</i></li>
+ </ol>
+ </li>
+ <li>Else, <i>fullUnicode</i> is <b>false</b>,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>captureI</i> is a <a
+ href="#sec-list-and-record-specification-type">List</a> of code units.</li>
+ <li>Let <i>capturedValue</i> be a string consisting of the code units of <i>captureI.</i></li>
+ </ol>
+ </li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>i</i>) , <i>capturedValue</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-get-regexp.prototype.flags">
+ <h1><span class="secnum" id="sec-21.2.5.3"><a href="#sec-get-regexp.prototype.flags"
+ title="link to this section">21.2.5.3</a></span> get RegExp.prototype.flags</h1>
+
+ <p><code>RegExp.prototype.flags</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>result</i> be the empty String.</li>
+ <li>Let <i>global</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"global"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>global</i>).</li>
+ <li>If <i>global</i> is <b>true</b>, append <code>"g"</code> as the last code unit of <i>result</i>.</li>
+ <li>Let <i>ignoreCase</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"ignoreCase"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ignoreCase</i>).</li>
+ <li>If <i>ignoreCase</i> is <b>true</b>, append <code>"i"</code> as the last code unit of <i>result</i>.</li>
+ <li>Let <i>multiline</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"multiline"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>multiline</i>).</li>
+ <li>If <i>multiline</i> is <b>true</b>, append <code>"m"</code> as the last code unit of <i>result</i>.</li>
+ <li>Let <i>unicode</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"unicode"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>unicode</i>).</li>
+ <li>If <i>unicode</i> is <b>true</b>, append <code>"u"</code> as the last code unit of <i>result</i>.</li>
+ <li>Let <i>sticky</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"sticky"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>sticky</i>).</li>
+ <li>If <i>sticky</i> is <b>true</b>, append <code>"y"</code> as the last code unit of <i>result</i>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-get-regexp.prototype.global">
+ <h1><span class="secnum" id="sec-21.2.5.4"><a href="#sec-get-regexp.prototype.global"
+ title="link to this section">21.2.5.4</a></span> get RegExp.prototype.global</h1>
+
+ <p><code>RegExp.prototype.global</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>R</i> does not have an [[OriginalFlags]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>flags</i> be the value of <i>R’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>flags</i> contains the code unit <code>"g"</code>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-get-regexp.prototype.ignorecase">
+ <h1><span class="secnum" id="sec-21.2.5.5"><a href="#sec-get-regexp.prototype.ignorecase"
+ title="link to this section">21.2.5.5</a></span> get RegExp.prototype.ignoreCase</h1>
+
+ <p><code>RegExp.prototype.ignoreCase</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>R</i> does not have an [[OriginalFlags]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>flags</i> be the value of <i>R’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>flags</i> contains the code unit <code>"i"</code>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-regexp.prototype-@@match">
+ <h1><span class="secnum" id="sec-21.2.5.6"><a href="#sec-regexp.prototype-@@match"
+ title="link to this section">21.2.5.6</a></span> RegExp.prototype [ @@match ] ( string )</h1>
+
+ <p>When the @@<code>match</code> method is called with argument <var>string</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>rx</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>rx</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>global</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>rx</i>,
+ <code>"global"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>global</i>).</li>
+ <li>If <i>global</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-regexpexec">RegExpExec</a>(<i>rx</i>, <i>S</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>global</i> is <b>true</b>,
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>rx</i>, <code>"lastIndex"</code>, 0,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>n</i> be 0.</li>
+ <li>Repeat,
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-regexpexec">RegExpExec</a>(<i>rx</i>, <i>S</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>If <i>result</i> is <b>null</b>, then
+ <ol class="block">
+ <li>If <i>n</i>=0, return <b>null</b>.</li>
+ <li>Else, return <i>A</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>result</i> is not <b>null</b>,
+ <ol class="block">
+ <li>Let <i>matchValue</i> be <a href="#sec-get-o-p">Get</a>(<i>result</i>, <code>"0"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>matchValue</i>).</li>
+ <li>Let <i>matchStr</i> be <a href="#sec-tostring">ToString</a>(<i>matchValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>matchStr</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>), <i>matchStr</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is <b>true</b>.</li>
+ <li>If <i>matchStr</i> is the empty String, then
+ <ol class="block">
+ <li>Let <i>thisIndex</i> be <a href="#sec-tolength">ToLength</a>(<a
+ href="#sec-get-o-p">Get</a>(<i>rx</i>, <code>"lastIndex"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>thisIndex</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>rx</i>, <code>"lastIndex"</code>,
+ <i>thisIndex</i>+1, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Increment <i>n</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.match]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The @@match property is used by the <a href="#sec-isregexp">IsRegExp</a> abstract
+ operation to identify objects that have the basic behaviour of regular expressions. The absence of a @@match property or
+ the existence of such a property whose value does not Boolean coerce to <b>true</b> indicates that the object is not
+ intended to be used as a regular expression object.</p>
+ </div>
+ </section>
+
+ <section id="sec-get-regexp.prototype.multiline">
+ <h1><span class="secnum" id="sec-21.2.5.7"><a href="#sec-get-regexp.prototype.multiline"
+ title="link to this section">21.2.5.7</a></span> get RegExp.prototype.multiline</h1>
+
+ <p><code>RegExp.prototype.multiline</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>R</i> does not have an [[OriginalFlags]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>flags</i> be the value of <i>R’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>flags</i> contains the code unit <code>"m"</code>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-regexp.prototype-@@replace">
+ <h1><span class="secnum" id="sec-21.2.5.8"><a href="#sec-regexp.prototype-@@replace"
+ title="link to this section">21.2.5.8</a></span> RegExp.prototype [ @@replace ] ( string, replaceValue )</h1>
+
+ <p>When the @@<code>replace</code> method is called with arguments <var>string</var> and <var>replaceValue</var> the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>rx</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>rx</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>lengthS</i> be the number of code unit elements in <i>S</i>.</li>
+ <li>Let <i>functionalReplace</i> be <a href="#sec-iscallable">IsCallable</a>(<i>replaceValue</i>).</li>
+ <li>If <i>functionalReplace</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>replaceValue</i> be <a href="#sec-tostring">ToString</a>(<i>replaceValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>replaceValue</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>global</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-get-o-p">Get</a>(<i>rx</i>,
+ <code>"global"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>global</i>).</li>
+ <li>If <i>global</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>rx</i>, <code>"lastIndex"</code>, 0,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>results</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>done</i> be <b>false</b>.</li>
+ <li>Repeat, while <i>done</i> is <b>false</b>
+ <ol class="block">
+ <li>Let <i>result</i> be <a href="#sec-regexpexec">RegExpExec</a>(<i>rx</i>, <i>S</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>If <i>result</i> is <b>null</b>, set <i>done</i> to <b>true</b>.</li>
+ <li>Else <i>result</i> is not <b>null</b>,
+ <ol class="block">
+ <li>Append <i>result</i> to the end of <i>results</i>.</li>
+ <li>If <i>global</i> is <b>false</b>, set <i>done</i> to <b>true</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>matchStr</i> be <a href="#sec-tostring">ToString</a>(<a
+ href="#sec-get-o-p">Get</a>(<i>result</i>, <code>"0"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>matchStr</i>).</li>
+ <li>If <i>matchStr</i> is the empty String, then
+ <ol class="block">
+ <li>Let <i>thisIndex</i> be <a href="#sec-tolength">ToLength</a>(<a
+ href="#sec-get-o-p">Get</a>(<i>rx</i>, <code>"lastIndex"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>thisIndex</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>rx</i>, <code>"lastIndex"</code>,
+ <i>thisIndex</i>+1, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>accumulatedResult</i> be the empty String value.</li>
+ <li>Let <i>nextSourcePosition</i> be 0.</li>
+ <li>Repeat, for each <i>result</i> in <i>results</i>,
+ <ol class="block">
+ <li>Let <i>nCaptures</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>result</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nCaptures</i>).</li>
+ <li>Let <i>nCaptures</i> be max(<i>nCaptures</i> − 1, 0).</li>
+ <li>Let <i>matched</i> be <a href="#sec-tostring">ToString</a>(<a href="#sec-get-o-p">Get</a>(<i>result</i>,
+ <code>"0"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>matched</i>).</li>
+ <li>Let <i>matchLength</i> be the number of code units in <i>matched</i>.</li>
+ <li>Let <i>position</i> be <a href="#sec-tointeger">ToInteger</a>(<a href="#sec-get-o-p">Get</a>(<i>result</i>,
+ <code>"index"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>position</i>).</li>
+ <li>Let <i>position</i> be max(min(<i>position</i>, <i>lengthS</i>), 0).</li>
+ <li>Let <i>n</i> be 1.</li>
+ <li>Let <i>captures</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Repeat while <i>n</i> ≤ <i>nCaptures</i>
+ <ol class="block">
+ <li>Let <i>capN</i> be <a href="#sec-get-o-p">Get</a>(<i>result</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>)).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>capN</i>) is not Undefined, let <i>capN</i>
+ be <a href="#sec-tostring">ToString</a>(<i>capN</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>capN</i>).</li>
+ <li>Append <i>capN</i> as the last element of <i>captures.</i></li>
+ <li>Let <i>n</i> be <i>n</i>+1</li>
+ </ol>
+ </li>
+ <li>If <i>functionalReplace</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>replacerArgs</i> be «<i>matched</i>».</li>
+ <li>Append in list order the elements of <i>captures</i> to the end of the <a
+ href="#sec-list-and-record-specification-type">List</a> <i>replacerArgs</i>.</li>
+ <li>Append <i>position</i> and <i>S</i> as the last two elements of <i>replacerArgs.</i></li>
+ <li>Let <i>replValue</i> be <a href="#sec-call">Call</a>(<i>replaceValue</i>, <b>undefined</b>,
+ <i>replacerArgs</i>).</li>
+ <li>Let <i>replacement</i> be <a href="#sec-tostring">ToString</a>(<i>replValue</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>replacement</i> be <a href="#sec-getreplacesubstitution">GetReplaceSubstitution</a>(<i>matched</i>,
+ <i>S</i>, <i>position</i>, <i>captures</i>, <i>replaceValue</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>replacement</i>).</li>
+ <li>If <i>position</i> ≥ <i>nextSourcePosition</i>, then
+ <ol class="block">
+ <li>NOTE	<i>position</i> should not normally move backwards. If it does, it is in indication of a
+ ill-behaving RegExp subclass or use of an access triggered side-effect to change the global flag or other
+ characteristics of <i>rx.</i> In such cases, the corresponding substitution is ignored.</li>
+ <li>Let <i>accumulatedResult</i> be the String formed by concatenating the code units of the current value of
+ <i>accumulatedResult</i> with the substring of <i>S</i> consisting of the code units from
+ <i>nextSourcePosition</i> (inclusive) up to <i>position</i> (exclusive) and with the code units of
+ <i>replacement</i>.</li>
+ <li>Let <i>nextSourcePosition</i> be <i>position</i> + <i>matchLength</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>nextSourcePosition</i> ≥ <i>lengthS</i>, return <i>accumulatedResult</i>.</li>
+ <li>Return the String formed by concatenating the code units of <i>accumulatedResult</i> with the substring of <i>S</i>
+ consisting of the code units from <i>nextSourcePosition</i> (inclusive) up through the final code unit of <i>S</i>
+ (inclusive).</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.replace]"</code>.</p>
+ </section>
+
+ <section id="sec-regexp.prototype-@@search">
+ <h1><span class="secnum" id="sec-21.2.5.9"><a href="#sec-regexp.prototype-@@search"
+ title="link to this section">21.2.5.9</a></span> RegExp.prototype [ @@search ] ( string )</h1>
+
+ <p>When the @@search method is called with argument <var>string</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>rx</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>rx</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>previousLastIndex</i> be <a href="#sec-get-o-p">Get</a>(<i>rx</i>, <code>"lastIndex"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>previousLastIndex</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>rx</i>, <code>"lastIndex"</code>, 0,
+ <b>true)</b></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>)</li>
+ <li>Let <i>result</i> be <a href="#sec-regexpexec">RegExpExec</a>(<i>rx</i>, <i>S</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>rx</i>, <code>"lastIndex"</code>,
+ <i>previousLastIndex</i>, <b>true)</b></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>)</li>
+ <li>If <i>result</i> is <b>null</b>, return –1.</li>
+ <li>Return <a href="#sec-get-o-p">Get</a>(<i>result</i>, <code>"index"</code>).</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.search]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>lastIndex</code> and <code>global</code> properties of this RegExp object are
+ ignored when performing the search. The <code>lastIndex</code> property is left unchanged.</p>
+ </div>
+ </section>
+
+ <section id="sec-get-regexp.prototype.source">
+ <h1><span class="secnum" id="sec-21.2.5.10"><a href="#sec-get-regexp.prototype.source"
+ title="link to this section">21.2.5.10</a></span> get RegExp.prototype.source</h1>
+
+ <p><code>RegExp.prototype.source</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>R</i> does not have an [[OriginalSource]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>If <i>R</i> does not have an [[OriginalFlags]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>src</i> be the value of <i>R’s</i> [[OriginalSource]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>flags</i> be the value of <i>R’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <a href="#sec-escaperegexppattern">EscapeRegExpPattern</a>(<i>src</i>, <i>flags</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-regexp.prototype-@@split">
+ <h1><span class="secnum" id="sec-21.2.5.11"><a href="#sec-regexp.prototype-@@split"
+ title="link to this section">21.2.5.11</a></span> RegExp.prototype [ @@split ] ( string, limit )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Returns an Array object into which substrings of the result of converting <i>string</i>
+ to a String have been stored. The substrings are determined by searching from left to right for matches of the
+ <b>this</b> value regular expression; these occurrences are not part of any substring in the returned array, but serve
+ to divide up the String value.</p>
+
+ <p>The <b>this</b> value may be an empty regular expression or a regular expression that can match an empty String. In
+ this case, <span style="font-family: sans-serif">regular expression</span> does not match the empty substring at the
+ beginning or end of the input String, nor does it match the empty substring at the end of the previous separator match.
+ (For example, if the regular expression matches the empty String, the String is split up into individual code unit
+ elements; the length of the result array equals the length of the String, and each substring contains one code unit.)
+ Only the first match at a given index of the <b>this</b> String is considered, even if backtracking could yield a
+ non-empty-substring match at that index. (For example, <code>/a*?/[Symbol.split]("ab")</code> evaluates to the array
+ <code>["a","b"]</code>, while <code>/a*/[Symbol.split]("ab")</code> evaluates to the array<code>["","b"]</code>.)</p>
+
+ <p>If the <i>string</i> is (or converts to) the empty String, the result depends on whether the regular expression can
+ match the empty String. If it can, the result array contains no elements. Otherwise, the result array contains one
+ element, which is the empty String.</p>
+
+ <p>If the regular expression that contains capturing parentheses, then each time <i>separator</i> is matched the results
+ (including any <b>undefined</b> results) of the capturing parentheses are spliced into the output array.
+ For example,</p>
+
+ <p><span style="font-family:
+ sans-serif">/<(\/)?([^<>]+)>/[Symbol.split]("A<B>bold</B>and<CODE>coded</CODE>")</span></p>
+
+ <p>evaluates to the array</p>
+
+ <p><span style="font-family: sans-serif">["A", undefined, "B", "bold", "/", "B", "and", undefined,"CODE", "coded", "/",
+ "CODE", ""]</span></p>
+
+ <p>If <i>limit</i> is not <b>undefined</b>, then the output array is truncated so that it contains no more than
+ <i>limit</i> elements.</p>
+ </div>
+
+ <p>When the @@<code>split</code> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>rx</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>rx</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>C</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>rx</i>, %RegExp%).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>Let <i>flags</i> be <a href="#sec-tostring">ToString</a>(<a href="#sec-get-o-p">Get</a>(<i>rx</i>,
+ <code>"<b>flags"</b></code>))</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>flags</i>).</li>
+ <li>If <i>flags</i> contains <code>"<b>u"</b></code>, let <i>unicodeMatching</i> be <b>true</b>.</li>
+ <li>Else, let <i>unicodeMatching</i> be <b>false</b>.</li>
+ <li>If <i>flags</i> contains <code>"<b>y"</b></code>, let <i>newFlags</i> be <i>flags</i>.</li>
+ <li>Else, let <i>newFlags</i> be the string that is the concatenation of <i>flags</i> and <code>"<b>y"</b></code>.</li>
+ <li>Let <i>splitter</i> be <a href="#sec-construct">Construct</a>(<i>C</i>, «<i>rx</i>,
+ <i>newFlags</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>splitter</i>).</li>
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ <li>Let <i>lengthA</i> be 0.</li>
+ <li>If <i>limit</i> is <b>undefined</b>, let <i>lim</i> = 2<sup>53</sup>–1; else let <i>lim</i> = <a
+ href="#sec-tolength">ToLength</a>(<i>limit</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lim</i>).</li>
+ <li>Let <i>size</i> be the number of elements in <i>S</i>.</li>
+ <li>Let <i>p</i> = 0.</li>
+ <li>If <i>lim</i> = 0, return <i>A</i>.</li>
+ <li>If <i>size</i> = 0, then
+ <ol class="block">
+ <li>Let <i>z</i> be <a href="#sec-regexpexec">RegExpExec</a>(<i>splitter</i>, <i>S</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>z</i>).</li>
+ <li>If <i>z</i> is not <b>null</b>, return <i>A</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The following call will never result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>,
+ <code>"<b>0</b>"</code>, <i>S</i>).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>q</i> = <i>p</i>.</li>
+ <li>Repeat, while <i>q</i> < <i>size</i>
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>splitter</i>, <code>"<b>lastIndex</b>"</code>,
+ <i>q</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Let <i>z</i> be <a href="#sec-regexpexec">RegExpExec</a>(<i>splitter</i>, <i>S</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>z</i>).</li>
+ <li>If <i>z</i> is <b>null</b>, then
+ <ol class="block">
+ <li>If <i>unicodeMatching</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>first</i> be the code unit value of the element at index <i>q</i> in the String <i>S</i>.</li>
+ <li>If <i>first</i> ≥ 0xD800 and <i>first</i> ≤ 0xDBFF and <i>q</i>+1 ≠ <i>size</i>, then
+ <ol class="block">
+ <li>Let <i>second</i> be the code unit value of the element at index <i>q</i>+1 in the String
+ <i>S</i>.</li>
+ <li>If <i>second</i> ≥ 0xDC00 and <i>second</i> ≤ 0xDFFF, then
+ <ol class="block">
+ <li>Let <i>q</i> = <i>q</i>+1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>q</i> = <i>q</i>+1.</li>
+ </ol>
+ </li>
+ <li>Else <i>z</i> is not <b>null</b>,
+ <ol class="block">
+ <li>Let <i>e</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>splitter</i>,
+ <code>"<b>lastIndex</b>"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>e</i>).</li>
+ <li>If <i>e</i> = <i>p</i>, then
+ <ol class="block">
+ <li>If <i>unicodeMatching</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>first</i> be the code unit value of the element at index <i>q</i> in the String
+ <i>S</i>.</li>
+ <li>If <i>first</i> ≥ 0xD800 and <i>first</i> ≤ 0xDBFF and <i>q</i>+1 ≠ <i>size</i>, then
+ <ol class="block">
+ <li>Let <i>second</i> be the code unit value of the element at index <i>q</i>+1 in the String
+ <i>S</i>.</li>
+ <li>If <i>second</i> ≥ 0xDC00 and <i>second</i> ≤ 0xDFFF, then
+ <ol class="block">
+ <li>Let <i>q</i> = <i>q</i>+1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>q</i> = <i>q</i>+1.</li>
+ </ol>
+ </li>
+ <li>Else <i>e</i> ≠ <i>p</i>,
+ <ol class="block">
+ <li>Let <i>T</i> be a String value equal to the substring of <i>S</i> consisting of the elements at indices
+ <i>p</i> (inclusive) through <i>q</i> (exclusive).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The following call will never result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>lengthA</i>), <i>T</i>).</li>
+ <li>Let <i>lengthA</i> be <i>lengthA</i> +1.</li>
+ <li>If <i>lengthA</i> = <i>lim</i>, return <i>A</i>.</li>
+ <li>Let <i>p</i> = <i>e</i>.</li>
+ <li>Let <i>i</i> = 0.</li>
+ <li>Let <i>numberOfCaptures</i> be <a href="#sec-tolength">ToLength</a>(<a
+ href="#sec-get-o-p">Get</a>(<i>z</i>, <code>"<b>length</b>"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>numberOfCaptures</i>).</li>
+ <li>Let <i>numberOfCaptures</i> be max(<i>numberOfCaptures</i>-1, 0).</li>
+ <li>Let <i>i</i> be 1.</li>
+ <li>Repeat, while <i>i</i> ≤ <i>numberOfCaptures</i>.
+ <ol class="block">
+ <li>Let <i>nextCapture</i> be <a href="#sec-get-o-p">Get</a>(<i>z</i>, <a
+ href="#sec-tostring">ToString</a>(<i>i</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextCapture</i>).</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>lengthA</i>), <i>nextCapture</i>).</li>
+ <li>Let <i>i</i> be <i>i</i> +1.</li>
+ <li>Let <i>lengthA</i> be <i>lengthA</i> +1.</li>
+ <li>If <i>lengthA</i> = <i>lim</i>, return <i>A</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>q</i> = <i>p</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>T</i> be a String value equal to the substring of <i>S</i> consisting of the elements at indices <i>p</i>
+ (inclusive) through <i>size</i> (exclusive).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The following call will never result in an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li><a href="#sec-call">Call</a> <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>lengthA</i>), <i>T</i> ).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the @@<code>split</code> method is <b>2</b>.</p>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.split]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The @@<code>split</code> method ignores the value of the <code>global</code> and
+ <code>sticky</code> properties of this RegExp object.</p>
+ </div>
+ </section>
+
+ <section id="sec-get-regexp.prototype.sticky">
+ <h1><span class="secnum" id="sec-21.2.5.12"><a href="#sec-get-regexp.prototype.sticky"
+ title="link to this section">21.2.5.12</a></span> get RegExp.prototype.sticky</h1>
+
+ <p><code>RegExp.prototype.sticky</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>R</i> does not have an [[OriginalFlags]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>flags</i> be the value of <i>R’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>flags</i> contains the code unit <code>"y"</code>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-regexp.prototype.test">
+ <h1><span class="secnum" id="sec-21.2.5.13"><a href="#sec-regexp.prototype.test"
+ title="link to this section">21.2.5.13</a></span> RegExp.prototype.test( S )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>string</i> be <a href="#sec-tostring">ToString</a>(<i>S</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>string</i>).</li>
+ <li>If <i>R</i> is %RegExpPrototype%, return <b>true</b>.</li>
+ <li>Let <i>match</i> be <a href="#sec-regexpexec">RegExpExec</a>(<i>R</i>, <i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>match</i>).</li>
+ <li>If <i>match</i> is not <b>null</b>, return <b>true</b>; else return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-regexp.prototype.tostring">
+ <h1><span class="secnum" id="sec-21.2.5.14"><a href="#sec-regexp.prototype.tostring"
+ title="link to this section">21.2.5.14</a></span> RegExp.prototype.toString ( )</h1>
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>pattern</i> be <a href="#sec-tostring">ToString</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"source"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>pattern</i>).</li>
+ <li>Let <i>flags</i> be <a href="#sec-tostring">ToString</a>(<a href="#sec-get-o-p">Get</a>(<i>R</i>,
+ <code>"flags"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>flags</i>).</li>
+ <li>Let <i>result</i> be the String value formed by concatenating <code>"<b>/</b>"</code>, <i>pattern</i>, and
+ <code>"<b>/</b>"</code>, and <i>flags</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The returned String has the form of a <i>RegularExpressionLiteral</i> that evaluates to
+ another RegExp object with the same behaviour as this object.</p>
+ </div>
+ </section>
+
+ <section id="sec-get-regexp.prototype.unicode">
+ <h1><span class="secnum" id="sec-21.2.5.15"><a href="#sec-get-regexp.prototype.unicode"
+ title="link to this section">21.2.5.15</a></span> get RegExp.prototype.unicode</h1>
+
+ <p><code>RegExp.prototype.unicode</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>R</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>R</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>R</i> does not have an [[OriginalFlags]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>flags</i> be the value of <i>R’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>flags</i> contains the code unit <code>"u"</code>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-regexp-instances">
+ <div class="front">
+ <h1><span class="secnum" id="sec-21.2.6"><a href="#sec-properties-of-regexp-instances"
+ title="link to this section">21.2.6</a></span> Properties of RegExp Instances</h1>
+
+ <p>RegExp instances are ordinary objects that inherit properties from the RegExp prototype object. RegExp instances have
+ internal slots [[RegExpMatcher]], [[OriginalSource]], and [[OriginalFlags]]. The value of the [[RegExpMatcher]] internal
+ slot is an implementation dependent representation of the <span class="nt">Pattern</span> of the RegExp object.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Prior to the 6<sup>th</sup> Edition, <code>RegExp</code> instances were specified as
+ having the own data properties <code>source</code>, <code>global</code>, <code>ignoreCase</code>, and
+ <code>multiline</code>. Those properties are now specified as accessor properties of <a
+ href="#sec-regexp.prototype">RegExp.prototype</a>.</p>
+ </div>
+
+ <p>RegExp instances also have the following property:</p>
+ </div>
+
+ <section id="sec-lastindex">
+ <h1><span class="secnum" id="sec-21.2.6.1"><a href="#sec-lastindex" title="link to this section">21.2.6.1</a></span>
+ lastIndex</h1>
+
+ <p>The value of the <code>lastIndex</code> property specifies the String index at which to start the next match. It is
+ coerced to an integer when used (<a href="#sec-regexpbuiltinexec">see 21.2.5.2.2</a>). This property shall have the
+ attributes { [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b> }.</p>
+ </section>
+ </section>
+ </section>
+</section>
+
+<section id="sec-indexed-collections">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22"><a href="#sec-indexed-collections" title="link to this section">22</a></span> Indexed
+ Collections</h1>
+ </div>
+
+ <section id="sec-array-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1"><a href="#sec-array-objects" title="link to this section">22.1</a></span> Array
+ Objects</h1>
+
+ <p>Array objects are exotic objects that give special treatment to a certain class of property names. See <a
+ href="#sec-array-exotic-objects">9.4.2</a> for a definition of this special treatment.</p>
+ </div>
+
+ <section id="sec-array-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.1"><a href="#sec-array-constructor" title="link to this section">22.1.1</a></span>
+ The Array Constructor</h1>
+
+ <p>The Array constructor is the %Array% intrinsic object and the initial value of the <code>Array</code> property of the
+ global object. When called as a constructor it creates and initializes a new exotic Array object. When <code>Array</code>
+ is called as a function rather than as a constructor, it also creates and initializes a new Array object. Thus the
+ function call <code><b>Array(</b>…<b>)</b></code> is equivalent to the object creation expression
+ <code><b>new Array(</b>…<b>)</b></code> with the same arguments.</p>
+
+ <p>The <code>Array</code> constructor is a single function whose behaviour is overloaded based upon the number and types
+ of its arguments.</p>
+
+ <p>The <code>Array</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the exotic
+ <code>Array</code> behaviour must include a <code>super</code> call to the <code>Array</code> constructor to initialize
+ subclass instances that are exotic Array objects. However, most of the <code>Array.prototype</code> methods are generic
+ methods that are not dependent upon their <code>this</code> value being an exotic Array object.</p>
+
+ <p>The <code>length</code> property of the <code>Array</code> constructor function is <b>1</b>.</p>
+ </div>
+
+ <section id="sec-array-constructor-array">
+ <h1><span class="secnum" id="sec-22.1.1.1"><a href="#sec-array-constructor-array"
+ title="link to this section">22.1.1.1</a></span> Array ( )</h1>
+
+ <p>This description applies if and only if the Array constructor is called with no arguments.</p>
+
+ <ol class="proc">
+ <li>Let <i>numberOfArgs</i> be the number of arguments passed to this function call.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numberOfArgs</i> = 0.</li>
+ <li>If NewTarget is <b>undefined</b><i>,</i> let <i>newTarget</i> be the active function object, else let
+ <i>newTarget</i> be NewTarget.</li>
+ <li>Let <i>proto</i> be <a href="#sec-getprototypefromconstructor">GetPrototypeFromConstructor</a>(<i>newTarget</i>,
+ <code>"%ArrayPrototype%"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>Return <a href="#sec-arraycreate">ArrayCreate</a>(0, <i>proto</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-array-len">
+ <h1><span class="secnum" id="sec-22.1.1.2"><a href="#sec-array-len" title="link to this section">22.1.1.2</a></span> Array
+ (len)</h1>
+
+ <p>This description applies if and only if the Array constructor is called with exactly one argument.</p>
+
+ <ol class="proc">
+ <li>Let <i>numberOfArgs</i> be the number of arguments passed to this function call.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numberOfArgs</i> = 1.</li>
+ <li>If NewTarget is <b>undefined</b><i>,</i> let <i>newTarget</i> be the active function object, else let
+ <i>newTarget</i> be NewTarget.</li>
+ <li>Let <i>proto</i> be <a href="#sec-getprototypefromconstructor">GetPrototypeFromConstructor</a>(<i>newTarget</i>,
+ <code>"%ArrayPrototype%"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>Let <i>array</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0, <i>proto</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>len</i>) is not Number, then
+ <ol class="block">
+ <li>Let <i>defineStatus</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>array</i>,
+ <code>"<b>0</b>"</code>, <i>len</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>defineStatus</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Let <i>intLen</i> be 1.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>intLen</i> be <a href="#sec-touint32">ToUint32</a>(<i>len</i>).</li>
+ <li>If <i>intLen</i> ≠ <i>len</i>, throw a <b>RangeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>array</i>, <code>"length"</code>, <i>intLen</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>setStatus</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <i>array</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-array-items">
+ <h1><span class="secnum" id="sec-22.1.1.3"><a href="#sec-array-items" title="link to this section">22.1.1.3</a></span>
+ Array (...items )</h1>
+
+ <p>This description applies if and only if the Array constructor is called with at least two arguments.</p>
+
+ <p>When the <code>Array</code> function is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>numberOfArgs</i> be the number of arguments passed to this function call.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>numberOfArgs</i> ≥ 2.</li>
+ <li>If NewTarget is <b>undefined</b><i>,</i> let <i>newTarget</i> be the active function object, else let
+ <i>newTarget</i> be NewTarget.</li>
+ <li>Let <i>proto</i> be <a href="#sec-getprototypefromconstructor">GetPrototypeFromConstructor</a>(<i>newTarget</i>,
+ <code>"%ArrayPrototype%"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>Let <i>array</i> be <a href="#sec-arraycreate">ArrayCreate</a>(<i>numberOfArgs</i>, <i>proto</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>array</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Let <i>items</i> be a zero-origined <a href="#sec-list-and-record-specification-type">List</a> containing the
+ argument items in order.</li>
+ <li>Repeat, while <i>k</i> < <i>numberOfArgs</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>itemK</i> be <i>k</i><sup>th</sup> element of <i>items</i>.</li>
+ <li>Let <i>defineStatus</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>array</i>,
+ <i>Pk</i>, <i>itemK</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>defineStatus</i> is not an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: the value of <i>array</i>’s <code>length</code> property is
+ <i>numberOfArgs</i>.</li>
+ <li>Return <i>array</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-array-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.2"><a href="#sec-properties-of-the-array-constructor"
+ title="link to this section">22.1.2</a></span> Properties of the Array Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Array
+ constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>1</b>), the Array constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-array.from">
+ <h1><span class="secnum" id="sec-22.1.2.1"><a href="#sec-array.from" title="link to this section">22.1.2.1</a></span>
+ Array.from ( items [ , mapfn [ , thisArg ] ] )</h1>
+
+ <p>When the <code>from</code> method is called with argument <var>items</var> and optional arguments <var>mapfn</var> and
+ <var>thisArg</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <i>mapfn</i> is <b>undefined</b>, let <i>mapping</i> be <b>false.</b></li>
+ <li>else
+ <ol class="block">
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>mapfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>mapping</i> be <b>true</b></li>
+ </ol>
+ </li>
+ <li>Let <i>usingIterator</i> be <a href="#sec-getmethod">GetMethod</a>(<i>items</i>, @@iterator).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>usingIterator</i>).</li>
+ <li>If <i>usingIterator</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>A</i> be <a href="#sec-construct">Construct</a>(<i>C</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(0).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>items</i>, <i>usingIterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <code>"length"</code>,
+ <i>k</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>If <i>mapping</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>mappedValue</i> be <a href="#sec-call">Call</a>(<i>mapfn</i>, <i>T</i>, «<i>nextValue</i>,
+ <i>k</i>»).</li>
+ <li>If <i>mappedValue</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ return <a href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>mappedValue</i>).</li>
+ <li>Let <i>mappedValue</i> be <i>mappedValue</i>.[[value]].</li>
+ </ol>
+ </li>
+ <li>Else, let <i>mappedValue</i> be <i>nextValue</i>.</li>
+ <li>Let <i>defineStatus</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>A</i>,
+ <i>Pk</i>, <i>mappedValue</i>).</li>
+ <li>If <i>defineStatus</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ return <a href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>defineStatus</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>items</i> is not an Iterable so assume it is an array-like
+ object.</li>
+ <li>Let <i>arrayLike</i> be <a href="#sec-toobject">ToObject</a>(<i>items</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>arrayLike</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>arrayLike</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>A</i> be <a href="#sec-construct">Construct</a>(<i>C</i>, «<i>len</i>»).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(<i>len</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>arrayLike</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>If <i>mapping</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>mappedValue</i> be <a href="#sec-call">Call</a>(<i>mapfn</i>, <i>T</i>, «<i>kValue</i>,
+ <i>k</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>mappedValue</i>).</li>
+ </ol>
+ </li>
+ <li>Else, let <i>mappedValue</i> be <i>kValue</i>.</li>
+ <li>Let <i>defineStatus</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>A</i>,
+ <i>Pk</i>, <i>mappedValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>defineStatus</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <code>"length"</code>, <i>len</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>from</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>from</code> function is an intentionally generic factory method; it does not
+ require that its <b>this</b> value be the Array constructor. Therefore it can be transferred to or inherited by any
+ other constructors that may be called with a single numeric argument.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.isarray">
+ <h1><span class="secnum" id="sec-22.1.2.2"><a href="#sec-array.isarray" title="link to this section">22.1.2.2</a></span>
+ Array.isArray ( arg )</h1>
+
+ <p>The <code>isArray</code> function takes one argument <var>arg</var>, and performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return <a href="#sec-isarray">IsArray</a>(<i>arg</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-array.of">
+ <h1><span class="secnum" id="sec-22.1.2.3"><a href="#sec-array.of" title="link to this section">22.1.2.3</a></span>
+ Array.of ( ...items )</h1>
+
+ <p>When the <code>of</code> method is called with any number of arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>len</i> be the actual number of arguments passed to this function.</li>
+ <li>Let <i>items</i> be the <a href="#sec-list-and-record-specification-type">List</a> of arguments passed to this
+ function.</li>
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>A</i> be <a href="#sec-construct">Construct</a>(<i>C</i>, «<i>len</i>»).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>A</i> be <a href="#sec-arraycreate">ArrayCreate</a>(<i>len</i>).</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>kValue</i> be <i>items</i>[<i>k</i>].</li>
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>defineStatus</i> be <a
+ href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>A</i>,<i>Pk</i>,
+ <i>kValue</i>.[[value]]).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>defineStatus</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <code>"length"</code>, <i>len</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>of</code> method is <b>0</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The <i>items</i> argument is assumed to be a well-formed rest argument value.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>of</code> function is an intentionally generic factory method; it does not
+ require that its <b>this</b> value be the Array constructor. Therefore it can be transferred to or inherited by other
+ constructors that may be called with a single numeric argument.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype">
+ <h1><span class="secnum" id="sec-22.1.2.4"><a href="#sec-array.prototype" title="link to this section">22.1.2.4</a></span>
+ Array.prototype</h1>
+
+ <p>The value of <code>Array.prototype</code> is %ArrayPrototype%, the intrinsic Array prototype object (<a
+ href="#sec-properties-of-the-array-prototype-object">22.1.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-get-array-@@species">
+ <h1><span class="secnum" id="sec-22.1.2.5"><a href="#sec-get-array-@@species"
+ title="link to this section">22.1.2.5</a></span> get Array [ @@species ]</h1>
+
+ <p><code>Array[@@species]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"get [Symbol.species]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Array prototype methods normally use their <code>this</code> object’s constructor
+ to create a derived object. However, a subclass constructor may over-ride that default behaviour by redefining its
+ @@species property.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-array-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.3"><a href="#sec-properties-of-the-array-prototype-object"
+ title="link to this section">22.1.3</a></span> Properties of the Array Prototype Object</h1>
+
+ <p>The Array prototype object is the intrinsic object %ArrayPrototype%. The Array prototype object is an Array exotic
+ objects and has the internal methods specified for such objects. It has a length property whose initial value is 0 and
+ whose attributes are <span style="font-family: Times New Roman">{ [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>,
+ [[Configurable]]: <b>false</b> }</span>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Array
+ prototype object is the intrinsic object %ObjectPrototype%.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The Array prototype object is specified to be an <a
+ href="#sec-array-exotic-objects">Array exotic object</a> to ensure compatibility with ECMAScript code that was created
+ prior to the 6<sup>th</sup> Edition of this specification.</p>
+ </div>
+ </div>
+
+ <section id="sec-array.prototype.concat">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.3.1"><a href="#sec-array.prototype.concat"
+ title="link to this section">22.1.3.1</a></span> Array.prototype.concat ( ...arguments )</h1>
+
+ <p>When the <code>concat</code> method is called with zero or more arguments, it returns an array containing the array
+ elements of the object followed by the array elements of each argument in order.</p>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>A</i> be <a href="#sec-arrayspeciescreate">ArraySpeciesCreate</a>(<i>O</i>, 0).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>n</i> be 0.</li>
+ <li>Let <i>items</i> be a <a href="#sec-list-and-record-specification-type">List</a> whose first element is <i>O</i>
+ and whose subsequent elements are, in left to right order, the arguments that were passed to this function
+ invocation.</li>
+ <li>Repeat, while <i>items</i> is not empty
+ <ol class="block">
+ <li>Remove the first element from <i>items</i> and let <i>E</i> be the value of the element.</li>
+ <li>Let <i>spreadable</i> be <a href="#sec-isconcatspreadable">IsConcatSpreadable</a>(<i>E</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>spreadable</i>).</li>
+ <li>If <i>spreadable</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>k</i> be 0.</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>E</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <i>n</i> + <i>len</i> > 2<sup>53</sup>-1, throw a <b>TypeError</b> exception.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>P</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>exists</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>E</i>, <i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>exists</i>).</li>
+ <li>If <i>exists</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>subElement</i> be <a href="#sec-get-o-p">Get</a>(<i>E</i>, <i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>subElement</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>
+ (<i>A</i>, <a href="#sec-tostring">ToString</a>(<i>n</i>), <i>subElement</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>n</i> by 1.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else <i>E</i> is added as a single item rather than spread,
+ <ol class="block">
+ <li>If <i>n</i>≥2<sup>53</sup>-1, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>status</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a> (<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>), <i>E</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Increase <i>n</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <code>"length"</code>, <i>n</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>concat</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The explicit setting of the <code>length</code> property in step 10 is necessary to
+ ensure that its value is correct in situations where the trailing elements of the result Array are not present.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>concat</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </div>
+
+ <section id="sec-isconcatspreadable">
+ <h1><span class="secnum" id="sec-22.1.3.1.1"><a href="#sec-isconcatspreadable"
+ title="link to this section">22.1.3.1.1</a></span> Runtime Semantics: IsConcatSpreadable ( O )</h1>
+
+ <p>The abstract operation IsConcatSpreadable with argument <i>O</i> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <b>false</b>.</li>
+ <li>Let <i>spreadable</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, @@isConcatSpreadable).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>spreadable</i>).</li>
+ <li>If <i>spreadable</i> is not <b>undefined</b>, return <a
+ href="#sec-toboolean">ToBoolean</a>(<i>spreadable</i>).</li>
+ <li>Return <a href="#sec-isarray">IsArray</a>(<i>O</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-array.prototype.constructor">
+ <h1><span class="secnum" id="sec-22.1.3.2"><a href="#sec-array.prototype.constructor"
+ title="link to this section">22.1.3.2</a></span> Array.prototype.constructor</h1>
+
+ <p>The initial value of <code>Array.prototype.constructor</code> is the intrinsic object %Array%.</p>
+ </section>
+
+ <section id="sec-array.prototype.copywithin">
+ <h1><span class="secnum" id="sec-22.1.3.3"><a href="#sec-array.prototype.copywithin"
+ title="link to this section">22.1.3.3</a></span> Array.prototype.copyWithin (target, start [ , end ] )</h1>
+
+ <p>The <code>copyWithin</code> method takes up to three arguments <var>target</var>, <var>start</var> and
+ <var>end</var>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <i>end</i> argument is optional with the length of the <b>this</b> object as its
+ default value. If <i>target</i> is negative, it is treated as <i>length</i>+<i>target</i> where <i>length</i> is the
+ length of the array. If <i>start</i> is negative, it is treated as <i>length</i>+<i>start</i>. If <i>end</i> is
+ negative, it is treated as <i>length</i>+<i>end</i>.</p>
+ </div>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>relativeTarget</i> be <a href="#sec-tointeger">ToInteger</a>(<i>target</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeTarget</i>).</li>
+ <li>If <i>relativeTarget</i> < 0, let <i>to</i> be max((<i>len</i> + <i>relativeTarget</i>),0); else let <i>to</i> be
+ min(<i>relativeTarget</i>, <i>len</i>).</li>
+ <li>Let <i>relativeStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeStart</i>).</li>
+ <li>If <i>relativeStart</i> < 0, let <i>from</i> be max((<i>len</i> + <i>relativeStart</i>),0); else let <i>from</i>
+ be min(<i>relativeStart</i>, <i>len</i>).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>relativeEnd</i> be <i>len</i>; else let <i>relativeEnd</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeEnd</i>).</li>
+ <li>If <i>relativeEnd</i> < 0, let <i>final</i> be max((<i>len</i> + <i>relativeEnd</i>),0); else let <i>final</i> be
+ min(<i>relativeEnd</i>, <i>len</i>).</li>
+ <li>Let <i>count</i> be min(<i>final</i>-<i>from</i>, <i>len</i>-<i>to</i>).</li>
+ <li>If <i>from</i><<i>to</i> and <i>to</i><<i>from</i>+<i>count</i>
+ <ol class="block">
+ <li>Let <i>direction</i> = -1.</li>
+ <li>Let <i>from</i> = <i>from</i> + <i>count</i> -1.</li>
+ <li>Let <i>to</i> = <i>to</i> + <i>count</i> -1.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>direction</i> = 1.</li>
+ </ol>
+ </li>
+ <li>Repeat, while <i>count</i> > 0
+ <ol class="block">
+ <li>Let <i>fromKey</i> be <a href="#sec-tostring">ToString</a>(<i>from</i>).</li>
+ <li>Let <i>toKey</i> be <a href="#sec-tostring">ToString</a>(<i>to</i>).</li>
+ <li>Let <i>fromPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>fromKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromPresent</i>).</li>
+ <li>If <i>fromPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>fromVal</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>fromKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromVal</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>toKey</i>, <i>fromVal</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>fromPresent</i> is <b>false</b>,
+ <ol class="block">
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>,
+ <i>toKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>from</i> be <i>from</i> + <i>direction</i>.</li>
+ <li>Let <i>to</i> be <i>to</i> + <i>direction</i>.</li>
+ <li>Let <i>count</i> be <i>count</i> − 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>copyWithin</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The <code>copyWithin</code> function is intentionally generic; it does not require
+ that its <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.entries">
+ <h1><span class="secnum" id="sec-22.1.3.4"><a href="#sec-array.prototype.entries"
+ title="link to this section">22.1.3.4</a></span> Array.prototype.entries ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Return <a href="#sec-createarrayiterator">CreateArrayIterator</a>(<i>O</i>, <code>"key+value"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-array.prototype.every">
+ <h1><span class="secnum" id="sec-22.1.3.5"><a href="#sec-array.prototype.every"
+ title="link to this section">22.1.3.5</a></span> Array.prototype.every ( callbackfn [ , thisArg] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that accepts
+ three arguments and returns a value that is coercible to the Boolean value <b>true</b> or <b>false</b>. <code>every</code>
+ calls <i>callbackfn</i> once for each element present in the array, in ascending order, until it finds one where
+ <i>callbackfn</i> returns <b>false</b>. If such an element is found, <code>every</code> immediately returns <b>false</b>.
+ Otherwise, if <i>callbackfn</i> returned <b>true</b> for all elements, <code>every</code> will return <b>true</b>.
+ <i>callbackfn</i> is called only for elements of the array which actually exist; it is not called for missing elements of
+ the array.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>callbackfn</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with three arguments: the value of the element, the index of the element, and
+ the object being traversed.</p>
+
+ <p class="Note"><code>every</code> does not directly mutate the object on which it is called but the object may be mutated
+ by the calls to <i>callbackfn</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>every</code> is set before the first call to <i>callbackfn</i>.
+ Elements which are appended to the array after the call to <code>every</code> begins will not be visited by
+ <i>callbackfn</i>. If existing elements of the array are changed, their value as passed to <i>callbackfn</i> will be the
+ value at the time <code>every</code> visits them; elements that are deleted after the call to <code>every</code> begins
+ and before being visited are not visited. <code>every</code> acts like the "for all" quantifier in mathematics. In
+ particular, for an empty array, it returns <b>true</b>.</p>
+
+ <p>When the <code>every</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>testResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a
+ href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>, «<i>kValue</i>, <i>k</i>,
+ <i>O</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>testResult</i>).</li>
+ <li>If <i>testResult</i> is <b>false</b>, return <b>false</b>.</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>every</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>every</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.fill">
+ <h1><span class="secnum" id="sec-22.1.3.6"><a href="#sec-array.prototype.fill"
+ title="link to this section">22.1.3.6</a></span> Array.prototype.fill (value [ , start [ , end ] ] )</h1>
+
+ <p>The <code>fill</code> method takes up to three arguments <var>value</var>, <var>start</var> and <var>end</var>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <i>start</i> and <i>end</i> arguments are optional with default values of 0 and the
+ length of the <b>this</b> object. If <i>start</i> is negative, it is treated as <i>length</i>+<i>start</i> where
+ <i>length</i> is the length of the array. If <i>end</i> is negative, it is treated as <i>length</i>+<i>end</i>.</p>
+ </div>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>relativeStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeStart</i>).</li>
+ <li>If <i>relativeStart</i> < 0, let <i>k</i> be max((<i>len</i> + <i>relativeStart</i>),0); else let <i>k</i> be
+ min(<i>relativeStart</i>, <i>len</i>).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>relativeEnd</i> be <i>len</i>; else let <i>relativeEnd</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeEnd</i>).</li>
+ <li>If <i>relativeEnd</i> < 0, let <i>final</i> be max((<i>len</i> + <i>relativeEnd</i>),0); else let <i>final</i> be
+ min(<i>relativeEnd</i>, <i>len</i>).</li>
+ <li>Repeat, while <i>k</i> < <i>final</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>Pk</i>, <i>value</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>fill</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The <code>fill</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.filter">
+ <h1><span class="secnum" id="sec-22.1.3.7"><a href="#sec-array.prototype.filter"
+ title="link to this section">22.1.3.7</a></span> Array.prototype.filter ( callbackfn [ , thisArg ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that accepts
+ three arguments and returns a value that is coercible to the Boolean value <b>true</b> or <b>false</b>.
+ <code>filter</code> calls <i>callbackfn</i> once for each element in the array, in ascending order, and constructs a new
+ array of all the values for which <i>callbackfn</i> returns <b>true</b>. <i>callbackfn</i> is called only for elements of
+ the array which actually exist; it is not called for missing elements of the array.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>callbackfn</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with three arguments: the value of the element, the index of the element, and
+ the object being traversed.</p>
+
+ <p class="Note"><code>filter</code> does not directly mutate the object on which it is called but the object may be
+ mutated by the calls to <i>callbackfn</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>filter</code> is set before the first call to <i>callbackfn</i>.
+ Elements which are appended to the array after the call to <code>filter</code> begins will not be visited by
+ <i>callbackfn</i>. If existing elements of the array are changed their value as passed to <i>callbackfn</i> will be the
+ value at the time <code>filter</code> visits them; elements that are deleted after the call to <code>filter</code> begins
+ and before being visited are not visited.</p>
+
+ <p>When the <code>filter</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>A</i> be <a href="#sec-arrayspeciescreate">ArraySpeciesCreate</a>(<i>O</i>, 0).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Let <i>to</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>selected</i> be <a href="#sec-toboolean">ToBoolean</a>(<a
+ href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>, «<i>kValue</i>, <i>k</i>,
+ <i>O</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>selected</i>).</li>
+ <li>If <i>selected</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a> (<i>A</i>,
+ <a href="#sec-tostring">ToString</a>(<i>to</i>), <i>kValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Increase <i>to</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>filter</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>filter</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.find">
+ <h1><span class="secnum" id="sec-22.1.3.8"><a href="#sec-array.prototype.find"
+ title="link to this section">22.1.3.8</a></span> Array.prototype.find ( predicate [ , thisArg ] )</h1>
+
+ <p>The <code>find</code> method is called with one or two arguments, <var>predicate</var> and <var>thisArg</var>.</p>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>predicate</i> should be a function that accepts
+ three arguments and returns a value that is coercible to a Boolean value. <code>find</code> calls <i>predicate</i> once
+ for each element of the array, in ascending order, until it finds one where <i>predicate</i> returns <b>true</b>. If such
+ an element is found, <code>find</code> immediately returns that element value. Otherwise, <code>find</code> returns
+ <b>undefined</b>.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>predicate</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>predicate</i> is called with three arguments: the value of the element, the index of the element, and
+ the object being traversed.</p>
+
+ <p class="Note"><code>find</code> does not directly mutate the object on which it is called but the object may be mutated
+ by the calls to <i>predicate</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>find</code> is set before the first call to <i>callbackfn</i>.
+ Elements that are appended to the array after the call to <code>find</code> begins will not be visited by
+ <i>callbackfn</i>. If existing elements of the array are changed, their value as passed to <i>predicate</i> will be the
+ value at the time that <code>find</code> visits them; elements that correspond to non-existent properties are treated as
+ if they the existed and have the value <b>undefined</b>.</p>
+
+ <p>When the <code>find</code> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>predicate</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>testResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>predicate</i>,
+ <i>T</i>, «<i>kValue</i>, <i>k</i>, <i>O</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>testResult</i>).</li>
+ <li>If <i>testResult</i> is <b>true</b>, return <i>kValue</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>find</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>find</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.findindex">
+ <h1><span class="secnum" id="sec-22.1.3.9"><a href="#sec-array.prototype.findindex"
+ title="link to this section">22.1.3.9</a></span> Array.prototype.findIndex ( predicate [ , thisArg ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>predicate</i> should be a function that accepts
+ three arguments and returns a value that is coercible to the Boolean value <b>true</b> or <b>false</b>.
+ <code>findIndex</code> calls <i>predicate</i> once for each element of the array, in ascending order, until it finds one
+ where <i>predicate</i> returns <b>true</b>. If such an element is found, <code>findIndex</code> immediately returns the
+ index of that element value. Otherwise, <code>findIndex</code> returns -1.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>predicate</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>predicate</i> is called with three arguments: the value of the element, the index of the element, and
+ the object being traversed.</p>
+
+ <p class="Note"><code>findIndex</code> does not directly mutate the object on which it is called but the object may be
+ mutated by the calls to <i>predicate</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>findIndex</code> is set before the first call to
+ <i>callbackfn</i>. Elements that are appended to the array after the call to <code>findIndex</code> begins will not be
+ visited by <i>callbackfn</i>. If existing elements of the array are changed, their value as passed to <i>predicate</i>
+ will be the value at the time that <code>findIndex</code> visits them; elements that are deleted after the call to
+ <code>findIndex</code> begins and before being visited are not visited.</p>
+
+ <p>When the <code>findIndex</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>predicate</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>testResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>predicate</i>,
+ <i>T</i>, «<i>kValue</i>, <i>k</i>, <i>O</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>testResult</i>).</li>
+ <li>If <i>testResult</i> is <b>true</b>, return <i>k</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return -1.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>findIndex</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>findIndex</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.foreach">
+ <h1><span class="secnum" id="sec-22.1.3.10"><a href="#sec-array.prototype.foreach"
+ title="link to this section">22.1.3.10</a></span> Array.prototype.forEach ( callbackfn [ , thisArg ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that accepts
+ three arguments. <code>forEach</code> calls <i>callbackfn</i> once for each element present in the array, in ascending
+ order. <i>callbackfn</i> is called only for elements of the array which actually exist; it is not called for missing
+ elements of the array.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>callbackfn</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with three arguments: the value of the element, the index of the element, and
+ the object being traversed.</p>
+
+ <p class="Note"><code>forEach</code> does not directly mutate the object on which it is called but the object may be
+ mutated by the calls to <i>callbackfn</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>forEach</code> is set before the first call to <i>callbackfn</i>.
+ Elements which are appended to the array after the call to <code>forEach</code> begins will not be visited by
+ <i>callbackfn</i>. If existing elements of the array are changed, their value as passed to callback will be the value at
+ the time <code>forEach</code> visits them; elements that are deleted after the call to <code>forEach</code> begins and
+ before being visited are not visited.</p>
+
+ <p>When the <code>forEach</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>funcResult</i> be <a href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>, «<i>kValue</i>,
+ <i>k</i>, <i>O</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>funcResult</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>forEach</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>forEach</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.indexof">
+ <h1><span class="secnum" id="sec-22.1.3.11"><a href="#sec-array.prototype.indexof"
+ title="link to this section">22.1.3.11</a></span> Array.prototype.indexOf ( searchElement [ , fromIndex ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<code>indexOf</code> compares <i>searchElement</i>
+ to the elements of the array, in ascending order, using the Strict Equality Comparison algorithm (<a
+ href="#sec-strict-equality-comparison">7.2.13</a>), and if found at one or more indices, returns the smallest such index;
+ otherwise, −1 is returned.</p>
+
+ <p class="Note">The optional second argument <i>fromIndex</i> defaults to 0 (i.e. the whole array is searched). If it is
+ greater than or equal to the length of the array, −1is returned, i.e. the array will not be searched. If it is
+ negative, it is used as the offset from the end of the array to compute <i>fromIndex</i>. If the computed index is less
+ than 0, the whole array will be searched.</p>
+
+ <p>When the <code>indexOf</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <i>len</i> is 0, return −1.</li>
+ <li>If argument <i>fromIndex</i> was passed let <i>n</i> be <a href="#sec-tointeger">ToInteger</a>(<i>fromIndex</i>);
+ else let <i>n</i> be 0.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>n</i>).</li>
+ <li>If <i>n</i> ≥ <i>len</i>, return −1.</li>
+ <li>If <i>n</i> ≥ 0, then
+ <ol class="block">
+ <li>Let <i>k</i> be <i>n</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>n</i><0,
+ <ol class="block">
+ <li>Let <i>k</i> be <i>len</i> - <a href="#sec-algorithm-conventions">abs</a>(<i>n</i>).</li>
+ <li>If <i>k</i> < 0, let <i>k</i> be 0.</li>
+ </ol>
+ </li>
+ <li>Repeat, while <i>k</i><<i>len</i>
+ <ol class="block">
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>elementK</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>elementK</i>).</li>
+ <li>Let <i>same</i> be the result of performing Strict Equality Comparison <i>searchElement</i> ===
+ <i>elementK</i>.</li>
+ <li>If <i>same</i> is <b>true,</b> return <i>k</i>.</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return -1.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>indexOf</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>indexOf</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.join">
+ <h1><span class="secnum" id="sec-22.1.3.12"><a href="#sec-array.prototype.join"
+ title="link to this section">22.1.3.12</a></span> Array.prototype.join (separator)</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	The elements of the array are converted to Strings,
+ and these Strings are then concatenated, separated by occurrences of the <i>separator</i>. If no separator is provided, a
+ single comma is used as the separator.</p>
+
+ <p>The <code>join</code> method takes one argument, <var>separator</var>, and performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <i>separator</i> is <b>undefined</b>, let <i>separator</i> be the single-element String <code>","</code>.</li>
+ <li>Let <i>sep</i> be <a href="#sec-tostring">ToString</a>(<i>separator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>sep</i>).</li>
+ <li>If <i>len</i> is zero, return the empty String.</li>
+ <li>Let <i>element0</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <code>"0"</code>).</li>
+ <li>If <i>element0</i> is <b>undefined</b> or <b>null</b>, let <i>R</i> be the empty String; otherwise, let <i>R</i> be
+ <a href="#sec-tostring">ToString</a>(<i>element0</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>R</i>).</li>
+ <li>Let <i>k</i> be <code>1</code>.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>S</i> be the String value produced by concatenating <i>R</i> and <i>sep</i>.</li>
+ <li>Let <i>element</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>)).</li>
+ <li>If <i>element</i> is <b>undefined</b> or <b>null</b>, let <i>next</i> be the empty String; otherwise, let
+ <i>next</i> be <a href="#sec-tostring">ToString</a>(<i>element</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>Let <i>R</i> be a String value produced by concatenating <i>S</i> and <i>next</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>R</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>join</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>join</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.keys">
+ <h1><span class="secnum" id="sec-22.1.3.13"><a href="#sec-array.prototype.keys"
+ title="link to this section">22.1.3.13</a></span> Array.prototype.keys ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Return <a href="#sec-createarrayiterator">CreateArrayIterator</a>(<i>O</i>, <code>"key"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-array.prototype.lastindexof">
+ <h1><span class="secnum" id="sec-22.1.3.14"><a href="#sec-array.prototype.lastindexof"
+ title="link to this section">22.1.3.14</a></span> Array.prototype.lastIndexOf ( searchElement [ , fromIndex ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<code>lastIndexOf</code> compares
+ <i>searchElement</i> to the elements of the array in descending order using the Strict Equality Comparison algorithm (<a
+ href="#sec-strict-equality-comparison">7.2.13</a>), and if found at one or more indices, returns the largest such index;
+ otherwise, −1 is returned.</p>
+
+ <p class="Note">The optional second argument <i>fromIndex</i> defaults to the array's length minus one (i.e. the whole
+ array is searched). If it is greater than or equal to the length of the array, the whole array will be searched. If it is
+ negative, it is used as the offset from the end of the array to compute <i>fromIndex</i>. If the computed index is less
+ than 0, −1is returned.</p>
+
+ <p>When the <code>lastIndexOf</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <i>len</i> is 0, return -1.</li>
+ <li>If argument <i>fromIndex</i> was passed let <i>n</i> be <a href="#sec-tointeger">ToInteger</a>(<i>fromIndex</i>);
+ else let <i>n</i> be <i>len</i>-1.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>n</i>).</li>
+ <li>If <i>n</i> ≥ 0, let <i>k</i> be min(<i>n</i>, <i>len</i> – 1).</li>
+ <li>Else <i>n</i> < 0,
+ <ol class="block">
+ <li>Let <i>k</i> be <i>len</i> - <a href="#sec-algorithm-conventions">abs</a>(<i>n</i>).</li>
+ </ol>
+ </li>
+ <li>Repeat, while <i>k</i>≥ 0
+ <ol class="block">
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>elementK</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>elementK</i>).</li>
+ <li>Let <i>same</i> be the result of performing Strict Equality Comparison <br><i>searchElement</i> ===
+ <i>elementK</i>.</li>
+ <li>If <i>same</i> is <b>true,</b> return <i>k</i>.</li>
+ </ol>
+ </li>
+ <li>Decrease <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return -1.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>lastIndexOf</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>lastIndexOf</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.map">
+ <h1><span class="secnum" id="sec-22.1.3.15"><a href="#sec-array.prototype.map"
+ title="link to this section">22.1.3.15</a></span> Array.prototype.map ( callbackfn [ , thisArg ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that accepts
+ three arguments. <code>map</code> calls <i>callbackfn</i> once for each element in the array, in ascending order, and
+ constructs a new Array from the results. <i>callbackfn</i> is called only for elements of the array which actually exist;
+ it is not called for missing elements of the array.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>callbackfn</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with three arguments: the value of the element, the index of the element, and
+ the object being traversed.</p>
+
+ <p class="Note"><code>map</code> does not directly mutate the object on which it is called but the object may be mutated
+ by the calls to <i>callbackfn</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>map</code> is set before the first call to <i>callbackfn</i>.
+ Elements which are appended to the array after the call to <code>map</code> begins will not be visited by
+ <i>callbackfn</i>. If existing elements of the array are changed, their value as passed to <i>callbackfn</i> will be the
+ value at the time <code>map</code> visits them; elements that are deleted after the call to <code>map</code> begins and
+ before being visited are not visited.</p>
+
+ <p>When the <code>map</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>A</i> be <a href="#sec-arrayspeciescreate">ArraySpeciesCreate</a>(<i>O</i>, <i>len</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>mappedValue</i> be <a href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>, «<i>kValue</i>,
+ <i>k</i>, <i>O</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>mappedValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a> (<i>A</i>,
+ <i>Pk</i>, <i>mappedValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>map</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>map</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.pop">
+ <h1><span class="secnum" id="sec-22.1.3.16"><a href="#sec-array.prototype.pop"
+ title="link to this section">22.1.3.16</a></span> Array.prototype.pop ( )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	The last element of the array is removed from the
+ array and returned.</p>
+
+ <p>When the <code>pop</code> method is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <i>len</i> is zero,
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <code>"length"</code>, 0,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </li>
+ <li>Else <i>len</i> > 0,
+ <ol class="block">
+ <li>Let <i>newLen</i> be <i>len</i>–1.</li>
+ <li>Let <i>indx</i> be <a href="#sec-tostring">ToString</a>(<i>newLen</i>).</li>
+ <li>Let <i>element</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>indx</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>element</i>).</li>
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>,
+ <i>indx</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <code>"length"</code>, <i>newLen</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>element</i>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>pop</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.push">
+ <h1><span class="secnum" id="sec-22.1.3.17"><a href="#sec-array.prototype.push"
+ title="link to this section">22.1.3.17</a></span> Array.prototype.push ( ...items )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	The arguments are appended to the end of the array,
+ in the order in which they appear. The new length of the array is returned as the result of the call.</p>
+
+ <p>When the <code>push</code> method is called with zero or more arguments the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>items</i> be a <a href="#sec-list-and-record-specification-type">List</a> whose elements are, in left to
+ right order, the arguments that were passed to this function invocation.</li>
+ <li>Let <i>argCount</i> be the number of elements in <i>items</i>.</li>
+ <li>If <i>len</i> + <i>argCount</i> > 2<sup>53</sup>-1, throw a <b>TypeError</b> exception.</li>
+ <li>Repeat, while <i>items</i> is not empty
+ <ol class="block">
+ <li>Remove the first element from <i>items</i> and let <i>E</i> be the value of the element.</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>len</i>), <i>E</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Let <i>len</i> be <i>len</i>+1.</li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <code>"length"</code>, <i>len</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>len</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>push</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>push</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.reduce">
+ <h1><span class="secnum" id="sec-22.1.3.18"><a href="#sec-array.prototype.reduce"
+ title="link to this section">22.1.3.18</a></span> Array.prototype.reduce ( callbackfn [ , initialValue ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that takes
+ four arguments. <code>reduce</code> calls the callback, as a function, once for each element present in the array, in
+ ascending order.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with four arguments: the <i>previousValue</i> (or value from the previous call
+ to <i>callbackfn</i>), the <i>currentValue</i> (value of the current element), the <i>currentIndex</i>, and the object
+ being traversed. The first time that callback is called, the <i>previousValue</i> and <i>currentValue</i> can be one of
+ two values. If an <i>initialValue</i> was provided in the call to <code>reduce</code>, then <i>previousValue</i> will be
+ equal to <i>initialValue</i> and <i>currentValue</i> will be equal to the first value in the array. If no
+ <i>initialValue</i> was provided, then <i>previousValue</i> will be equal to the first value in the array and
+ <i>currentValue</i> will be equal to the second. It is a <b>TypeError</b> if the array contains no elements and
+ <i>initialValue</i> is not provided.</p>
+
+ <p class="Note"><code>reduce</code> does not directly mutate the object on which it is called but the object may be
+ mutated by the calls to <i>callbackfn</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>reduce</code> is set before the first call to <i>callbackfn</i>.
+ Elements that are appended to the array after the call to <code>reduce</code> begins will not be visited by
+ <i>callbackfn</i>. If existing elements of the array are changed, their value as passed to <i>callbackfn</i> will be the
+ value at the time <code>reduce</code> visits them; elements that are deleted after the call to <code>reduce</code> begins
+ and before being visited are not visited.</p>
+
+ <p>When the <code>reduce</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>len</i> is 0 and <i>initialValue</i> is not present, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>If <i>initialValue</i> is present, then
+ <ol class="block">
+ <li>Set <i>accumulator</i> to <i>initialValue</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>initialValue</i> is not present,
+ <ol class="block">
+ <li>Let <i>kPresent</i> be <b>false</b>.</li>
+ <li>Repeat, while <i>kPresent</i> is <b>false</b> and <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>accumulator</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>accumulator</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>If <i>kPresent</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>accumulator</i> be <a href="#sec-call">Call</a>(<i>callbackfn</i>, <b>undefined</b>,
+ «<i>accumulator</i>, <i>kValue</i>, <i>k</i>, <i>O</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>accumulator</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>accumulator</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>reduce</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>reduce</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.reduceright">
+ <h1><span class="secnum" id="sec-22.1.3.19"><a href="#sec-array.prototype.reduceright"
+ title="link to this section">22.1.3.19</a></span> Array.prototype.reduceRight ( callbackfn [ , initialValue ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that takes
+ four arguments. <code>reduceRight</code> calls the callback, as a function, once for each element present in the array, in
+ descending order.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with four arguments: the <i>previousValue</i> (or value from the previous call
+ to <i>callbackfn</i>), the <i>currentValue</i> (value of the current element), the <i>currentIndex</i>, and the object
+ being traversed. The first time the function is called, the <i>previousValue</i> and <i>currentValue</i> can be one of two
+ values. If an <i>initialValue</i> was provided in the call to <code>reduceRight</code>, then <i>previousValue</i> will be
+ equal to <i>initialValue</i> and <i>currentValue</i> will be equal to the last value in the array. If no
+ <i>initialValue</i> was provided, then <i>previousValue</i> will be equal to the last value in the array and
+ <i>currentValue</i> will be equal to the second-to-last value. It is a <b>TypeError</b> if the array contains no elements
+ and <i>initialValue</i> is not provided.</p>
+
+ <p class="Note"><code>reduceRight</code> does not directly mutate the object on which it is called but the object may be
+ mutated by the calls to <i>callbackfn</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>reduceRight</code> is set before the first call to
+ <i>callbackfn</i>. Elements that are appended to the array after the call to <code>reduceRight</code> begins will not be
+ visited by <i>callbackfn</i>. If existing elements of the array are changed by <i>callbackfn</i>, their value as passed to
+ <i>callbackfn</i> will be the value at the time <code>reduceRight</code> visits them; elements that are deleted after the
+ call to <code>reduceRight</code> begins and before being visited are not visited.</p>
+
+ <p>When the <code>reduceRight</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>len</i> is 0 and <i>initialValue</i> is not present, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>k</i> be <i>len</i>-1.</li>
+ <li>If <i>initialValue</i> is present, then
+ <ol class="block">
+ <li>Set <i>accumulator</i> to <i>initialValue</i>.</li>
+ </ol>
+ </li>
+ <li>Else <i>initialValue</i> is not present,
+ <ol class="block">
+ <li>Let <i>kPresent</i> be <b>false</b>.</li>
+ <li>Repeat, while <i>kPresent</i> is <b>false</b> and <i>k</i> ≥ 0
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>accumulator</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>accumulator</i>).</li>
+ </ol>
+ </li>
+ <li>Decrease <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>If <i>kPresent</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Repeat, while <i>k</i> ≥ 0
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>accumulator</i> be <a href="#sec-call">Call</a>(<i>callbackfn</i>, <b>undefined</b>,
+ «<i>accumulator</i>, <i>kValue</i>, <i>k</i>, »).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>accumulator</i>).</li>
+ </ol>
+ </li>
+ <li>Decrease <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>accumulator</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>reduceRight</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>reduceRight</code> function is intentionally generic; it does not require that
+ its this value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.reverse">
+ <h1><span class="secnum" id="sec-22.1.3.20"><a href="#sec-array.prototype.reverse"
+ title="link to this section">22.1.3.20</a></span> Array.prototype.reverse ( )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	The elements of the array are rearranged so as to
+ reverse their order. The object is returned as the result of the call.</p>
+
+ <p>When the <code>reverse</code> method is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>middle</i> be <a href="#sec-algorithm-conventions">floor</a>(<i>len</i>/2).</li>
+ <li>Let <i>lower</i> be <b>0</b>.</li>
+ <li>Repeat, while <i>lower</i> ≠ <i>middle</i>
+ <ol class="block">
+ <li>Let <i>upper</i> be <i>len</i>− <i>lower</i> −1.</li>
+ <li>Let <i>upperP</i> be <a href="#sec-tostring">ToString</a>(<i>upper</i>).</li>
+ <li>Let <i>lowerP</i> be <a href="#sec-tostring">ToString</a>(<i>lower</i>).</li>
+ <li>Let <i>lowerExists</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>lowerP</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lowerExists</i>).</li>
+ <li>If <i>lowerExists</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>lowerValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>lowerP</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>lowerValue</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>upperExists</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>upperP</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>upperExists</i>).</li>
+ <li>If <i>upperExists</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>upperValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>upper</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>upperValue</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>lowerExists</i> is <b>true</b> and <i>upperExists</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>lowerP</i>, <i>upperValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>upperP</i>, <i>lowerValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else if <i>lowerExists</i> is <b>false</b> and <i>upperExists</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>lowerP</i>, <i>upperValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a> (<i>O</i>,
+ <i>upperP</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else if <i>lowerExists</i> is <b>true</b> and <i>upperExists</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a> (<i>O</i>,
+ <i>lowerP</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>upperP</i>, <i>lowerValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else both <i>lowerExists</i> and <i>upperExists</i> are <b>false</b>,
+ <ol class="block">
+ <li>No action is required.</li>
+ </ol>
+ </li>
+ <li>Increase <i>lower</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>O</i> .</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>reverse</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.shift">
+ <h1><span class="secnum" id="sec-22.1.3.21"><a href="#sec-array.prototype.shift"
+ title="link to this section">22.1.3.21</a></span> Array.prototype.shift ( )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	The first element of the array is removed from the
+ array and returned.</p>
+
+ <p>When the <code>shift</code> method is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <i>len</i> is zero, then
+ <ol class="block">
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <code>"length"</code>, 0,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </li>
+ <li>Let <i>first</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <code>"<b>0</b>"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>first</i>).</li>
+ <li>Let <i>k</i> be 1.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>from</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>to</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>–1).</li>
+ <li>Let <i>fromPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromPresent</i>).</li>
+ <li>If <i>fromPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>fromVal</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromVal</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>to</i>, <i>fromVal</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>fromPresent</i> is <b>false</b>,
+ <ol class="block">
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>,
+ <i>to</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>len</i>–1)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <code>"length"</code>, <i>len</i>–1,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>first</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>shift</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.slice">
+ <h1><span class="secnum" id="sec-22.1.3.22"><a href="#sec-array.prototype.slice"
+ title="link to this section">22.1.3.22</a></span> Array.prototype.slice (start, end)</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	The <code>slice</code> method takes two arguments,
+ <i>start</i> and <i>end</i>, and returns an array containing the elements of the array from element <i>start</i> up to,
+ but not including, element <i>end</i> (or through the end of the array if <i>end</i> is <b>undefined</b>). If <i>start</i>
+ is negative, it is treated as <i>length</i>+<i>start</i> where <i>length</i> is the length of the array. If <i>end</i> is
+ negative, it is treated as <i>length</i>+<i>end</i> where <i>length</i> is the length of the array.</p>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>relativeStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeStart</i>).</li>
+ <li>If <i>relativeStart</i> < 0, let <i>k</i> be max((<i>len</i> + <i>relativeStart</i>),0); else let <i>k</i> be
+ min(<i>relativeStart</i>, <i>len</i>).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>relativeEnd</i> be <i>len</i>; else let <i>relativeEnd</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeEnd</i>).</li>
+ <li>If <i>relativeEnd</i> < 0, let <i>final</i> be max((<i>len</i> + <i>relativeEnd</i>),0); else let <i>final</i> be
+ min(<i>relativeEnd</i>, <i>len</i>).</li>
+ <li>Let <i>count</i> be max(<i>final</i> – <i>k</i>, 0).</li>
+ <li>Let <i>A</i> be <a href="#sec-arrayspeciescreate">ArraySpeciesCreate</a>(<i>O</i>, <i>count</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>n</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>final</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>), <i>kValue</i> ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ <li>Increase <i>n</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <code>"length"</code>, <i>n</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>slice</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The explicit setting of the <code>length</code> property of the result Array in step
+ 19 is necessary to ensure that its value is correct in situations where the trailing elements of the result Array are
+ not present.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>slice</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.some">
+ <h1><span class="secnum" id="sec-22.1.3.23"><a href="#sec-array.prototype.some"
+ title="link to this section">22.1.3.23</a></span> Array.prototype.some ( callbackfn [ , thisArg ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that accepts
+ three arguments and returns a value that is coercible to the Boolean value <b>true</b> or <b>false</b>. <code>some</code>
+ calls <i>callbackfn</i> once for each element present in the array, in ascending order, until it finds one where
+ <i>callbackfn</i> returns <b>true</b>. If such an element is found, <code>some</code> immediately returns <b>true</b>.
+ Otherwise, <code>some</code> returns <b>false</b>. <i>callbackfn</i> is called only for elements of the array which
+ actually exist; it is not called for missing elements of the array.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>callbackfn</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with three arguments: the value of the element, the index of the element, and
+ the object being traversed.</p>
+
+ <p class="Note"><code>some</code> does not directly mutate the object on which it is called but the object may be mutated
+ by the calls to <i>callbackfn</i>.</p>
+
+ <p class="Note">The range of elements processed by <code>some</code> is set before the first call to <i>callbackfn</i>.
+ Elements that are appended to the array after the call to <code>some</code> begins will not be visited by
+ <i>callbackfn</i>. If existing elements of the array are changed, their value as passed to <i>callbackfn</i> will be the
+ value at the time that <code>some</code> visits them; elements that are deleted after the call to <code>some</code> begins
+ and before being visited are not visited. <code>some</code> acts like the "exists" quantifier in mathematics. In
+ particular, for an empty array, it returns <b>false</b>.</p>
+
+ <p>When the <code>some</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kPresent</i>).</li>
+ <li>If <i>kPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>testResult</i> be <a href="#sec-toboolean">ToBoolean</a>(<a
+ href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>, «<i>kValue</i>, <i>k</i>, and
+ <i>O</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>testResult</i>).</li>
+ <li>If <i>testResult</i> is <b>true</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>some</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>some</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.sort">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.3.24"><a href="#sec-array.prototype.sort"
+ title="link to this section">22.1.3.24</a></span> Array.prototype.sort (comparefn)</h1>
+
+ <p>The elements of this array are sorted. The sort is not necessarily stable (that is, elements that compare equal do
+ not necessarily remain in their original order). If <var>comparefn</var> is not <b>undefined</b>, it should be a
+ function that accepts two arguments <var>x</var> and <var>y</var> and returns a negative value if <var>x</var> <span
+ style="font-family: Times New Roman"><</span> <var>y</var>, zero if <var>x</var> <span style="font-family: Times New
+ Roman">=</span> <var>y</var>, or a positive value if <var>x</var> <span style="font-family: Times New Roman">></span>
+ <var>y</var>.</p>
+
+ <p>Within this specification of the <code>sort</code> method, an Array object, <var>obj</var>, is said to be
+ <i>sparse</i> if the following algorithm returns <b>true</b>:</p>
+
+ <ol class="proc">
+ <li>Let <i>len</i> be <a href="#sec-get-o-p">Get</a>(<i>obj</i>, <code>"length"</code>).</li>
+ <li>For each integer <i>i</i> in the range 0≤<i>i</i><<a href="#sec-touint32">ToUint32</a>(<i>len</i>)
+ <ol class="block">
+ <li>Let <i>elem</i> be <i>obj</i>.[[GetOwnProperty]](<a href="#sec-tostring">ToString</a>(<i>i</i>)).</li>
+ <li>If <i>elem</i> is <b>undefined</b>, return <b>true</b>.</li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <p>Upon entry, the following steps are performed to initialize evaluation of the <code>sort</code> function:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>obj</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ </ol>
+
+ <p>The <i>sort order</i> is the ordering of the array index property values of <var>obj</var> after completion of this
+ function. The result of the <code>sort</code> function is then determined as follows:</p>
+
+ <p>If <var>comparefn</var> is not <b>undefined</b> and is not a consistent comparison function for the elements of this
+ array (see below), the sort order is implementation-defined. The sort order is also implementation-defined if
+ <var>comparefn</var> is <b>undefined</b> and <a href="#sec-sortcompare">SortCompare</a> ({ REF _Ref393437395 \n \h
+ }22.1.3.24.1) does not act as a consistent comparison function.</p>
+
+ <p>Let <var>proto</var> be the result of calling the [[GetPrototypeOf]] internal method of <var>obj</var>. If
+ <var>proto</var> is not <b>null</b> and there exists an integer <var>j</var> such that all of the conditions below are
+ satisfied then the sort order is implementation-defined:</p>
+
+ <ul>
+ <li><var>obj</var> is sparse (<a href="#sec-array-objects">22.1</a>)</li>
+ <li>0 ≤ <var>j</var> < <var>len</var></li>
+ <li><a href="#sec-hasproperty">HasProperty</a>(<var>proto</var>, <span style="font-family: Times New Roman"><a
+ href="#sec-tostring">ToString</a>(<i>j</i>))</span> is <b>true</b>.</li>
+ </ul>
+
+ <p>The sort order is also implementation defined if <var>obj</var> is sparse and any of the following conditions are
+ true:</p>
+
+ <ul>
+ <li>
+ <p><a href="#sec-isextensible-o">IsExtensible</a>(<span style="font-family: Times New Roman"><i>obj</i>)</span> is
+ <b>false</b>.</p>
+ </li>
+
+ <li>
+ <p>Any array index property of <var>obj</var> whose name is a nonnegative integer less than <var>len</var> is a data
+ property whose [[Configurable]] attribute is <b>false</b>.</p>
+ </li>
+ </ul>
+
+ <p>The sort order is also implementation defined if any of the following conditions are true:</p>
+
+ <ul>
+ <li>
+ <p>If <var>obj</var> is an exotic object (including Proxy exotic objects) whose behaviour for [[Get]], [[Set]],
+ [[Delete]], and [[GetOwnProperty]] is different from the ordinary object behaviour for these internal methods.</p>
+ </li>
+
+ <li>
+ <p>If any array index property of <var>obj</var> whose name is a nonnegative integer less than <var>len</var> is an
+ accessor property or is a data property whose [[Writable]] attribute is <span class="value">false</span>.</p>
+ </li>
+
+ <li>
+ <p>If <var>comparefn</var> is <span class="value">undefined</span> and the applicaton of <a
+ href="#sec-tostring">ToString</a> to any value passed as an argument to <a href="#sec-sortcompare">SortCompare</a>
+ modifies <var>obj</var> or any object on <var>obj</var>’s prototype chain.</p>
+ </li>
+
+ <li>
+ <p>If <var>comparefn</var> is <span class="value">undefined</span> and all applicatons of <a
+ href="#sec-tostring">ToString</a>, to any specific value passed as an argument to <a
+ href="#sec-sortcompare">SortCompare</a>, do not produce the same result.</p>
+ </li>
+ </ul>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Perform an implementation-dependent sequence of calls to the [[Get]] and [[Set]], internal methods of <i>obj</i>,
+ to the <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a> and <a
+ href="#sec-hasownproperty">HasOwnProperty</a> abstract operation with <i>obj</i> as the first argument, and to <a
+ href="#sec-sortcompare">SortCompare</a> (described below), such that:
+ <ul>
+ <li>
+ <p>The <a href="#sec-object-type">property key</a> argument for each call to [[Get]], [[Set]], <a
+ href="#sec-hasownproperty">HasOwnProperty</a>, or <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>
+ is the string representation of a nonnegative integer less than <i>len</i>.</p>
+ </li>
+
+ <li>
+ <p>The arguments for calls to <a href="#sec-sortcompare">SortCompare</a> are values returned by a previous call
+ to the [[Get]] internal method, unless the properties accessed by those previous calls did not exist according
+ to <a href="#sec-hasownproperty">HasOwnProperty</a>. If both perspective arguments to <a
+ href="#sec-sortcompare">SortCompare</a> correspond to non-existent properties, use +0 instead of calling <a
+ href="#sec-sortcompare">SortCompare</a>. If only the first perspective argument is non-existent use +1. If only
+ the second perspective argument is non-existent use −1.</p>
+ </li>
+
+ <li>
+ <p>If <i>obj</i> is not sparse then <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a> must not be
+ called.</p>
+ </li>
+
+ <li>
+ <p>If any [[Set]] call returns <b>false</b> a <b>TypeError</b> exception is thrown.</p>
+ </li>
+
+ <li>
+ <p>If an <a href="#sec-completion-record-specification-type">abrupt completion</a> is returned from any of these
+ operations, it is immediately returned as the value of this function.</p>
+ </li>
+ </ul>
+ </li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+
+ <p>Unless the sort order is specified above to be implementation-defined, the returned object must have the following
+ two characteristics:</p>
+
+ <ul>
+ <li>
+ <p>There must be some mathematical permutation <span style="font-family: Times New Roman">π</span> of the
+ nonnegative integers less than <var>len</var>, such that for every nonnegative integer <var>j</var> less than
+ <var>len</var>, if property <span style="font-family: Times New Roman">old[<i>j</i>]</span> existed, then <span
+ style="font-family: Times New Roman">new[π(<i>j</i>)]</span> is exactly the same value as <span
+ style="font-family: Times New Roman">old[<i>j</i>]</span>. But if property <span style="font-family: Times New
+ Roman">old[<i>j</i>]</span> did not exist, then <span style="font-family: Times New
+ Roman">new[π(<i>j</i>)]</span> does not exist.</p>
+ </li>
+
+ <li>
+ <p>Then for all nonnegative integers <var>j</var> and <var>k</var>, each less than <var>len</var>, if <span
+ style="font-family: Times New Roman"><a href="#sec-sortcompare">SortCompare</a>(old[<i>j</i>], old[<i>k</i>]) <
+ 0</span> (see <a href="#sec-sortcompare">SortCompare</a> below), then <span style="font-family: Times New
+ Roman">new[<b>π</b>(<i>j</i>)] <</span> <span style="font-family: Times New
+ Roman">new[<b>π</b>(<i>k</i>)]</span>.</p>
+ </li>
+ </ul>
+
+ <p>Here the notation <span style="font-family: Times New Roman">old[<i>j</i>]</span> is used to refer to the
+ hypothetical result of calling the [[Get]] internal method of <var>obj</var> with argument <var>j</var> before this
+ function is executed, and the notation <span style="font-family: Times New Roman">new[<i>j</i>]</span> to refer to the
+ hypothetical result of calling the [[Get]] internal method of <var>obj</var> with argument <var>j</var> after this
+ function has been executed.</p>
+
+ <p>A function <var>comparefn</var> is a consistent comparison function for a set of values <var>S</var> if all of the
+ requirements below are met for all values <var>a</var>, <var>b</var>, and <var>c</var> (possibly the same value) in the
+ set <var>S</var>: The notation <span style="font-family: Times New
+ Roman"><i>a</i> <<sub>CF</sub></span> <var>b</var> means <span style="font-family: Times New
+ Roman"><i>comparefn</i>(<i>a</i>,<i>b</i>) < 0</span>; <span style="font-family: Times New
+ Roman"><i>a</i> =<sub>CF</sub></span> <var>b</var> means <span style="font-family: Times New
+ Roman"><i>comparefn</i>(<i>a</i>,<i>b</i>) = 0</span> (of either sign); and <span style="font-family: Times
+ New Roman"><i>a</i> ><sub>CF</sub></span> <var>b</var> means <span style="font-family: Times New
+ Roman"><i>comparefn</i>(<i>a</i>,<i>b</i>) > 0</span>.</p>
+
+ <ul>
+ <li>
+ <p>Calling <i>comparefn</i>(<i>a</i>,<i>b</i>) always returns the same value <i>v</i> when given a specific pair of
+ values <i>a</i> and <i>b</i> as its two arguments. Furthermore, <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>v</i>) is Number, and <i>v</i> is not NaN. Note that this
+ implies that exactly one of <i>a</i> <<sub>CF</sub> <i>b</i>,
+ <i>a</i> =<sub>CF</sub> <i>b</i>, and <i>a</i> ><sub>CF</sub> <i>b</i> will be true for a
+ given pair of <i>a</i> and <i>b</i>.</p>
+ </li>
+
+ <li>
+ <p>Calling <i>comparefn</i>(<i>a</i>,<i>b</i>) does not modify <i>obj</i> or any object on <i>obj</i>’s
+ prototype chain.</p>
+ </li>
+
+ <li>
+ <p><i>a</i> =<sub>CF</sub> <i>a</i> (reflexivity)</p>
+ </li>
+
+ <li>
+ <p>If <i>a</i> =<sub>CF</sub> <i>b</i>, then <i>b</i> =<sub>CF</sub> <i>a</i> (symmetry)</p>
+ </li>
+
+ <li>
+ <p>If <i>a</i> =<sub>CF</sub> <i>b</i> and <i>b</i> =<sub>CF</sub> <i>c</i>, then
+ <i>a</i> =<sub>CF</sub> <i>c</i> (transitivity of =<sub>CF</sub>)</p>
+ </li>
+
+ <li>
+ <p>If <i>a</i> <<sub>CF</sub> <i>b</i> and <i>b</i> <<sub>CF</sub> <i>c</i>, then
+ <i>a</i> <<sub>CF</sub> <i>c</i> (transitivity of <<sub>CF</sub>)</p>
+ </li>
+
+ <li>
+ <p>If <i>a</i> ><sub>CF</sub> <i>b</i> and <i>b</i> ><sub>CF</sub> <i>c</i>, then
+ <i>a</i> ><sub>CF</sub> <i>c</i> (transitivity of ><sub>CF</sub>)</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The above conditions are necessary and sufficient to ensure that <i>comparefn</i>
+ divides the set <i>S</i> into equivalence classes and that these equivalence classes are totally ordered.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>sort</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be an Array object. Therefore, it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </div>
+
+ <section id="sec-sortcompare">
+ <h1><span class="secnum" id="sec-22.1.3.24.1"><a href="#sec-sortcompare"
+ title="link to this section">22.1.3.24.1</a></span> Runtime Semantics: SortCompare( x, y )</h1>
+
+ <p>When the SortCompare abstract operation is called with two arguments <var>x</var> and <var>y</var>, the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <i>x</i> and <i>y</i> are both <b>undefined</b>, return +0.</li>
+ <li>If <i>x</i> is <b>undefined</b>, return 1.</li>
+ <li>If <i>y</i> is <b>undefined</b>, return −1.</li>
+ <li>If the argument <i>comparefn</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-tonumber">ToNumber</a>(<a href="#sec-call">Call</a>(<i>comparefn</i>,
+ <b>undefined</b>, «<i>x</i>, <i>y</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <i>v</i> is <b>NaN</b>, return +0.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>xString</i> be <a href="#sec-tostring">ToString</a>(<i>x</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>xString</i>).</li>
+ <li>Let <i>yString</i> be <a href="#sec-tostring">ToString</a>(<i>y</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>yString</i>).</li>
+ <li>If <i>xString</i> < <i>yString</i>, return −1.</li>
+ <li>If <i>xString</i> > <i>yString</i>, return 1.</li>
+ <li>Return +0.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> Because non-existent property values always compare greater than <b>undefined</b>
+ property values, and <b>undefined</b> always compares greater than any other value, <b>undefined</b> property values
+ always sort to the end of the result, followed by non-existent property values.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Method calls performed by the <a href="#sec-tostring">ToString</a> abstract
+ operations in steps 5 and 7 have the potential to cause SortCompare to not behave as a consistent comparison
+ function.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-array.prototype.splice">
+ <h1><span class="secnum" id="sec-22.1.3.25"><a href="#sec-array.prototype.splice"
+ title="link to this section">22.1.3.25</a></span> Array.prototype.splice (start, deleteCount , ...items )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	When the <code>splice</code> method is called with
+ two or more arguments <i>start</i>, <i>deleteCount</i> and zero or more <i>items</i>, the <i>deleteCount</i> elements of
+ the array starting at integer index <i>start</i> are replaced by the arguments <i>items</i>. An Array object containing
+ the deleted elements (if any) is returned.</p>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>relativeStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeStart</i>).</li>
+ <li>If <i>relativeStart</i> < 0, let <i>actualStart</i> be max((<i>len</i> + <i>relativeStart</i>),0); else let
+ <i>actualStart</i> be min(<i>relativeStart</i>, <i>len</i>).</li>
+ <li>If the number of actual arguments is 0, then
+ <ol class="block">
+ <li>Let <i>insertCount</i> be 0.</li>
+ <li>Let <i>actualDeleteCount</i> be 0.</li>
+ </ol>
+ </li>
+ <li>Else if the number of actual arguments is 1, then
+ <ol class="block">
+ <li>Let <i>insertCount</i> be 0.</li>
+ <li>Let <i>actualDeleteCount</i> be <i>len</i> - <i>actualStart</i></li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>insertCount</i> be the number of actual arguments minus 2.</li>
+ <li>Let <i>dc</i> be <a href="#sec-tointeger">ToInteger</a>(<i>deleteCount</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>dc</i>).</li>
+ <li>Let <i>actualDeleteCount</i> be min(max(<i>dc</i>,0), <i>len</i> – <i>actualStart</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>len+insertCount</i>−<i>actualDeleteCount</i> > 2<sup>53</sup>-1, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>A</i> be <a href="#sec-arrayspeciescreate">ArraySpeciesCreate</a>(<i>O</i>, <i>actualDeleteCount</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>actualDeleteCount</i>
+ <ol class="block">
+ <li>Let <i>from</i> be <a href="#sec-tostring">ToString</a>(<i>actualStart</i>+<i>k</i>).</li>
+ <li>Let <i>fromPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromPresent</i>).</li>
+ <li>If <i>fromPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>fromValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O,</i> <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>), <i>fromValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Increment <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <code>"length"</code>,
+ <i>actualDeleteCount</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Let <i>items</i> be a <a href="#sec-list-and-record-specification-type">List</a> whose elements are, in left to
+ right order, the portion of the actual argument list starting with the third argument. The list is empty if fewer
+ than three arguments were passed.</li>
+ <li>Let <i>itemCount</i> be the number of elements in <i>items</i>.</li>
+ <li>If <i>itemCount</i> < <i>actualDeleteCount</i>, then
+ <ol class="block">
+ <li>Let <i>k</i> be <i>actualStart</i>.</li>
+ <li>Repeat, while <i>k</i> < (<i>len</i> – <i>actualDeleteCount</i>)
+ <ol class="block">
+ <li>Let <i>from</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>+<i>actualDeleteCount</i>).</li>
+ <li>Let <i>to</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>+<i>itemCount</i>).</li>
+ <li>Let <i>fromPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromPresent</i>).</li>
+ <li>If <i>fromPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>fromValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromValue</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>to</i>, <i>fromValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>fromPresent</i> is <b>false</b>,
+ <ol class="block">
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>,
+ <i>to</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>k</i> be <i>len</i>.</li>
+ <li>Repeat, while <i>k</i> > (<i>len</i> – <i>actualDeleteCount</i> + <i>itemCount</i>)
+ <ol class="block">
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>–1)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ <li>Decrease <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else if <i>itemCount</i> > <i>actualDeleteCount</i>, then
+ <ol class="block">
+ <li>Let <i>k</i> be (<i>len</i> – <i>actualDeleteCount</i>).</li>
+ <li>Repeat, while <i>k</i> > <i>actualStart</i>
+ <ol class="block">
+ <li>Let <i>from</i> be <a href="#sec-tostring">ToString</a>(<i>k</i> + <i>actualDeleteCount</i> – 1).</li>
+ <li>Let <i>to</i> be <a href="#sec-tostring">ToString</a>(<i>k</i> + <i>itemCount</i> – 1)</li>
+ <li>Let <i>fromPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromPresent</i>).</li>
+ <li>If <i>fromPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>fromValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromValue</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>to</i>, <i>fromValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>fromPresent</i> is <b>false</b>,
+ <ol class="block">
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>,
+ <i>to</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Decrease <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>k</i> be <i>actualStart</i>.</li>
+ <li>Repeat, while <i>items</i> is not empty
+ <ol class="block">
+ <li>Remove the first element from <i>items</i> and let <i>E</i> be the value of that element.</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>), <i>E</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <code>"length"</code>, <i>len</i> –
+ <i>actualDeleteCount</i> + <i>itemCount</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>splice</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The explicit setting of the <code>length</code> property of the result Array in step
+ 18 is necessary to ensure that its value is correct in situations where its trailing elements are not present.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>splice</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.tolocalestring">
+ <h1><span class="secnum" id="sec-22.1.3.26"><a href="#sec-array.prototype.tolocalestring"
+ title="link to this section">22.1.3.26</a></span> Array.prototype.toLocaleString ( [ reserved1 [ , reserved2 ] ]
+ )</h1>
+
+ <p>An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the
+ <code>Array.prototype.toLocaleString</code> method as specified in the ECMA-402 specification. If an ECMAScript
+ implementation does not include the ECMA-402 API the following specification of the <code>toLocaleString</code> method is
+ used.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The first edition of ECMA-402 did not include a replacement specification for the
+ <code>Array.prototype.toLocaleString</code> method.</p>
+ </div>
+
+ <p>The meanings of the optional parameters to this method are defined in the ECMA-402 specification; implementations that
+ do not include ECMA-402 support must not use those parameter positions for anything else.</p>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>array</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>array</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>array</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>separator</i> be the String value for the list-separator String appropriate for the host environment’s
+ current locale (this is derived in an implementation-defined way).</li>
+ <li>If <i>len</i> is zero, return the empty String.</li>
+ <li>Let <i>firstElement</i> be <a href="#sec-get-o-p">Get</a>(<i>array</i>, <code>"0"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>firstElement</i>).</li>
+ <li>If <i>firstElement</i> is <b>undefined</b> or <b>null</b>, then
+ <ol class="block">
+ <li>Let <i>R</i> be the empty String.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>R</i> be <a href="#sec-tostring">ToString</a>(<a href="#sec-invoke">Invoke</a>(<i>firstElement</i>,
+ <code>"toLocaleString"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>R</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>k</i> be <code>1</code>.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>S</i> be a String value produced by concatenating <i>R</i> and <i>separator</i>.</li>
+ <li>Let <i>nextElement</i> be <a href="#sec-get-o-p">Get</a>(<i>array</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextElement</i>).</li>
+ <li>If <i>nextElement</i> is <b>undefined</b> or <b>null</b>, then
+ <ol class="block">
+ <li>Let <i>R</i> be the empty String.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>R</i> be <a href="#sec-tostring">ToString</a>(<a href="#sec-invoke">Invoke</a>(<i>nextElement</i>,
+ <code>"toLocaleString"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>R</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>R</i> be a String value produced by concatenating <i>S</i> and <i>R</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>R</i>.</li>
+ </ol>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE 1</span>	The elements of the array are converted to Strings
+ using their <code>toLocaleString</code> methods, and these Strings are then concatenated, separated by occurrences of a
+ separator String that has been derived in an implementation-defined locale-specific way. The result of calling this
+ function is intended to be analogous to the result of <code>toString</code>, except that the result of this function is
+ intended to be locale-specific.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>toLocaleString</code> function is intentionally generic; it does not require
+ that its <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.tostring">
+ <h1><span class="secnum" id="sec-22.1.3.27"><a href="#sec-array.prototype.tostring"
+ title="link to this section">22.1.3.27</a></span> Array.prototype.toString ( )</h1>
+
+ <p>When the <code>toString</code> method is called, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>array</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>array</i>).</li>
+ <li>Let <i>func</i> be <a href="#sec-get-o-p">Get</a>(<i>array</i>, <code>"join"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>func</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>func</i>) is <b>false</b>, let <i>func</i> be the intrinsic function
+ %ObjProto_toString% (<a href="#sec-object.prototype.tostring">19.1.3.6</a>).</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>func</i>, <i>array</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>toString</code> function is intentionally generic; it does not require that
+ its <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a
+ method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.unshift">
+ <h1><span class="secnum" id="sec-22.1.3.28"><a href="#sec-array.prototype.unshift"
+ title="link to this section">22.1.3.28</a></span> Array.prototype.unshift ( ...items )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	The arguments are prepended to the start of the
+ array, such that their order within the array is the same as the order in which they appear in the argument list.</p>
+
+ <p>When the <code>unshift</code> method is called with zero or more arguments <var>item1</var>, <var>item2</var>, etc.,
+ the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>O</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>argCount</i> be the number of actual arguments.</li>
+ <li>If <i>argCount</i> > 0, then
+ <ol class="block">
+ <li>If <i>len</i>+ <i>argCount</i> > 2<sup>53</sup>-1, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>k</i> be <i>len</i>.</li>
+ <li>Repeat, while <i>k</i> > 0,
+ <ol class="block">
+ <li>Let <i>from</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>–1).</li>
+ <li>Let <i>to</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>+<i>argCount</i> –1).</li>
+ <li>Let <i>fromPresent</i> be <a href="#sec-hasproperty">HasProperty</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromPresent</i>).</li>
+ <li>If <i>fromPresent</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>fromValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>from</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fromValue</i>).</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <i>to</i>, <i>fromValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Else <i>fromPresent</i> is <b>false</b>,
+ <ol class="block">
+ <li>Let <i>deleteStatus</i> be <a href="#sec-deletepropertyorthrow">DeletePropertyOrThrow</a>(<i>O</i>,
+ <i>to</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>deleteStatus</i>).</li>
+ </ol>
+ </li>
+ <li>Decrease <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>j</i> be 0.</li>
+ <li>Let <i>items</i> be a <a href="#sec-list-and-record-specification-type">List</a> whose elements are, in left to
+ right order, the arguments that were passed to this function invocation.</li>
+ <li>Repeat, while <i>items</i> is not empty
+ <ol class="block">
+ <li>Remove the first element from <i>items</i> and let <i>E</i> be the value of that element.</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <a
+ href="#sec-tostring">ToString</a>(<i>j</i>), <i>E</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Increase <i>j</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>O</i>, <code>"length"</code>,
+ <i>len</i>+<i>argCount</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Return <i>len</i>+<i>argCount</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>unshift</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>unshift</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-array.prototype.values">
+ <h1><span class="secnum" id="sec-22.1.3.29"><a href="#sec-array.prototype.values"
+ title="link to this section">22.1.3.29</a></span> Array.prototype.values ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Return <a href="#sec-createarrayiterator">CreateArrayIterator</a>(<i>O</i>, <code>"value"</code>).</li>
+ </ol>
+
+ <p>This function is the %ArrayProto_values% intrinsic object.</p>
+ </section>
+
+ <section id="sec-array.prototype-@@iterator">
+ <h1><span class="secnum" id="sec-22.1.3.30"><a href="#sec-array.prototype-@@iterator"
+ title="link to this section">22.1.3.30</a></span> Array.prototype [ @@iterator ] ( )</h1>
+
+ <p>The initial value of the @@iterator property is the same function object as the initial value of the <b><a
+ href="#sec-array.prototype.values">Array.prototype.values</a></b> property.</p>
+ </section>
+
+ <section id="sec-array.prototype-@@unscopables">
+ <h1><span class="secnum" id="sec-22.1.3.31"><a href="#sec-array.prototype-@@unscopables"
+ title="link to this section">22.1.3.31</a></span> Array.prototype [ @@unscopables ]</h1>
+
+ <p>The initial value of the @@unscopables data property is an object created by the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>blackList</i> be <a href="#sec-objectcreate">ObjectCreate</a>(<b>null</b>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>blackList</i>, <code>"copyWithin"</code>,
+ <b>true</b>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>blackList</i>, <code>"entries"</code>,
+ <b>true</b>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>blackList</i>, <code>"fill"</code>,
+ <b>true</b>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>blackList</i>, <code>"find"</code>,
+ <b>true</b>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>blackList</i>, <code>"findIndex"</code>,
+ <b>true</b>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>blackList</i>, <code>"keys"</code>,
+ <b>true</b>).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>blackList</i>, <b>"<code>values"</code></b>,
+ <b>true</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: Each of the above calls will return <b>true</b>.</li>
+ <li>Return <i>blackList</i>.</li>
+ </ol>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <span class="value">false</span>,
+ [[Configurable]]: <span class="value">true</span> }.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The own property names of this object are property names that were not included as
+ standard properties of <code>Array.prototype</code> prior to the sixth edition of this specification. These names are
+ ignored for <code>with</code> statement binding purposes in order to preserve the behaviour of existing code that might
+ use one of these names as a binding in an outer scope that is shadowed by a <code>with</code> statement whose binding
+ object is an Array object.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-array-instances">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.4"><a href="#sec-properties-of-array-instances"
+ title="link to this section">22.1.4</a></span> Properties of Array Instances</h1>
+
+ <p>Array instances are Array exotic objects and have the internal methods specified for such objects. Array instances
+ inherit properties from the Array prototype object.</p>
+
+ <p>Array instances have a <code>length</code> property, and a set of enumerable properties with array index names.</p>
+ </div>
+
+ <section id="sec-properties-of-array-instances-length">
+ <h1><span class="secnum" id="sec-22.1.4.1"><a href="#sec-properties-of-array-instances-length"
+ title="link to this section">22.1.4.1</a></span> length</h1>
+
+ <p>The <code>length</code> property of an Array instance is a data property whose value is always numerically greater than
+ the name of every configurable own property whose name is an array index.</p>
+
+ <p>The <code>length</code> property initially has the attributes <span style="font-family: Times New Roman">{
+ [[Writable]]: <b>true</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>false</b> }</span>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Attempting to set the length property of an Array object to a value that is numerically
+ less than or equal to the largest numeric own property name of an existing array indexed configurable property of the
+ array will result in the length being set to a numeric value that is one greater than that largest numeric own property
+ name. See <a href="#sec-array-exotic-objects-defineownproperty-p-desc">9.4.2.1</a>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-array-iterator-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.5"><a href="#sec-array-iterator-objects"
+ title="link to this section">22.1.5</a></span> Array Iterator Objects</h1>
+
+ <p>An Array Iterator is an object, that represents a specific iteration over some specific Array instance object. There is
+ not a named constructor for Array Iterator objects. Instead, Array iterator objects are created by calling certain methods
+ of Array instance objects.</p>
+ </div>
+
+ <section id="sec-createarrayiterator">
+ <h1><span class="secnum" id="sec-22.1.5.1"><a href="#sec-createarrayiterator"
+ title="link to this section">22.1.5.1</a></span> CreateArrayIterator Abstract Operation</h1>
+
+ <p>Several methods of Array objects return Iterator objects. The abstract operation CreateArrayIterator with arguments
+ <var>array</var> and <var>kind</var> is used to create such iterator objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>array</i>) is Object.</li>
+ <li>Let <i>iterator</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%ArrayIteratorPrototype%,
+ «‍[[IteratedObject]], [[ArrayIteratorNextIndex]], [[ArrayIterationKind]]»).</li>
+ <li>Set <i>iterator’s</i> [[IteratedObject]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>array</i>.</li>
+ <li>Set <i>iterator’s</i> [[ArrayIteratorNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to 0.</li>
+ <li>Set <i>iterator’s</i> [[ArrayIterationKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <i>kind</i>.</li>
+ <li>Return <i>iterator</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%arrayiteratorprototype%-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.1.5.2"><a href="#sec-%arrayiteratorprototype%-object"
+ title="link to this section">22.1.5.2</a></span> The %ArrayIteratorPrototype% Object</h1>
+
+ <p>All Array Iterator Objects inherit properties from the %ArrayIteratorPrototype% intrinsic object. The
+ %ArrayIteratorPrototype% object is an ordinary object and its [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the %IteratorPrototype% intrinsic object (<a
+ href="#sec-%iteratorprototype%-object">25.1.2</a>). In addition, %ArrayIteratorPrototype% has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-%arrayiteratorprototype%.next">
+ <h1><span class="secnum" id="sec-22.1.5.2.1"><a href="#sec-%arrayiteratorprototype%.next"
+ title="link to this section">22.1.5.2.1</a></span> %ArrayIteratorPrototype%.next( )</h1>
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have all of the internal slots of an Array Iterator Instance (<a
+ href="#sec-properties-of-array-iterator-instances">22.1.5.3</a>), throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>a</i> be the value of the [[IteratedObject]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>a</i> is <b>undefined</b>, return <a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ <li>Let <i>index</i> be the value of the [[ArrayIteratorNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>itemKind</i> be the value of the [[ArrayIterationKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>a</i> has a [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>,
+ then
+ <ol class="block">
+ <li>Let <i>len</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>a</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>index</i> ≥ <i>len</i>, then
+ <ol class="block">
+ <li>Set the value of the [[IteratedObject]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of <i>O</i> to <b>undefined</b>.</li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Set the value of the [[ArrayIteratorNextIndex]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of <i>O</i> to <i>index</i>+1.</li>
+ <li>If <i>itemKind</i> is <b>"<code>key</code>"</b>, return <a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>index</i>, <b>false</b>).</li>
+ <li>Let <i>elementKey</i> be <a href="#sec-tostring">ToString</a>(<i>index</i>).</li>
+ <li>Let <i>elementValue</i> be <a href="#sec-get-o-p">Get</a>(<i>a</i>, <i>elementKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>elementValue</i>).</li>
+ <li>If <i>itemKind</i> is <b>"<code>value</code>"</b>, let <i>result</i> be <i>elementValue</i>.</li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>itemKind</i> is <b>"<code>key+value</code>"</b>.</li>
+ <li>Let <i>result</i> be <a href="#sec-createarrayfromlist">CreateArrayFromList</a>(«<i>index</i>,
+ <i>elementValue</i>»).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>result</i>, <b>false</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%arrayiteratorprototype%-@@tostringtag">
+ <h1><span class="secnum" id="sec-22.1.5.2.2"><a href="#sec-%arrayiteratorprototype%-@@tostringtag"
+ title="link to this section">22.1.5.2.2</a></span> %ArrayIteratorPrototype% [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Array Iterator</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-array-iterator-instances">
+ <h1><span class="secnum" id="sec-22.1.5.3"><a href="#sec-properties-of-array-iterator-instances"
+ title="link to this section">22.1.5.3</a></span> Properties of Array Iterator Instances</h1>
+
+ <p>Array Iterator instances are ordinary objects that inherit properties from the %ArrayIteratorPrototype% intrinsic
+ object. Array Iterator instances are initially created with the internal slots listed in <a href="#table-48">Table
+ 48</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-48">Table 48</span> — Internal Slots of Array Iterator Instances</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[IteratedObject]]</td>
+ <td>The object whose array elements are being iterated.</td>
+ </tr>
+ <tr>
+ <td>[[ArrayIteratorNextIndex]]</td>
+ <td>The integer index of the next array index to be examined by this iteration.</td>
+ </tr>
+ <tr>
+ <td>[[ArrayIterationKind]]</td>
+ <td>A string value that identifies what is to be returned for each element of the iteration. The possible values are: <b>"<code>key</code>"</b>, <b>"<code>value</code>"</b>, <b>"<code>key+value</code>"</b>.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-typedarray-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2"><a href="#sec-typedarray-objects" title="link to this section">22.2</a></span>
+ <i>TypedArray</i> Objects</h1>
+
+ <p><i>TypedArray</i> objects present an array-like view of an underlying binary data buffer (<a
+ href="#sec-arraybuffer-objects">24.1</a>). Each element of a <i>TypedArray</i> instance has the same underlying binary
+ scalar data type. There is a distinct <i>TypedArray</i> constructor, listed in <a href="#table-49">Table 49</a>, for each of
+ the nine supported element types. Each constructor in <a href="#table-49">Table 49</a> has a corresponding distinct
+ prototype object.</p>
+
+ <figure>
+ <figcaption><span id="table-49">Table 49</span> – The <i>TypedArray</i> Constructors</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="background-color: #BFBFBF">Constructor Name and Intrinsic</th>
+ <td style="background-color: #BFBFBF"><span style="background-color: #C0C0C0">Element</span> <span style="background-color: #C0C0C0">Type</span></td>
+ <th style="background-color: #BFBFBF">Element Size</th>
+ <th style="background-color: #BFBFBF">Conversion Operation</th>
+ <th style="background-color: #BFBFBF">Description</th>
+ <th style="background-color: #BFBFBF">Equivalent C Type</th>
+ </tr>
+ <tr>
+ <td><a href="#sec-int8array">Int8Array</a><br>%Int8Array%</td>
+ <td>Int8</td>
+ <td>1</td>
+ <td><a href="#sec-toint8">ToInt8</a></td>
+ <td>8-bit 2’s complement signed integer</td>
+ <td>signed char</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-uint8array">Uint8Array</a> <br>%Uint8Array%</td>
+ <td>Uint8</td>
+ <td>1</td>
+ <td><a href="#sec-touint8">ToUint8</a></td>
+ <td>8-bit unsigned integer</td>
+ <td>unsigned char</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-uint8clampedarray">Uint8ClampedArray</a><br>%Uint8ClampedArray%</td>
+ <td>Uint8C</td>
+ <td>1</td>
+ <td><a href="#sec-touint8clamp">ToUint8Clamp</a></td>
+ <td>8-bit unsigned integer (clamped conversion)</td>
+ <td>unsigned char</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-int16array">Int16Array</a> <br>%Int16Array%</td>
+ <td>Int16</td>
+ <td>2</td>
+ <td><a href="#sec-toint16">ToInt16</a></td>
+ <td>16-bit 2’s complement signed integer</td>
+ <td>short</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-uint16array">Uint16Array</a> <br>%Uint16Array%</td>
+ <td>Uint16</td>
+ <td>2</td>
+ <td><a href="#sec-touint16">ToUint16</a></td>
+ <td>16-bit unsigned integer</td>
+ <td>unsigned short</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-int32array">Int32Array</a> <br>%Int32Array%</td>
+ <td>Int32</td>
+ <td>4</td>
+ <td><a href="#sec-toint32">ToInt32</a></td>
+ <td>32-bit 2’s complement signed integer</td>
+ <td>int</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-uint32array">Uint32Array</a> <br>%Uint32Array%</td>
+ <td>Uint32</td>
+ <td>4</td>
+ <td><a href="#sec-touint32">ToUint32</a></td>
+ <td>32-bit unsigned integer</td>
+ <td>unsigned int</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-float32array">Float32Array</a> <br>%Float32Array%</td>
+ <td>Float32</td>
+ <td>4</td>
+ <td></td>
+ <td>32-bit IEEE floating point</td>
+ <td>float</td>
+ </tr>
+ <tr>
+ <td><a href="#sec-float64array">Float64Array</a> <br>%Float64Array%</td>
+ <td>Float64</td>
+ <td>8</td>
+ <td></td>
+ <td>64-bit IEEE floating point</td>
+ <td>double</td>
+ </tr>
+ </table>
+ </figure>
+
+ <p>In the definitions below, references to <i>TypedArray</i> should be replaced with the appropriate constructor name from
+ the above table. The phrase “the element size in bytes” refers to the value in the Element Size column of the
+ table in the row corresponding to the constructor. The phrase “element Type” refers to the value in the Element
+ Type column for that row.</p>
+ </div>
+
+ <section id="sec-%typedarray%-intrinsic-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.1"><a href="#sec-%typedarray%-intrinsic-object"
+ title="link to this section">22.2.1</a></span> The %TypedArray% Intrinsic Object</h1>
+
+ <p>The %TypedArray% intrinsic object is a constructor function object that all of the <i>TypedArray</i> constructor object
+ inherit from. %TypedArray% and its corresponding prototype object provide common properties that are inherited by all
+ <i>TypedArray</i> constructors and their instances. The %TypedArray% intrinsic does not have a global name or appear as a
+ property of the global object.</p>
+
+ <p>The %TypedArray% intrinsic function object is designed to act as the superclass of the various <i>TypedArray</i>
+ constructors. Those constructors use %TypedArray% to initialize their instances by invoking %TypedArray% as if by making a
+ <code>super</code> call. The %TypedArray% intrinsic function is not designed to be directly called in any other way. If
+ %TypedArray% is directly called or called as part of a <code>new</code> expression an exception is thrown.</p>
+
+ <p>The %TypedArray% intrinsic function constructor is a single function whose behaviour is overloaded based upon the
+ number and types of its arguments. The actual behaviour of a <code>super</code> call of %TypedArray% depends upon the
+ number and kind of arguments that are passed to it.</p>
+ </div>
+
+ <section id="sec-%typedarray%-length">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.1.1"><a href="#sec-%typedarray%-length"
+ title="link to this section">22.2.1.1</a></span> %TypedArray% ( length )</h1>
+
+ <p>This description applies only if the %TypedArray% function is called with at least one argument and the Type of the
+ first argument is not Object.</p>
+
+ <p>%TypedArray% called with argument <var>length</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>length</i>) is not Object.</li>
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>numberLength</i> be <a href="#sec-tonumber">ToNumber</a>(<i>length</i>).</li>
+ <li>Let <i>elementLength</i> be <a href="#sec-tolength">ToLength</a>(<i>numberLength</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>elementLength</i>).</li>
+ <li>If <a href="#sec-samevaluezero">SameValueZero</a>(<i>numberLength</i>, <i>elementLength</i>) is <b>false</b>,
+ throw a <b>RangeError</b> exception.</li>
+ <li>Return <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(NewTarget, <i>elementLength</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-allocatetypedarray">
+ <h1><span class="secnum" id="sec-22.2.1.1.1"><a href="#sec-allocatetypedarray"
+ title="link to this section">22.2.1.1.1</a></span> Runtime Semantics: AllocateTypedArray (newTarget, length )</h1>
+
+ <p>The abstract operation AllocateTypedArray with argument <var>newTarget</var> and optional argument <var>length</var>
+ is used to validate and create an instance of a TypedArray constructor. If the <var>length</var> argument is passed an
+ ArrayBuffer of that length is also allocated and associated with the new Typed Array instance. AllocateTypedArray
+ provides common semantics that is used by all of the %TypeArray% overloads and other methods. AllocateTypedArray
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-isconstructor">IsConstructor</a>(<i>newTarget</i>)
+ is <b>true</b>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(%TypedArray%, <i>newTarget</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>NOTE <span style="font-family: Times New Roman">%TypedArray%</span> throws an exception when invoked via either a
+ function call or the <code>new</code> operator. It can only be successfully invoked by a <span
+ class="nt">SuperCall</span>.</li>
+ <li>Let <i>constructorName</i> be <b>undefined</b>.</li>
+ <li>Let <i>subclass</i> be <i>newTarget</i>.</li>
+ <li>Repeat while <i>constructorName</i> is <b>undefined</b>
+ <ol class="block">
+ <li>If <i>subclass</i> is <b>null</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(%TypedArray%, <i>subclass</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>If <i>subclass</i> has a [[TypedArrayConstructorName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, let <i>constructorName</i> be the
+ value of <i>subclass</i>’s [[TypedArrayConstructorName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>subclass</i> be <i>subclass</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>subclass</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>proto</i> be <a href="#sec-getprototypefromconstructor">GetPrototypeFromConstructor</a>(<i>newTarget</i>,
+ <code>"%TypedArrayPrototype%"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>proto</i>).</li>
+ <li>Let <i>obj</i> be <a href="#sec-integerindexedobjectcreate">IntegerIndexedObjectCreate</a> (<i>proto</i>,
+ «‍[[ViewedArrayBuffer]], [[TypedArrayName]], [[ByteLength]], [[ByteOffset]], [[ArrayLength]]»
+ ).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>obj</i> is <b>undefined</b>.</li>
+ <li>Set <i>obj</i>’s [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>constructorName</i>.</li>
+ <li>If <i>length</i> was not passed, then
+ <ol class="block">
+ <li>Set <i>obj</i>’s [[ByteLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to 0.</li>
+ <li>Set <i>obj</i>’s [[ByteOffset]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to 0.</li>
+ <li>Set <i>obj</i>’s [[ArrayLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to 0.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>elementSize</i> be the Element Size value in <a href="#table-49">Table 49</a> for
+ <i>constructorName</i>.</li>
+ <li>Let <i>byteLength</i> be <i>elementSize</i> × <i>length</i>.</li>
+ <li>Let <i>data</i> be <a href="#sec-allocatearraybuffer">AllocateArrayBuffer</a>(<span style="font-family:
+ sans-serif">%ArrayBuffer%</span>, <i>byteLength</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>data</i>).</li>
+ <li>Set <i>obj’s</i> [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <i>data</i>.</li>
+ <li>Set <i>obj</i>’s [[ByteLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>byteLength</i>.</li>
+ <li>Set <i>obj</i>’s [[ByteOffset]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to 0.</li>
+ <li>Set <i>obj</i>’s [[ArrayLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>length</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-%typedarray%-typedarray">
+ <h1><span class="secnum" id="sec-22.2.1.2"><a href="#sec-%typedarray%-typedarray"
+ title="link to this section">22.2.1.2</a></span> %TypedArray% ( typedArray )</h1>
+
+ <p>This description applies only if the %TypedArray% function is called with at least one argument and the Type of the
+ first argument is Object and that object has a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>%TypedArray% called with argument <var>typedArray</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>typedArray</i>) is Object and <i>typedArray</i> has a
+ [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>O</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(NewTarget).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>srcArray</i> be <i>typedArray</i>.</li>
+ <li>Let <i>srcData</i> be the value of <i>srcArray’s</i> [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>srcData</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>constructorName</i> be the string value of <i>O</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>constructorName</i>.</li>
+ <li>Let <i>elementLength</i> be the value of <i>srcArray’s</i> [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>srcName</i> be the string value of <i>srcArray’s</i> [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>srcType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>srcName</i>.</li>
+ <li>Let <i>srcElementSize</i> be the Element Size value in <a href="#table-49">Table 49</a> for <i>srcName</i>.</li>
+ <li>Let <i>srcByteOffset</i> be the value of <i>srcArray</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Element Size value in <a href="#table-49">Table 49</a> for
+ <i>constructorName</i>.</li>
+ <li>Let <i>byteLength</i> be <i>elementSize</i> × <i>elementLength</i>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>elementType</i>,<i>srcType</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>data</i> be <a href="#sec-clonearraybuffer">CloneArrayBuffer</a>(<i>srcData</i>,
+ <i>srcByteOffset</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>data</i>).</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>bufferConstructor</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>srcData</i>,
+ %ArrayBuffer%).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>bufferConstructor</i>).</li>
+ <li>Let <i>data</i> be <a href="#sec-allocatearraybuffer">AllocateArrayBuffer</a>(<i>bufferConstructor</i>,
+ <i>byteLength</i>).</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>srcData</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>srcByteIndex</i> be <i>srcByteOffset</i>.</li>
+ <li>Let <i>targetByteIndex</i> be 0.</li>
+ <li>Let <i>count</i> be <i>elementLength</i>.</li>
+ <li>Repeat, while <i>count</i> >0
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-getvaluefrombuffer">GetValueFromBuffer</a>(<i>srcData</i>,
+ <i>srcByteIndex</i>, <i>srcType</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-setvalueinbuffer">SetValueInBuffer</a>(<i>data</i>,
+ <i>targetByteIndex</i>, <i>elementType</i>, <i>value</i>).</li>
+ <li>Set <i>srcByteIndex</i> to <i>srcByteIndex</i> + <i>srcElementSize</i>.</li>
+ <li>Set <i>targetByteIndex</i> to <i>targetByteIndex</i> + <i>elementSize</i>.</li>
+ <li>Decrement <i>count</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set <i>O’s</i> [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>data</i>.</li>
+ <li>Set <i>O</i>’s [[ByteLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>byteLength</i>.</li>
+ <li>Set <i>O</i>’s [[ByteOffset]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ 0.</li>
+ <li>Set <i>O</i>’s [[ArrayLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>elementLength</i>.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%-object">
+ <h1><span class="secnum" id="sec-22.2.1.3"><a href="#sec-%typedarray%-object"
+ title="link to this section">22.2.1.3</a></span> %TypedArray% ( object )</h1>
+
+ <p>This description applies only if the %TypedArray% function is called with at least one argument and the Type of the
+ first argument is Object and that object does not have either a [[TypedArrayName]] or an [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>%TypedArray% called with argument <var>object</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>object</i>) is Object and <i>object</i> does not have
+ either a [[TypedArrayName]] or an [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <a href="#sec-typedarrayfrom">TypedArrayFrom</a>(NewTarget, <i>object</i>, <b>undefined</b>,
+ <b>undefined</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%-buffer-byteoffset-length">
+ <h1><span class="secnum" id="sec-22.2.1.4"><a href="#sec-%typedarray%-buffer-byteoffset-length"
+ title="link to this section">22.2.1.4</a></span> %TypedArray% ( buffer [ , byteOffset [ , length ] ] )</h1>
+
+ <p>This description applies only if the %TypedArray% function is called with at least one argument and the Type of the
+ first argument is Object and that object has an [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>%TypedArray% called with arguments <span style="font-family: Times New Roman"><i>buffer</i>, <i>byteOffset</i>, and
+ <i>length</i></span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>buffer</i>) is Object and <i>buffer</i> has an
+ [[ArrayBufferData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>O</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(NewTarget).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Let <i>constructorName</i> be the string value of <i>O</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value in <a href="#table-49">Table 49</a> for
+ <i>constructorName</i>.</li>
+ <li>Let <i>offset</i> be <a href="#sec-tointeger">ToInteger</a>(<i>byteOffset</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>offset</i>).</li>
+ <li>If <i>offset</i> < 0, throw a <b>RangeError</b> exception.</li>
+ <li>If <i>offset</i> <a href="#sec-algorithm-conventions">modulo</a> <i>elementSize</i> ≠ 0, throw a
+ <b>RangeError</b> exception.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>bufferByteLength</i> be the value of <i>buffer’s</i> [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>length</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>If <i>bufferByteLength</i> <a href="#sec-algorithm-conventions">modulo</a> <i>elementSize</i> ≠ 0, throw a
+ <b>RangeError</b> exception.</li>
+ <li>Let <i>newByteLength</i> be <i>bufferByteLength</i> – <i>offset</i>.</li>
+ <li>If <i>newByteLength</i> < 0, throw a <b>RangeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>newLength</i> be <a href="#sec-tolength">ToLength</a>(<i>length</i>)<i>.</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>newLength</i>).</li>
+ <li>Let <i>newByteLength</i> be <i>newLength</i> × <i>elementSize</i>.</li>
+ <li>If <i>offset</i>+<i>newByteLength</i> > <i>bufferByteLength</i>, throw a <b>RangeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Set <i>O’s</i> [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>buffer</i>.</li>
+ <li>Set <i>O</i>’s [[ByteLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>newByteLength</i>.</li>
+ <li>Set <i>O</i>’s [[ByteOffset]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>offset</i>.</li>
+ <li>Set <i>O</i>’s [[ArrayLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>newByteLength /</i> <i>elementSize</i> .</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%-all-other-argument-combinations">
+ <h1><span class="secnum" id="sec-22.2.1.5"><a href="#sec-%typedarray%-all-other-argument-combinations"
+ title="link to this section">22.2.1.5</a></span> %TypedArray% ( all other argument combinations )</h1>
+
+ <p>If the %TypedArray% function is called with arguments that do not match any of the preceding argument descriptions a
+ <b>TypeError</b> exception is thrown.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-%typedarray%-intrinsic-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.2"><a href="#sec-properties-of-the-%typedarray%-intrinsic-object"
+ title="link to this section">22.2.2</a></span> Properties of the %TypedArray% Intrinsic Object</h1>
+
+ <p>The %TypedArray% intrinsic object is a built-in function object. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of %TypedArray% is the intrinsic object
+ %FunctionPrototype% (<a href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides a <code>length</code> property whose value is 3 and a <code>name</code> property whose value is
+ <code>"TypedArray"</code>, %TypedArray% has the following properties:</p>
+ </div>
+
+ <section id="sec-%typedarray%.from">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.2.1"><a href="#sec-%typedarray%.from"
+ title="link to this section">22.2.2.1</a></span> %TypedArray%.from ( source [ , mapfn [ , thisArg ] ] )</h1>
+
+ <p>When the <code>from</code> method is called with argument <var>source</var>, and optional arguments <i>mapfn</i> and
+ <i>thisArg</i>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>mapfn</i> was supplied, let <i>f</i> be <i>mapfn</i>; otherwise let <i>f</i> be <b>undefined</b>.</li>
+ <li>If <i>f</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>f</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ </ol>
+ </li>
+ <li>If <i>thisArg</i> was supplied, let <i>t</i> be <i>thisArg</i>; else let <i>t</i> be <b>undefined</b>.</li>
+ <li>Return <a href="#sec-typedarrayfrom">TypedArrayFrom</a>(<i>C</i>, <i>source</i>, <i>f</i>, <i>t</i>).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>from</code> method is <b>1</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>from</code> function is an intentionally generic factory method; it does not
+ require that its <b>this</b> value be a TypedArray constructor. Therefore it can be transferred to or inherited by any
+ other constructors that may be called with a single numeric argument. This function uses [[Set]] to store elements
+ into a newly created object and assume that the constructor sets the <code>length</code> property of the new object to
+ the argument value passed to it.</p>
+ </div>
+ </div>
+
+ <section id="sec-typedarrayfrom">
+ <h1><span class="secnum" id="sec-22.2.2.1.1"><a href="#sec-typedarrayfrom"
+ title="link to this section">22.2.2.1.1</a></span> Runtime Semantics: TypedArrayFrom( constructor, items, mapfn,
+ thisArg )</h1>
+
+ <p>When the TypedArrayFrom abstract operation is called with arguments <span style="font-family: Times New
+ Roman"><i>constructor</i>,</span> <var>items</var>, <var>mapfn</var>, and <var>thisArg</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be <i>constructor</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is
+ <b>true</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>mapfn</i> is either a callable Object or
+ <b>undefined</b>.</li>
+ <li>If <i>mapfn</i> is <b>undefined</b>, let <i>mapping</i> be <b>false.</b></li>
+ <li>else
+ <ol class="block">
+ <li>Let <i>T</i> be <i>thisArg</i>.</li>
+ <li>Let <i>mapping</i> be <b>true</b></li>
+ </ol>
+ </li>
+ <li>Let <i>usingIterator</i> be <a href="#sec-getmethod">GetMethod</a>(<i>items</i>, @@iterator).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>usingIterator</i>).</li>
+ <li>If <i>usingIterator</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>items</i>, <i>usingIterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iterator</i>).</li>
+ <li>Let <i>values</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>next</i> be <b>true</b>.</li>
+ <li>Repeat, while <i>next</i> is not <b>false</b>
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iterator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is not <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Append <i>nextValue</i> to the end of the <a href="#sec-list-and-record-specification-type">List</a>
+ <i>values</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>len</i> be the number of elements in <i>values</i>.</li>
+ <li>Let <i>targetObj</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(<i>C</i>, <i>len</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetObj</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be the first element of <i>values</i> and remove that element from <i>list</i>.</li>
+ <li>If <i>mapping</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>mappedValue</i> be <a href="#sec-call">Call</a>(<i>mapfn</i>, <i>T</i>, «<i>kValue</i>,
+ <i>k</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>mappedValue</i>).</li>
+ </ol>
+ </li>
+ <li>Else, let <i>mappedValue</i> be <i>kValue</i>.</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>targetObj</i>, <i>Pk</i>,
+ <i>mappedValue</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>values</i> is now an empty <a
+ href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Return <i>targetObj</i>.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>items</i> is not an Iterable so assume it is an array-like
+ object.</li>
+ <li>Let <i>arrayLike</i> be <a href="#sec-toobject">ToObject</a>(<i>items</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>arrayLike</i>).</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>arrayLike</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>targetObj</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(<i>C</i>, <i>len</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetObj</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>arrayLike</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>If <i>mapping</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>mappedValue</i> be <a href="#sec-call">Call</a>(<i>mapfn</i>, <i>T</i>, «<i>kValue</i>,
+ <i>k</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>mappedValue</i>).</li>
+ </ol>
+ </li>
+ <li>Else, let <i>mappedValue</i> be <i>kValue</i>.</li>
+ <li>Let <i>setStatus</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>targetObj</i>, <i>Pk</i>,
+ <i>mappedValue</i>, <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>setStatus</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>targetObj</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-%typedarray%.of">
+ <h1><span class="secnum" id="sec-22.2.2.2"><a href="#sec-%typedarray%.of" title="link to this section">22.2.2.2</a></span>
+ %TypedArray%.of ( ...items )</h1>
+
+ <p>When the <code>of</code> method is called with any number of arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>len</i> be the actual number of arguments passed to this function.</li>
+ <li>Let <i>items</i> be the <a href="#sec-list-and-record-specification-type">List</a> of arguments passed to this
+ function.</li>
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>newObj</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(<i>C</i>, <i>len</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>newObj</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>kValue</i> be <i>items</i>[<i>k</i>].</li>
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>newObj</i>, <i>Pk</i>, <i>kValue</i>,
+ <b>true</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>newObj</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>of</code> method is <b>0</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> The <i>items</i> argument is assumed to be a well-formed rest argument value.</p>
+ </div>
+ </section>
+
+ <section id="sec-%typedarray%.prototype">
+ <h1><span class="secnum" id="sec-22.2.2.3"><a href="#sec-%typedarray%.prototype"
+ title="link to this section">22.2.2.3</a></span> %TypedArray%.prototype</h1>
+
+ <p>The initial value of %TypedArray%.prototype is the %TypedArrayPrototype% intrinsic object (<a
+ href="#sec-properties-of-the-%typedarrayprototype%-object">22.2.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">false</span> }.</p>
+ </section>
+
+ <section id="sec-get-%typedarray%-@@species">
+ <h1><span class="secnum" id="sec-22.2.2.4"><a href="#sec-get-%typedarray%-@@species"
+ title="link to this section">22.2.2.4</a></span> get %TypedArray% [ @@species ]</h1>
+
+ <p><code>%TypedArray%[@@species]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"get [Symbol.species]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Typed Array prototype methods normally their <code>this</code> object’s
+ constructor to create a derived object. However, a subclass constructor may over-ride that default behaviour by
+ redefining its @@species property.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-%typedarrayprototype%-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.3"><a href="#sec-properties-of-the-%typedarrayprototype%-object"
+ title="link to this section">22.2.3</a></span> Properties of the %TypedArrayPrototype% Object</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ %TypedArrayPrototype% object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The %TypedArrayPrototype% object is an ordinary object.
+ It does not have a [[ViewedArrayBuffer]] or or any other of the internal slots that are specific to <i>TypedArray</i>
+ instance objects.</p>
+ </div>
+
+ <section id="sec-get-%typedarray%.prototype.buffer">
+ <h1><span class="secnum" id="sec-22.2.3.1"><a href="#sec-get-%typedarray%.prototype.buffer"
+ title="link to this section">22.2.3.1</a></span> get %TypedArray%.prototype.buffer</h1>
+
+ <p>%TypedArray%.<code>prototype.buffer</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>buffer</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-get-%typedarray%.prototype.bytelength">
+ <h1><span class="secnum" id="sec-22.2.3.2"><a href="#sec-get-%typedarray%.prototype.bytelength"
+ title="link to this section">22.2.3.2</a></span> get %TypedArray%.prototype.byteLength</h1>
+
+ <p>%TypedArray%.<code>prototype.byteLength</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, return 0.</li>
+ <li>Let <i>size</i> be the value of <i>O</i>’s [[ByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>size</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-get-%typedarray%.prototype.byteoffset">
+ <h1><span class="secnum" id="sec-22.2.3.3"><a href="#sec-get-%typedarray%.prototype.byteoffset"
+ title="link to this section">22.2.3.3</a></span> get %TypedArray%.prototype.byteOffset</h1>
+
+ <p>%TypedArray%.<code>prototype.byteOffset</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, return 0.</li>
+ <li>Let <i>offset</i> be the value of <i>O</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>offset</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.constructor">
+ <h1><span class="secnum" id="sec-22.2.3.4"><a href="#sec-%typedarray%.prototype.constructor"
+ title="link to this section">22.2.3.4</a></span> %TypedArray%.prototype.constructor</h1>
+
+ <p>The initial value of %TypedArray%.prototype.constructor is the %TypedArray% intrinsic object.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.copywithin">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.3.5"><a href="#sec-%typedarray%.prototype.copywithin"
+ title="link to this section">22.2.3.5</a></span> %TypedArray%.prototype.copyWithin (target, start [, end ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.copyWithin</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.copywithin">Array.prototype.copyWithin</a></code> as defined in <a
+ href="#sec-array.prototype.copywithin">22.1.3.3</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code> and the actual copying of values in step 17 must be performed in a manner that perserves the
+ bit-level encoding of the source data</p>
+
+ <p>The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value is an object that
+ has a fixed length and whose integer indexed properties are not sparse. However, such optimization must not introduce
+ any observable changes in the specified behaviour of the algorithm.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>copyWithin</code> method is <b>2</b>.</p>
+ </div>
+
+ <section id="sec-validatetypedarray">
+ <h1><span class="secnum" id="sec-22.2.3.5.1"><a href="#sec-validatetypedarray"
+ title="link to this section">22.2.3.5.1</a></span> Runtime Semantics: ValidateTypedArray ( O )</h1>
+
+ <p>When called with argument <i>O</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>If <i>O</i> does not have a [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>buffer</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.entries">
+ <h1><span class="secnum" id="sec-22.2.3.6"><a href="#sec-%typedarray%.prototype.entries"
+ title="link to this section">22.2.3.6</a></span> %TypedArray%.prototype.entries ( )</h1>
+
+ <p>When <code>entries</code> is called with <b>this</b> value <var>O</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>valid</i> be <a href="#sec-validatetypedarray">ValidateTypedArray</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Return <a href="#sec-createarrayiterator">CreateArrayIterator</a>(<i>O</i>, <code>"key+value"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.every">
+ <h1><span class="secnum" id="sec-22.2.3.7"><a href="#sec-%typedarray%.prototype.every"
+ title="link to this section">22.2.3.7</a></span> %TypedArray%.prototype.every ( callbackfn [ , thisArg ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.every</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.every">Array.prototype.every</a></code> as defined in <a
+ href="#sec-array.prototype.every">22.1.3.5</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm and must take into account the
+ possibility that calls to <var>callbackfn</var> may cause the <b>this</b> value to become detached.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>every</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.fill">
+ <h1><span class="secnum" id="sec-22.2.3.8"><a href="#sec-%typedarray%.prototype.fill"
+ title="link to this section">22.2.3.8</a></span> %TypedArray%.prototype.fill (value [ , start [ , end ] ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.fill</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.fill">Array.prototype.fill</a></code> as defined in <a
+ href="#sec-array.prototype.fill">22.1.3.6</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>fill</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.filter">
+ <h1><span class="secnum" id="sec-22.2.3.9"><a href="#sec-%typedarray%.prototype.filter"
+ title="link to this section">22.2.3.9</a></span> %TypedArray%.prototype.filter ( callbackfn [ , thisArg ] )</h1>
+
+ <p>The interpretation and use of the arguments of %TypedArray%<code>.prototype.filter</code> are the same as for <code><a
+ href="#sec-array.prototype.filter">Array.prototype.filter</a></code> as defined in <a
+ href="#sec-array.prototype.filter">22.1.3.7</a>.</p>
+
+ <p>When the <code>filter</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>valid</i> be <a href="#sec-validatetypedarray">ValidateTypedArray</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Let <i>len</i> be the value of <i>O’s</i> [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>defaultConstructor</i> be the intrinsic object listed in column one of <a href="#table-49">Table 49</a> for
+ the value of <i>O</i>’s [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</li>
+ <li>Let <i>C</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>O</i>, <i>defaultConstructor</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>Let <i>kept</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Let <i>captured</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>selected</i> be <a href="#sec-toboolean">ToBoolean</a>(<a href="#sec-call">Call</a>(<i>callbackfn</i>,
+ <i>T</i>, «<i>kValue</i>, <i>k</i>, <i>O</i>»)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>selected</i>).</li>
+ <li>If <i>selected</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Append <i>kValue</i> to the end of <i>kept</i>.</li>
+ <li>Increase <i>captured</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Let <i>A</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(<i>C</i>, <i>captured</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>n</i> be 0.</li>
+ <li>For each element <i>e</i> of <i>kept</i>
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>), <i>e</i>, <b>true</b> ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Increment <i>n</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>This function is not generic. The <b>this</b> value must be an object with a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The <code>length</code> property of the <code>filter</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.find">
+ <h1><span class="secnum" id="sec-22.2.3.10"><a href="#sec-%typedarray%.prototype.find"
+ title="link to this section">22.2.3.10</a></span> %TypedArray%.prototype.find (predicate [ , thisArg ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.find</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.find">Array.prototype.find</a></code> as defined in <a
+ href="#sec-array.prototype.find">22.1.3.8</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm and must take into account the
+ possibility that calls to <var>predicate</var> may cause the <b>this</b> value to become detached.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>find</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.findindex">
+ <h1><span class="secnum" id="sec-22.2.3.11"><a href="#sec-%typedarray%.prototype.findindex"
+ title="link to this section">22.2.3.11</a></span> %TypedArray%.prototype.findIndex ( predicate [ , thisArg ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.findIndex</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.findindex">Array.prototype.findIndex</a></code> as defined in <a
+ href="#sec-array.prototype.findindex">22.1.3.9</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm and must take into account the
+ possibility that calls to <var>predicate</var> may cause the <b>this</b> value to become detached.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>findIndex</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.foreach">
+ <h1><span class="secnum" id="sec-22.2.3.12"><a href="#sec-%typedarray%.prototype.foreach"
+ title="link to this section">22.2.3.12</a></span> %TypedArray%.prototype.forEach ( callbackfn [ , thisArg ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.forEach</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.foreach">Array.prototype.forEach</a></code> as defined in <a
+ href="#sec-array.prototype.foreach">22.1.3.10</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm and must take into account the
+ possibility that calls to <var>callbackfn</var> may cause the <b>this</b> value to become detached.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>forEach</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.indexof">
+ <h1><span class="secnum" id="sec-22.2.3.13"><a href="#sec-%typedarray%.prototype.indexof"
+ title="link to this section">22.2.3.13</a></span> %TypedArray%.prototype.indexOf (searchElement [ , fromIndex ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.indexOf</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.indexof">Array.prototype.indexOf</a></code> as defined in <a
+ href="#sec-array.prototype.indexof">22.1.3.11</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>indexOf</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.join">
+ <h1><span class="secnum" id="sec-22.2.3.14"><a href="#sec-%typedarray%.prototype.join"
+ title="link to this section">22.2.3.14</a></span> %TypedArray%.prototype.join ( separator )</h1>
+
+ <p>%TypedArray%<code>.prototype.join</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.join">Array.prototype.join</a></code> as defined in <a
+ href="#sec-array.prototype.join">22.1.3.12</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.keys">
+ <h1><span class="secnum" id="sec-22.2.3.15"><a href="#sec-%typedarray%.prototype.keys"
+ title="link to this section">22.2.3.15</a></span> %TypedArray%.prototype.keys ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>valid</i> be <a href="#sec-validatetypedarray">ValidateTypedArray</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Return <a href="#sec-createarrayiterator">CreateArrayIterator</a>(<i>O</i>, <code>"key"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.lastindexof">
+ <h1><span class="secnum" id="sec-22.2.3.16"><a href="#sec-%typedarray%.prototype.lastindexof"
+ title="link to this section">22.2.3.16</a></span> %TypedArray%.prototype.lastIndexOf ( searchElement [ , fromIndex ]
+ )</h1>
+
+ <p>%TypedArray%<code>.prototype.lastIndexOf</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.lastindexof">Array.prototype.lastIndexOf</a></code> as defined in <a
+ href="#sec-array.prototype.lastindexof">22.1.3.14</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>lastIndexOf</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-get-%typedarray%.prototype.length">
+ <h1><span class="secnum" id="sec-22.2.3.17"><a href="#sec-get-%typedarray%.prototype.length"
+ title="link to this section">22.2.3.17</a></span> get %TypedArray%.prototype.length</h1>
+
+ <p>%TypedArray%.<code>prototype.length</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> has [[ViewedArrayBuffer]] and [[ArrayLength]] internal
+ slots.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, return 0.</li>
+ <li>Let <i>length</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>length</i>.</li>
+ </ol>
+
+ <p>This function is not generic. The <b>this</b> value must be an object with a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.map">
+ <h1><span class="secnum" id="sec-22.2.3.18"><a href="#sec-%typedarray%.prototype.map"
+ title="link to this section">22.2.3.18</a></span> %TypedArray%.prototype.map ( callbackfn [ , thisArg ] )</h1>
+
+ <p>The interpretation and use of the arguments of %TypedArray%<code>.prototype.map</code> are the same as for <code><a
+ href="#sec-array.prototype.map">Array.prototype.map</a></code> as defined in <a
+ href="#sec-array.prototype.map">22.1.3.15</a>.</p>
+
+ <p>When the <code>map</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>valid</i> be <a href="#sec-validatetypedarray">ValidateTypedArray</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Let <i>len</i> be the value of <i>O’s</i> [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>defaultConstructor</i> be the intrinsic object listed in column one of <a href="#table-49">Table 49</a> for
+ the value of <i>O</i>’s [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</li>
+ <li>Let <i>C</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>O</i>, <i>defaultConstructor</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>Let <i>A</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(<i>C</i>, <i>len</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>mappedValue</i> be <a href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>, «<i>kValue</i>,
+ <i>k</i>, <i>O</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>mappedValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <i>Pk</i>, <i>mappedValue</i>, <b>true</b>
+ ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>This function is not generic. The <b>this</b> value must be an object with a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The <code>length</code> property of the <code>map</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.reduce">
+ <h1><span class="secnum" id="sec-22.2.3.19"><a href="#sec-%typedarray%.prototype.reduce"
+ title="link to this section">22.2.3.19</a></span> %TypedArray%.prototype.reduce ( callbackfn [ , initialValue ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.reduce</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.reduce">Array.prototype.reduce</a></code> as defined in <a
+ href="#sec-array.prototype.reduce">22.1.3.18</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm and must take into account the
+ possibility that calls to <var>callbackfn</var> may cause the <b>this</b> value to become detached.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>reduce</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.reduceright">
+ <h1><span class="secnum" id="sec-22.2.3.20"><a href="#sec-%typedarray%.prototype.reduceright"
+ title="link to this section">22.2.3.20</a></span> %TypedArray%.prototype.reduceRight ( callbackfn [ , initialValue ]
+ )</h1>
+
+ <p>%TypedArray%<code>.prototype.reduceRight</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.reduceright">Array.prototype.reduceRight</a></code> as defined in <a
+ href="#sec-array.prototype.reduceright">22.1.3.19</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm and must take into account the
+ possibility that calls to <var>callbackfn</var> may cause the <b>this</b> value to become detached.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>reduceRight</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.reverse">
+ <h1><span class="secnum" id="sec-22.2.3.21"><a href="#sec-%typedarray%.prototype.reverse"
+ title="link to this section">22.2.3.21</a></span> %TypedArray%.prototype.reverse ( )</h1>
+
+ <p>%TypedArray%<code>.prototype.reverse</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.reverse">Array.prototype.reverse</a></code> as defined in <a
+ href="#sec-array.prototype.reverse">22.1.3.20</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.set-overloaded-offset">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.3.22"><a href="#sec-%typedarray%.prototype.set-overloaded-offset"
+ title="link to this section">22.2.3.22</a></span> %TypedArray%.prototype.set ( overloaded [ , offset ])</h1>
+
+ <p>%TypedArray%<code>.prototype.set</code> is a single function whose behaviour is overloaded based upon the type of its
+ first argument.</p>
+
+ <p>This function is not generic. The <b>this</b> value must be an object with a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The <code>length</code> property of the <code>set</code> method is <b>1</b>.</p>
+ </div>
+
+ <section id="sec-%typedarray%.prototype.set-array-offset">
+ <h1><span class="secnum" id="sec-22.2.3.22.1"><a href="#sec-%typedarray%.prototype.set-array-offset"
+ title="link to this section">22.2.3.22.1</a></span> %TypedArray%.prototype.set (array [ , offset ] )</h1>
+
+ <p>Set multiple values in this <i>TypedArray</i>, reading the values from the object <i>array</i>. The optional
+ <i>offset</i> value indicates the first element index in this <i>TypedArray</i> where values are written. If omitted, it
+ is assumed to be 0.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>array</i> does not have a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>. If it does, the definition in <a
+ href="#sec-%typedarray%.prototype.set-typedarray-offset">22.2.3.22.2</a> applies.</li>
+ <li>Let <i>target</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>target</i> does not have a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>target</i> has a [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>targetOffset</i> be <a href="#sec-tointeger">ToInteger</a> (<i>offset</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetOffset</i>).</li>
+ <li>If <i>targetOffset</i> < 0, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>targetBuffer</i> be the value of <i>target</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>targetBuffer</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Let <i>targetLength</i> be the value of <i>target</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>targetName</i> be the string value of <i>target</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>targetElementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table
+ 49</a> for <i>targetName</i>.</li>
+ <li>Let <i>targetType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>targetName</i>.</li>
+ <li>Let <i>targetByteOffset</i> be the value of <i>target</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>src</i> be <a href="#sec-toobject">ToObject</a>(<i>array</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>src</i>).</li>
+ <li>Let <i>srcLen</i> be <a href="#sec-get-o-p">Get</a>(<i>src</i>, <code>"length"</code>).</li>
+ <li>Let <i>srcLength</i> be <a href="#sec-tolength">ToLength</a>(<i>srcLen</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>srcLength</i>).</li>
+ <li>If <i>srcLength</i> + <i>targetOffset</i> > <i>targetLength</i>, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>targetByteIndex</i> be <i>targetOffset</i> × <i>targetElementSize</i> + <i>targetByteOffset</i>.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Let <i>limit</i> be <i>targetByteIndex</i> + <i>targetElementSize</i> × min(<i>srcLength</i>,
+ <i>targetLength</i> – <i>targetOffset</i>).</li>
+ <li>Repeat, while <i>targetByteIndex</i> < <i>limit</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>src</i>, <i>Pk</i>).</li>
+ <li>Let <i>kNumber</i> be <a href="#sec-tonumber">ToNumber</a>(<i>kValue</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kNumber</i>).</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>targetBuffer</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Perform <a href="#sec-setvalueinbuffer">SetValueInBuffer</a>(<i>targetBuffer</i>, <i>targetByteIndex</i>,
+ <i>targetType</i>, <i>kNumber</i>).</li>
+ <li>Set <i>k</i> to <i>k</i> + 1.</li>
+ <li>Set <i>targetByteIndex</i> to <i>targetByteIndex</i> + <i>targetElementSize</i>.</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.set-typedarray-offset">
+ <h1><span class="secnum" id="sec-22.2.3.22.2"><a href="#sec-%typedarray%.prototype.set-typedarray-offset"
+ title="link to this section">22.2.3.22.2</a></span> %TypedArray%.prototype.set(typedArray [, offset ] )</h1>
+
+ <p>Set multiple values in this <i>TypedArray</i>, reading the values from the <var>typedArray</var> argument object. The
+ optional <i>offset</i> value indicates the first element index in this <i>TypedArray</i> where values are written. If
+ omitted, it is assumed to be 0.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>typedArray</i> has a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>. If it does not, the definition in <a
+ href="#sec-%typedarray%.prototype.set-array-offset">22.2.3.22.1</a> applies.</li>
+ <li>Let <i>target</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>target</i> does not have a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>target</i> has a [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>targetOffset</i> be <a href="#sec-tointeger">ToInteger</a> (<i>offset</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetOffset</i>).</li>
+ <li>If <i>targetOffset</i> < 0, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>targetBuffer</i> be the value of <i>target</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>targetBuffer</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Let <i>targetLength</i> be the value of <i>target</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>srcBuffer</i> be the value of <i>typedArray</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>srcBuffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>targetName</i> be the string value of <i>target</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>targetType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>targetName</i>.</li>
+ <li>Let <i>targetElementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table
+ 49</a> for <i>targetName</i>.</li>
+ <li>Let <i>targetByteOffset</i> be the value of <i>target</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>srcName</i> be the string value of <i>typedArray</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>srcType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>srcName</i> .</li>
+ <li>Let <i>srcElementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table
+ 49</a> for <i>srcName</i>.</li>
+ <li>Let <i>srcLength</i> be the value of <i>typedArray</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>srcByteOffset</i> be the value of <i>typedArray</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>srcLength</i> + <i>targetOffset</i> > <i>targetLength</i>, throw a <b>RangeError</b> exception.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>srcBuffer</i>, <i>targetBuffer</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>srcBuffer</i> be <a href="#sec-clonearraybuffer">CloneArrayBuffer</a>(<i>targetBuffer</i>,
+ <i>srcByteOffset</i>, %ArrayBuffer%).</li>
+ <li>NOTE: <span style="font-family: Times New Roman">%ArrayBuffer%</span> is used to clone <span
+ style="font-family: Times New Roman"><i>targetBuffer</i></span> because is it known to not have any observable
+ side-effects.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>srcBuffer</i>).</li>
+ <li>Let <i>srcByteIndex</i> be 0.</li>
+ </ol>
+ </li>
+ <li>Else, let <i>srcByteIndex</i> be <i>srcByteOffset</i>.</li>
+ <li>Let <i>targetByteIndex</i> be <i>targetOffset</i> × <i>targetElementSize</i> + <i>targetByteOffset</i>.</li>
+ <li>Let <i>limit</i> be <i>targetByteIndex</i> + <i>targetElementSize</i> × min(<i>srcLength</i>,
+ <i>targetLength</i> – <i>targetOffset</i>).</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>srcType</i>, <i>targetType</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Repeat, while <i>targetByteIndex</i> < <i>limit</i>
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-getvaluefrombuffer">GetValueFromBuffer</a>(<i>srcBuffer</i>,
+ <i>srcByteIndex</i>, <i>srcType</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-setvalueinbuffer">SetValueInBuffer</a> (<i>targetBuffer</i>,
+ <i>targetByteIndex</i>, <i>targetType</i>, <i>value</i>).</li>
+ <li>Set <i>srcByteIndex</i> to <i>srcByteIndex</i> + <i>srcElementSize</i>.</li>
+ <li>Set <i>targetByteIndex</i> to <i>targetByteIndex</i> + <i>targetElementSize</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>NOTE: If <var>srcType</var> and <var>targetType</var> are the same the transfer must be performed in a manner
+ that perserves the bit-level encoding of the source data.</li>
+ <li>Repeat, while <i>targetByteIndex</i> < <i>limit</i>
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-getvaluefrombuffer">GetValueFromBuffer</a>(<i>srcBuffer</i>,
+ <i>srcByteIndex</i>, <code>"Uint8"</code>).</li>
+ <li>Perform <a href="#sec-setvalueinbuffer">SetValueInBuffer</a> (<i>targetBuffer</i>, <i>targetByteIndex</i>,
+ <code>"Uint8"</code>, <i>value</i>).</li>
+ <li>Set <i>srcByteIndex</i> to <i>srcByteIndex</i> + 1.</li>
+ <li>Set <i>targetByteIndex</i> to <i>targetByteIndex</i> + 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.slice">
+ <h1><span class="secnum" id="sec-22.2.3.23"><a href="#sec-%typedarray%.prototype.slice"
+ title="link to this section">22.2.3.23</a></span> %TypedArray%.prototype.slice ( start, end )</h1>
+
+ <p>The interpretation and use of the arguments of %TypedArray%<code>.prototype.slice</code> are the same as for <code><a
+ href="#sec-array.prototype.slice">Array.prototype.slice</a></code> as defined in <a
+ href="#sec-array.prototype.slice">22.1.3.22</a>. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>valid</i> be <a href="#sec-validatetypedarray">ValidateTypedArray</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Let <i>len</i> be the value of <i>O’s</i> [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>relativeStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeStart</i>).</li>
+ <li>If <i>relativeStart</i> < 0, let <i>k</i> be max((<i>len</i> + <i>relativeStart</i>),0); else let <i>k</i> be
+ min(<i>relativeStart</i>, <i>len</i>).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>relativeEnd</i> be <i>len</i>; else let <i>relativeEnd</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeEnd</i>).</li>
+ <li>If <i>relativeEnd</i> < 0, let <i>final</i> be max((<i>len</i> + <i>relativeEnd</i>),0); else let <i>final</i> be
+ min(<i>relativeEnd</i>, <i>len</i>).</li>
+ <li>Let <i>count</i> be max(<i>final</i> – <i>k</i>, 0).</li>
+ <li>Let <i>defaultConstructor</i> be the intrinsic object listed in column one of <a href="#table-49">Table 49</a> for
+ the value of <i>O</i>’s [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</li>
+ <li>Let <i>C</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>O</i>, <i>defaultConstructor</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>Let <i>A</i> be <a href="#sec-allocatetypedarray">AllocateTypedArray</a>(<i>C</i>, <i>count</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>A</i>).</li>
+ <li>Let <i>srcType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>defaultConstructor</i>.</li>
+ <li>Let <i>targetType</i> be the string value of the Element Type value in <a href="#table-49">Table 49</a> for
+ <i>C</i>.</li>
+ <li>Let <i>srcBuffer</i> be the value of <i>typedArray</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>srcType</i>, <i>targetType</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>n</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>final</i>
+ <ol class="block">
+ <li>Let <i>Pk</i> be <a href="#sec-tostring">ToString</a>(<i>k</i>).</li>
+ <li>Let <i>kValue</i> be <a href="#sec-get-o-p">Get</a>(<i>O</i>, <i>Pk</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>kValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-set-o-p-v-throw">Set</a>(<i>A</i>, <a
+ href="#sec-tostring">ToString</a>(<i>n</i>), <i>kValue</i>, <b>true</b> ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Increase <i>k</i> by 1.</li>
+ <li>Increase <i>n</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>srcBuffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>srcBuffer</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Let <i>targetBuffer</i> be the value of <i>A</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table
+ 49</a> for <i>srcType</i>.</li>
+ <li>NOTE: If <var>srcType</var> and <var>targetType</var> are the same the transfer must be performed in a manner
+ that perserves the bit-level encoding of the source data.</li>
+ <li>Let <i>srcByteIndex</i> be 0.</li>
+ <li>Let <i>targetByteIndex</i> be <i>k</i> × <i>ElementSize</i>.</li>
+ <li>Repeat, while <i>targetByteIndex</i> < <i>count</i> × <i>ElementSize</i>
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-getvaluefrombuffer">GetValueFromBuffer</a>(<i>srcBuffer</i>,
+ <i>srcByteIndex</i>, <code>"Uint8"</code>).</li>
+ <li>Perform <a href="#sec-setvalueinbuffer">SetValueInBuffer</a> (<i>targetBuffer</i>, <i>targetByteIndex</i>,
+ <code>"Uint8"</code>, <i>value</i>).</li>
+ <li>Increase <i>srcByteIndex</i> by 1.</li>
+ <li>Increase <i>targetByteIndex</i> by 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <i>A</i>.</li>
+ </ol>
+
+ <p>This function is not generic. The <b>this</b> value must be an object with a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The <code>length</code> property of the <code>slice</code> method is <b>2</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.some">
+ <h1><span class="secnum" id="sec-22.2.3.24"><a href="#sec-%typedarray%.prototype.some"
+ title="link to this section">22.2.3.24</a></span> %TypedArray%.prototype.some ( callbackfn [ , thisArg ] )</h1>
+
+ <p>%TypedArray%<code>.prototype.some</code> is a distinct function that implements the same algorithm as <code><a
+ href="#sec-array.prototype.some">Array.prototype.some</a></code> as defined in <a
+ href="#sec-array.prototype.some">22.1.3.23</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm and must take into account the
+ possibility that calls to <var>callbackfn</var> may cause the <b>this</b> value to become detached.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+
+ <p>The <code>length</code> property of the <code>some</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.sort">
+ <h1><span class="secnum" id="sec-22.2.3.25"><a href="#sec-%typedarray%.prototype.sort"
+ title="link to this section">22.2.3.25</a></span> %TypedArray%.prototype.sort ( comparefn )</h1>
+
+ <p>%TypedArray%<code>.prototype.sort</code> is a distinct function that, except as described below, implements the same
+ requirements as those of <code><a href="#sec-array.prototype.sort">Array.prototype.sort</a></code> as defined in <a
+ href="#sec-array.prototype.sort">22.1.3.24</a>. The implementation of the %TypedArray%<code>.prototype.sort</code>
+ specification may be optimized with the knowledge that the <b>this</b> value is an object that has a fixed length and
+ whose integer indexed properties are not sparse. The only internal methods of the <b>this</b> object that the algorithm
+ may call are [[Get]] and [[Set]].</p>
+
+ <p>This function is not generic. The <b>this</b> value must be an object with a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>Upon entry, the following steps are performed to initialize evaluation of the <code>sort</code> function. These steps
+ are used instead of the entry steps in <a href="#sec-array.prototype.sort">22.1.3.24</a>:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be the <b>this</b> value as the argument.</li>
+ <li>Let <i>buffer</i> be <a href="#sec-validatetypedarray">ValidateTypedArray</a>(<i>obj</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>buffer</i>).</li>
+ <li>Let <i>len</i> be the value of <i>obj</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+
+ <p>The following version of <a href="#sec-sortcompare">SortCompare</a> is used by
+ %TypedArray%<code>.prototype.sort</code>. It performs a numeric comparison rather than the string comparison used in <a
+ href="#sec-array.prototype.sort">22.1.3.24</a>.</p>
+
+ <p>When the TypedArray <a href="#sec-sortcompare">SortCompare</a> abstract operation is called with two arguments
+ <var>x</var> and <var>y</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: Both <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) and <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>y</i>) is Number.</li>
+ <li>If the argument <i>comparefn</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-call">Call</a>(<i>comparefn</i>, <b>undefined</b>, «<i>x</i>,
+ <i>y</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>v</i> is <b>NaN</b>, return +0.</li>
+ <li>Return <i>v</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>x</i> and <i>y</i> are both <b>NaN</b>, return +0.</li>
+ <li>If <i>x</i> is <b>NaN</b>, return 1.</li>
+ <li>If <i>y</i> is <b>NaN</b>, return −1.</li>
+ <li>If <i>x</i> < <i>y</i>, return −1.</li>
+ <li>If <i>x</i> > <i>y</i>, return 1.</li>
+ <li>Return +0.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> Because <b>NaN</b> always compares greater than any other value, <b>NaN</b> property
+ values always sort to the end of the result when a <i>comparefn</i> is not provided.</p>
+ </div>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.subarray">
+ <h1><span class="secnum" id="sec-22.2.3.26"><a href="#sec-%typedarray%.prototype.subarray"
+ title="link to this section">22.2.3.26</a></span> %TypedArray%.prototype.subarray( [ begin [ , end ] ] )</h1>
+
+ <p>Returns a new <i>TypedArray</i> object whose element types is the same as this <i>TypedArray</i> and whose ArrayBuffer
+ is the same as the ArrayBuffer of this <i>TypedArray</i>, referencing the elements at <var>begin</var>, inclusive, up to
+ <var>end</var>, exclusive. If either <var>begin</var> or <var>end</var> is negative, it refers to an index from the end of
+ the array, as opposed to from the beginning.</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>O</i> has a [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>srcLength</i> be the value of <i>O</i>’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>beginInt</i> be <a href="#sec-tointeger">ToInteger</a>(<i>begin</i>)</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>beginInt</i>).</li>
+ <li>If <i>beginInt</i> < 0, let <i>beginInt</i> be <i>srcLength</i> + <i>beginInt</i>.</li>
+ <li>Let <i>beginIndex</i> be min(<i>srcLength</i>, max(0, <i>beginInt</i>)).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>end</i> be <i>srcLength</i>.</li>
+ <li>Let <i>endInt</i> be <a href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>endInt</i>).</li>
+ <li>If <i>endInt</i> < 0, let <i>endInt</i> be <i>srcLength</i> + <i>endInt</i>.</li>
+ <li>Let <i>endIndex</i> be max(0,min(<i>srcLength</i>, <i>endInt</i>)).</li>
+ <li>If <i>endIndex</i> < <i>beginIndex</i>, let <i>endIndex</i> be <i>beginIndex</i>.</li>
+ <li>Let <i>newLength</i> be <i>endIndex</i> - <i>beginIndex</i>.</li>
+ <li>Let <i>constructorName</i> be the string value of <i>O</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table 49</a>
+ for <i>constructorName</i>.</li>
+ <li>Let <i>srcByteOffset</i> be the value of <i>O</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>beginByteOffset</i> be <i>srcByteOffset</i> + <i>beginIndex</i> × <i>elementSize</i>.</li>
+ <li>Let <i>defaultConstructor</i> be the intrinsic object listed in column one of <a href="#table-49">Table 49</a> for
+ <i>constructorName</i>.</li>
+ <li>Let <i>constructor</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>O</i>,
+ <i>defaultConstructor</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>constructor</i>).</li>
+ <li>Let <i>argumentsList</i> be «<i>buffer</i>, <i>beginByteOffset</i>, <i>newLength</i>».</li>
+ <li>Return <a href="#sec-construct">Construct</a>(<i>constructor</i>, <i>argumentsList</i>).</li>
+ </ol>
+
+ <p>This function is not generic. The <b>this</b> value must be an object with a [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The <code>length</code> property of the <code>subarray</code> method is <b>2</b>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.tolocalestring">
+ <h1><span class="secnum" id="sec-22.2.3.27"><a href="#sec-%typedarray%.prototype.tolocalestring"
+ title="link to this section">22.2.3.27</a></span> %TypedArray%.prototype.toLocaleString ([ reserved1 [ , reserved2 ]
+ ])</h1>
+
+ <p>%TypedArray%<code>.prototype.toLocaleString</code> is a distinct function that implements the same algorithm as
+ <code>Array.prototype.</code> <code>toLocaleString</code> as defined in <a
+ href="#sec-array.prototype.tolocalestring">22.1.3.26</a> except that the <b>this</b> object’s [[ArrayLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is accessed in place of performing a [[Get]] of
+ <code>"length"</code>. The implementation of the algorithm may be optimized with the knowledge that the <b>this</b> value
+ is an object that has a fixed length and whose integer indexed properties are not sparse. However, such optimization must
+ not introduce any observable changes in the specified behaviour of the algorithm.</p>
+
+ <p>This function is not generic. <a href="#sec-validatetypedarray">ValidateTypedArray</a> is applied to the <b>this</b>
+ value prior to evaluating the algorithm. If its result is an <a href="#sec-completion-record-specification-type">abrupt
+ completion</a> that exception is thrown instead of evaluating the algorithm.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.tostring">
+ <h1><span class="secnum" id="sec-22.2.3.28"><a href="#sec-%typedarray%.prototype.tostring"
+ title="link to this section">22.2.3.28</a></span> %TypedArray%.prototype.toString ( )</h1>
+
+ <p>The initial value of the %TypedArray%.prototype.toString data property is the same built-in function object as the <a
+ href="#sec-array.prototype.tostring">Array.prototype.toString</a> method defined in <a
+ href="#sec-array.prototype.tostring">22.1.3.27</a>.</p>
+ </section>
+
+ <section id="sec-%typedarray%.prototype.values">
+ <h1><span class="secnum" id="sec-22.2.3.29"><a href="#sec-%typedarray%.prototype.values"
+ title="link to this section">22.2.3.29</a></span> %TypedArray%.prototype.values ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>Let <i>valid</i> be <a href="#sec-validatetypedarray">ValidateTypedArray</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>valid</i>).</li>
+ <li>Return <a href="#sec-createarrayiterator">CreateArrayIterator</a>(<i>O</i>, <code>"value"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%typedarray%.prototype-@@iterator">
+ <h1><span class="secnum" id="sec-22.2.3.30"><a href="#sec-%typedarray%.prototype-@@iterator"
+ title="link to this section">22.2.3.30</a></span> %TypedArray%.prototype [ @@iterator ] ( )</h1>
+
+ <p>The initial value of the @@iterator property is the same function object as the initial value of the
+ %TypedArray%<b>.prototype.values</b> property.</p>
+ </section>
+
+ <section id="sec-get-%typedarray%.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-22.2.3.31"><a href="#sec-get-%typedarray%.prototype-@@tostringtag"
+ title="link to this section">22.2.3.31</a></span> get %TypedArray%.prototype [ @@toStringTag ]</h1>
+
+ <p>%TypedArray%.<code>prototype[@@toStringTag]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <b>undefined</b>.</li>
+ <li>If <i>O</i> does not have a [[TypedArrayName]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, return <b>undefined</b>.</li>
+ <li>Let <i>name</i> be the value of <i>O</i>’s [[TypedArrayName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>name</i> is a String value.</li>
+ <li>Return <i>name</i>.</li>
+ </ol>
+
+ <p>This property has the attributes { [[Enumerable]]: <span class="value">false</span>, [[Configurable]]: <span
+ class="value">true</span> }.</p>
+
+ <p>The initial value of the <code>name</code> property of this function is <code>"get [Symbol.toStringTag]"</code>.</p>
+ </section>
+ </section>
+
+ <section id="sec-typedarray-constructors">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.4"><a href="#sec-typedarray-constructors"
+ title="link to this section">22.2.4</a></span> The <i>TypedArray</i> Constructors</h1>
+
+ <p>Each of these <i>TypedArray</i> constructor objects is an intrinsic object that has the structure described below,
+ differing only in the name used as the constructor name instead of <i>TypedArray</i>, in <a href="#table-49">Table
+ 49</a>.</p>
+
+ <p>The <i>TypedArray</i> constructors are not intended to be called as a function and will throw an exception when called
+ in that manner.</p>
+
+ <p>The <i>TypedArray</i> constructors are designed to be subclassable. They may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <i>TypedArray</i> behaviour must include a <code>super</code> call to the <i>TypedArray</i> constructor to create and
+ initialize the subclass instance with the internal state necessary to support the %TypedArray<code>%.prototype</code>
+ built-in methods.</p>
+ </div>
+
+ <section id="sec-typedarray">
+ <h1><span class="secnum" id="sec-22.2.4.1"><a href="#sec-typedarray" title="link to this section">22.2.4.1</a></span>
+ <i>TypedArray</i>( ... argumentsList)</h1>
+
+ <p>A <i>TypedArray</i> constructor with a list of arguments <i>argumentsList</i> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>here</i> be the active function.</li>
+ <li>Let <i>super</i> be <i>here</i>.[[GetPrototypeOf]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>super</i>).</li>
+ <li>If <a href="#sec-isconstructor">IsConstructor</a> (<i>super</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>argumentsList</i> be the <i>argumentsList</i> argument of the [[Construct]] internal method that invoked the
+ active function.</li>
+ <li>Return <a href="#sec-construct">Construct</a>(<i>super</i>, <i>argumentsList</i>, NewTarget).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-typedarray-constructors">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.5"><a href="#sec-properties-of-the-typedarray-constructors"
+ title="link to this section">22.2.5</a></span> Properties of the <i>TypedArray</i> Constructors</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of each
+ <i>TypedArray</i> constructor is the %TypedArray% intrinsic object (<a
+ href="#sec-%typedarray%-intrinsic-object">22.2.1</a>).</p>
+
+ <p>Each <i>TypedArray</i> constructor has a [[TypedArrayConstructorName]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> property whose value is the String value of the
+ constructor name specified for it in <a href="#table-49">Table 49</a>.</p>
+
+ <p>Each <i>TypedArray</i> constructor has a <code>name</code> property whose value is the String value of the constructor
+ name specified for it in <a href="#table-49">Table 49</a>.</p>
+
+ <p>Besides a <code>length</code> property (whose value is 3), each <i>TypedArray</i> constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-typedarray.bytes_per_element">
+ <h1><span class="secnum" id="sec-22.2.5.1"><a href="#sec-typedarray.bytes_per_element"
+ title="link to this section">22.2.5.1</a></span> <i>TypedArray</i>.BYTES_PER_ELEMENT</h1>
+
+ <p>The value of <i>TypedArray</i>.BYTES_PER_ELEMENT is the Number value of the Element Size value specified in <a
+ href="#table-49">Table 49</a> for <i>TypedArray</i>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-typedarray.prototype">
+ <h1><span class="secnum" id="sec-22.2.5.2"><a href="#sec-typedarray.prototype"
+ title="link to this section">22.2.5.2</a></span> <i>TypedArray</i>.prototype</h1>
+
+ <p>The initial value of <i>TypedArray</i>.prototype is the corresponding <i>TypedArray</i> prototype intrinsic object (<a
+ href="#sec-properties-of-typedarray-prototype-objects">22.2.6</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">false</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-typedarray-prototype-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-22.2.6"><a href="#sec-properties-of-typedarray-prototype-objects"
+ title="link to this section">22.2.6</a></span> Properties of <i>TypedArray</i> Prototype Objects</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of a
+ <i>TypedArray</i> prototype object is the intrinsic object %TypedArrayPrototype% (<a
+ href="#sec-properties-of-the-%typedarrayprototype%-object">22.2.3</a>). A <i>TypedArray</i> prototype object is an
+ ordinary object. It does not have a [[ViewedArrayBuffer]] or or any other of the internal slots that are specific to
+ <i>TypedArray</i> instance objects.</p>
+ </div>
+
+ <section id="sec-typedarray.prototype.bytes_per_element">
+ <h1><span class="secnum" id="sec-22.2.6.1"><a href="#sec-typedarray.prototype.bytes_per_element"
+ title="link to this section">22.2.6.1</a></span> <i>TypedArray</i>.prototype.BYTES_PER_ELEMENT</h1>
+
+ <p>The value of <i>TypedArray</i>.prototype.BYTES_PER_ELEMENT is the Number value of the Element Size value specified in
+ <a href="#table-49">Table 49</a> for <i>TypedArray</i>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-typedarray.prototype.constructor">
+ <h1><span class="secnum" id="sec-22.2.6.2"><a href="#sec-typedarray.prototype.constructor"
+ title="link to this section">22.2.6.2</a></span> <i>TypedArray</i>.prototype.constructor</h1>
+
+ <p>The initial value of a <i>TypedArray</i>.prototype.constructor is the corresponding %<i>TypedArray</i>% intrinsic
+ object.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-typedarray-instances">
+ <h1><span class="secnum" id="sec-22.2.7"><a href="#sec-properties-of-typedarray-instances"
+ title="link to this section">22.2.7</a></span> Properties of <i>TypedArray</i> Instances</h1>
+
+ <p><i>TypedArray</i> instances are Integer Indexed exotic objects. Each <i>TypedArray</i> instances inherits properties from
+ the corresponding <i>TypedArray</i> prototype object. Each <i>TypedArray</i> instances have the following internal slots:
+ [[TypedArrayName]], [[ViewedArrayBuffer]], [[ByteLength]], [[ByteOffset]], and [[ArrayLength]].</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-keyed-collection">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23"><a href="#sec-keyed-collection" title="link to this section">23</a></span> Keyed
+ Collection</h1>
+ </div>
+
+ <section id="sec-map-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.1"><a href="#sec-map-objects" title="link to this section">23.1</a></span> Map
+ Objects</h1>
+
+ <p>Map objects are collections of key/value pairs where both the keys and values may be arbitrary <a
+ href="#sec-ecmascript-language-types">ECMAScript language values</a>. A distinct key value may only occur in one key/value
+ pair within the Map’s collection. Distinct key values are discriminated using the <a
+ href="#sec-samevaluezero">SameValueZero</a> comparison algorithm.</p>
+
+ <p>Map object must be implemented using either hash tables or other mechanisms that, on average, provide access times that
+ are sublinear on the number of elements in the collection. The data structures used in this Map objects specification is
+ only intended to describe the required observable semantics of Map objects. It is not intended to be a viable implementation
+ model.</p>
+ </div>
+
+ <section id="sec-map-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.1.1"><a href="#sec-map-constructor" title="link to this section">23.1.1</a></span> The
+ Map Constructor</h1>
+
+ <p>The Map constructor is the %Map% intrinsic object and the initial value of the <code>Map</code> property of the global
+ object. When called as a constructor it creates and initializes a new Map object. <code>Map</code> is not intended to be
+ called as a function and will throw an exception when called in that manner.</p>
+
+ <p>The <code>Map</code> constructor is designed to be subclassable. It may be used as the value in an <code>extends</code>
+ clause of a class definition. Subclass constructors that intend to inherit the specified <code>Map</code> behaviour must
+ include a <code>super</code> call to the <code>Map</code> constructor to create and initialize the subclass instance with
+ the internal state necessary to support the <code>Map.prototype</code> built-in methods.</p>
+ </div>
+
+ <section id="sec-map-iterable">
+ <h1><span class="secnum" id="sec-23.1.1.1"><a href="#sec-map-iterable" title="link to this section">23.1.1.1</a></span>
+ Map ( [ iterable ] )</h1>
+
+ <p>When the <code>Map</code> function is called with optional argument the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>map</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%MapPrototype%"</code>, «‍[[MapData]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>map</i>).</li>
+ <li>Set <i>map’s</i> [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to a
+ new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <i>iterable</i> is not present, let <i>iterable</i> be <b>undefined</b>.</li>
+ <li>If <i>iterable</i> is either <b>undefined</b> or <b>null</b>, let <i>iter</i> be <b>undefined</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>adder</i> be <a href="#sec-get-o-p">Get</a>(<i>map</i>, <code>"set"</code>)<b>.</b></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>adder</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>adder</i>) is <b>false</b>, throw a <b>TypeError</b>
+ Exception.</li>
+ <li>Let <i>iter</i> be <a href="#sec-getiterator">GetIterator</a>(<i>iterable</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iter</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>iter</i> is <b>undefined</b>, return <i>map</i>.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iter</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, return <i>map</i>.</li>
+ <li>Let <i>nextItem</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextItem</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>nextItem</i>) is not Object,
+ <ol class="block">
+ <li>Let <i>error</i> be <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">throw</span>, [[value]]: a newly created <b>TypeError</b> object,
+ [[target]]:<span style="font-family: sans-serif">empty</span>}.</li>
+ <li>Return <a href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>error</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>k</i> be <a href="#sec-get-o-p">Get</a>(<i>nextItem</i>, <code>"0"</code>).</li>
+ <li>If <i>k</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>k</i>).</li>
+ <li>Let <i>v</i> be <a href="#sec-get-o-p">Get</a>(<i>nextItem</i>, <code>"1"</code>).</li>
+ <li>If <i>v</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>v</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>adder</i>, <i>map</i>, «<i>k</i>.[[value]],
+ <i>v</i>.[[value]]»).</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If the parameter <i>iterable</i> is present, it is expected to be an object that
+ implements an @@iterator method that returns an iterator object that produces a two element array-like object whose
+ first element is a value that will be used as a Map key and whose second element is the value to associate with that
+ key.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-map-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.1.2"><a href="#sec-properties-of-the-map-constructor"
+ title="link to this section">23.1.2</a></span> Properties of the Map Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Map
+ constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>0</b>), the Map constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-map.prototype">
+ <h1><span class="secnum" id="sec-23.1.2.1"><a href="#sec-map.prototype" title="link to this section">23.1.2.1</a></span>
+ Map.prototype</h1>
+
+ <p>The initial value of <code>Map.prototype</code> is the intrinsic object %MapPrototype% (<a
+ href="#sec-properties-of-the-map-prototype-object">23.1.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-get-map-@@species">
+ <h1><span class="secnum" id="sec-23.1.2.2"><a href="#sec-get-map-@@species"
+ title="link to this section">23.1.2.2</a></span> get Map [ @@species ]</h1>
+
+ <p><code>Map[@@species]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"get [Symbol.species]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Map prototype methods normally use their <code>this</code> object’s constructor to
+ create a derived object. However, a subclass constructor may over-ride that default behaviour by redefining its
+ @@species property.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-map-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.1.3"><a href="#sec-properties-of-the-map-prototype-object"
+ title="link to this section">23.1.3</a></span> Properties of the Map Prototype Object</h1>
+
+ <p>The Map prototype object is the intrinsic object %MapPrototype%. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Map prototype object is the intrinsic
+ object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The Map prototype object
+ is an ordinary object. It does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </div>
+
+ <section id="sec-map.prototype.clear">
+ <h1><span class="secnum" id="sec-23.1.3.1"><a href="#sec-map.prototype.clear"
+ title="link to this section">23.1.3.1</a></span> Map.prototype.clear ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>Set <i>p</i>.[[key]] to <span style="font-family: sans-serif">empty</span><i>.</i></li>
+ <li>Set <i>p</i>.[[value]] to <span style="font-family: sans-serif">empty</span><i>.</i></li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The existing [[MapData]] <a href="#sec-list-and-record-specification-type">List</a> is
+ preserved because there may be existing MapIterator objects that are <a href="#sec-execution-contexts">suspended</a>
+ midway through iterating over that <a href="#sec-list-and-record-specification-type">List</a>.</p>
+ </div>
+ </section>
+
+ <section id="sec-map.prototype.constructor">
+ <h1><span class="secnum" id="sec-23.1.3.2"><a href="#sec-map.prototype.constructor"
+ title="link to this section">23.1.3.2</a></span> Map.prototype.constructor</h1>
+
+ <p>The initial value of <code>Map.prototype.constructor</code> is the intrinsic object %Map%.</p>
+ </section>
+
+ <section id="sec-map.prototype.delete">
+ <h1><span class="secnum" id="sec-23.1.3.3"><a href="#sec-map.prototype.delete"
+ title="link to this section">23.1.3.3</a></span> Map.prototype.delete ( key )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevaluezero">SameValueZero</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>p</i>.[[key]] to <span style="font-family: sans-serif">empty</span><i>.</i></li>
+ <li>Set <i>p</i>.[[value]] to <span style="font-family: sans-serif">empty</span><i>.</i></li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value <b>empty</b> is used as a specification device to indicate that an entry has
+ been deleted. Actual implementations may take other actions such as physically removing the entry from internal data
+ structures.</p>
+ </div>
+ </section>
+
+ <section id="sec-map.prototype.entries">
+ <h1><span class="secnum" id="sec-23.1.3.4"><a href="#sec-map.prototype.entries"
+ title="link to this section">23.1.3.4</a></span> Map.prototype.entries ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createmapiterator">CreateMapIterator</a>(<i>M</i>, <code>"key+value"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-map.prototype.foreach">
+ <h1><span class="secnum" id="sec-23.1.3.5"><a href="#sec-map.prototype.foreach"
+ title="link to this section">23.1.3.5</a></span> Map.prototype.forEach ( callbackfn [ , thisArg ] )</h1>
+
+ <p class="Note"><span style="font-family: sans-serif">NOTE</span>	<i>callbackfn</i> should be a function that accepts
+ three arguments. <code>forEach</code> calls <i>callbackfn</i> once for each key/value pair present in the map object, in
+ key insertion order. <i>callbackfn</i> is called only for keys of the map which actually exist; it is not called for keys
+ that have been deleted from the map.</p>
+
+ <p class="Note">If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>callbackfn</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p class="Note"><i>callbackfn</i> is called with three arguments: the value of the item, the key of the item, and the Map
+ object being traversed.</p>
+
+ <p class="Note"><code>forEach</code> does not directly mutate the object on which it is called but the object may be
+ mutated by the calls to <i>callbackfn</i>.</p>
+
+ <p>When the <code>forEach</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>e</i> that is an element of <i>entries,</i> in original key insertion
+ order
+ <ol class="block">
+ <li>If <i>e</i>.[[key]] is not <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>Let <i>funcResult</i> be <a href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>,
+ «<i>e</i>.[[value]], <i>e</i>.[[key]], <i>M</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>funcResult</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>forEach</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-map.prototype.get">
+ <h1><span class="secnum" id="sec-23.1.3.6"><a href="#sec-map.prototype.get"
+ title="link to this section">23.1.3.6</a></span> Map.prototype.get ( key )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevaluezero">SameValueZero</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, return
+ <i>p</i>.[[value]].</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-map.prototype.has">
+ <h1><span class="secnum" id="sec-23.1.3.7"><a href="#sec-map.prototype.has"
+ title="link to this section">23.1.3.7</a></span> Map.prototype.has ( key )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevaluezero">SameValueZero</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, return
+ <b>true</b><i>.</i></li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-map.prototype.keys">
+ <h1><span class="secnum" id="sec-23.1.3.8"><a href="#sec-map.prototype.keys"
+ title="link to this section">23.1.3.8</a></span> Map.prototype.keys ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createmapiterator">CreateMapIterator</a>(<i>M</i>, <code>"key"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-map.prototype.set">
+ <h1><span class="secnum" id="sec-23.1.3.9"><a href="#sec-map.prototype.set"
+ title="link to this section">23.1.3.9</a></span> Map.prototype.set ( key , value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevaluezero">SameValueZero</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>p</i>.[[value]] to <i>value.</i></li>
+ <li>Return <i>M</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>key</i> is −0, let <i>key</i> be +0.</li>
+ <li>Let <i>p</i> be the Record {[[key]]: <i>key</i>, [[value]]: <i>value</i>}.</li>
+ <li>Append <i>p</i> as the last element of <i>entries</i>.</li>
+ <li>Return <i>M</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-get-map.prototype.size">
+ <h1><span class="secnum" id="sec-23.1.3.10"><a href="#sec-get-map.prototype.size"
+ title="link to this section">23.1.3.10</a></span> get Map.prototype.size</h1>
+
+ <p>Map.prototype.size is an accessor property whose set accessor function is <span class="value">undefined</span>. Its get
+ accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>count</i> be 0.</li>
+ <li>For each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span>, set <i>count</i> to
+ <i>count</i>+1.</li>
+ </ol>
+ </li>
+ <li>Return <i>count</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-map.prototype.values">
+ <h1><span class="secnum" id="sec-23.1.3.11"><a href="#sec-map.prototype.values"
+ title="link to this section">23.1.3.11</a></span> Map.prototype.values ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createmapiterator">CreateMapIterator</a>(<i>M</i>, <code>"value"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-map.prototype-@@iterator">
+ <h1><span class="secnum" id="sec-23.1.3.12"><a href="#sec-map.prototype-@@iterator"
+ title="link to this section">23.1.3.12</a></span> Map.prototype [ @@iterator ]( )</h1>
+
+ <p>The initial value of the @@iterator property is the same function object as the initial value of the <b>entries</b>
+ property.</p>
+ </section>
+
+ <section id="sec-map.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-23.1.3.13"><a href="#sec-map.prototype-@@tostringtag"
+ title="link to this section">23.1.3.13</a></span> Map.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Map</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-map-instances">
+ <h1><span class="secnum" id="sec-23.1.4"><a href="#sec-properties-of-map-instances"
+ title="link to this section">23.1.4</a></span> Properties of Map Instances</h1>
+
+ <p>Map instances are ordinary objects that inherit properties from the Map prototype. Map instances also have a [[MapData]]
+ <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </section>
+
+ <section id="sec-map-iterator-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.1.5"><a href="#sec-map-iterator-objects"
+ title="link to this section">23.1.5</a></span> Map Iterator Objects</h1>
+
+ <p>A Map Iterator is an object, that represents a specific iteration over some specific Map instance object. There is not
+ a named constructor for Map Iterator objects. Instead, map iterator objects are created by calling certain methods of Map
+ instance objects.</p>
+ </div>
+
+ <section id="sec-createmapiterator">
+ <h1><span class="secnum" id="sec-23.1.5.1"><a href="#sec-createmapiterator"
+ title="link to this section">23.1.5.1</a></span> CreateMapIterator Abstract Operation</h1>
+
+ <p>Several methods of Map objects return Iterator objects. The abstract operation CreateMapIterator with arguments
+ <var>map</var> and <var>kind</var> is used to create such iterator objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>map</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>map</i> does not have a [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>iterator</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%MapIteratorPrototype%, «‍[[Map]],
+ [[MapNextIndex]], [[MapIterationKind]]»).</li>
+ <li>Set <i>iterator’s</i> [[Map]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>map</i>.</li>
+ <li>Set <i>iterator’s</i> [[MapNextIndex]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to 0.</li>
+ <li>Set <i>iterator’s</i> [[MapIterationKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>kind</i>.</li>
+ <li>Return <i>iterator</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%mapiteratorprototype%-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.1.5.2"><a href="#sec-%mapiteratorprototype%-object"
+ title="link to this section">23.1.5.2</a></span> The %MapIteratorPrototype% Object</h1>
+
+ <p>All Map Iterator Objects inherit properties from the %MapIteratorPrototype% intrinsic object. The
+ %MapIteratorPrototype% intrinsic object is an ordinary object and its [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the %IteratorPrototype% intrinsic object (<a
+ href="#sec-%iteratorprototype%-object">25.1.2</a>). In addition, %MapIteratorPrototype% has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-%mapiteratorprototype%.next">
+ <h1><span class="secnum" id="sec-23.1.5.2.1"><a href="#sec-%mapiteratorprototype%.next"
+ title="link to this section">23.1.5.2.1</a></span> %MapIteratorPrototype%.next ( )</h1>
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have all of the internal slots of a Map Iterator Instance (<a
+ href="#sec-properties-of-map-iterator-instances">23.1.5.3</a>), throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>m</i> be the value of the [[Map]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of <i>O</i>.</li>
+ <li>Let <i>index</i> be the value of the [[MapNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>itemKind</i> be the value of the [[MapIterationKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>m</i> is <b>undefined</b>, return <a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>)</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>m</i> has a [[MapData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of the
+ [[MapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>m</i>.</li>
+ <li>Repeat while <i>index</i> is less than the total number of elements of <i>entries</i>. The number of elements must
+ be redetermined each time this method is evaluated.
+ <ol class="block">
+ <li>Let <i>e</i> be the Record {[[key]], [[value]]} that is the value of <i>entries</i>[<i>index</i>].</li>
+ <li>Set <i>index</i> to <i>index</i>+1;</li>
+ <li>Set the [[MapNextIndex]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>O</i> to <i>index</i>.</li>
+ <li>If <i>e</i>.[[key]] is not <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>If <i>itemKind</i> is <b>"<code>key</code>"</b>, let <i>result</i> be <i>e</i>.[[key]].</li>
+ <li>Else if <i>itemKind</i> is <b>"<code>value</code>"</b>, let <i>result</i> be <i>e</i>.[[value]].</li>
+ <li>Else,
+ <ol class="block">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>itemKind</i> is <code>"key+value"</code>.</li>
+ <li>Let <i>result</i> be <a
+ href="#sec-createarrayfromlist">CreateArrayFromList</a>(«<i>e</i>.[[key]],
+ <i>e</i>.[[value]]»).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>result</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set the [[Map]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i> to
+ <b>undefined</b>.</li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%mapiteratorprototype%-@@tostringtag">
+ <h1><span class="secnum" id="sec-23.1.5.2.2"><a href="#sec-%mapiteratorprototype%-@@tostringtag"
+ title="link to this section">23.1.5.2.2</a></span> %MapIteratorPrototype% [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Map Iterator</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-map-iterator-instances">
+ <h1><span class="secnum" id="sec-23.1.5.3"><a href="#sec-properties-of-map-iterator-instances"
+ title="link to this section">23.1.5.3</a></span> Properties of Map Iterator Instances</h1>
+
+ <p>Map Iterator instances are ordinary objects that inherit properties from the %MapIteratorPrototype% intrinsic object.
+ Map Iterator instances are initially created with the internal slots described in <a href="#table-50">Table 50</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-50">Table 50</span> — Internal Slots of Map Iterator Instances</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[Map]]</td>
+ <td>The Map object that is being iterated.</td>
+ </tr>
+ <tr>
+ <td>[[MapNextIndex]]</td>
+ <td>The integer index of the next Map data element to be examined by this iterator.</td>
+ </tr>
+ <tr>
+ <td>[[MapIterationKind]]</td>
+ <td>A string value that identifies what is to be returned for each element of the iteration. The possible values are: <b>"<code>key</code>"</b>, <b>"<code>value</code>"</b>, <b>"<code>key+value</code>"</b>.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-set-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.2"><a href="#sec-set-objects" title="link to this section">23.2</a></span> Set
+ Objects</h1>
+
+ <p>Set objects are collections of <a href="#sec-ecmascript-language-types">ECMAScript language values</a>. A distinct value
+ may only occur once as an element of a Set’s collection. Distinct values are discriminated using the <a
+ href="#sec-samevaluezero">SameValueZero</a> comparison algorithm.</p>
+
+ <p>Set objects must be implemented using either hash tables or other mechanisms that, on average, provide access times that
+ are sublinear on the number of elements in the collection. The data structures used in this Set objects specification is
+ only intended to describe the required observable semantics of Set objects. It is not intended to be a viable implementation
+ model.</p>
+ </div>
+
+ <section id="sec-set-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.2.1"><a href="#sec-set-constructor" title="link to this section">23.2.1</a></span> The
+ Set Constructor</h1>
+
+ <p>The Set constructor is the %Set% intrinsic object and the initial value of the <code>Set</code> property of the global
+ object. When called as a constructor it creates and initializes a new Set object. <code>Set</code> is not intended to be
+ called as a function and will throw an exception when called in that manner.</p>
+
+ <p>The <code>Set</code> constructor is designed to be subclassable. It may be used as the value in an <code>extends</code>
+ clause of a class definition. Subclass constructors that intend to inherit the specified <code>Set</code> behaviour must
+ include a <code>super</code> call to the <code>Set</code> constructor to create and initialize the subclass instance with
+ the internal state necessary to support the <code>Set.prototype</code> built-in methods.</p>
+ </div>
+
+ <section id="sec-set-iterable">
+ <h1><span class="secnum" id="sec-23.2.1.1"><a href="#sec-set-iterable" title="link to this section">23.2.1.1</a></span>
+ Set ( [ iterable ] )</h1>
+
+ <p>When the <code>Set</code> function is called with optional argument <var>iterable</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>set</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%SetPrototype%"</code>, «‍[[SetData]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>set</i>).</li>
+ <li>Set <i>set’s</i> [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to a
+ new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <i>iterable</i> is not present, let <i>iterable</i> be <b>undefined</b>.</li>
+ <li>If <i>iterable</i> is either <b>undefined</b> or <b>null</b>, let <i>iter</i> be <b>undefined</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>adder</i> be <a href="#sec-get-o-p">Get</a>(<i>set</i>, <code>"add"</code>)<b>.</b></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>adder</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>adder</i>) is <b>false</b>, throw a <b>TypeError</b>
+ Exception.</li>
+ <li>Let <i>iter</i> be <a href="#sec-getiterator">GetIterator</a>(<i>iterable</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iter</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>iter</i> is <b>undefined</b>, return <i>set</i>.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iter</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, return <i>set</i>.</li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>adder</i>, <i>set</i>,
+ «<i>nextValue</i>.[[value]]»).</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Using a method call for inserting values during initialization enables subclasses to
+ that redefine <code>add</code> to still make a super call to the inherited constructor.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-set-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.2.2"><a href="#sec-properties-of-the-set-constructor"
+ title="link to this section">23.2.2</a></span> Properties of the Set Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Set
+ constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>0</b>), the Set constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-set.prototype">
+ <h1><span class="secnum" id="sec-23.2.2.1"><a href="#sec-set.prototype" title="link to this section">23.2.2.1</a></span>
+ Set.prototype</h1>
+
+ <p>The initial value of <code>Set.prototype</code> is the intrinsic %SetPrototype% object (<a
+ href="#sec-properties-of-the-set-prototype-object">23.2.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-get-set-@@species">
+ <h1><span class="secnum" id="sec-23.2.2.2"><a href="#sec-get-set-@@species"
+ title="link to this section">23.2.2.2</a></span> get Set [ @@species ]</h1>
+
+ <p><code>Set[@@species]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"get [Symbol.species]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Set prototype methods normally use their <code>this</code> object’s constructor to
+ create a derived object. However, a subclass constructor may over-ride that default behaviour by redefining its
+ @@species property.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-set-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.2.3"><a href="#sec-properties-of-the-set-prototype-object"
+ title="link to this section">23.2.3</a></span> Properties of the Set Prototype Object</h1>
+
+ <p>The Set prototype object is the intrinsic object %SetPrototype%. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Set prototype object is the intrinsic
+ object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The Set prototype object
+ is an ordinary object. It does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </div>
+
+ <section id="sec-set.prototype.add">
+ <h1><span class="secnum" id="sec-23.2.3.1"><a href="#sec-set.prototype.add"
+ title="link to this section">23.2.3.1</a></span> Set.prototype.add ( value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevaluezero">SameValueZero</a>(<i>e</i>, <i>value</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Return <i>S</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>value</i> is −0, let <i>value</i> be +0.</li>
+ <li>Append <i>value</i> as the last element of <i>entries</i>.</li>
+ <li>Return <i>S</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-set.prototype.clear">
+ <h1><span class="secnum" id="sec-23.2.3.2"><a href="#sec-set.prototype.clear"
+ title="link to this section">23.2.3.2</a></span> Set.prototype.clear ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>Replace the element of <i>entries</i> whose value is <i>e</i> with an element whose value is <span
+ style="font-family: sans-serif">empty</span><i>.</i></li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-set.prototype.constructor">
+ <h1><span class="secnum" id="sec-23.2.3.3"><a href="#sec-set.prototype.constructor"
+ title="link to this section">23.2.3.3</a></span> Set.prototype.constructor</h1>
+
+ <p>The initial value of <code>Set.prototype.constructor</code> is the intrinsic object %Set%.</p>
+ </section>
+
+ <section id="sec-set.prototype.delete">
+ <h1><span class="secnum" id="sec-23.2.3.4"><a href="#sec-set.prototype.delete"
+ title="link to this section">23.2.3.4</a></span> Set.prototype.delete ( value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries</i>,
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevaluezero">SameValueZero</a>(<i>e</i>, <i>value</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Replace the element of <i>entries</i> whose value is <i>e</i> with an element whose value is <span
+ style="font-family: sans-serif">empty</span><i>.</i></li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value <b>empty</b> is used as a specification device to indicate that an entry has
+ been deleted. Actual implementations may take other actions such as physically removing the entry from internal data
+ structures.</p>
+ </div>
+ </section>
+
+ <section id="sec-set.prototype.entries">
+ <h1><span class="secnum" id="sec-23.2.3.5"><a href="#sec-set.prototype.entries"
+ title="link to this section">23.2.3.5</a></span> Set.prototype.entries ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createsetiterator">CreateSetIterator</a>(<i>S</i>, <b>"<code>key+value</code>"</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For iteration purposes, a Set appears similar to a Map where each entry has the same
+ value for its key and value.</p>
+ </div>
+ </section>
+
+ <section id="sec-set.prototype.foreach">
+ <h1><span class="secnum" id="sec-23.2.3.6"><a href="#sec-set.prototype.foreach"
+ title="link to this section">23.2.3.6</a></span> Set.prototype.forEach ( callbackfn [ , thisArg ] )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> <i>callbackfn</i> should be a function that accepts three arguments.
+ <code>forEach</code> calls <i>callbackfn</i> once for each value present in the set object, in value insertion order.
+ <i>callbackfn</i> is called only for values of the Set which actually exist; it is not called for keys that have been
+ deleted from the set.</p>
+
+ <p>If a <i>thisArg</i> parameter is provided, it will be used as the <b>this</b> value for each invocation of
+ <i>callbackfn</i>. If it is not provided, <b>undefined</b> is used instead.</p>
+
+ <p><i>callbackfn</i> is called with three arguments: the first two arguments are a value contained in the Set. The same
+ value of passed for both arguments. The Set object being traversed is passed as the third argument.</p>
+
+ <p>The <i>callbackfn</i> is called with three arguments to be consistent with the call back functions used by
+ <code>forEach</code> methods for Map and Array. For Sets, each item value is considered to be both the key and the
+ value.</p>
+
+ <p><code>forEach</code> does not directly mutate the object on which it is called but the object may be mutated by the
+ calls to <i>callbackfn</i>.</p>
+
+ <p>Each value is normally visited only once. However, a value will be revisited if it is deleted after it has been
+ visited and then re-added before the to <code>forEach</code> call completes. Values that are deleted after the call to
+ <code>forEach</code> begins and before being visited are not visited unless the value is added again before the to
+ <code>forEach</code> call completes. New values added, after the call to <code>forEach</code> begins are visited.</p>
+ </div>
+
+ <p>When the <code>forEach</code> method is called with one or two arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>callbackfn</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>thisArg</i> was supplied, let <i>T</i> be <i>thisArg</i>; else let <i>T</i> be <b>undefined</b>.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries,</i> in original insertion order
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>Let <i>funcResult</i> be <a href="#sec-call">Call</a>(<i>callbackfn</i>, <i>T</i>, «<i>e</i>,
+ <i>e</i>, <i>S</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>funcResult</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>forEach</code> method is <b>1</b>.</p>
+ </section>
+
+ <section id="sec-set.prototype.has">
+ <h1><span class="secnum" id="sec-23.2.3.7"><a href="#sec-set.prototype.has"
+ title="link to this section">23.2.3.7</a></span> Set.prototype.has ( value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevaluezero">SameValueZero</a>(<i>e</i>, <i>value</i>) is <b>true</b>, return
+ <b>true</b><i>.</i></li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-set.prototype.keys">
+ <h1><span class="secnum" id="sec-23.2.3.8"><a href="#sec-set.prototype.keys"
+ title="link to this section">23.2.3.8</a></span> Set.prototype.keys ( )</h1>
+
+ <p>The initial value of the <code>keys</code> property is the same function object as the initial value of the
+ <code>values</code> property.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> For iteration purposes, a Set appears similar to a Map where each entry has the same
+ value for its key and value.</p>
+ </div>
+ </section>
+
+ <section id="sec-get-set.prototype.size">
+ <h1><span class="secnum" id="sec-23.2.3.9"><a href="#sec-get-set.prototype.size"
+ title="link to this section">23.2.3.9</a></span> get Set.prototype.size</h1>
+
+ <p><code>Set.prototype.size</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>count</i> be 0.</li>
+ <li>For each <i>e</i> that is an element of <i>entries</i>
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span>, set <i>count</i> to <i>count</i>+1.</li>
+ </ol>
+ </li>
+ <li>Return <i>count</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-set.prototype.values">
+ <h1><span class="secnum" id="sec-23.2.3.10"><a href="#sec-set.prototype.values"
+ title="link to this section">23.2.3.10</a></span> Set.prototype.values ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createsetiterator">CreateSetIterator</a>(<i>S</i>, <b>"<code>value</code>"</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-set.prototype-@@iterator">
+ <h1><span class="secnum" id="sec-23.2.3.11"><a href="#sec-set.prototype-@@iterator"
+ title="link to this section">23.2.3.11</a></span> Set.prototype [ @@iterator ] ( )</h1>
+
+ <p>The initial value of the @@iterator property is the same function object as the initial value of the
+ <code>values</code> property.</p>
+ </section>
+
+ <section id="sec-set.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-23.2.3.12"><a href="#sec-set.prototype-@@tostringtag"
+ title="link to this section">23.2.3.12</a></span> Set.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Set</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-set-instances">
+ <h1><span class="secnum" id="sec-23.2.4"><a href="#sec-properties-of-set-instances"
+ title="link to this section">23.2.4</a></span> Properties of Set Instances</h1>
+
+ <p>Set instances are ordinary objects that inherit properties from the Set prototype. After initialization by the Set
+ constructor, Set instances also have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>.</p>
+ </section>
+
+ <section id="sec-set-iterator-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.2.5"><a href="#sec-set-iterator-objects"
+ title="link to this section">23.2.5</a></span> Set Iterator Objects</h1>
+
+ <p>A Set Iterator is an ordinary object, with the structure defined below, that represents a specific iteration over some
+ specific Set instance object. There is not a named constructor for Set Iterator objects. Instead, set iterator objects are
+ created by calling certain methods of Set instance objects.</p>
+ </div>
+
+ <section id="sec-createsetiterator">
+ <h1><span class="secnum" id="sec-23.2.5.1"><a href="#sec-createsetiterator"
+ title="link to this section">23.2.5.1</a></span> CreateSetIterator Abstract Operation</h1>
+
+ <p>Several methods of Set objects return Iterator objects. The abstract operation CreateSetIterator with arguments
+ <var>set</var> and <var>kind</var> is used to create such iterator objects. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>set</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>set</i> does not have a [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>iterator</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%SetIteratorPrototype%,
+ «‍[[IteratedSet]], [[SetNextIndex]], [[SetIterationKind]]»).</li>
+ <li>Set <i>iterator’s</i> [[IteratedSet]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>set</i>.</li>
+ <li>Set <i>iterator’s</i> [[SetNextIndex]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to 0.</li>
+ <li>Set <i>iterator’s</i> [[SetIterationKind]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>kind</i>.</li>
+ <li>Return <i>iterator</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-%setiteratorprototype%-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.2.5.2"><a href="#sec-%setiteratorprototype%-object"
+ title="link to this section">23.2.5.2</a></span> The %SetIteratorPrototype% Object</h1>
+
+ <p>All Set Iterator Objects inherit properties from the %SetIteratorPrototype% intrinsic object. The
+ %SetIteratorPrototype% intrinsic object is an ordinary object and its [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is the %IteratorPrototype% intrinsic object (<a
+ href="#sec-%iteratorprototype%-object">25.1.2</a>). In addition, %SetIteratorPrototype% has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-%setiteratorprototype%.next">
+ <h1><span class="secnum" id="sec-23.2.5.2.1"><a href="#sec-%setiteratorprototype%.next"
+ title="link to this section">23.2.5.2.1</a></span> %SetIteratorPrototype%.next ( )</h1>
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have all of the internal slots of a Set Iterator Instance (<a
+ href="#sec-properties-of-set-iterator-instances">23.2.5.3</a>), throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>s</i> be the value of the [[IteratedSet]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>index</i> be the value of the [[SetNextIndex]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>Let <i>itemKind</i> be the value of the [[SetIterationKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i>.</li>
+ <li>If <i>s</i> is <b>undefined</b>, return <a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>s</i> has a [[SetData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of the
+ [[SetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>s</i>.</li>
+ <li>Repeat while <i>index</i> is less than the total number of elements of <i>entries</i>. The number of elements must
+ be redetermined each time this method is evaluated.
+ <ol class="block">
+ <li>Let <i>e</i> be <i>entries</i>[<i>index</i>].</li>
+ <li>Set <i>index</i> to <i>index</i>+1;</li>
+ <li>Set the [[SetNextIndex]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>O</i> to <i>index</i>.</li>
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span>, then
+ <ol class="block">
+ <li>If <i>itemKind</i> is <b>"<code>key+value</code>"</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<a
+ href="#sec-createarrayfromlist">CreateArrayFromList</a>(«<i>e</i>, <i>e</i>»),
+ <b>false</b>).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>e</i>, <b>false</b>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Set the [[IteratedSet]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>O</i> to
+ <b>undefined</b>.</li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-%setiteratorprototype%-@@tostringtag">
+ <h1><span class="secnum" id="sec-23.2.5.2.2"><a href="#sec-%setiteratorprototype%-@@tostringtag"
+ title="link to this section">23.2.5.2.2</a></span> %SetIteratorPrototype% [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Set Iterator</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-set-iterator-instances">
+ <h1><span class="secnum" id="sec-23.2.5.3"><a href="#sec-properties-of-set-iterator-instances"
+ title="link to this section">23.2.5.3</a></span> Properties of Set Iterator Instances</h1>
+
+ <p>Set Iterator instances are ordinary objects that inherit properties from the %SetIteratorPrototype% intrinsic object.
+ Set Iterator instances are initially created with the internal slots specified in <a href="#table-51">Table 51</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-51">Table 51</span> — Internal Slots of Set Iterator Instances</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="background-color: #BFBFBF">Internal Slot</th>
+ <th style="background-color: #BFBFBF">Description</th>
+ </tr>
+ <tr>
+ <td>[[IteratedSet]]</td>
+ <td>The Set object that is being iterated.</td>
+ </tr>
+ <tr>
+ <td>[[SetNextIndex]]</td>
+ <td>The integer index of the next Set data element to be examined by this iterator</td>
+ </tr>
+ <tr>
+ <td>[[SetIterationKind]]</td>
+ <td>A string value that identifies what is to be returned for each element of the iteration. The possible values are: <b>"<code>key</code>"</b>, <b>"<code>value</code>"</b>, <b>"<code>key+value</code>"</b>. <b>"<code>key</code>"</b> and <b>"<code>value</code>"</b> have the same meaning.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-weakmap-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.3"><a href="#sec-weakmap-objects" title="link to this section">23.3</a></span> WeakMap
+ Objects</h1>
+
+ <p>WeakMap objects are collections of key/value pairs where the keys are objects and values may be arbitrary <a
+ href="#sec-ecmascript-language-types">ECMAScript language values</a>. A WeakMap may be queried to see if it contains an
+ key/value pair with a specific key, but no mechanisms is provided for enumerating the objects it holds as keys. If an object
+ that is being used as the key of a WeakMap key/value pair is only reachable by following a chain of references that start
+ within that WeakMap, then that key/value pair is inaccessible and is automatically removed from the WeakMap. WeakMap
+ implementations must detect and remove such key/value pairs and any associated resources.</p>
+
+ <p>An implementation may impose an arbitrarily determined latency between the time a key/value pair of a WeakMap becomes
+ inaccessible and the time when the key/value pair is removed from the WeakMap. If this latency was observable to ECMAScript
+ program, it would be a source of indeterminacy that could impact program execution. For that reason, an ECMAScript
+ implementation must not provide any means to observe a key of a WeakMap that does not require the observer to present the
+ observed key.</p>
+
+ <p>WeakMap objects must be implemented using either hash tables or other mechanisms that, on average, provide access times
+ that are sublinear on the number of key/value pairs in the collection. The data structure used in this WeakMap objects
+ specification are only intended to describe the required observable semantics of WeakMap objects. It is not intended to be a
+ viable implementation model.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> WeakMap and WeakSets are intended to provide mechanisms for dynamically associating state
+ with an object in a manner that does not “leak” memory resources if, in the absence of the WeakMap or WeakSet,
+ the object otherwise became inaccessible and subject to resource reclamation by the implementation’s garbage
+ collection mechanisms. Achieving this characteristic can be achieved by using an inverted per-object mapping of weak map
+ instances to keys. Alternatively each weak map may internally store its key to value mappings but this approach requires
+ coordination between the WeakMap or WeakSet implementation and the garbage collector. The following references describe
+ mechanism that may be useful to implementations of WeakMap and WeakSets:</p>
+
+ <p>Barry Hayes. 1997. Ephemerons: a new finalization mechanism. In <i>Proceedings of the 12th ACM SIGPLAN conference on
+ Object-oriented programming, systems, languages, and applications (OOPSLA '97)</i>, A. Michael Berman (Ed.). ACM, New
+ York, NY, USA, 176-183. <a
+ href="http://doi.acm.org/10.1145/263698.263733">http://doi.acm.org/10.1145/263698.263733</a>.</p>
+
+ <p>Alexandra Barros, Roberto Ierusalimschy, Eliminating Cycles in Weak Tables. Journal of Universal Computer Science -
+ J.UCS , vol. 14, no. 21, pp. 3481-3497, 2008. <a
+ href="http://www.jucs.org/jucs_14_21/eliminating_cycles_in_weak">http://www.jucs.org/jucs_14_21/eliminating_cycles_in_weak</a></p>
+ </div>
+ </div>
+
+ <section id="sec-weakmap-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.3.1"><a href="#sec-weakmap-constructor" title="link to this section">23.3.1</a></span>
+ The WeakMap Constructor</h1>
+
+ <p>The WeakMap constructor is the %WeakMap% intrinsic object and the initial value of the <code>WeakMap</code> property of
+ the global object. When called as a constructor it creates and initializes a new WeakMap object. <code>WeakMap</code> is
+ not intended to be called as a function and will throw an exception when called in that manner.</p>
+
+ <p>The <code>WeakMap</code> constructor is designed to be subclassable. It may be used as the value in an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>WeakMap</code> behaviour must include a <code>super</code> call to the <code>WeakMap</code> constructor to create
+ and initialize the subclass instance with the internal state necessary to support the <code><a
+ href="#sec-weakmap.prototype">WeakMap.prototype</a></code> built-in methods.</p>
+ </div>
+
+ <section id="sec-weakmap-iterable">
+ <h1><span class="secnum" id="sec-23.3.1.1"><a href="#sec-weakmap-iterable"
+ title="link to this section">23.3.1.1</a></span> WeakMap ( [ iterable ] )</h1>
+
+ <p>When the <code>WeakMap</code> function is called with optional argument <var>iterable</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>map</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%WeakMapPrototype%"</code>, «‍[[WeakMapData]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>map</i>).</li>
+ <li>Set <i>map’s</i> [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ to a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <i>iterable</i> is not present, let <i>iterable</i> be <b>undefined</b>.</li>
+ <li>If <i>iterable</i> is either <b>undefined</b> or <b>null</b>, let <i>iter</i> be <b>undefined</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>adder</i> be <a href="#sec-get-o-p">Get</a>(<i>map</i>, <code>"set"</code>)<b>.</b></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>adder</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>adder</i>) is <b>false</b>, throw a <b>TypeError</b>
+ Exception.</li>
+ <li>Let <i>iter</i> be <a href="#sec-getiterator">GetIterator</a>(<i>iterable</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iter</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>iter</i> is <b>undefined</b>, return <i>map</i>.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iter</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, return <i>map</i>.</li>
+ <li>Let <i>nextItem</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextItem</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>nextItem</i>) is not Object,
+ <ol class="block">
+ <li>Let <i>error</i> be <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">throw</span>, [[value]]: a newly created <b>TypeError</b> object,
+ [[target]]:<span style="font-family: sans-serif">empty</span>}.</li>
+ <li>Return <a href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>error</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>k</i> be <a href="#sec-get-o-p">Get</a>(<i>nextItem</i>, <code>"0"</code>).</li>
+ <li>If <i>k</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>k</i>).</li>
+ <li>Let <i>v</i> be <a href="#sec-get-o-p">Get</a>(<i>nextItem</i>, <code>"1"</code>).</li>
+ <li>If <i>v</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>v</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>adder</i>, <i>map</i>, «<i>k</i>.[[value]],
+ <i>v</i>.[[value]]»).</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> If the parameter <i>iterable</i> is present, it is expected to be an object that
+ implements an @@iterator method that returns an iterator object that produces a two element array-like object whose
+ first element is a value that will be used as a WeakMap key and whose second element is the value to associate with that
+ key.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-weakmap-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.3.2"><a href="#sec-properties-of-the-weakmap-constructor"
+ title="link to this section">23.3.2</a></span> Properties of the WeakMap Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ WeakMap constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>0</b>), the WeakMap constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-weakmap.prototype">
+ <h1><span class="secnum" id="sec-23.3.2.1"><a href="#sec-weakmap.prototype"
+ title="link to this section">23.3.2.1</a></span> WeakMap.prototype</h1>
+
+ <p>The initial value of <code>WeakMap.prototype</code> is the intrinsic object %WeakMapPrototype% (<a
+ href="#sec-properties-of-the-weakmap-prototype-object">23.3.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-weakmap-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.3.3"><a href="#sec-properties-of-the-weakmap-prototype-object"
+ title="link to this section">23.3.3</a></span> Properties of the WeakMap Prototype Object</h1>
+
+ <p>The WeakMap prototype object is the intrinsic object %WeakMapPrototype%. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the WeakMap prototype object is the intrinsic
+ object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The WeakMap prototype
+ object is an ordinary object. It does not have a [[WeakMapData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </div>
+
+ <section id="sec-weakmap.prototype.constructor">
+ <h1><span class="secnum" id="sec-23.3.3.1"><a href="#sec-weakmap.prototype.constructor"
+ title="link to this section">23.3.3.1</a></span> WeakMap.prototype.constructor</h1>
+
+ <p>The initial value of <code>WeakMap.prototype.constructor</code> is the intrinsic object %WeakMap%.</p>
+ </section>
+
+ <section id="sec-weakmap.prototype.delete">
+ <h1><span class="secnum" id="sec-23.3.3.2"><a href="#sec-weakmap.prototype.delete"
+ title="link to this section">23.3.3.2</a></span> WeakMap.prototype.delete ( key )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>key</i>) is not Object, return <b>false</b>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>p</i>.[[key]] to <span style="font-family: sans-serif">empty</span><i>.</i></li>
+ <li>Set <i>p</i>.[[value]] to <span style="font-family: sans-serif">empty</span><i>.</i></li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value <b>empty</b> is used as a specification device to indicate that an entry has
+ been deleted. Actual implementations may take other actions such as physically removing the entry from internal data
+ structures.</p>
+ </div>
+ </section>
+
+ <section id="sec-weakmap.prototype.get">
+ <h1><span class="secnum" id="sec-23.3.3.3"><a href="#sec-weakmap.prototype.get"
+ title="link to this section">23.3.3.3</a></span> WeakMap.prototype.get ( key )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>key</i>) is not Object, return
+ <b>undefined</b>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, return
+ <i>p</i>.[[value]].</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b><i>.</i></li>
+ </ol>
+ </section>
+
+ <section id="sec-weakmap.prototype.has">
+ <h1><span class="secnum" id="sec-23.3.3.4"><a href="#sec-weakmap.prototype.has"
+ title="link to this section">23.3.3.4</a></span> WeakMap.prototype.has ( key )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>key</i>) is not Object, return <b>false</b>.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, return
+ <b>true</b><i>.</i></li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-weakmap.prototype.set">
+ <h1><span class="secnum" id="sec-23.3.3.5"><a href="#sec-weakmap.prototype.set"
+ title="link to this section">23.3.3.5</a></span> WeakMap.prototype.set ( key , value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>M</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>M</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>M</i> does not have a [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>M</i>’s [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>key</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Repeat for each Record {[[key]], [[value]]} <i>p</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>p</i>.[[key]] is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>p</i>.[[key]], <i>key</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>p</i>.[[value]] to <i>value.</i></li>
+ <li>Return <i>M</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>p</i> be the Record {[[key]]: <i>key</i>, [[value]]: <i>value</i>}.</li>
+ <li>Append <i>p</i> as the last element of <i>entries</i>.</li>
+ <li>Return <i>M</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-weakmap.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-23.3.3.6"><a href="#sec-weakmap.prototype-@@tostringtag"
+ title="link to this section">23.3.3.6</a></span> WeakMap.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>WeakMap</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-weakmap-instances">
+ <h1><span class="secnum" id="sec-23.3.4"><a href="#sec-properties-of-weakmap-instances"
+ title="link to this section">23.3.4</a></span> Properties of WeakMap Instances</h1>
+
+ <p>WeakMap instances are ordinary objects that inherit properties from the WeakMap prototype. WeakMap instances also have a
+ [[WeakMapData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </section>
+ </section>
+
+ <section id="sec-weakset-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.4"><a href="#sec-weakset-objects" title="link to this section">23.4</a></span> WeakSet
+ Objects</h1>
+
+ <p>WeakSet objects are collections of objects. A distinct object may only occur once as an element of a WeakSet’s
+ collection. A WeakSet may be queried to see if it contains a specific object, but no mechanisms is provided for enumerating
+ the objects it holds. If an object that is contain by a WeakSet is only reachable by following a chain of references that
+ start within that WeakSet, then that object is inaccessible and is automatically removed from the WeakSet. WeakSet
+ implementations must detect and remove such objects and any associated resources.</p>
+
+ <p>An implementation may impose an arbitrarily determined latency between the time an object contained in a WeakSet becomes
+ inaccessible and the time when the object is removed from the WeakSet. If this latency was observable to ECMAScript program,
+ it would be a source of indeterminacy that could impact program execution. For that reason, an ECMAScript implementation
+ must not provide any means to determine if a WeakSet contains a particular object that does not require the observer to
+ present the observed object.</p>
+
+ <p>WeakSet objects must be implemented using either hash tables or other mechanisms that, on average, provide access times
+ that are sublinear on the number of elements in the collection. The data structure used in this WeakSet objects
+ specification is only intended to describe the required observable semantics of WeakSet objects. It is not intended to be a
+ viable implementation model.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> See the NOTE in <a href="#sec-weakmap-objects">23.3</a>.</p>
+ </div>
+ </div>
+
+ <section id="sec-weakset-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.4.1"><a href="#sec-weakset-constructor" title="link to this section">23.4.1</a></span>
+ The WeakSet Constructor</h1>
+
+ <p>The WeakSet constructor is the %WeakSet% intrinsic object and the initial value of the <code>WeakSet</code> property of
+ the global object. When called as a constructor it creates and initializes a new WeakSet object. <code>WeakSet</code> is
+ not intended to be called as a function and will throw an exception when called in that manner.</p>
+
+ <p>The <code>WeakSet</code> constructor is designed to be subclassable. It may be used as the value in an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>WeakSet</code> behaviour must include a <code>super</code> call to the <code>WeakSet</code> constructor to create
+ and initialize the subclass instance with the internal state necessary to support the <code><a
+ href="#sec-weakset.prototype">WeakSet.prototype</a></code> built-in methods.</p>
+ </div>
+
+ <section id="sec-weakset-iterable">
+ <h1><span class="secnum" id="sec-23.4.1.1"><a href="#sec-weakset-iterable"
+ title="link to this section">23.4.1.1</a></span> WeakSet ( [ iterable ] )</h1>
+
+ <p>When the <code>WeakSet</code> function is called with optional argument <var>iterable</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>set</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%WeakSetPrototype%"</code>, «‍[[WeakSetData]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>set</i>).</li>
+ <li>Set <i>set’s</i> [[WeakSetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>
+ to a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>If <i>iterable</i> is not present, let <i>iterable</i> be <b>undefined</b>.</li>
+ <li>If <i>iterable</i> is either <b>undefined</b> or <b>null</b>, let <i>iter</i> be <b>undefined</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>adder</i> be <a href="#sec-get-o-p">Get</a>(<i>set</i>, <code>"add"</code>)<b>.</b></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>adder</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>adder</i>) is <b>false</b>, throw a <b>TypeError</b>
+ Exception.</li>
+ <li>Let <i>iter</i> be <a href="#sec-getiterator">GetIterator</a>(<i>iterable</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>iter</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>iter</i> is <b>undefined</b>, return <i>set</i>.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iter</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, return <i>set</i>.</li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>adder</i>, <i>set</i>, «<i>nextValue</i>
+ »).</li>
+ <li>If <i>status</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, return <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iter</i>, <i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-weakset-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.4.2"><a href="#sec-properties-of-the-weakset-constructor"
+ title="link to this section">23.4.2</a></span> Properties of the WeakSet Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ WeakSet constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>0</b>), the WeakSet constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-weakset.prototype">
+ <h1><span class="secnum" id="sec-23.4.2.1"><a href="#sec-weakset.prototype"
+ title="link to this section">23.4.2.1</a></span> WeakSet.prototype</h1>
+
+ <p>The initial value of <code>WeakSet.prototype</code> is the intrinsic %WeakSetPrototype% object (<a
+ href="#sec-properties-of-the-weakset-prototype-object">23.4.3</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-weakset-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-23.4.3"><a href="#sec-properties-of-the-weakset-prototype-object"
+ title="link to this section">23.4.3</a></span> Properties of the WeakSet Prototype Object</h1>
+
+ <p>The WeakSet prototype object is the intrinsic object %WeakSetPrototype%. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the WeakSet prototype object is the intrinsic
+ object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The WeakSet prototype
+ object is an ordinary object. It does not have a [[WeakSetData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </div>
+
+ <section id="sec-weakset.prototype.add">
+ <h1><span class="secnum" id="sec-23.4.3.1"><a href="#sec-weakset.prototype.add"
+ title="link to this section">23.4.3.1</a></span> WeakSet.prototype.add ( value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[WeakSetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[WeakSetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>e</i>, <i>value</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Return <i>S</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Append <i>value</i> as the last element of <i>entries</i>.</li>
+ <li>Return <i>S</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-weakset.prototype.constructor">
+ <h1><span class="secnum" id="sec-23.4.3.2"><a href="#sec-weakset.prototype.constructor"
+ title="link to this section">23.4.3.2</a></span> WeakSet.prototype.constructor</h1>
+
+ <p>The initial value of <code>WeakSet.prototype.constructor</code> is the %WeakSet% intrinsic object.</p>
+ </section>
+
+ <section id="sec-weakset.prototype.delete">
+ <h1><span class="secnum" id="sec-23.4.3.3"><a href="#sec-weakset.prototype.delete"
+ title="link to this section">23.4.3.3</a></span> WeakSet.prototype.delete ( value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[WeakSetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is not Object, return <b>false</b>.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[WeakSetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries</i>,
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>e</i>, <i>value</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Replace the element of <i>entries</i> whose value is <i>e</i> with an element whose value is <span
+ style="font-family: sans-serif">empty</span><i>.</i></li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value <b>empty</b> is used as a specification device to indicate that an entry has
+ been deleted. Actual implementations may take other actions such as physically removing the entry from internal data
+ structures.</p>
+ </div>
+ </section>
+
+ <section id="sec-weakset.prototype.has">
+ <h1><span class="secnum" id="sec-23.4.3.4"><a href="#sec-weakset.prototype.has"
+ title="link to this section">23.4.3.4</a></span> WeakSet.prototype.has ( value )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>S</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>S</i> does not have a [[WeakSetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>entries</i> be the <a href="#sec-list-and-record-specification-type">List</a> that is the value of
+ <i>S</i>’s [[WeakSetData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is not Object, return <b>false.</b></li>
+ <li>Repeat for each <i>e</i> that is an element of <i>entries,</i>
+ <ol class="block">
+ <li>If <i>e</i> is not <span style="font-family: sans-serif">empty</span> and <a
+ href="#sec-samevalue">SameValue</a>(<i>e</i>, <i>value</i>), return <b>true</b><i>.</i></li>
+ </ol>
+ </li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-weakset.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-23.4.3.5"><a href="#sec-weakset.prototype-@@tostringtag"
+ title="link to this section">23.4.3.5</a></span> WeakSet.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <code>"WeakSet"</code>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-weakset-instances">
+ <h1><span class="secnum" id="sec-23.4.4"><a href="#sec-properties-of-weakset-instances"
+ title="link to this section">23.4.4</a></span> Properties of WeakSet Instances</h1>
+
+ <p>WeakSet instances are ordinary objects that inherit properties from the WeakSet prototype. After initialization by the
+ WeakSet constructor, WeakSet instances also have a [[WeakSetData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-structured-data">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24"><a href="#sec-structured-data" title="link to this section">24</a></span> Structured
+ Data</h1>
+ </div>
+
+ <section id="sec-arraybuffer-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.1"><a href="#sec-arraybuffer-objects" title="link to this section">24.1</a></span>
+ ArrayBuffer Objects</h1>
+ </div>
+
+ <section id="sec-abstract-operations-for-arraybuffer-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.1.1"><a href="#sec-abstract-operations-for-arraybuffer-objects"
+ title="link to this section">24.1.1</a></span> Abstract Operations For ArrayBuffer Objects</h1>
+ </div>
+
+ <section id="sec-allocatearraybuffer">
+ <h1><span class="secnum" id="sec-24.1.1.1"><a href="#sec-allocatearraybuffer"
+ title="link to this section">24.1.1.1</a></span> AllocateArrayBuffer( constructor, byteLength )</h1>
+
+ <p>The abstract operation AllocateArrayBuffer with arguments <var>constructor</var> and <var>byteLength</var> is used to
+ create an ArrayBuffer object. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>obj</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(<i>constructor</i>,
+ <code>"%ArrayBufferPrototype%"</code>, «‍[[ArrayBufferData]], [[ArrayBufferByteLength]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>obj</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>byteLength</i> is a positive integer.</li>
+ <li>Let <i>block</i> be <a href="#sec-createbytedatablock">CreateByteDataBlock</a>(<i>byteLength</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>block</i>).</li>
+ <li>Set <i>obj’s</i> [[ArrayBufferData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>block</i>.</li>
+ <li>Set <i>obj</i>’s [[ArrayBufferByteLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>byteLength</i>.</li>
+ <li>Return <i>obj</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-isdetachedbuffer">
+ <h1><span class="secnum" id="sec-24.1.1.2"><a href="#sec-isdetachedbuffer"
+ title="link to this section">24.1.1.2</a></span> IsDetachedBuffer( arrayBuffer )</h1>
+
+ <p>The abstract operation IsDetachedBuffer with argument <var>arrayBuffer</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>arrayBuffer</i>) is Object and it has an
+ [[ArrayBufferData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>arrayBuffer’s</i> [[ArrayBufferData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> is <b>null</b>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-detacharraybuffer">
+ <h1><span class="secnum" id="sec-24.1.1.3"><a href="#sec-detacharraybuffer"
+ title="link to this section">24.1.1.3</a></span> DetachArrayBuffer( arrayBuffer )</h1>
+
+ <p>The abstract operation DetachArrayBuffer with argument <var>arrayBuffer</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>arrayBuffer</i>) is Object and it has [[ArrayBufferData]]
+ and [[ArrayBufferByteLength]] internal slots.</li>
+ <li>Set <i>arrayBuffer’s</i> [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <b>null</b>.</li>
+ <li>Set <i>arrayBuffer</i>’s [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to 0.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>null</b>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Detaching an ArrayBuffer instance disassociates the <a href="#sec-data-blocks">Data
+ Block</a> used as its backing store from the instance and sets the byte length of the buffer to 0. No operations defined
+ by this specification uses the DetachArrayBuffer abstract operation. However, an ECMAScript implementation or host
+ environment may define such operations.</p>
+ </div>
+ </section>
+
+ <section id="sec-clonearraybuffer">
+ <h1><span class="secnum" id="sec-24.1.1.4"><a href="#sec-clonearraybuffer"
+ title="link to this section">24.1.1.4</a></span> CloneArrayBuffer( srcBuffer, srcByteOffset [, cloneConstructor]
+ )</h1>
+
+ <p>The abstract operation CloneArrayBuffer takes two parameters, an ArrayBuffer <var>srcBuffer</var>, an integer
+ <var>srcByteOffset</var> and optional parameter <var>cloneConstructor</var>. It creates a new ArrayBuffer whose data is a
+ copy of <var>srcBuffer’s</var> data starting at <var>srcByteOffset</var>. This operation performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>srcBuffer</i>) is Object and it has an [[ArrayBufferData]]
+ <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>cloneConstructor</i> is not present, then
+ <ol class="block">
+ <li>Let <i>cloneConstructor</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>srcBuffer</i>,
+ %ArrayBuffer%).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>cloneConstructor</i>).</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>srcBuffer</i>) is <b>true</b>, throw a
+ <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Else, <a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-isconstructor">IsConstructor</a>(<i>cloneConstructor</i>) is <b>true</b>.</li>
+ <li>Let <i>srcLength</i> be the value of <i>srcBuffer</i>’s [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>srcByteOffset</i> ≤ <i>srcLength</i>.</li>
+ <li>Let <i>cloneLength</i> be <i>srcLength</i> – <i>srcByteOffset.</i></li>
+ <li>Let <i>srcBlock</i> be the value of <i>srcBuffer’s</i> [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>targetBuffer</i> be <a href="#sec-allocatearraybuffer">AllocateArrayBuffer</a>(<i>cloneConstructor</i>,
+ <i>cloneLength</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>targetBuffer</i>).</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>srcBuffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>targetBlock</i> be the value of <i>targetBuffer’s</i> [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Perform <a href="#sec-copydatablockbytes">CopyDataBlockBytes</a>(<i>targetBlock</i>, 0, <i>srcBlock</i>,
+ <i>srcByteOffset</i>, <i>cloneLength</i>).</li>
+ <li>Return <i>targetBuffer</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-getvaluefrombuffer">
+ <h1><span class="secnum" id="sec-24.1.1.5"><a href="#sec-getvaluefrombuffer"
+ title="link to this section">24.1.1.5</a></span> GetValueFromBuffer ( arrayBuffer, byteIndex, type, isLittleEndian
+ )</h1>
+
+ <p>The abstract operation GetValueFromBuffer takes four parameters, an ArrayBuffer <var>arrayBuffer</var>, an integer
+ <var>byteIndex</var>, a String <var>type</var>, and optionally a Boolean <var>isLittleEndian</var>. This operation
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>arrayBuffer</i>) is <b>false</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: There are sufficient bytes in <i>arrayBuffer</i> starting at
+ <i>byteIndex</i> to represent a value of <i>type</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>byteIndex</i> is a positive integer.</li>
+ <li>Let <i>block</i> be <i>arrayBuffer’s</i> [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table 49</a>
+ for Element Type <i>type</i>.</li>
+ <li>Let <i>rawValue</i> be a <a href="#sec-list-and-record-specification-type">List</a> of <i>elementSize</i>
+ containing, in order<i>,</i> the <i>elementSize</i> sequence of bytes starting with
+ <i>block</i>[<i>byteIndex</i>].</li>
+ <li>If <i>isLittleEndian</i> is not present, set <i>isLittleEndian</i> to either <b>true</b> or <b>false</b>. The choice
+ is implementation dependent and should be the alternative that is most efficient for the implementation. An
+ implementation must use the same value each time this step is executed and the same value must be used for the
+ corresponding step in the <a href="#sec-setvalueinbuffer">SetValueInBuffer</a> abstract operation.</li>
+ <li>If <i>isLittleEndian</i> is <b>false</b>, reverse the order of the elements of <i>rawValue</i>.</li>
+ <li>If <i>type</i> is <code>"Float32"</code>, then
+ <ol class="block">
+ <li>Let <i>value</i> be the byte elements of <i>rawValue</i> concatenated and interpreted as a little-endian bit
+ string encoding of an IEEE 754-2008 binary32 value.</li>
+ <li>If <i>value</i> is an IEEE 754-2008 binary32 NaN value, return the <b>NaN</b> Number value.</li>
+ <li>Return the Number value that corresponds to <i>value</i>.</li>
+ </ol>
+ </li>
+ <li>If <i>type</i> is <code>"Float64"</code>, then
+ <ol class="block">
+ <li>Let <i>value</i> be the byte elements of <i>rawValue</i> concatenated and interpreted as a little-endian bit
+ string encoding of an IEEE 754-2008 binary64 value.</li>
+ <li>If <i>value</i> is an IEEE 754-2008 binary64 NaN value, return the <b>NaN</b> Number value.</li>
+ <li>Return the Number value that corresponds to <i>value</i>.</li>
+ </ol>
+ </li>
+ <li>If the first code unit of <i>type</i> is <code>"U"</code>, then
+ <ol class="block">
+ <li>Let <i>intValue</i> be the byte elements of <i>rawValue</i> concatenated and interpreted as a bit string
+ encoding of an unsigned little-endian binary number.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>intValue</i> be the byte elements of <i>rawValue</i> concatenated and interpreted as a bit string
+ encoding of a binary little-endian 2’s complement number of bit length <i>elementSize</i> × 8.</li>
+ </ol>
+ </li>
+ <li>Return the Number value that corresponds to <i>intValue</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-setvalueinbuffer">
+ <h1><span class="secnum" id="sec-24.1.1.6"><a href="#sec-setvalueinbuffer"
+ title="link to this section">24.1.1.6</a></span> SetValueInBuffer ( arrayBuffer, byteIndex, type, value,
+ isLittleEndian )</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">SetValueInBuffer</span> takes five parameters, an
+ ArrayBuffer <var>arrayBuffer</var>, an integer <var>byteIndex</var>, a String <var>type</var>, a Number <i>value</i>, and
+ optionally a Boolean <var>isLittleEndian</var>. This operation performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>arrayBuffer</i>) is <b>false</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: There are sufficient bytes in <i>arrayBuffer</i> starting at
+ <i>byteIndex</i> to represent a value of <i>type</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>byteIndex</i> is a positive integer.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Number.</li>
+ <li>Let <i>block</i> be <i>arrayBuffer’s</i> [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>block</i> is not <b>undefined</b>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table 49</a>
+ for Element Type <i>type</i>.</li>
+ <li>If <i>isLittleEndian</i> is not present, set <i>isLittleEndian</i> to either <b>true</b> or <b>false</b>. The choice
+ is implementation dependent and should be the alternative that is most efficient for the implementation. An
+ implementation must use the same value each time this step is executed and the same value must be used for the
+ corresponding step in the <a href="#sec-getvaluefrombuffer">GetValueFromBuffer</a> abstract operation.</li>
+ <li>If <i>type</i> is <code>"Float32"</code>, then
+ <ol class="block">
+ <li>Set <i>rawValue</i> to a <a href="#sec-list-and-record-specification-type">List</a> containing the 4 bytes that
+ are the result of converting <i>value</i> to IEEE-754-2008 binary32 format using “Round to nearest, ties
+ to even” rounding mode. If <i>isLittleEndian</i> is <b>false</b>, the bytes are arranged in big endian
+ order. Otherwise, the bytes are arranged in little endian order. If <i>value</i> is <b>NaN</b>, <i>rawValue</i>
+ may be set to any implementation chosen non-signaling NaN encoding. An implementation must always choose the
+ same non-signaling NaN encoding for a distinct Not-a-Number value.</li>
+ </ol>
+ </li>
+ <li>Else, if <i>type</i> is <code>"Float64"</code>, then
+ <ol class="block">
+ <li>Set <i>rawValue</i> to a <a href="#sec-list-and-record-specification-type">List</a> containing the 8 bytes that
+ are the IEEE-754-2008 binary64 format encoding of <i>value</i>. If <i>isLittleEndian</i> is <b>false</b>, the
+ bytes are arranged in big endian order. Otherwise, the bytes are arranged in little endian order. If
+ <i>value</i> is <b>NaN</b>, <i>rawValue</i> may be set to any implementation chosen non-signaling NaN encoding.
+ An implementation must always choose the same non-signaling NaN encoding for a distinct Not-a-Number value.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>n</i> be the Number value of the Element Size specified in <a href="#table-49">Table 49</a> for Element
+ Type <i>type</i>.</li>
+ <li>Let <i>convOp</i> be the abstract operation named in the Conversion Operation column in <a
+ href="#table-49">Table 49</a> for Element Type <i>type</i>.</li>
+ <li>Let <i>intValue</i> be <i>convOp</i>(<i>value</i>).</li>
+ <li>If <i>intValue</i> ≥ 0, then
+ <ol class="block">
+ <li>Let <i>rawBytes</i> be a <a href="#sec-list-and-record-specification-type">List</a> containing the
+ <i>n</i>-byte binary encoding of <i>intValue</i>. If <i>isLittleEndian</i> is <b>false</b>, the bytes are
+ ordered in big endian order. Otherwise, the bytes are ordered in little endian order.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>rawBytes</i> be a <a href="#sec-list-and-record-specification-type">List</a> containing the
+ <i>n</i>-byte binary 2’s complement encoding of <i>intValue</i>. If <i>isLittleEndian</i> is
+ <b>false</b>, the bytes are ordered in big endian order. Otherwise, the bytes are ordered in little endian
+ order.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Store the individual bytes of <i>rawBytes</i> into <i>block</i>, in order, starting at
+ <i>block</i>[<i>byteIndex</i>].</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a> (<b>undefined</b>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-arraybuffer-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.1.2"><a href="#sec-arraybuffer-constructor"
+ title="link to this section">24.1.2</a></span> The ArrayBuffer Constructor</h1>
+
+ <p>The ArrayBuffer constructor is the %ArrayBuffer% intrinsic object and the initial value of the <code>ArrayBuffer</code>
+ property of the global object. When called as a constructor it creates and initializes a new ArrayBuffer object.
+ <code>ArrayBuffer</code> is not intended to be called as a function and will throw an exception when called in that
+ manner.</p>
+
+ <p>The <code>ArrayBuffer</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>ArrayBuffer</code> behaviour must include a <code>super</code> call to the <code>ArrayBuffer</code> constructor to
+ create and initialize subclass instances with the internal state necessary to support the <code><a
+ href="#sec-arraybuffer.prototype">ArrayBuffer.prototype</a></code> built-in methods.</p>
+ </div>
+
+ <section id="sec-arraybuffer-length">
+ <h1><span class="secnum" id="sec-24.1.2.1"><a href="#sec-arraybuffer-length"
+ title="link to this section">24.1.2.1</a></span> ArrayBuffer( length )</h1>
+
+ <p>ArrayBuffer called with argument <var>length</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>numberLength</i> be <a href="#sec-tonumber">ToNumber</a>(<i>length</i>).</li>
+ <li>Let <i>byteLength</i> be <a href="#sec-tolength">ToLength</a>(<i>numberLength</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>byteLength</i>).</li>
+ <li>If <a href="#sec-samevaluezero">SameValueZero</a>(<i>numberLength</i>, <i>byteLength</i>) is <b>false</b>, throw a
+ <b>RangeError</b> exception.</li>
+ <li>Return <a href="#sec-allocatearraybuffer">AllocateArrayBuffer</a>(NewTarget, <i>byteLength</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-arraybuffer-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.1.3"><a href="#sec-properties-of-the-arraybuffer-constructor"
+ title="link to this section">24.1.3</a></span> Properties of the ArrayBuffer Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ ArrayBuffer constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides its <code>length</code> property (whose value is 1), the ArrayBuffer constructor has the following
+ properties:</p>
+ </div>
+
+ <section id="sec-arraybuffer.isview">
+ <h1><span class="secnum" id="sec-24.1.3.1"><a href="#sec-arraybuffer.isview"
+ title="link to this section">24.1.3.1</a></span> ArrayBuffer.isView ( arg )</h1>
+
+ <p>The isView function takes one argument <var>arg</var>, and performs the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>arg</i>) is not Object, return <b>false</b>.</li>
+ <li>If <i>arg</i> has a [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, return <b>true</b>.</li>
+ <li>Return <b>false</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arraybuffer.prototype">
+ <h1><span class="secnum" id="sec-24.1.3.2"><a href="#sec-arraybuffer.prototype"
+ title="link to this section">24.1.3.2</a></span> ArrayBuffer.prototype</h1>
+
+ <p>The initial value of ArrayBuffer.prototype is the intrinsic object %ArrayBufferPrototype% (<a
+ href="#sec-properties-of-the-arraybuffer-prototype-object">24.1.4</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-get-arraybuffer-@@species">
+ <h1><span class="secnum" id="sec-24.1.3.3"><a href="#sec-get-arraybuffer-@@species"
+ title="link to this section">24.1.3.3</a></span> get ArrayBuffer [ @@species ]</h1>
+
+ <p><code>ArrayBuffer[@@species]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"get [Symbol.species]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> ArrayBuffer prototype methods normally use their <code>this</code> object’s
+ constructor to create a derived object. However, a subclass constructor may over-ride that default behaviour by
+ redefining its @@species property.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-arraybuffer-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.1.4"><a href="#sec-properties-of-the-arraybuffer-prototype-object"
+ title="link to this section">24.1.4</a></span> Properties of the ArrayBuffer Prototype Object</h1>
+
+ <p>The ArrayBuffer prototype object is the intrinsic object %ArrayBufferPrototype%. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the ArrayBuffer prototype object is the
+ intrinsic object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The ArrayBuffer
+ prototype object is an ordinary object. It does not have an [[ArrayBufferData]] or [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </div>
+
+ <section id="sec-get-arraybuffer.prototype.bytelength">
+ <h1><span class="secnum" id="sec-24.1.4.1"><a href="#sec-get-arraybuffer.prototype.bytelength"
+ title="link to this section">24.1.4.1</a></span> get ArrayBuffer.prototype.byteLength</h1>
+
+ <p><code>ArrayBuffer.prototype.byteLength</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have an [[ArrayBufferData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>O</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>length</i> be the value of <i>O</i>’s [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>length</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arraybuffer.prototype.constructor">
+ <h1><span class="secnum" id="sec-24.1.4.2"><a href="#sec-arraybuffer.prototype.constructor"
+ title="link to this section">24.1.4.2</a></span> ArrayBuffer.prototype.constructor</h1>
+
+ <p>The initial value of ArrayBuffer.prototype.constructor is the intrinsic object %ArrayBuffer%.</p>
+ </section>
+
+ <section id="sec-arraybuffer.prototype.slice">
+ <h1><span class="secnum" id="sec-24.1.4.3"><a href="#sec-arraybuffer.prototype.slice"
+ title="link to this section">24.1.4.3</a></span> ArrayBuffer.prototype.slice ( start, end )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have an [[ArrayBufferData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>O</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>len</i> be the value of <i>O</i>’s [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>relativeStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeStart</i>).</li>
+ <li>If <i>relativeStart</i> < 0, let <i>first</i> be max((<i>len</i> + <i>relativeStart</i>),0); else let
+ <i>first</i> be min(<i>relativeStart</i>, <i>len</i>).</li>
+ <li>If <i>end</i> is <b>undefined</b>, let <i>relativeEnd</i> be <i>len</i>; else let <i>relativeEnd</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>end</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>relativeEnd</i>).</li>
+ <li>If <i>relativeEnd</i> < 0, let <i>final</i> be max((<i>len</i> + <i>relativeEnd</i>),0); else let <i>final</i> be
+ min(<i>relativeEnd</i>, <i>len</i>).</li>
+ <li>Let <i>newLen</i> be max(<i>final</i>-<i>first</i>,0).</li>
+ <li>Let <i>ctor</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>O</i>, %ArrayBuffer%).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>ctor</i>).</li>
+ <li>Let <i>new</i> be <a href="#sec-construct">Construct</a>(<i>ctor</i>, «<i>newLen</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>new</i>).</li>
+ <li>If <i>new</i> does not have an [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>new</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>new</i>, <i>O</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If the value of <i>new</i>’s [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> < <i>newLen</i>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>NOTE: Side-effects of the above steps may have <span style="font-family: Times New Roman">detached</span>
+ <i>O</i>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>O</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>fromBuf</i> be the value of <i>O</i>’s [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>toBuf</i> be the value of <i>new</i>’s [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Perform <a href="#sec-copydatablockbytes">CopyDataBlockBytes</a>(<i>toBuf</i>, 0, <i>fromBuf</i>, <i>first</i>,
+ <i>newLen</i>).</li>
+ <li>Return <i>new</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-arraybuffer.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-24.1.4.4"><a href="#sec-arraybuffer.prototype-@@tostringtag"
+ title="link to this section">24.1.4.4</a></span> ArrayBuffer.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>ArrayBuffer</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-arraybuffer-instances">
+ <h1><span class="secnum" id="sec-24.1.5"><a href="#sec-properties-of-the-arraybuffer-instances"
+ title="link to this section">24.1.5</a></span> Properties of the ArrayBuffer Instances</h1>
+
+ <p>ArrayBuffer instances inherit properties from the ArrayBuffer prototype object. ArrayBuffer instances each have an
+ [[ArrayBufferData]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> and an
+ [[ArrayBufferByteLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>ArrayBuffer instances whose [[ArrayBufferData]] is <b>null</b> are considered to be detached and all operators to access
+ or modify data contained in the ArrayBuffer instance will fail.</p>
+ </section>
+ </section>
+
+ <section id="sec-dataview-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.2"><a href="#sec-dataview-objects" title="link to this section">24.2</a></span> DataView
+ Objects</h1>
+ </div>
+
+ <section id="sec-abstract-operations-for-dataview-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.2.1"><a href="#sec-abstract-operations-for-dataview-objects"
+ title="link to this section">24.2.1</a></span> Abstract Operations For DataView Objects</h1>
+ </div>
+
+ <section id="sec-getviewvalue">
+ <h1><span class="secnum" id="sec-24.2.1.1"><a href="#sec-getviewvalue" title="link to this section">24.2.1.1</a></span>
+ GetViewValue ( view, requestIndex, isLittleEndian, type )</h1>
+
+ <p>The abstract operation GetViewValue with arguments <var>view</var>, <var>requestIndex</var>, <var>isLittleEndian</var>,
+ and <var>type</var> is used by functions on DataView instances is to retrieve values from the view’s buffer. It
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>view</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>view</i> does not have a [[DataView]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>numberIndex</i> be <a href="#sec-tonumber">ToNumber</a>(<i>requestIndex</i>)</li>
+ <li>Let <i>getIndex</i> be <a href="#sec-tointeger">ToInteger</a>(<i>numberIndex</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>getIndex</i>).</li>
+ <li>If <i>numberIndex</i> ≠ <i>getIndex</i> or <i>getIndex</i> < 0, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>isLittleEndian</i> be <a href="#sec-toboolean">ToBoolean</a>(<i>isLittleEndian</i>).</li>
+ <li>Let <i>buffer</i> be the value of <i>view’s</i> [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>viewOffset</i> be the value of <i>view’s</i> [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>viewSize</i> be the value of <i>view’s</i> [[ByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table 49</a>
+ for Element Type <i>type</i>.</li>
+ <li>If <i>getIndex</i> +<i>elementSize</i> > <i>viewSize</i>, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>bufferIndex</i> be <i>getIndex</i> + <i>viewOffset</i>.</li>
+ <li>Return <a href="#sec-getvaluefrombuffer">GetValueFromBuffer</a>(<i>buffer</i>, <i>bufferIndex</i>, <i>type</i>,
+ <i>isLittleEndian</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-setviewvalue">
+ <h1><span class="secnum" id="sec-24.2.1.2"><a href="#sec-setviewvalue" title="link to this section">24.2.1.2</a></span>
+ SetViewValue ( view, requestIndex, isLittleEndian, type, value )</h1>
+
+ <p>The abstract operation SetViewValue with arguments <var>view</var>, <var>requestIndex</var>, <var>isLittleEndian</var>,
+ <var>type</var>, and <var>value</var> is used by functions on DataView instances to store values into the view’s
+ buffer. It performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>view</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>view</i> does not have a [[DataView]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>numberIndex</i> be <a href="#sec-tonumber">ToNumber</a>(<i>requestIndex</i>)</li>
+ <li>Let <i>getIndex</i> be <a href="#sec-tointeger">ToInteger</a>(<i>numberIndex</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>getIndex</i>).</li>
+ <li>If <i>numberIndex</i> ≠ <i>getIndex</i> or <i>getIndex</i> < 0, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>isLittleEndian</i> be <a href="#sec-toboolean">ToBoolean</a>(<i>isLittleEndian</i>).</li>
+ <li>Let <i>buffer</i> be the value of <i>view’s</i> [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>viewOffset</i> be the value of <i>view’s</i> [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>viewSize</i> be the value of <i>view’s</i> [[ByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>elementSize</i> be the Number value of the Element Size value specified in <a href="#table-49">Table 49</a>
+ for Element Type <i>type</i>.</li>
+ <li>If <i>getIndex</i> +<i>elementSize</i> > <i>viewSize</i>, throw a <b>RangeError</b> exception.</li>
+ <li>Let <i>bufferIndex</i> be <i>getIndex</i> + <i>viewOffset</i>.</li>
+ <li>Return <a href="#sec-setvalueinbuffer">SetValueInBuffer</a>(<i>buffer</i>, <i>bufferIndex</i>, <i>type</i>,
+ <i>value</i>, <i>isLittleEndian</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The algorithms for <a href="#sec-getviewvalue">GetViewValue</a> and SetViewValue are
+ identical except for their final steps.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-dataview-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.2.2"><a href="#sec-dataview-constructor"
+ title="link to this section">24.2.2</a></span> The DataView Constructor</h1>
+
+ <p>The DataView constructor is the %DataView% intrinsic object and the initial value of the <code>DataView</code> property
+ of the global object. When called as a constructor it creates and initializes a new DataView object. <code>DataView</code>
+ is not intended to be called as a function and will throw an exception when called in that manner.</p>
+
+ <p>The <code>DataView</code> constructor is designed to be subclassable. It may be used as the value of an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>DataView</code> behaviour must include a <code>super</code> call to the <code>DataView</code> constructor to create
+ and initialize subclass instances with the internal state necessary to support the <code><a
+ href="#sec-dataview.prototype">DataView.prototype</a></code> built-in methods.</p>
+ </div>
+
+ <section id="sec-dataview-buffer-byteoffset-bytelength">
+ <h1><span class="secnum" id="sec-24.2.2.1"><a href="#sec-dataview-buffer-byteoffset-bytelength"
+ title="link to this section">24.2.2.1</a></span> DataView (buffer [ , byteOffset [ , byteLength ] ] )</h1>
+
+ <p><code>DataView</code> called with arguments <span style="font-family: Times New Roman"><i>buffer</i>,
+ <i>byteOffset</i>, and <i>length</i></span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>buffer</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>buffer</i> does not have an [[ArrayBufferData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>numberOffset</i> be <a href="#sec-tonumber">ToNumber</a>(<i>byteOffset</i>).</li>
+ <li>Let <i>offset</i> be <a href="#sec-tointeger">ToInteger</a>(<i>numberOffset</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>offset</i>).</li>
+ <li>If <i>numberOffset</i> ≠ <i>offset</i> or <i>offset</i> < 0, throw a <b>RangeError</b> exception.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>bufferByteLength</i> be the value of <i>buffer’s</i> [[ArrayBufferByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>offset</i> > <i>bufferByteLength</i>, throw a <b>RangeError</b> exception.</li>
+ <li>If <i>byteLength</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>viewByteLength</i> be <i>bufferByteLength</i> – <i>offset</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>viewLength</i> be <a href="#sec-tolength">ToLength</a>(<i>byteLength</i>)<i>.</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>viewLength</i>).</li>
+ <li>Let <i>viewByteLength</i> be <i>viewLength</i>.</li>
+ <li>If <i>offset</i>+<i>viewByteLength</i> > <i>bufferByteLength</i>, throw a <b>RangeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>Let <i>O</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%DataViewPrototype%"</code>, «‍[[DataView]], [[ViewedArrayBuffer]], [[ByteLength]],
+ [[ByteOffset]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Set <i>O’s</i> [[DataView]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <b>true</b>.</li>
+ <li>Set <i>O’s</i> [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>buffer</i>.</li>
+ <li>Set <i>O</i>’s [[ByteLength]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>viewByteLength</i>.</li>
+ <li>Set <i>O</i>’s [[ByteOffset]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <i>offset</i>.</li>
+ <li>Return <i>O</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-dataview-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.2.3"><a href="#sec-properties-of-the-dataview-constructor"
+ title="link to this section">24.2.3</a></span> Properties of the DataView Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ <code>DataView</code> constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is 3), the DataView constructor has the following properties:</p>
+ </div>
+
+ <section id="sec-dataview.prototype">
+ <h1><span class="secnum" id="sec-24.2.3.1"><a href="#sec-dataview.prototype"
+ title="link to this section">24.2.3.1</a></span> DataView.prototype</h1>
+
+ <p>The initial value of <code>DataView.prototype</code> is the intrinsic object %DataViewPrototype% (<a
+ href="#sec-properties-of-the-dataview-prototype-object">24.2.4</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-dataview-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.2.4"><a href="#sec-properties-of-the-dataview-prototype-object"
+ title="link to this section">24.2.4</a></span> Properties of the DataView Prototype Object</h1>
+
+ <p>The DataView prototype object is the intrinsic object %DataViewPrototype%. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the DataView prototype object is the intrinsic
+ object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The DataView prototype
+ object is an ordinary object. It does not have a [[DataView]], [[ViewedArrayBuffer]], [[ByteLength]], or [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+ </div>
+
+ <section id="sec-get-dataview.prototype.buffer">
+ <h1><span class="secnum" id="sec-24.2.4.1"><a href="#sec-get-dataview.prototype.buffer"
+ title="link to this section">24.2.4.1</a></span> get DataView.prototype.buffer</h1>
+
+ <p><code>DataView.prototype.buffer</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>buffer</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-get-dataview.prototype.bytelength">
+ <h1><span class="secnum" id="sec-24.2.4.2"><a href="#sec-get-dataview.prototype.bytelength"
+ title="link to this section">24.2.4.2</a></span> get DataView.prototype.byteLength</h1>
+
+ <p><code>DataView</code>.<code>prototype.byteLength</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>size</i> be the value of <i>O</i>’s [[ByteLength]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>size</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-get-dataview.prototype.byteoffset">
+ <h1><span class="secnum" id="sec-24.2.4.3"><a href="#sec-get-dataview.prototype.byteoffset"
+ title="link to this section">24.2.4.3</a></span> get DataView.prototype.byteOffset</h1>
+
+ <p><code>DataView</code>.<code>prototype.byteOffset</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>O</i> does not have a [[ViewedArrayBuffer]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>buffer</i> be the value of <i>O</i>’s [[ViewedArrayBuffer]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-isdetachedbuffer">IsDetachedBuffer</a>(<i>buffer</i>) is <b>true</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>offset</i> be the value of <i>O</i>’s [[ByteOffset]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Return <i>offset</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.constructor">
+ <h1><span class="secnum" id="sec-24.2.4.4"><a href="#sec-dataview.prototype.constructor"
+ title="link to this section">24.2.4.4</a></span> DataView.prototype.constructor</h1>
+
+ <p>The initial value of <code>DataView.prototype.constructor</code> is the intrinsic object %DataView%.</p>
+ </section>
+
+ <section id="sec-dataview.prototype.getfloat32">
+ <h1><span class="secnum" id="sec-24.2.4.5"><a href="#sec-dataview.prototype.getfloat32"
+ title="link to this section">24.2.4.5</a></span> DataView.prototype.getFloat32 ( byteOffset [ , littleEndian ] )</h1>
+
+ <p>When the <code>getFloat32</code> method is called with argument <var>byteOffset</var> and optional argument
+ <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Float32"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.getfloat64">
+ <h1><span class="secnum" id="sec-24.2.4.6"><a href="#sec-dataview.prototype.getfloat64"
+ title="link to this section">24.2.4.6</a></span> DataView.prototype.getFloat64 ( byteOffset [ , littleEndian ] )</h1>
+
+ <p>When the <code>getFloat64</code> method is called with argument <var>byteOffset</var> and optional argument
+ <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Float64"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.getint8">
+ <h1><span class="secnum" id="sec-24.2.4.7"><a href="#sec-dataview.prototype.getint8"
+ title="link to this section">24.2.4.7</a></span> DataView.prototype.getInt8 ( byteOffset )</h1>
+
+ <p>When the <code>getInt8</code> method is called with argument <var>byteOffset</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <b>true</b>,
+ <code>"Int8"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.getint16">
+ <h1><span class="secnum" id="sec-24.2.4.8"><a href="#sec-dataview.prototype.getint16"
+ title="link to this section">24.2.4.8</a></span> DataView.prototype.getInt16 ( byteOffset [ , littleEndian ] )</h1>
+
+ <p>When the <code>getInt16</code> method is called with argument <var>byteOffset</var> and optional argument
+ <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Int16"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.getint32">
+ <h1><span class="secnum" id="sec-24.2.4.9"><a href="#sec-dataview.prototype.getint32"
+ title="link to this section">24.2.4.9</a></span> DataView.prototype.getInt32 ( byteOffset [ , littleEndian ] )</h1>
+
+ <p>When the <code>getInt32</code> method is called with argument <var>byteOffset</var> and optional argument
+ <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>undefined</b>.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Int32"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.getuint8">
+ <h1><span class="secnum" id="sec-24.2.4.10"><a href="#sec-dataview.prototype.getuint8"
+ title="link to this section">24.2.4.10</a></span> DataView.prototype.getUint8 ( byteOffset )</h1>
+
+ <p>When the <code>getUint8</code> method is called with argument <var>byteOffset</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <b>true</b>,
+ <code>"Uint8"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.getuint16">
+ <h1><span class="secnum" id="sec-24.2.4.11"><a href="#sec-dataview.prototype.getuint16"
+ title="link to this section">24.2.4.11</a></span> DataView.prototype.getUint16 ( byteOffset [ , littleEndian ] )</h1>
+
+ <p>When the <code>getUint16</code> method is called with argument <var>byteOffset</var> and optional argument
+ <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Uint16"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.getuint32">
+ <h1><span class="secnum" id="sec-24.2.4.12"><a href="#sec-dataview.prototype.getuint32"
+ title="link to this section">24.2.4.12</a></span> DataView.prototype.getUint32 ( byteOffset [ , littleEndian ] )</h1>
+
+ <p>When the <code>getUint32</code> method is called with argument <var>byteOffset</var> and optional argument
+ <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-getviewvalue">GetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Uint32"</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setfloat32">
+ <h1><span class="secnum" id="sec-24.2.4.13"><a href="#sec-dataview.prototype.setfloat32"
+ title="link to this section">24.2.4.13</a></span> DataView.prototype.setFloat32 ( byteOffset, value [ , littleEndian ]
+ )</h1>
+
+ <p>When the <code>setFloat32</code> method is called with arguments <var>byteOffset</var> and <var>value</var> and
+ optional argument <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Float32"</code>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setfloat64">
+ <h1><span class="secnum" id="sec-24.2.4.14"><a href="#sec-dataview.prototype.setfloat64"
+ title="link to this section">24.2.4.14</a></span> DataView.prototype.setFloat64 ( byteOffset, value [ , littleEndian ]
+ )</h1>
+
+ <p>When the <code>setFloat64</code> method is called with arguments <var>byteOffset</var> and <var>value</var> and
+ optional argument <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Float64"</code>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setint8">
+ <h1><span class="secnum" id="sec-24.2.4.15"><a href="#sec-dataview.prototype.setint8"
+ title="link to this section">24.2.4.15</a></span> DataView.prototype.setInt8 ( byteOffset, value )</h1>
+
+ <p>When the <code>setInt8</code> method is called with arguments <var>byteOffset</var> and <var>value</var> the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <b>true</b>, <code>"Int8"</code>,
+ <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setint16">
+ <h1><span class="secnum" id="sec-24.2.4.16"><a href="#sec-dataview.prototype.setint16"
+ title="link to this section">24.2.4.16</a></span> DataView.prototype.setInt16 ( byteOffset, value [ , littleEndian ]
+ )</h1>
+
+ <p>When the <code>setInt16</code> method is called with arguments <var>byteOffset</var> and <var>value</var> and optional
+ argument <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Int16"</code>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setint32">
+ <h1><span class="secnum" id="sec-24.2.4.17"><a href="#sec-dataview.prototype.setint32"
+ title="link to this section">24.2.4.17</a></span> DataView.prototype.setInt32 ( byteOffset, value [ , littleEndian ]
+ )</h1>
+
+ <p>When the <code>setInt32</code> method is called with arguments <var>byteOffset</var> and <var>value</var> and optional
+ argument <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Int32"</code>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setuint8">
+ <h1><span class="secnum" id="sec-24.2.4.18"><a href="#sec-dataview.prototype.setuint8"
+ title="link to this section">24.2.4.18</a></span> DataView.prototype.setUint8 ( byteOffset, value )</h1>
+
+ <p>When the <code>setUint8</code> method is called with arguments <var>byteOffset</var> and <var>value</var> the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <b>true</b>, <code>"Uint8"</code>,
+ <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setuint16">
+ <h1><span class="secnum" id="sec-24.2.4.19"><a href="#sec-dataview.prototype.setuint16"
+ title="link to this section">24.2.4.19</a></span> DataView.prototype.setUint16 ( byteOffset, value [ , littleEndian ]
+ )</h1>
+
+ <p>When the <code>setUint16</code> method is called with arguments <var>byteOffset</var> and <var>value</var> and optional
+ argument <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Uint16"</code>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype.setuint32">
+ <h1><span class="secnum" id="sec-24.2.4.20"><a href="#sec-dataview.prototype.setuint32"
+ title="link to this section">24.2.4.20</a></span> DataView.prototype.setUint32 ( byteOffset, value [ , littleEndian ]
+ )</h1>
+
+ <p>When the <code>setUint32</code> method is called with arguments <var>byteOffset</var> and <var>value</var> and optional
+ argument <i>littleEndian</i> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>v</i> be the <b>this</b> value.</li>
+ <li>If <i>littleEndian</i> is not present, let <i>littleEndian</i> be <b>false</b>.</li>
+ <li>Return <a href="#sec-setviewvalue">SetViewValue</a>(<i>v</i>, <i>byteOffset</i>, <i>littleEndian</i>,
+ <code>"Uint32"</code>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-dataview.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-24.2.4.21"><a href="#sec-dataview.prototype-@@tostringtag"
+ title="link to this section">24.2.4.21</a></span> DataView.prototype[ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>DataView</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-dataview-instances">
+ <h1><span class="secnum" id="sec-24.2.5"><a href="#sec-properties-of-dataview-instances"
+ title="link to this section">24.2.5</a></span> Properties of DataView Instances</h1>
+
+ <p>DataView instances are ordinary objects that inherit properties from the DataView prototype object. DataView instances
+ each have a [[DataView]], [[ViewedArrayBuffer]], [[ByteLength]], and [[ByteOffset]] internal slots.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The value of the [[DataView]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is not used within this specification. The simple
+ presence of that <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is used within the
+ specification to identify objects created using the <code>DataView</code> constructor.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-json-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.3"><a href="#sec-json-object" title="link to this section">24.3</a></span> The JSON
+ Object</h1>
+
+ <p>The JSON object is the %JSON% intrinsic object and the initial value of the <code>JSON</code> property of the global
+ object.The JSON object is a single ordinary object that contains two functions, <b>parse</b> and <b>stringify</b>, that are
+ used to parse and construct JSON texts. The JSON Data Interchange Format is defined in ECMA-404. The JSON interchange format
+ used in this specification is exactly that described by ECMA-404.</p>
+
+ <p>Conforming implementations of <code><a href="#sec-json.parse">JSON.parse</a></code> and <code><a
+ href="#sec-json.stringify">JSON.stringify</a></code> must support the exact interchange format described in this
+ specification without any deletions or extensions to the format.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the JSON
+ object is the intrinsic object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The
+ value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the JSON object
+ is set to <b>true</b>.</p>
+
+ <p>The JSON object does not have a [[Construct]] internal method; it is not possible to use the JSON object as a constructor
+ with the <code>new</code> operator.</p>
+
+ <p>The JSON object does not have a [[Call]] internal method; it is not possible to invoke the JSON object as a function.</p>
+ </div>
+
+ <section id="sec-json.parse">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.3.1"><a href="#sec-json.parse" title="link to this section">24.3.1</a></span>
+ JSON.parse ( text [ , reviver ] )</h1>
+
+ <p>The <code>parse</code> function parses a JSON text (a JSON-formatted String) and produces an ECMAScript value. The JSON
+ format is a subset of the syntax for ECMAScript literals, Array Initializers and Object Initializers. After parsing, JSON
+ objects are realized as ECMAScript objects. JSON arrays are realized as ECMAScript Array instances. JSON strings, numbers,
+ booleans, and null are realized as ECMAScript Strings, Numbers, Booleans, and <b>null</b>.</p>
+
+ <p>The optional <i>reviver</i> parameter is a function that takes two parameters, <i>key</i> and <i>value</i>. It can
+ filter and transform the results. It is called with each of the <i>key</i>/<i>value</i> pairs produced by the parse, and
+ its return value is used instead of the original value. If it returns what it received, the structure is not modified. If
+ it returns <b>undefined</b> then the property is deleted from the result.</p>
+
+ <ol class="proc">
+ <li>Let <i>JText</i> be <a href="#sec-tostring">ToString</a>(<i>text</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>JText</i>).</li>
+ <li>Parse <i>JText</i> interpreted as UTF-16 encoded Unicode points (<a
+ href="#sec-ecmascript-language-types-string-type">6.1.4</a>) as a JSON text as specified in <br>ECMA-404. Throw a
+ <b>SyntaxError</b> exception if <i>JText</i> is not a valid JSON text as defined in that specification.</li>
+ <li>Let <i>scriptText</i> be the result of concatenating <code>"("</code>, <i>JText</i>, and <code>");"</code>.</li>
+ <li>Let <i>completion</i> be the result of parsing and evaluating <i>scriptText</i> as if it was the source text of an
+ ECMAScript <i>Script</i>. but using the alternative definition of <i>DoubleStringCharacter</i> provided below. The
+ extended PropertyDefinitionEvaluation semantics defined in <a
+ href="#sec-__proto__-property-names-in-object-initializers">B.3.1</a> must not be used during the evaluation.</li>
+ <li>Let <i>unfiltered</i> be <i>completion</i>.[[value]].</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>unfiltered</i> will be either a primitive value or an object
+ that is defined by either an <i>ArrayLiteral</i> or an <i>ObjectLiteral</i>.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>reviver</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>root</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%ObjectPrototype%).</li>
+ <li>Let <i>rootName</i> be the empty String.</li>
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>root</i>, <i>rootName</i>,
+ <i>unfiltered</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is <b>true</b>.</li>
+ <li>Return <a href="#sec-internalizejsonproperty">InternalizeJSONProperty</a>(<i>root</i>, <i>rootName</i>).</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Return <i>unfiltered</i>.</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>JSON allows Unicode code units 0x2028 (LINE SEPARATOR) and 0x2029 (PARAGRAPH SEPARATOR) to directly appear in <span
+ class="nt">String</span> literals without using an escape sequence. This is enabled by using the following alternative
+ definition of <span class="nt">DoubleStringCharacter</span> when parsing <var>scriptText</var> in step 5:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DoubleStringCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">"</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <span class="gprose">U+0000 through U+001F</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">EscapeSequence</span></div>
+ </div>
+
+ <ul>
+ <li>
+ <p>The SV of <span class="prod"><span class="nt">DoubleStringCharacter</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">"</code> <span
+ class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span></span> U+0000 <b>through</b> U+001F
+ is the <a href="#sec-utf16encoding">UTF16Encoding</a> (<a href="#sec-utf16encoding">10.1.1</a>) of the code point
+ value of <i>SourceCharacter</i>.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The syntax of a valid JSON text is a subset of the ECMAScript <i>PrimaryExpression</i>
+ syntax. Hence a valid JSON text is also a valid <i>PrimaryExpression</i>. Step 3 above verifies that <i>JText</i>
+ conforms to that subset. When <i>scriptText</i> is parsed and evaluated as a <i>Script</i> the result will be either a
+ String, Number, Boolean, or Null primitive value or an Object defined as if by an <i>ArrayLiteral</i> or
+ <i>ObjectLiteral</i>.</p>
+ </div>
+ </div>
+
+ <section id="sec-internalizejsonproperty">
+ <h1><span class="secnum" id="sec-24.3.1.1"><a href="#sec-internalizejsonproperty"
+ title="link to this section">24.3.1.1</a></span> Runtime Semantics: InternalizeJSONProperty( holder, name)</h1>
+
+ <p>The abstract operation InternalizeJSONProperty is a recursive abstract operation that takes two parameters: a
+ <var>holder</var> object and the String <var>name</var> of a property in that object. InternalizeJSONProperty uses the
+ value of <var>reviver</var> that was originally passed to the above parse function.</p>
+
+ <ol class="proc">
+ <li>Let <i>val</i> be <a href="#sec-get-o-p">Get</a>(<i>holder</i>, <i>name</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>val</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>val</i>) is Object, then
+ <ol class="block">
+ <li>Let <i>isArray</i> be <a href="#sec-isarray">IsArray</a>(<i>val</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isArray</i>).</li>
+ <li>If <i>isArray</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Set <i>I</i> to 0.</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>val</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Repeat while <i>I</i> < <i>len</i>,
+ <ol class="block">
+ <li>Let <i>newElement</i> be InternalizeJSONProperty(<i>val</i>, <a
+ href="#sec-tostring">ToString</a>(<i>I</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>newElement</i>).</li>
+ <li>If <i>newElement</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>val</i>.[[Delete]](<a href="#sec-tostring">ToString</a>(<i>I</i>)).</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>val</i>, <a
+ href="#sec-tostring">ToString</a>(<i>I</i>), <i>newElement</i>).</li>
+ <li>NOTE This algorithm intentionally does not throw an exception if status is <b>false</b>.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>Add 1 to <i>I</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>keys</i> be <a href="#sec-enumerableownnames">EnumerableOwnNames</a>(<i>val</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keys</i>).</li>
+ <li>For each String <i>P</i> in <i>keys</i> do,
+ <ol class="block">
+ <li>Let <i>newElement</i> be InternalizeJSONProperty(<i>val</i>, <i>P</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>newElement</i>).</li>
+ <li>If <i>newElement</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>val</i>.[[Delete]](<i>P</i>).</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>val</i>, <i>P</i>,
+ <i>newElement</i>).</li>
+ <li>NOTE This algorithm intentionally does not throw an exception if status is <b>false</b>.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-call">Call</a>(<i>reviver</i>, <i>holder</i>, «<i>name</i>, <i>val</i>»).</li>
+ </ol>
+
+ <p>It is not permitted for a conforming implementation of <code><a href="#sec-json.parse">JSON.parse</a></code> to extend
+ the JSON grammars. If an implementation wishes to support a modified or extended JSON interchange format it must do so by
+ defining a different parse function.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> In the case where there are duplicate name Strings within an object, lexically preceding
+ values for the same key shall be overwritten.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-json.stringify">
+ <div class="front">
+ <h1><span class="secnum" id="sec-24.3.2"><a href="#sec-json.stringify" title="link to this section">24.3.2</a></span>
+ JSON.stringify ( value [ , replacer [ , space ] ] )</h1>
+
+ <p>The <code>stringify</code> function returns a String in UTF-16 encoded JSON format representing an ECMAScript value. It
+ can take three parameters. The <var>value</var> parameter is an ECMAScript value, which is usually an object or array,
+ although it can also be a String, Boolean, Number or <b>null</b>. The optional <var>replacer</var> parameter is either a
+ function that alters the way objects and arrays are stringified, or an array of Strings and Numbers that acts as a white
+ list for selecting the object properties that will be stringified. The optional <var>space</var> parameter is a String or
+ Number that allows the result to have white space injected into it to improve human readability.</p>
+
+ <p>These are the steps in stringifying an object:</p>
+
+ <ol class="proc">
+ <li>Let <i>stack</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>indent</i> be the empty String.</li>
+ <li>Let <i>PropertyList</i> and <i>ReplacerFunction</i> be <b>undefined</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>replacer</i>) is Object, then
+ <ol class="block">
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>replacer</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>ReplacerFunction</i> be <i>replacer</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>isArray</i> be <a href="#sec-isarray">IsArray</a>(<i>replacer</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isArray</i>).</li>
+ <li>If <i>isArray</i> is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>PropertyList</i> be an empty <a href="#sec-list-and-record-specification-type">List</a></li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>replacer</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat while <i>k</i><<i>len</i>.
+ <ol class="block">
+ <li>Let <i>v</i> be <a href="#sec-get-o-p">Get</a>(<i>replacer</i>, <a
+ href="#sec-tostring">ToString</a>(<i>k</i>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>v</i>).</li>
+ <li>Let <i>item</i> be <b>undefined</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>v</i>) is String, let <i>item</i> be
+ <i>v.</i></li>
+ <li>Else if <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>v</i>) is Number, let
+ <i>item</i> be <a href="#sec-tostring">ToString</a>(<i>v</i>).</li>
+ <li>Else if <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>v</i>) is Object, then
+ <ol class="block">
+ <li>If <i>v</i> has a [[StringData]] or [[NumberData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, let <i>item</i> be <a
+ href="#sec-tostring">ToString</a>(<i>v</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>item</i>).</li>
+ </ol>
+ </li>
+ <li>If <i>item</i> is not <b>undefined</b> and <i>item</i> is not currently an element of
+ <i>PropertyList</i>, then
+ <ol class="block">
+ <li>Append <i>item</i> to the end of <i>PropertyList</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>k</i> be <i>k</i>+1.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>space</i>) is Object, then
+ <ol class="block">
+ <li>If <i>space</i> has a [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, then
+ <ol class="block">
+ <li>Let <i>space</i> be <a href="#sec-tonumber">ToNumber</a>(<i>space</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>space</i>).</li>
+ </ol>
+ </li>
+ <li>Else if <i>space</i> has a [[StringData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, then
+ <ol class="block">
+ <li>Let <i>space</i> be <a href="#sec-tostring">ToString</a>(<i>space</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>space</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>space</i>) is Number, then
+ <ol class="block">
+ <li>Let <i>space</i> be min(10, <a href="#sec-tointeger">ToInteger</a>(<i>space</i>)).</li>
+ <li>Set <i>gap</i> to a String containing <i>space</i> occurrences of code unit 0x0020 (SPACE). This will be the
+ empty String if <i>space</i> is less than 1.</li>
+ </ol>
+ </li>
+ <li>Else if <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>space</i>) is String, then
+ <ol class="block">
+ <li>If the number of elements in <i>space</i> is 10 or less, set <i>gap</i> to <i>space</i> otherwise set <i>gap</i>
+ to a String consisting of the first 10 elements of <i>space</i>.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Set <i>gap</i> to the empty String.</li>
+ </ol>
+ </li>
+ <li>Let <i>wrapper</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%ObjectPrototype%).</li>
+ <li>Let <i>status</i> be <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>wrapper</i>, the empty String,
+ <i>value</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is <b>true</b>.</li>
+ <li>Return <a href="#sec-serializejsonproperty">SerializeJSONProperty</a>(the empty String, <i>wrapper</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> JSON structures are allowed to be nested to any depth, but they must be acyclic. If
+ <i>value</i> is or contains a cyclic structure, then the stringify function must throw a <b>TypeError</b> exception.
+ This is an example of a value that cannot be stringified:</p>
+
+ <pre>a = [];</pre>
+ <pre>a[0] = a;</pre>
+ <pre>my_text = JSON.stringify(a); // This must throw a TypeError.</pre>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> Symbolic primitive values are rendered as follows:</p>
+
+ <ul>
+ <li>The <b>null</b> value is rendered in JSON text as the String <code>null</code>.</li>
+ <li>The <b>undefined</b> value is not rendered.</li>
+ <li>The <b>true</b> value is rendered in JSON text as the String <code>true</code>.</li>
+ <li>The <b>false</b> value is rendered in JSON text as the String <code>false</code>.</li>
+ </ul>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 3</span> String values are wrapped in QUOTATION MARK (<code>"</code>) code units. The code
+ units <code>"</code> and <code>\</code> are escaped with <code>\</code> prefixes. Control characters code units are
+ replaced with escape sequences <code>\u</code>HHHH, or with the shorter forms, <code>\b</code> (backspace),
+ <code>\f</code> (form feed), <code>\n</code> (LINE FEED), <code>\r</code> (carriage return), <code>\t</code> (CHARACTER
+ TABULATION).</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 4</span> Finite numbers are stringified as if by calling <a
+ href="#sec-tostring">ToString</a><b>(</b><i>number</i><b>)</b>. <b>NaN</b> and Infinity regardless of sign are
+ represented as the String <code>null</code>.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 5</span> Values that do not have a JSON representation (such as <b>undefined</b> and functions)
+ do not produce a String. Instead they produce the <b>undefined</b> value. In arrays these values are represented as the
+ String <code>null</code>. In objects an unrepresentable value causes the property to be excluded from
+ stringification.</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 6</span> An object is rendered as an left CURLY BRACKET followed by zero or more properties,
+ separated with a COMMA, closed with a right CURLY BRACKET. A property is a quoted String representing the key or
+ property name, a colon, and then the stringified property value. An array is rendered as an opening left square bracket
+ followed by zero or more values, separated with a COMMA, closed with a right square bracket.</p>
+ </div>
+ </div>
+
+ <section id="sec-serializejsonproperty">
+ <h1><span class="secnum" id="sec-24.3.2.1"><a href="#sec-serializejsonproperty"
+ title="link to this section">24.3.2.1</a></span> Runtime Semantics: SerializeJSONProperty (key, holder )</h1>
+
+ <p>The abstract operation SerializeJSONProperty with arguments <var>key</var>, <span style="font-family: Times New
+ Roman">and</span> <var>holder</var> has access to <span class="nt">ReplacerFunction</span> from the invocation of the
+ <code>stringify</code> method. Its algorithm is as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>value</i> be <a href="#sec-get-o-p">Get</a>(<i>holder</i>, <i>key</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object, then
+ <ol class="block">
+ <li>Let <i>toJSON</i> be <a href="#sec-get-o-p">Get</a>(<i>value</i>, <code>"toJSON"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>toJSON</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>toJSON</i>) is <b>true</b>
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-call">Call</a>(<i>toJSON</i>, <i>value</i>,
+ «<i>key</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>ReplacerFunction</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-call">Call</a>(<i>ReplacerFunction</i>, <i>holder</i>, «<i>key</i>,
+ <i>value</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object, then
+ <ol class="block">
+ <li>If <i>value</i> has a [[NumberData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, then
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-tonumber">ToNumber</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ <li>Else if <i>value</i> has a [[StringData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, then
+ <ol class="block">
+ <li>Let <i>value</i> be <a href="#sec-tostring">ToString</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ <li>Else if <i>value</i> has a [[BooleanData]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, then
+ <ol class="block">
+ <li>Let <i>value</i> be the value of the [[BooleanData]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>value</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>value</i> is <b>null</b>, return <code>"null"</code>.</li>
+ <li>If <i>value</i> is <b>true</b>, return <code>"true"</code>.</li>
+ <li>If <i>value</i> is <b>false</b>, return <code>"false"</code>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is String, return <a
+ href="#sec-quotejsonstring">QuoteJSONString</a>(<i>value</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Number, then
+ <ol class="block">
+ <li>If <i>value</i> is finite, return <a href="#sec-tostring">ToString</a>(<i>value</i>).</li>
+ <li>Else, return <code>"null"</code>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>value</i>) is Object, and <a
+ href="#sec-iscallable">IsCallable</a>(<i>value</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>isArray</i> be <a href="#sec-isarray">IsArray</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>isArray</i>).</li>
+ <li>If <i>isArray</i> is <b>true</b>, return <a
+ href="#sec-serializejsonarray">SerializeJSONArray</a>(<i>value</i>).</li>
+ <li>Else, return <a href="#sec-serializejsonobject">SerializeJSONObject</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-quotejsonstring">
+ <h1><span class="secnum" id="sec-24.3.2.2"><a href="#sec-quotejsonstring" title="link to this section">24.3.2.2</a></span>
+ Runtime Semantics: QuoteJSONString Abstract Operation</h1>
+
+ <p>The abstract operation QuoteJSONString with argument <var>value</var> wraps a String value in QUOTATION MARK code units
+ and escapes certain other code units within it.</p>
+
+ <ol class="proc">
+ <li>Let <i>product</i> be code unit 0x0022 (QUOTATION MARK).</li>
+ <li>For each code unit <i>C</i> in <i>value</i>
+ <ol class="block">
+ <li>If <i>C</i> is 0x0022 (quOTATion mark) or 0x005C (reverse solidus)
+ <ol class="block">
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and code unit 0x005C (reverse solidus).</li>
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and <i>C</i>.</li>
+ </ol>
+ </li>
+ <li>Else if <i>C</i> is 0x0008 (backspace), 0x000C (form feed), 0x000A (LINE FEED), 0x000D (carriage return), or
+ 0x000B (LINE TABULATION)
+ <ol class="block">
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and code unit 0x005C (reverse solidus).</li>
+ <li>Let <i>abbrev</i> be the string value corresponding to the value of <i>C</i> as follows:
+ <table class="lightweight">
+ <tr>
+ <td>backspace</td>
+ <td><span class="string value">"b"</span></td>
+ </tr>
+ <tr>
+ <td>form feed (FF)</td>
+ <td><span class="string value">"f"</span></td>
+ </tr>
+ <tr>
+ <td>LINE FEED (LF)</td>
+ <td><span class="string value">"n"</span></td>
+ </tr>
+ <tr>
+ <td>carriage return (CR)</td>
+ <td><span class="string value">"r"</span></td>
+ </tr>
+ <tr>
+ <td>LINE TABULATION</td>
+ <td><span class="string value">"t"</span></td>
+ </tr>
+ </table>
+ </li>
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and <i>abbrev</i>.</li>
+ </ol>
+ </li>
+ <li>Else if <i>C</i> has a code unit value less than 0x0020 (SPACE)
+ <ol class="block">
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and code unit 0x005C (reverse solidus).</li>
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and <code>"u"</code>.</li>
+ <li>Let <i>hex</i> be the string result of converting the numeric code unit value of <i>C</i> to a String of
+ four hexadecimal digits. Alphabetic hexadecimal digits are presented as lowercase Latin letters.</li>
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and <i>hex</i>.</li>
+ </ol>
+ </li>
+ <li>Else
+ <ol class="block">
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and <i>C</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>product</i> be the concatenation of <i>product</i> and code unit 0x0022 (QUOTATION MARK).</li>
+ <li>Return <i>product</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-serializejsonobject">
+ <h1><span class="secnum" id="sec-24.3.2.3"><a href="#sec-serializejsonobject"
+ title="link to this section">24.3.2.3</a></span> Runtime Semantics: SerializeJSONObject ( value )</h1>
+
+ <p>The abstract operation SerializeJSONObject with argument <var>value</var> serializes an object. It has access to the
+ <var>stack</var>, <var>indent</var>, <var>gap</var>, and <span class="nt">PropertyList</span> of the invocation of the
+ <code>stringify</code> method.</p>
+
+ <ol class="proc">
+ <li>If <i>stack</i> contains <i>value</i>, throw a <b>TypeError</b> exception because the structure is cyclical.</li>
+ <li>Append <i>value</i> to <i>stack</i>.</li>
+ <li>Let <i>stepback</i> be <i>indent</i>.</li>
+ <li>Let <i>indent</i> be the concatenation of <i>indent</i> and <i>gap</i>.</li>
+ <li>If <i>PropertyList</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>K</i> be <i>PropertyList</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>K</i> be <a href="#sec-enumerableownnames">EnumerableOwnNames</a>(<i>value</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>partial</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>For each element <i>P</i> of <i>K</i>,
+ <ol class="block">
+ <li>Let <i>strP</i> be <a href="#sec-serializejsonproperty">SerializeJSONProperty</a>(<i>P</i>, <i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>strP</i>).</li>
+ <li>If <i>strP</i> is not <b>undefined</b>, then
+ <ol class="block">
+ <li>Let <i>member</i> be <a href="#sec-quotejsonstring">QuoteJSONString</a>(<i>P</i>).</li>
+ <li>Let <i>member</i> be the concatenation of <i>member</i> and the string <code>":</code>".</li>
+ <li>If <i>gap</i> is not the empty String, then
+ <ol class="block">
+ <li>Let <i>member</i> be the concatenation of <i>member</i> and code unit 0x0020 (SPACE).</li>
+ </ol>
+ </li>
+ <li>Let <i>member</i> be the concatenation of <i>member</i> and <i>strP</i>.</li>
+ <li>Append <i>member</i> to <i>partial</i>.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>If <i>partial</i> is empty, then
+ <ol class="block">
+ <li>Let <i>final</i> be <code>"{}"</code>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>If <i>gap</i> is the empty String
+ <ol class="block">
+ <li>Let <i>properties</i> be a String formed by concatenating all the element Strings of <i>partial</i> with
+ each adjacent pair of Strings separated with code unit 0x002C (comma). A comma is not inserted either before
+ the first String or after the last String.</li>
+ <li>Let <i>final</i> be the result of concatenating <b><code>"{"</code>,</b> <i>properties</i>, and
+ <code>"}"</code>.</li>
+ </ol>
+ </li>
+ <li>Else <i>gap</i> is not the empty String
+ <ol class="block">
+ <li>Let <i>separator</i> be the result of concatenating code unit 0x002C (comma), code unit 0x000A (line feed),
+ and <i>indent</i>.</li>
+ <li>Let <i>properties</i> be a String formed by concatenating all the element Strings of <i>partial</i> with
+ each adjacent pair of Strings separated with <i>separator</i>. The <i>separator</i> String is not inserted
+ either before the first String or after the last String.</li>
+ <li>Let <i>final</i> be the result of concatenating <code>"{"</code>, code unit 0x000A (line feed),
+ <i>indent</i>, <i>properties</i>, code unit 0x000A, <i>stepback</i>, and <code>"}</code>".</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Remove the last element of <i>stack</i>.</li>
+ <li>Let <i>indent</i> be <i>stepback</i>.</li>
+ <li>Return <i>final</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-serializejsonarray">
+ <h1><span class="secnum" id="sec-24.3.2.4"><a href="#sec-serializejsonarray"
+ title="link to this section">24.3.2.4</a></span> Runtime Semantics: SerializeJSONArray( value )</h1>
+
+ <p>The abstract operation SerializeJSONArray with argument <var>value</var> serializes an array. It has access to the
+ <var>stack</var>, <var>indent</var>, and <var>gap</var> of the invocation of the <code>stringify</code> method. The
+ representation of arrays includes only the elements between zero and <code>array.length</code> <span style="font-family:
+ Times New Roman">– 1</span> inclusive. Properties whose keys are not array indexes are excluded from the
+ stringification. An array is stringified as an opening left square bracket, elements separated by comma, and a closing
+ right square bracket.</p>
+
+ <ol class="proc">
+ <li>If <i>stack</i> contains <i>value</i>, throw a <b>TypeError</b> exception because the structure is cyclical.</li>
+ <li>Append <i>value</i> to <i>stack</i>.</li>
+ <li>Let <i>stepback</i> be <i>indent</i>.</li>
+ <li>Let <i>indent</i> be the concatenation of <i>indent</i> and <i>gap</i>.</li>
+ <li>Let <i>partial</i> be an empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>len</i> be <a href="#sec-tolength">ToLength</a>(<a href="#sec-get-o-p">Get</a>(<i>value</i>,
+ <code>"length"</code>)).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>len</i>).</li>
+ <li>Let <i>index</i> be 0.</li>
+ <li>Repeat while <i>index</i> < <i>len</i>
+ <ol class="block">
+ <li>Let <i>strP</i> be <a href="#sec-serializejsonproperty">SerializeJSONProperty</a>(<a
+ href="#sec-tostring">ToString</a>(<i>index</i>), <i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>strP</i>).</li>
+ <li>If <i>strP</i> is <b>undefined</b>, then
+ <ol class="block">
+ <li>Append <code>"null"</code> to <i>partial</i>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Append <i>strP</i> to <i>partial</i>.</li>
+ </ol>
+ </li>
+ <li>Increment <i>index</i> by 1.</li>
+ </ol>
+ </li>
+ <li>If <i>partial</i> is empty, then
+ <ol class="block">
+ <li>Let <i>final</i> be <code>"[]"</code>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>If <i>gap</i> is the empty String, then
+ <ol class="block">
+ <li>Let <i>properties</i> be a String formed by concatenating all the element Strings of <i>partial</i> with
+ each adjacent pair of Strings separated with code unit 0x002C (comma). A comma is not inserted either before
+ the first String or after the last String.</li>
+ <li>Let <i>final</i> be the result of concatenating <b><code>"["</code>,</b> <i>properties</i>, and
+ <code>"]"</code>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>separator</i> be the result of concatenating code unit 0x002C (comma), code unit 0x000A (line feed),
+ and <i>indent</i>.</li>
+ <li>Let <i>properties</i> be a String formed by concatenating all the element Strings of <i>partial</i> with
+ each adjacent pair of Strings separated with <i>separator</i>. The <i>separator</i> String is not inserted
+ either before the first String or after the last String.</li>
+ <li>Let <i>final</i> be the result of concatenating <code>"["</code>, code unit 0x000A (line feed),
+ <i>indent</i>, <i>properties</i>, code unit 0x000A, <i>stepback</i>, and <code>"]</code>".</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Remove the last element of <i>stack</i>.</li>
+ <li>Let <i>indent</i> be <i>stepback</i>.</li>
+ <li>Return <i>final</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-json-@@tostringtag">
+ <h1><span class="secnum" id="sec-24.3.3"><a href="#sec-json-@@tostringtag" title="link to this section">24.3.3</a></span>
+ JSON [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>JSON</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-control-abstraction-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25"><a href="#sec-control-abstraction-objects" title="link to this section">25</a></span>
+ Control Abstraction Objects</h1>
+ </div>
+
+ <section id="sec-iteration">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.1"><a href="#sec-iteration" title="link to this section">25.1</a></span> Iteration</h1>
+ </div>
+
+ <section id="sec-common-iteration-interfaces">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.1.1"><a href="#sec-common-iteration-interfaces"
+ title="link to this section">25.1.1</a></span> Common Iteration Interfaces</h1>
+
+ <p>An interface is a set of property keys whose associated values match a specific specification. Any object that provides
+ all the properties as described by an interface’s specification <i>conforms</i> to that interface. An interface is
+ not represented by a distinct object. There may be many separately implemented objects that conform to any interface. An
+ individual object may conform to multiple interfaces.</p>
+ </div>
+
+ <section id="sec-iterable-interface">
+ <h1><span class="secnum" id="sec-25.1.1.1"><a href="#sec-iterable-interface"
+ title="link to this section">25.1.1.1</a></span> The <i>Iterable</i> Interface</h1>
+
+ <p>The <i>Iterable</i> interface includes the property described in <a href="#table-52">Table 52</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-52">Table 52</span> — <i>Iterable</i> Interface Required Properties</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Property</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Value</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Requirements</th>
+ </tr>
+ <tr>
+ <td style="border-top: 0px solid black"><code>@@iterator</code></td>
+ <td style="border-top: 0px solid black">A function that returns an <i>Iterator</i> object.</td>
+ <td style="border-top: 0px solid black">The returned object must conform to the <i>Iterator</i> interface.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-iterator-interface">
+ <h1><span class="secnum" id="sec-25.1.1.2"><a href="#sec-iterator-interface"
+ title="link to this section">25.1.1.2</a></span> The <i>Iterator</i> Interface</h1>
+
+ <p>An object that implements the <i>Iterator</i> interface must include the property in <a href="#table-53">Table
+ 53</a>.Such objects may also implement the properties in <a href="#table-53">Table 53</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-53">Table 53</span> — <i>Iterator</i> Interface Required Properties</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Property</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Value</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Requirements</th>
+ </tr>
+ <tr>
+ <td style="border-top: 0px solid black"><code>next</code></td>
+ <td style="border-top: 0px solid black">A function that returns an <i>IteratorResult</i> object.</td>
+ <td style="border-top: 0px solid black">The returned object must conform to the <i>IteratorResult</i> interface. If a previous call to the <code>next</code> method of an <i>Iterator</i> has returned an <i>IteratorResult</i> object whose <code>done</code> property is <b>true</b>, then all subsequent calls to the <code>next</code> method of that object should also return an <i>IteratorResult</i> object whose <code>done</code> property is <b>true</b>. However, this requirement is not enforced.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Arguments may be passed to the next function but their interpretation and validity is
+ dependent upon the target <i>Iterator</i>. The for-of statement and other common users of <i>Iterators</i> do not pass
+ any arguments, so <i>Iterator</i> objects that expect to be used in such a manner must be prepared to deal with being
+ called with no arguments.</p>
+ </div>
+
+ <figure>
+ <figcaption><span id="table-54">Table 54</span> — <i>Iterator</i> Interface Optional Properties</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Property</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Value</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Requirements</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 0px solid black; border-top: 0px solid black"><code>return</code></td>
+ <td style="border-bottom: 0px solid black; border-top: 0px solid black">A function that returns an <i>IteratorResult</i> object.</td>
+ <td style="border-bottom: 0px solid black; border-top: 0px solid black">The returned object must conform to the <i>IteratorResult</i> interface. Invoking this method notifies the <i>Iterator</i> object that the caller does not intend to make any more <code>next</code> method calls to the <i>Iterator</i>. The returned <i>IteratorResult</i> object will typically have a <code>done</code> property whose value <b>true</b>, and a <code>value</code> property is the value passed as the argument of the <code>return</code> method. However, this requirement is not enforced.</td>
+ </tr>
+ <tr>
+ <td style="border-top: 0px solid black"><code>throw</code></td>
+ <td style="border-top: 0px solid black">A function that returns an <i>IteratorResult</i> object.</td>
+ <td style="border-top: 0px solid black">The returned object must conform to the <i>IteratorResult</i> interface. Invoking this method notifies the <i>Iterator</i> object that the caller has detected an error condition. The argument may be used to identify the error condition and typically will be an exception object. A typical response is to <code>throw</code> the value passed as the argument. If the method does not <code>throw</code>, the returned <i>IteratorResult</i> object will typically have a <code>done</code> property whose value <b>true</b>.</td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Typically callers of these methods should check for their existence before invoking
+ them. Certain ECMAScript language features including <code>for</code>-<code>of</code>, <code>yield*</code>, and array
+ destructuring call these methods after performing an existence check. Most ECMAScript library functions that accept
+ <i>Iterable</i> objects as arguments also conditionally call them.</p>
+ </div>
+ </section>
+
+ <section id="sec-iteratorresult-interface">
+ <h1><span class="secnum" id="sec-25.1.1.3"><a href="#sec-iteratorresult-interface"
+ title="link to this section">25.1.1.3</a></span> The IteratorResult Interface</h1>
+
+ <p>The <i>IteratorResult</i> interface includes the properties listed in <a href="#table-55">Table 55</a>:</p>
+
+ <figure>
+ <figcaption><span id="table-55">Table 55</span> — <i>IteratorResult</i> Interface Properties</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Property</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Value</th>
+ <th style="background-color: #A6A6A6; border-bottom: 0px solid black; border-top: 1px solid #000080">Requirements</th>
+ </tr>
+ <tr>
+ <td style="border-bottom: 0px solid black; border-top: 0px solid black"><code>done</code></td>
+ <td style="border-bottom: 0px solid black; border-top: 0px solid black">Either <span class="value">true</span> or <span class="value">false</span>.</td>
+ <td style="border-bottom: 0px solid black; border-top: 0px solid black">This is the result status of an <i>iterator</i> <code>next</code> method call. If the end of the iterator was reached <code>done</code> is <span class="value">true</span>. If the end was not reached <code>done</code> is <span class="value">false</span> and a value is available. If a <code>done</code> property (either own or inherited does not exist), it is consider to have the value <span class="value">false</span>.</td>
+ </tr>
+ <tr>
+ <td style="border-top: 0px solid black"><code>value</code></td>
+ <td style="border-top: 0px solid black">Any <a href="#sec-ecmascript-language-types">ECMAScript language value</a>.</td>
+ <td style="border-top: 0px solid black">If done is <span class="value">false</span>, this is the current iteration element value. If done is <span class="value">true</span>, this is the return value of the iterator, if it supplied one. If the iterator does not have a return value, <code>value</code> is <span class="value">undefined</span>. In that case, the <code>value</code> property may be absent from the conforming object if it does not inherit an explicit <code>value</code> property.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+
+ <section id="sec-%iteratorprototype%-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.1.2"><a href="#sec-%iteratorprototype%-object"
+ title="link to this section">25.1.2</a></span> The %IteratorPrototype% Object</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ %IteratorPrototype% object is the intrinsic object %ObjectPrototype% (<a
+ href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The %IteratorPrototype% object is an ordinary object.
+ The initial value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ %IteratorPrototype% object is <b>true</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> All objects defined in this specification that implement the Iterator interface also
+ inherit from %IteratorPrototype%. ECMAScript code may also define objects that inherit from %IteratorPrototype%. The
+ %IteratorPrototype% object provides a place where additional methods that are applicable to all iterator objects may be
+ added.</p>
+
+ <p>The following expression is one way that ECMAScript code can access the %IteratorPrototype% object:</p>
+
+ <pre><a href="#sec-object.getprototypeof">Object.getPrototypeOf</a>(<a href="#sec-object.getprototypeof">Object.getPrototypeOf</a>([][Symbol.iterator]()))</pre>
+ </div>
+ </div>
+
+ <section id="sec-%iteratorprototype%-@@iterator">
+ <h1><span class="secnum" id="sec-25.1.2.1"><a href="#sec-%iteratorprototype%-@@iterator"
+ title="link to this section">25.1.2.1</a></span> %IteratorPrototype% [ @@iterator ] ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.iterator]"</code>.</p>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-generatorfunction-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.2"><a href="#sec-generatorfunction-objects" title="link to this section">25.2</a></span>
+ GeneratorFunction Objects</h1>
+
+ <p>Generator Function objects are constructor functions that are usually created by evaluating <span
+ class="nt">GeneratorDeclaration</span>, <span class="nt">GeneratorExpression</span>, and <span
+ class="nt">GeneratorMethod</span> syntactic productions. They may also be created by calling the %GeneratorFunction%
+ intrinsic.</p>
+
+ <figure>
+ <img alt="A staggering variety of boxes and arrows." height="958" src="figure-2.png" width="968">
+ <figcaption>Figure 2 (Informative) — Generator Objects Relationships</figcaption>
+ </figure>
+ </div>
+
+ <section id="sec-generatorfunction-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.2.1"><a href="#sec-generatorfunction-constructor"
+ title="link to this section">25.2.1</a></span> The GeneratorFunction Constructor</h1>
+
+ <p>The <code>GeneratorFunction</code> constructor is the %GeneratorFunction% intrinsic. When
+ <code>GeneratorFunction</code> is called as a function rather than as a constructor, it creates and initializes a new
+ GeneratorFunction object. Thus the function call <code>GeneratorFunction</code> <code><b>(</b>…<b>)</b></code> is
+ equivalent to the object creation expression <code>new GeneratorFunction</code> <code><b>(</b>…<b>)</b></code> with
+ the same arguments.</p>
+
+ <p><code>GeneratorFunction</code> is designed to be subclassable. It may be used as the value of an <code>extends</code>
+ clause of a class definition. Subclass constructors that intend to inherit the specified <code>GeneratorFunction</code>
+ behaviour must include a <code>super</code> call to the <code>GeneratorFunction</code> constructor to create and
+ initialize subclass instances with the internal slots necessary for built-in GeneratorFunction behaviour. All ECMAScript
+ syntactic forms for defining generator function objects create direct instances of <code>GeneratorFunction</code>. There
+ is no syntactic means to create instances of <code>GeneratorFunction</code> subclasses.</p>
+ </div>
+
+ <section id="sec-generatorfunction">
+ <h1><span class="secnum" id="sec-25.2.1.1"><a href="#sec-generatorfunction"
+ title="link to this section">25.2.1.1</a></span> GeneratorFunction (p1, p2, … , pn, body)</h1>
+
+ <p>The last argument specifies the body (executable code) of a generator function; any preceding arguments specify formal
+ parameters.</p>
+
+ <p>When the <code>GeneratorFunction</code> function is called with some arguments <var>p1</var>, <var>p2</var>, … ,
+ <var>pn</var>, <var>body</var> (where <var>n</var> might be <span style="font-family: Times New Roman">0</span>, that is,
+ there are no “<var>p</var>” arguments, and where <var>body</var> might also not be provided), the following
+ steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the active function object.</li>
+ <li>Let <i>args</i> be the <i>argumentsList</i> that was passed to this function by [[Call]] or [[Construct]].</li>
+ <li>Return <a href="#sec-createdynamicfunction">CreateDynamicFunction</a>(<i>C</i>, NewTarget, <code>"generator"</code>,
+ <i>args</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> See NOTE for <a href="#sec-function-p1-p2-pn-body">19.2.1.1</a>.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-generatorfunction-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.2.2"><a href="#sec-properties-of-the-generatorfunction-constructor"
+ title="link to this section">25.2.2</a></span> Properties of the GeneratorFunction Constructor</h1>
+
+ <p>The <code>GeneratorFunction</code> constructor is a standard built-in function object that inherits from the
+ <code>Function</code> constructor. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the <code>GeneratorFunction</code> constructor
+ is the intrinsic object %Function%.</p>
+
+ <p>The value of the [[Extensible]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ GeneratorFunction constructor is <b>true</b>.</p>
+
+ <p>The value of the <code>name</code> property of the GeneratorFunction is <code>"<b>GeneratorFunction</b>"</code>.</p>
+
+ <p>The <code>GeneratorFunction</code> constructor has the following properties:</p>
+ </div>
+
+ <section id="sec-generatorfunction.length">
+ <h1><span class="secnum" id="sec-25.2.2.1"><a href="#sec-generatorfunction.length"
+ title="link to this section">25.2.2.1</a></span> GeneratorFunction.length</h1>
+
+ <p>This is a data property with a value of 1. This property has the attributes { [[Writable]]: <b>false</b>,
+ [[Enumerable]]: <b>false</b>, [[Configurable]]: <b>true</b> }.</p>
+ </section>
+
+ <section id="sec-generatorfunction.prototype">
+ <h1><span class="secnum" id="sec-25.2.2.2"><a href="#sec-generatorfunction.prototype"
+ title="link to this section">25.2.2.2</a></span> GeneratorFunction.prototype</h1>
+
+ <p>The initial value of <code>GeneratorFunction.prototype</code> is the intrinsic object %Generator%.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-generatorfunction-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.2.3"><a href="#sec-properties-of-the-generatorfunction-prototype-object"
+ title="link to this section">25.2.3</a></span> Properties of the GeneratorFunction Prototype Object</h1>
+
+ <p>The GeneratorFunction prototype object is an ordinary object. It is not a function object and does not have an
+ [[ECMAScriptCode]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> or any other of the
+ internal slots listed in <a href="#table-27">Table 27</a> or <a href="#table-56">Table 56</a>. In addition to being the
+ value of the prototype property of the %GeneratorFunction% intrinsic and is itself the %Generator% intrinsic.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ GeneratorFunction prototype object is the %FunctionPrototype% intrinsic object. The initial value of the [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the GeneratorFunction prototype object is
+ <b>true</b>.</p>
+ </div>
+
+ <section id="sec-generatorfunction.prototype.constructor">
+ <h1><span class="secnum" id="sec-25.2.3.1"><a href="#sec-generatorfunction.prototype.constructor"
+ title="link to this section">25.2.3.1</a></span> GeneratorFunction.prototype.constructor</h1>
+
+ <p>The initial value of <code>GeneratorFunction.prototype.constructor</code> is the intrinsic object
+ %GeneratorFunction%.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+
+ <section id="sec-generatorfunction.prototype.prototype">
+ <h1><span class="secnum" id="sec-25.2.3.2"><a href="#sec-generatorfunction.prototype.prototype"
+ title="link to this section">25.2.3.2</a></span> GeneratorFunction.prototype.prototype</h1>
+
+ <p>The value of <code>GeneratorFunction.prototype.prototype</code> is the %GeneratorPrototype% intrinsic object.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+
+ <section id="sec-generatorfunction.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-25.2.3.3"><a href="#sec-generatorfunction.prototype-@@tostringtag"
+ title="link to this section">25.2.3.3</a></span> GeneratorFunction.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>GeneratorFunction</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-generatorfunction-instances">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.2.4"><a href="#sec-generatorfunction-instances"
+ title="link to this section">25.2.4</a></span> GeneratorFunction Instances</h1>
+
+ <p>Every GeneratorFunction instance is an <a href="#sec-ecmascript-function-objects">ECMAScript function object</a> and
+ has the internal slots listed in <a href="#table-27">Table 27</a>. The value of the [[FunctionKind]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> for all such instances is
+ "<code>generator</code>".</p>
+
+ <p>Each GeneratorFunction instance has the following own properties:</p>
+ </div>
+
+ <section id="sec-generatorfunction-instances-length">
+ <h1><span class="secnum" id="sec-25.2.4.1"><a href="#sec-generatorfunction-instances-length"
+ title="link to this section">25.2.4.1</a></span> length</h1>
+
+ <p>The value of the <code>length</code> property is an integer that indicates the typical number of arguments expected by
+ the GeneratorFunction. However, the language permits the function to be invoked with some other number of arguments. The
+ behaviour of a GeneratorFunction when invoked on a number of arguments other than the number specified by its
+ <code>length</code> property depends on the function.</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>true</b> }.</p>
+ </section>
+
+ <section id="sec-generatorfunction-instances-prototype">
+ <h1><span class="secnum" id="sec-25.2.4.2"><a href="#sec-generatorfunction-instances-prototype"
+ title="link to this section">25.2.4.2</a></span> prototype</h1>
+
+ <p>Whenever a GeneratorFunction instance is created another ordinary object is also created and is the initial value of
+ the generator function’s <code>prototype</code> property. The value of the prototype property is used to initialize
+ the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of a newly created Generator
+ object before the generator function object is invoked as a constructor for that newly created object.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Unlike function instances, the object that is the value of the a
+ GeneratorFunction’s <code>prototype</code> property does not have a <code>constructor</code> property whose value
+ is the GeneratorFunction instance.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-generator-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.3"><a href="#sec-generator-objects" title="link to this section">25.3</a></span>
+ Generator Objects</h1>
+
+ <p>A Generator object is an instance of a generator function and conforms to both the <i>Iterator</i> and <i>Iterable</i>
+ interfaces.</p>
+
+ <p>Generator instances directly inherit properties from the object that is the value of the <code>prototype</code> property
+ of the Generator function that created the instance. Generator instances indirectly inherit properties from the Generator
+ Prototype intrinsic, %GeneratorPrototype%.</p>
+ </div>
+
+ <section id="sec-properties-of-generator-prototype">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.3.1"><a href="#sec-properties-of-generator-prototype"
+ title="link to this section">25.3.1</a></span> Properties of Generator Prototype</h1>
+
+ <p>The Generator prototype object is the %GeneratorPrototype% intrinsic. It is also the initial value of the
+ <code>prototype</code> property of the %Generator% intrinsic (the <a
+ href="#sec-generatorfunction.prototype">GeneratorFunction.prototype</a>).</p>
+
+ <p>The Generator prototype is an ordinary object. It is not a Generator instance and does not have a [[GeneratorState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ Generator prototype object is the intrinsic object %IteratorPrototype% (<a
+ href="#sec-%iteratorprototype%-object">25.1.2</a>). The initial value of the [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Function prototype object is
+ <b>true</b>.</p>
+
+ <p>All Generator instances indirectly inherit properties of the Generator prototype object.</p>
+ </div>
+
+ <section id="sec-generator.prototype.constructor">
+ <h1><span class="secnum" id="sec-25.3.1.1"><a href="#sec-generator.prototype.constructor"
+ title="link to this section">25.3.1.1</a></span> Generator.prototype.constructor</h1>
+
+ <p>The initial value of <code>Generator.prototype.constructor</code> is the intrinsic object %Generator%.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+
+ <section id="sec-generator.prototype.next">
+ <h1><span class="secnum" id="sec-25.3.1.2"><a href="#sec-generator.prototype.next"
+ title="link to this section">25.3.1.2</a></span> Generator.prototype.next ( value )</h1>
+
+ <p>The <code>next</code> method performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>g</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-generatorresume">GeneratorResume</a>(<i>g</i>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator.prototype.return">
+ <h1><span class="secnum" id="sec-25.3.1.3"><a href="#sec-generator.prototype.return"
+ title="link to this section">25.3.1.3</a></span> Generator.prototype.return ( value )</h1>
+
+ <p>The <code>return</code> method performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>g</i> be the <b>this</b> value.</li>
+ <li>Let <i>C</i> be <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">return</span>, [[value]]: <i>value</i>, [[target]]: <span style="font-family:
+ sans-serif">empty</span>}.</li>
+ <li>Return <a href="#sec-generatorresumeabrupt">GeneratorResumeAbrupt</a>(<i>g</i>, <i>C</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator.prototype.throw">
+ <h1><span class="secnum" id="sec-25.3.1.4"><a href="#sec-generator.prototype.throw"
+ title="link to this section">25.3.1.4</a></span> Generator.prototype.throw ( exception )</h1>
+
+ <p>The <code>throw</code> method performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>g</i> be the <b>this</b> value.</li>
+ <li>Let <i>C</i> be <a href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span
+ style="font-family: sans-serif">throw</span>, [[value]]: <i>exception</i>, [[target]]: <span style="font-family:
+ sans-serif">empty</span>}.</li>
+ <li>Return <a href="#sec-generatorresumeabrupt">GeneratorResumeAbrupt</a>(<i>g</i>, <i>C</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-generator.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-25.3.1.5"><a href="#sec-generator.prototype-@@tostringtag"
+ title="link to this section">25.3.1.5</a></span> Generator.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Generator</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-generator-instances">
+ <h1><span class="secnum" id="sec-25.3.2"><a href="#sec-properties-of-generator-instances"
+ title="link to this section">25.3.2</a></span> Properties of Generator Instances</h1>
+
+ <p>Generator instances are initially created with the internal slots described in <a href="#table-56">Table 56</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-56">Table 56</span> — Internal Slots of Generator Instances</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[GeneratorState]]</td>
+ <td>The current execution state of the generator. The possible values are: <b>undefined</b>, <code>"suspendedStart"</code><span style="font-family: Times New Roman">,</span> <code>"suspendedYield"</code><span style="font-family: Times New Roman">,</span> <code>"executing"</code>, and <code>"completed"</code><span style="font-family: Times New Roman">.</span></td>
+ </tr>
+ <tr>
+ <td>[[GeneratorContext]]</td>
+ <td>The <a href="#sec-execution-contexts">execution context</a> that is used when executing the code of this generator.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-generator-abstract-operations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.3.3"><a href="#sec-generator-abstract-operations"
+ title="link to this section">25.3.3</a></span> Generator Abstract Operations</h1>
+ </div>
+
+ <section id="sec-generatorstart">
+ <h1><span class="secnum" id="sec-25.3.3.1"><a href="#sec-generatorstart" title="link to this section">25.3.3.1</a></span>
+ GeneratorStart (generator, generatorBody)</h1>
+
+ <p>The abstract operation GeneratorStart with arguments <span style="font-family: Times New Roman"><i>generator</i> and
+ <i>generatorBody</i></span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: The value of <i>generator’s</i> [[GeneratorState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <b>undefined</b>.</li>
+ <li>Let <i>genContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Set the Generator component of <i>genContext</i> to <i>generator.</i></li>
+ <li>Set the code evaluation state of <i>genContext</i> such that when evaluation is resumed for that <a
+ href="#sec-execution-contexts">execution context</a> the following steps will be performed:
+ <ol class="nested proc">
+ <li>Let <i>result</i> be the result of evaluating <i>generatorBody</i>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: If we return here, the generator either threw an exception or
+ performed either an implicit or explicit return.</li>
+ <li>Remove <i>genContext</i> from <a href="#sec-execution-contexts">the execution context stack</a> and restore the
+ <a href="#sec-execution-contexts">execution context</a> that is at the top of <a
+ href="#sec-execution-contexts">the execution context stack</a> as <a href="#sec-execution-contexts">the running
+ execution context</a>.</li>
+ <li>Set <i>generator’s</i> [[GeneratorState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <code>"completed"</code>.</li>
+ <li>Once a generator enters the <code>"completed"</code> state it never leaves it and its associated <a
+ href="#sec-execution-contexts">execution context</a> is never resumed. Any execution state associated with
+ <i>generator</i> can be discarded at this point.</li>
+ <li>If <i>result</i> is a normal completion, let <i>resultValue</i> be <b>undefined</b>.</li>
+ <li>Else,
+ <ol class="block">
+ <li>If <i>result</i>.[[type]] is <span style="font-family: sans-serif">return</span>, let <i>resultValue</i> be
+ <i>result</i>.[[value]].</li>
+ <li>Else, return <i>result</i>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>resultValue</i>, <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Set <i>generator’s</i> [[GeneratorContext]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <i>genContext</i>.</li>
+ <li>Set <i>generator’s</i> [[GeneratorState]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <code>"suspendedStart"</code>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<b>undefined</b>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-generatorvalidate">
+ <h1><span class="secnum" id="sec-25.3.3.2"><a href="#sec-generatorvalidate"
+ title="link to this section">25.3.3.2</a></span> GeneratorValidate ( generator )</h1>
+
+ <p>The abstract operation GeneratorValidate with argument <var>generator</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>generator</i>) is not Object, throw a
+ <b>TypeError</b> exception.</li>
+ <li>If <i>generator</i> does not have a [[GeneratorState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, throw a <b>TypeError</b> exception.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>generator</i> also has a [[GeneratorContext]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>state</i> be the value of <i>generator’s</i> [[GeneratorState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>state</i> is <code>"executing"</code>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <i>state</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generatorresume">
+ <h1><span class="secnum" id="sec-25.3.3.3"><a href="#sec-generatorresume" title="link to this section">25.3.3.3</a></span>
+ GeneratorResume ( generator, value )</h1>
+
+ <p>The abstract operation GeneratorResume with arguments <span style="font-family: Times New Roman"><i>generator</i> and
+ <i>value</i></span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>state</i> be <a href="#sec-generatorvalidate">GeneratorValidate</a>(<i>generator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>state</i>).</li>
+ <li>If <i>state</i> is <code>"completed"</code>, return <a
+ href="#sec-createiterresultobject">CreateIterResultObject</a>(<b>undefined</b>, <b>true</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>state</i> is either <code>"suspendedStart"</code> or
+ <code>"suspendedYield"</code>.</li>
+ <li>Let <i>genContext</i> be the value of <i>generator’s</i> [[GeneratorContext]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>methodContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <i>methodContext</i>.</li>
+ <li>Set <i>generator’s</i> [[GeneratorState]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <code>"executing"</code>.</li>
+ <li>Push <i>genContext</i> onto <a href="#sec-execution-contexts">the execution context stack</a>; <i>genContext</i> is
+ now <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Resume the <a href="#sec-execution-contexts">suspended</a> evaluation of <i>genContext</i> using <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>value</i>) as the result of the operation that <a
+ href="#sec-execution-contexts">suspended</a> it. Let <i>result</i> be the value returned by the resumed
+ computation.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: When we return here, <i>genContext</i> has already been removed
+ from <a href="#sec-execution-contexts">the execution context stack</a> and <i>methodContext</i> is <a
+ href="#sec-execution-contexts">the currently running execution context</a>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generatorresumeabrupt">
+ <h1><span class="secnum" id="sec-25.3.3.4"><a href="#sec-generatorresumeabrupt"
+ title="link to this section">25.3.3.4</a></span> GeneratorResumeAbrupt(generator, abruptCompletion)</h1>
+
+ <p>The abstract operation GeneratorResumeAbrupt with arguments <span style="font-family: Times New Roman"><i>generator</i>
+ and <i>abruptCompletion</i></span> performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>state</i> be <a href="#sec-generatorvalidate">GeneratorValidate</a>(<i>generator</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>state</i>).</li>
+ <li>If <i>state</i> is <code>"suspendedStart"</code>, then
+ <ol class="block">
+ <li>Set <i>generator’s</i> [[GeneratorState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <code>"completed"</code>.</li>
+ <li>Once a generator enters the <code>"completed"</code> state it never leaves it and its associated <a
+ href="#sec-execution-contexts">execution context</a> is never resumed. Any execution state associated with
+ <i>generator</i> can be discarded at this point.</li>
+ <li>Let <i>state</i> be <code>"completed"</code>.</li>
+ </ol>
+ </li>
+ <li>If <i>state</i> is <code>"completed"</code>, then
+ <ol class="block">
+ <li>If <i>abruptCompletion</i>.[[type]] is <span style="font-family: sans-serif">return</span>, then
+ <ol class="block">
+ <li>Return <a href="#sec-createiterresultobject">CreateIterResultObject</a>(<i>abruptCompletion</i>.[[value]],
+ <b>true</b>).</li>
+ </ol>
+ </li>
+ <li>Return <i>abruptCompletion</i>.</li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>state</i> is <code>"suspendedYield"</code>.</li>
+ <li>Let <i>genContext</i> be the value of <i>generator’s</i> [[GeneratorContext]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>methodContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li><a href="#sec-execution-contexts">Suspend</a> <i>methodContext</i>.</li>
+ <li>Set <i>generator’s</i> [[GeneratorState]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to <code>"executing"</code>.</li>
+ <li>Push <i>genContext</i> onto <a href="#sec-execution-contexts">the execution context stack</a>; <i>genContext</i> is
+ now <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Resume the <a href="#sec-execution-contexts">suspended</a> evaluation of <i>genContext</i> using
+ <i>abruptCompletion</i> as the result of the operation that <a href="#sec-execution-contexts">suspended</a> it. Let
+ <i>result</i> be the value returned by the resumed computation.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: When we return here, <i>genContext</i> has already been removed
+ from <a href="#sec-execution-contexts">the execution context stack</a> and <i>methodContext</i> is <a
+ href="#sec-execution-contexts">the currently running execution context</a>.</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-generatoryield">
+ <h1><span class="secnum" id="sec-25.3.3.5"><a href="#sec-generatoryield" title="link to this section">25.3.3.5</a></span>
+ GeneratorYield ( iterNextObj )</h1>
+
+ <p>The abstract operation GeneratorYield with argument <var>iterNextObj</var> performs the following steps:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>iterNextObj</i> is an Object that implements the
+ <i>IteratorResult</i> interface.</li>
+ <li>Let <i>genContext</i> be <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>genContext</i> is the <a
+ href="#sec-execution-contexts">execution context</a> of a generator.</li>
+ <li>Let <i>generator</i> be the value of the Generator component of <i>genContext</i>.</li>
+ <li>Set the value of <i>generator’s</i> [[GeneratorState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <code>"suspendedYield"</code>.</li>
+ <li>Remove <i>genContext</i> from <a href="#sec-execution-contexts">the execution context stack</a> and restore the <a
+ href="#sec-execution-contexts">execution context</a> that is at the top of <a href="#sec-execution-contexts">the
+ execution context stack</a> as <a href="#sec-execution-contexts">the running execution context</a>.</li>
+ <li>Set the code evaluation state of <i>genContext</i> such that when evaluation is resumed with a <a
+ href="#sec-completion-record-specification-type">Completion</a> <i>resumptionValue</i> the following steps will be
+ performed:
+ <ol class="nested proc">
+ <li>Return <i>resumptionValue</i>.</li>
+ <li>NOTE: This returns to the evaluation of the <span class="nt">YieldExpression</span> production that originally
+ called this abstract operation.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<i>iterNextObj</i>).</li>
+ <li><span style="font-family: sans-serif">NOTE: This returns to the evaluation of the operation that had most
+ previously resumed evaluation of</span> <i>genContext</i>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-promise-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4"><a href="#sec-promise-objects" title="link to this section">25.4</a></span> Promise
+ Objects</h1>
+
+ <p>A Promise is an object that is used as a placeholder for the eventual results of a deferred (and possibly asynchronous)
+ computation.</p>
+
+ <p>Any Promise object is in one of three mutually exclusive states: <i>fulfilled</i>, <i>rejected</i>, and
+ <i>pending</i>:</p>
+
+ <ul>
+ <li>
+ <p>A promise <code>p</code> is fulfilled if <code>p.then(f, r)</code> will immediately enqueue a Job to call the
+ function <code>f</code>.</p>
+ </li>
+
+ <li>
+ <p>A promise <code>p</code> is rejected if <code>p.then(f, r)</code> will immediately enqueue a Job to call the function
+ <code>r</code>.</p>
+ </li>
+
+ <li>
+ <p>A promise is pending if it is neither fulfilled nor rejected.</p>
+ </li>
+ </ul>
+
+ <p>A promise is said to be <i>settled</i> if it is not pending, i.e. if it is either fulfilled or rejected.</p>
+
+ <p>A promise is <i>resolved</i> if it is settled or if it has been "locked in" to match the state of another promise.
+ Attempting to resolve or reject a resolved promise has no effect. A promise is <i>unresolved</i> if it is not resolved. An
+ unresolved promise is always in the pending state. A resolved promise may be pending, fulfilled or rejected.</p>
+ </div>
+
+ <section id="sec-promise-abstract-operations">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.1"><a href="#sec-promise-abstract-operations"
+ title="link to this section">25.4.1</a></span> Promise Abstract Operations</h1>
+ </div>
+
+ <section id="sec-promisecapability-records">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.1.1"><a href="#sec-promisecapability-records"
+ title="link to this section">25.4.1.1</a></span> PromiseCapability Records</h1>
+
+ <p>A PromiseCapability is a Record value used to encapsulate a promise object along with the functions that are capable
+ of resolving or rejecting that promise object. PromiseCapability records are produced by the <a
+ href="#sec-newpromisecapability">NewPromiseCapability</a> abstract operation.</p>
+
+ <p>PromiseCapability Records have the fields listed in <a href="#table-57">Table 57</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-57">Table 57</span> — PromiseCapability Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[Promise]]</td>
+ <td>An object</td>
+ <td>An object that is usable as a promise.</td>
+ </tr>
+ <tr>
+ <td>[[Resolve]]</td>
+ <td>A function object</td>
+ <td>The function that is used to resolve the given promise object.</td>
+ </tr>
+ <tr>
+ <td>[[Reject]]</td>
+ <td>A function object</td>
+ <td>The function that is used to reject the given promise object.</td>
+ </tr>
+ </table>
+ </figure>
+ </div>
+
+ <section id="sec-ifabruptrejectpromise">
+ <h1><span class="secnum" id="sec-25.4.1.1.1"><a href="#sec-ifabruptrejectpromise"
+ title="link to this section">25.4.1.1.1</a></span> IfAbruptRejectPromise ( value, capability )</h1>
+
+ <p>IfAbruptRejectPromise is a short hand for a sequence of algorithm steps that use a PromiseCapability record. An
+ algorithm step of the form:</p>
+
+ <ol class="proc">
+ <li>IfAbruptRejectPromise(<i>value</i>, <i>capability</i>).</li>
+ </ol>
+
+ <p>means the same thing as:</p>
+
+ <ol class="proc">
+ <li>If <i>value</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ <ol class="block">
+ <li>Let <i>rejectResult</i> be <a href="#sec-call">Call</a>(<i>capability</i>.[[Reject]], <b>undefined</b>,
+ «<i>value</i>.[[value]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rejectResult</i>).</li>
+ <li>Return <i>capability</i>.[[Promise]].</li>
+ </ol>
+ </li>
+ <li>Else if <i>value</i> is a <a href="#sec-completion-record-specification-type">Completion Record</a>, let
+ <i>value</i> be <i>value</i>.[[value]].</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-promisereaction-records">
+ <h1><span class="secnum" id="sec-25.4.1.2"><a href="#sec-promisereaction-records"
+ title="link to this section">25.4.1.2</a></span> PromiseReaction Records</h1>
+
+ <p>The PromiseReaction is a Record value used to store information about how a promise should react when it becomes
+ resolved or rejected with a given value. PromiseReaction records are created by the <code>then</code> method of the
+ Promise prototype, and are used by a <a href="#sec-promisereactionjob">PromiseReactionJob</a>.</p>
+
+ <p>PromiseReaction records have the fields listed in <a href="#table-58">Table 58</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-58">Table 58</span> — PromiseReaction Record Fields</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-right: 0px solid black; border-top: 2px solid #000000">Field Name</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Value</th>
+ <th style="border-bottom: 1px solid #000000; border-right: 1px solid #000000; border-top: 2px solid #000000">Meaning</th>
+ </tr>
+ <tr>
+ <td>[[Capabilities]]</td>
+ <td>A PromiseCapability record</td>
+ <td>The capabilities of the promise for which this record provides a reaction handler.</td>
+ </tr>
+ <tr>
+ <td>[[Handler]]</td>
+ <td>A function object or a String</td>
+ <td>The function that should be applied to the incoming value, and whose return value will govern what happens to the derived promise. If [[Handler]] is <code>"Identity"</code> it is equivalent to a function that simply returns its first argument. If [[Handler]] is <code>"Thrower"</code> it is equivalent to a function that throws its first argument as an exception.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+
+ <section id="sec-createresolvingfunctions">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.1.3"><a href="#sec-createresolvingfunctions"
+ title="link to this section">25.4.1.3</a></span> CreateResolvingFunctions ( promise )</h1>
+
+ <p>When CreateResolvingFunctions is performed with argument <var>promise</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>alreadyResolved</i> be a new Record { [[value]]: <b>false</b> }.</li>
+ <li>Let <i>resolve</i> be a new built-in function object as defined in Promise Resolve Functions (<a
+ href="#sec-promise-resolve-functions">25.4.1.3.2</a>).</li>
+ <li>Set the [[Promise]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>resolve</i>
+ to <i>promise</i>.</li>
+ <li>Set the [[AlreadyResolved]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>resolve</i> to <i>alreadyResolved</i>.</li>
+ <li>Let <i>reject</i> be a new built-in function object as defined in Promise Reject Functions (<a
+ href="#sec-promise-reject-functions">25.4.1.3.1</a>).</li>
+ <li>Set the [[Promise]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>reject</i>
+ to <i>promise</i>.</li>
+ <li>Set the [[AlreadyResolved]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>reject</i> to <i>alreadyResolved</i>.</li>
+ <li>Return a new Record { [[Resolve]]: <i>resolve</i>, [[Reject]]: <i>reject</i> }.</li>
+ </ol>
+ </div>
+
+ <section id="sec-promise-reject-functions">
+ <h1><span class="secnum" id="sec-25.4.1.3.1"><a href="#sec-promise-reject-functions"
+ title="link to this section">25.4.1.3.1</a></span> Promise Reject Functions</h1>
+
+ <p>A promise reject function is an anonymous built-in function that has [[Promise]] and [[AlreadyResolved]] internal
+ slots.</p>
+
+ <p>When a promise reject function <var>F</var> is called with argument <var>reason</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> has a [[Promise]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value is an Object.</li>
+ <li>Let <i>promise</i> be the value of <i>F</i>'s [[Promise]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>alreadyResolved</i> be the value of <i>F</i>'s [[AlreadyResolved]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>alreadyResolved</i>.[[value]] is <b>true</b>, return <b>undefined</b>.</li>
+ <li>Set <i>alreadyResolved</i>.[[value]] to <b>true</b>.</li>
+ <li>Return <a href="#sec-rejectpromise">RejectPromise</a>(<i>promise</i>, <i>reason</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-promise-resolve-functions">
+ <h1><span class="secnum" id="sec-25.4.1.3.2"><a href="#sec-promise-resolve-functions"
+ title="link to this section">25.4.1.3.2</a></span> Promise Resolve Functions</h1>
+
+ <p>A promise resolve function is an anonymous built-in function that has [[Promise]] and [[AlreadyResolved]] internal
+ slots.</p>
+
+ <p>When a promise resolve function <var>F</var> is called with argument <var>resolution</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> has a [[Promise]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value is an Object.</li>
+ <li>Let <i>promise</i> be the value of <i>F</i>'s [[Promise]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>alreadyResolved</i> be the value of <i>F</i>'s [[AlreadyResolved]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>alreadyResolved</i>.[[value]] is <b>true</b>, return <b>undefined</b>.</li>
+ <li>Set <i>alreadyResolved</i>.[[value]] to <b>true</b>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>resolution</i>, <i>promise</i>) is <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>selfResolutionError</i> be a newly-created <b>TypeError</b> object.</li>
+ <li>Return <a href="#sec-rejectpromise">RejectPromise</a>(<i>promise</i>, <i>selfResolutionError</i>).</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>resolution</i>) is not Object, then
+ <ol class="block">
+ <li>Return <a href="#sec-fulfillpromise">FulfillPromise</a>(<i>promise</i>, <i>resolution</i>).</li>
+ </ol>
+ </li>
+ <li>Let <i>then</i> be <a href="#sec-get-o-p">Get</a>(<i>resolution</i>, <code>"then"</code>).</li>
+ <li>If <i>then</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Return <a href="#sec-rejectpromise">RejectPromise</a>(<i>promise</i>, <i>then</i>.[[value]]).</li>
+ </ol>
+ </li>
+ <li>Let <i>then</i> be <i>then</i>.[[value]].</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>then</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Return <a href="#sec-fulfillpromise">FulfillPromise</a>(<i>promise</i>, <i>resolution</i>).</li>
+ </ol>
+ </li>
+ <li>Perform <a href="#sec-enqueuejob">EnqueueJob</a> (<code>"PromiseJobs"</code>, <a
+ href="#sec-promiseresolvethenablejob">PromiseResolveThenableJob</a>, «‍<i>promise</i>,
+ <i>resolution</i>, <i>then</i>»)</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-fulfillpromise">
+ <h1><span class="secnum" id="sec-25.4.1.4"><a href="#sec-fulfillpromise" title="link to this section">25.4.1.4</a></span>
+ FulfillPromise ( promise, value)</h1>
+
+ <p>When the FulfillPromise abstract operation is called with arguments <var>promise</var> and <var>value</var> the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: the value of <i>promise</i>'s [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <code>"pending"</code>.</li>
+ <li>Let <i>reactions</i> be the value of <i>promise</i>'s [[PromiseFulfillReactions]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseResult]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <i>value</i>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseFulfillReactions]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <b>undefined</b>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseRejectReactions]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <b>undefined</b>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <code>"fulfilled"</code>.</li>
+ <li>Return <a href="#sec-triggerpromisereactions">TriggerPromiseReactions</a>(<i>reactions</i>, <i>value</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-newpromisecapability">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.1.5"><a href="#sec-newpromisecapability"
+ title="link to this section">25.4.1.5</a></span> NewPromiseCapability ( C )</h1>
+
+ <p>The abstract operation NewPromiseCapability takes a constructor function, and attempts to use that constructor
+ function in the fashion of the built-in <code>Promise</code> constructor to create a Promise object and extract its
+ resolve and reject functions. The promise plus the resolve and reject functions are used to initialize a new
+ PromiseCapability record which is returned as the value of this abstract operation.</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>C</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>NOTE <span style="font-family: Times New Roman"><i>C</i></span> is assumed to be a constructor function that
+ supports the parameter conventions of the <code>Promise</code> constructor (<a href="#sec-promise-executor">see
+ 25.4.3.1</a>).</li>
+ <li>Let <i>promiseCapability</i> be a new PromiseCapability { [[Promise]]: <b>undefined</b>, [[Resolve]]:
+ <b>undefined</b>, [[Reject]]: <b>undefined</b> }.</li>
+ <li>Let <i>executor</i> be a new built-in function object as defined in <a
+ href="#sec-getcapabilitiesexecutor-functions">GetCapabilitiesExecutor Functions</a> (<a
+ href="#sec-getcapabilitiesexecutor-functions">25.4.1.5.1</a>).</li>
+ <li>Set the [[Capability]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>executor</i> to <i>promiseCapability</i>.</li>
+ <li>Let <i>promise</i> be <a href="#sec-construct">Construct</a>(<i>C</i>, «<i>executor</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>promise</i>).</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>promiseCapability</i>.[[Resolve]]) is <b>false</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>promiseCapability</i>.[[Reject]]) is <b>false</b>, throw a
+ <b>TypeError</b> exception.</li>
+ <li>Set <i>promiseCapability</i>.[[Promise]] to <i>promise</i>.</li>
+ <li>Return <i>promiseCapability</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This abstract operation supports Promise subclassing, as it is generic on any
+ constructor that calls a passed executor function argument in the same way as the Promise constructor. It is used to
+ generalize static methods of the Promise constructor to any subclass.</p>
+ </div>
+ </div>
+
+ <section id="sec-getcapabilitiesexecutor-functions">
+ <h1><span class="secnum" id="sec-25.4.1.5.1"><a href="#sec-getcapabilitiesexecutor-functions"
+ title="link to this section">25.4.1.5.1</a></span> GetCapabilitiesExecutor Functions</h1>
+
+ <p>A GetCapabilitiesExecutor function is an anonymous built-in function that has a [[Capability]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>When a GetCapabilitiesExecutor function <var>F</var> is called with arguments <var>resolve</var> and
+ <var>reject</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>F</i> has a [[Capability]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> whose value is a PromiseCapability
+ Record.</li>
+ <li>Let <i>promiseCapability</i> be the value of <i>F</i>'s [[Capability]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>promiseCapability</i>.[[Resolve]] is not <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <i>promiseCapability</i>.[[Reject]] is not <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Set <i>promiseCapability</i>.[[Resolve]] to <i>resolve</i>.</li>
+ <li>Set <i>promiseCapability</i>.[[Reject]] to <i>reject</i>.</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-ispromise">
+ <h1><span class="secnum" id="sec-25.4.1.6"><a href="#sec-ispromise" title="link to this section">25.4.1.6</a></span>
+ IsPromise ( x )</h1>
+
+ <p>The abstract operation IsPromise checks for the promise brand on an object.</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>x</i>) is not Object, return <b>false</b>.</li>
+ <li>If <i>x</i> does not have a [[PromiseState]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a>, return <b>false</b>.</li>
+ <li>Return <b>true</b>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-rejectpromise">
+ <h1><span class="secnum" id="sec-25.4.1.7"><a href="#sec-rejectpromise" title="link to this section">25.4.1.7</a></span>
+ RejectPromise ( promise, reason)</h1>
+
+ <p>When the RejectPromise abstract operation is called with arguments <var>promise</var> and <var>reason</var> the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: the value of <i>promise</i>'s [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <code>"pending"</code>.</li>
+ <li>Let <i>reactions</i> be the value of <i>promise</i>'s [[PromiseRejectReactions]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseResult]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <i>reason</i>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseFulfillReactions]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <b>undefined</b>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseRejectReactions]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <b>undefined</b>.</li>
+ <li>Set the value of <i>promise</i>'s [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <code>"rejected"</code>.</li>
+ <li>Return <a href="#sec-triggerpromisereactions">TriggerPromiseReactions</a>(<i>reactions</i>, <i>reason</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-triggerpromisereactions">
+ <h1><span class="secnum" id="sec-25.4.1.8"><a href="#sec-triggerpromisereactions"
+ title="link to this section">25.4.1.8</a></span> TriggerPromiseReactions ( reactions, argument )</h1>
+
+ <p>The abstract operation TriggerPromiseReactions takes a collection of functions to trigger in the next Job, and calls
+ them, passing each the given argument. Typically, these reactions will modify a previously-returned promise, possibly
+ calling in to a user-supplied handler before doing so.</p>
+
+ <ol class="proc">
+ <li>Repeat for each <i>reaction</i> in <i>reactions</i>, in original insertion order
+ <ol class="block">
+ <li>Perform <a href="#sec-enqueuejob">EnqueueJob</a>(<code>"<b>PromiseJobs</b>"</code><span style="font-family:
+ sans-serif">,</span> <a href="#sec-promisereactionjob">PromiseReactionJob</a>, «‍<i>reaction</i>,
+ <i>argument</i>»).</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-promise-jobs">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.2"><a href="#sec-promise-jobs" title="link to this section">25.4.2</a></span>
+ Promise Jobs</h1>
+ </div>
+
+ <section id="sec-promisereactionjob">
+ <h1><span class="secnum" id="sec-25.4.2.1"><a href="#sec-promisereactionjob"
+ title="link to this section">25.4.2.1</a></span> PromiseReactionJob ( reaction, argument )</h1>
+
+ <p>The job PromiseReactionJob with parameters <var>reaction</var> and <var>argument</var> applies the appropriate handler
+ to the incoming value, and uses the handler's return value to resolve or reject the derived promise associated with that
+ handler.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>reaction</i> is a PromiseReaction Record.</li>
+ <li>Let <i>promiseCapability</i> be <i>reaction</i>.[[Capabilities]].</li>
+ <li>Let <i>handler</i> be <i>reaction</i>.[[Handler]].</li>
+ <li>If <i>handler</i> is <code>"Identity"</code>, let <i>handlerResult</i> be <a
+ href="#sec-normalcompletion">NormalCompletion</a>(<i>argument</i>).</li>
+ <li>Else if <i>handler</i> is <code>"Thrower"</code>, let <i>handlerResult</i> be <a
+ href="#sec-completion-record-specification-type">Completion</a>{[[type]]: <span style="font-family:
+ sans-serif">throw</span>, [[value]]: <i>argument</i>, [[target]]: <span style="font-family:
+ sans-serif">empty</span>}.</li>
+ <li>Else, let <i>handlerResult</i> be <a href="#sec-call">Call</a>(<i>handler</i>, <b>undefined</b>,
+ «<i>argument</i>»).</li>
+ <li>If <i>handlerResult</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>promiseCapability</i>.[[Reject]], <b>undefined</b>,
+ «<i>handlerResult</i>.[[value]]»).</li>
+ <li>NextJob <i>status</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>handlerResult</i> be <i>handlerResult</i>.[[value]].</li>
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>promiseCapability</i>.[[Resolve]], <b>undefined</b>,
+ «<i>handlerResult</i>»)<i>.</i></li>
+ <li>NextJob <i>status</i>.</li>
+ </ol>
+ </section>
+
+ <section id="sec-promiseresolvethenablejob">
+ <h1><span class="secnum" id="sec-25.4.2.2"><a href="#sec-promiseresolvethenablejob"
+ title="link to this section">25.4.2.2</a></span> PromiseResolveThenableJob ( promiseToResolve, thenable, then)</h1>
+
+ <p>The job PromiseResolveThenableJob with parameters <var>promiseToResolve</var>, <var>thenable</var>, and <var>then</var>
+ performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>resolvingFunctions</i> be <a
+ href="#sec-createresolvingfunctions">CreateResolvingFunctions</a>(<i>promiseToResolve</i>).</li>
+ <li>Let <i>thenCallResult</i> be <a href="#sec-call">Call</a>(<i>then</i>, <i>thenable</i>,
+ «<i>resolvingFunctions</i>.[[Resolve]], <i>resolvingFunctions</i>.[[Reject]]»).</li>
+ <li>If <i>thenCallResult</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>resolvingFunctions</i>.[[Reject]], <b>undefined</b>,
+ «<i>thenCallResult</i>.[[value]]»)<i>.</i></li>
+ <li>NextJob <i>status.</i></li>
+ </ol>
+ </li>
+ <li>NextJob <i>thenCallResult</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This Job uses the supplied thenable and its <code>then</code> method to resolve the
+ given promise. This process must take place as a Job to ensure that the evaluation of the <code>then</code> method
+ occurs after evaluation of any surrounding code has completed.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-promise-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.3"><a href="#sec-promise-constructor" title="link to this section">25.4.3</a></span>
+ The Promise Constructor</h1>
+
+ <p>The Promise constructor is the %Promise% intrinsic object and the initial value of the <code>Promise</code> property of
+ the global object. When called as a constructor it creates and initializes a new Promise object. <code>Promise</code> is
+ not intended to be called as a function and will throw an exception when called in that manner.</p>
+
+ <p>The <code>Promise</code> constructor is designed to be subclassable. It may be used as the value in an
+ <code>extends</code> clause of a class definition. Subclass constructors that intend to inherit the specified
+ <code>Promise</code> behaviour must include a <code>super</code> call to the <code>Promise</code> constructor to create
+ and initialize the subclass instance with the internal state necessary to support the <code>Promise</code> and
+ <code>Promise.prototype</code> built-in methods.</p>
+ </div>
+
+ <section id="sec-promise-executor">
+ <h1><span class="secnum" id="sec-25.4.3.1"><a href="#sec-promise-executor"
+ title="link to this section">25.4.3.1</a></span> Promise ( executor )</h1>
+
+ <p>When the <code>Promise</code> function is called with argument <var>executor</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>executor</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>promise</i> be <a href="#sec-ordinarycreatefromconstructor">OrdinaryCreateFromConstructor</a>(NewTarget,
+ <code>"%PromisePrototype%"</code>, «‍[[PromiseState]], [[PromiseConstructor]], [[PromiseResult]],
+ [[PromiseFulfillReactions]], [[PromiseRejectReactions]]» ).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>promise</i>).</li>
+ <li>Set the value of <i>promise’s</i> [[PromiseConstructor]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to NewTarget.</li>
+ <li>Set <i>promise</i>'s [[PromiseState]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to
+ <code>"pending"</code>.</li>
+ <li>Set <i>promise</i>'s [[PromiseFulfillReactions]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Set <i>promise</i>'s [[PromiseRejectReactions]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> to a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>resolvingFunctions</i> be <a
+ href="#sec-createresolvingfunctions">CreateResolvingFunctions</a>(<i>promise</i>).</li>
+ <li>Let <i>completion</i> be <a href="#sec-call">Call</a>(<i>executor</i>, <b>undefined</b>,
+ «<i>resolvingFunctions</i>.[[Resolve]], <i>resolvingFunctions</i>.[[Reject]]»).</li>
+ <li>If <i>completion</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <a href="#sec-call">Call</a>(<i>resolvingFunctions</i>.[[Reject]], <b>undefined</b>,
+ «<i>completion</i>.[[value]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>promise</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <i>executor</i> argument must be a function object. It is called for initiating and
+ reporting completion of the possibly deferred action represented by this Promise object. The executor is called with two
+ arguments: <i>resolve</i> and <i>reject</i>. These are functions that may be used by the <i>executor</i> function to
+ report eventual completion or failure of the deferred computation. Returning from the executor function does not mean
+ that the deferred action has been completed but only that the request to eventually perform the deferred action has been
+ accepted.</p>
+
+ <p>The <i>resolve</i> function that is passed to an <i>executor</i> function accepts a single argument. The
+ <i>executor</i> code may eventually call the <i>resolve</i> function to indicate that it wishes to resolve the
+ associated Promise object. The argument passed to the <i>resolve</i> function represents the eventual value of the
+ deferred action and can be either the actual fulfillment value or another Promise object which will provide the value if
+ it is fulfilled.</p>
+
+ <p>The <i>reject</i> function that is passed to an <i>executor</i> function accepts a single argument. The
+ <i>executor</i> code may eventually call the <i>reject</i> function to indicate that the associated Promise is rejected
+ and will never be fulfilled. The argument passed to the <i>reject</i> function is used as the rejection value of the
+ promise. Typically it will be an <code>Error</code> object.</p>
+
+ <p>The resolve and reject functions passed to an <i>executor</i> function by the Promise constructor have the capability
+ to actually resolve and reject the associated promise. Subclasses may have different constructor behaviour that passes
+ in customized values for resolve and reject.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-promise-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.4"><a href="#sec-properties-of-the-promise-constructor"
+ title="link to this section">25.4.4</a></span> Properties of the Promise Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ <code>Promise</code> constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>Besides the <code>length</code> property (whose value is 1), the Promise constructor has the following properties:</p>
+ </div>
+
+ <section id="sec-promise.all">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.4.1"><a href="#sec-promise.all" title="link to this section">25.4.4.1</a></span>
+ Promise.all ( iterable )</h1>
+
+ <p>The <code>all</code> function returns a new promise which is fulfilled with an array of fulfillment values for the
+ passed promises, or rejects with the reason of the first passed promise that rejects. It resolves all elements of the
+ passed iterable to promises as it runs this algorithm.</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>C</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-get-o-p">Get</a>(<i>C</i>, @@species).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>If <i>S</i> is neither <b>undefined</b> nor <b>null</b>, let <i>C</i> be <i>S</i>.</li>
+ <li>Let <i>promiseCapability</i> be <a href="#sec-newpromisecapability">NewPromiseCapability</a>(<i>C</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>promiseCapability</i>).</li>
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>iterable</i>).</li>
+ <li><a href="#sec-ifabruptrejectpromise">IfAbruptRejectPromise</a>(<i>iterator</i>, <i>promiseCapability</i>).</li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <i>iterator</i>, [[done]]: <b>false</b>}.</li>
+ <li>Let <i>result</i> be <a href="#sec-performpromiseall">PerformPromiseAll</a>(<i>iterator</i>, <i>C</i>,
+ <i>promiseCapability</i>).</li>
+ <li>If <i>result</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>,
+ <ol class="block">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, let <i>result</i> be <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator</i>, <i>result</i>).</li>
+ <li><a href="#sec-ifabruptrejectpromise">IfAbruptRejectPromise</a>(<i>result</i>, <i>promiseCapability</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+
+ <p class="Note">Note: The <code>all</code> function requires its <b>this</b> value to be a constructor function that
+ supports the parameter conventions of the <code>Promise</code> constructor.</p>
+ </div>
+
+ <section id="sec-performpromiseall">
+ <h1><span class="secnum" id="sec-25.4.4.1.1"><a href="#sec-performpromiseall"
+ title="link to this section">25.4.4.1.1</a></span> Runtime Semantics: PerformPromiseAll( iteratorRecord,
+ constructor, resultCapability)</h1>
+
+ <p>When the PerformPromiseAll abstract operation is called with arguments <var>iteratorRecord, constructor,</var> and
+ <var>resultCapability</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>constructor</i> is a constructor function.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>resultCapability</i> is a PromiseCapability record.</li>
+ <li>Let <i>values</i> be a new empty <a href="#sec-list-and-record-specification-type">List</a>.</li>
+ <li>Let <i>remainingElementsCount</i> be a new Record { [[value]]: 1 }.</li>
+ <li>Let <i>index</i> be 0.</li>
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>,
+ <ol class="block">
+ <li>Set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li>Set <i>remainingElementsCount</i>.[[value]] to <i>remainingElementsCount</i>.[[value]] − 1.</li>
+ <li>If <i>remainingElementsCount</i>.[[value]] is 0,
+ <ol class="block">
+ <li>Let <i>valuesArray</i> be <a
+ href="#sec-createarrayfromlist">CreateArrayFromList</a>(<i>values</i>).</li>
+ <li>Let <i>resolveResult</i> be <a href="#sec-call">Call</a>(<i>resultCapability</i>.[[Resolve]],
+ <b>undefined</b>, «<i>valuesArray</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resolveResult</i>)</li>
+ </ol>
+ </li>
+ <li>Return <i>resultCapability</i>.[[Promise]].</li>
+ </ol>
+ </li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>nextValue</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Append <b>undefined</b> to <i>values</i>.</li>
+ <li>Let <i>nextPromise</i> be <a href="#sec-invoke">Invoke</a>(<i>constructor</i>, <code>"resolve"</code>,
+ «‍<i>nextValue</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextPromise</i> ).</li>
+ <li>Let <i>resolveElement</i> be a new built-in function object as defined in <a
+ href="#sec-promise.all">Promise.all</a> Resolve Element Functions.</li>
+ <li>Set the [[AlreadyCalled]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>resolveElement</i> to a new Record { [[value]]: <b>false</b> }.</li>
+ <li>Set the [[Index]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>resolveElement</i> to <i>index</i>.</li>
+ <li>Set the [[Values]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>resolveElement</i> to <i>values</i>.</li>
+ <li>Set the [[Capabilities]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>resolveElement</i> to <i>resultCapability</i>.</li>
+ <li>Set the [[RemainingElements]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>resolveElement</i> to <i>remainingElementsCount</i>.</li>
+ <li>Set <i>remainingElementsCount</i>.[[value]] to <i>remainingElementsCount</i>.[[value]] + 1.</li>
+ <li>Let <i>result</i> be <a href="#sec-invoke">Invoke</a>(<i>nextPromise</i>, <code>"then"</code>,
+ «‍<i>resolveElement</i>, <i>resultCapability</i>.[[Reject]]»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</li>
+ <li>Set <i>index</i> to <i>index</i> + 1.</li>
+ </ol>
+ </li>
+ </ol>
+ </section>
+
+ <section id="sec-promise.all-resolve-element-functions">
+ <h1><span class="secnum" id="sec-25.4.4.1.2"><a href="#sec-promise.all-resolve-element-functions"
+ title="link to this section">25.4.4.1.2</a></span> Promise.all Resolve Element Functions</h1>
+
+ <p>A <a href="#sec-promise.all">Promise.all</a> resolve element function is an anonymous built-in function that is used
+ to resolve a specific <a href="#sec-promise.all">Promise.all</a> element. Each <a
+ href="#sec-promise.all">Promise.all</a> resolve element function has [[Index]], [[Values]], [[Capabilities]],
+ [[RemainingElements]], and [[AlreadyCalled]] internal slots.</p>
+
+ <p>When a <a href="#sec-promise.all">Promise.all</a> resolve element function <var>F</var> is called with argument
+ <var>x</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>alreadyCalled</i> be the value of <i>F</i>'s [[AlreadyCalled]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>alreadyCalled</i>.[[value]] is <b>true</b>, return <b>undefined</b>.</li>
+ <li>Set <i>alreadyCalled</i>.[[value]] to <b>true</b>.</li>
+ <li>Let <i>index</i> be the value of <i>F</i>'s [[Index]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>values</i> be the value of <i>F</i>'s [[Values]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>promiseCapability</i> be the value of <i>F</i>'s [[Capabilities]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>remainingElementsCount</i> be the value of <i>F</i>'s [[RemainingElements]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Set <i>values</i>[<i>index</i>] to <i>x</i>.</li>
+ <li>Set <i>remainingElementsCount</i>.[[value]] to <i>remainingElementsCount</i>.[[value]] - 1.</li>
+ <li>If <i>remainingElementsCount</i>.[[value]] is 0,
+ <ol class="block">
+ <li>Let <i>valuesArray</i> be <a href="#sec-createarrayfromlist">CreateArrayFromList</a>(<i>values</i>).</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>promiseCapability</i>.[[Resolve]], <b>undefined</b>,
+ «<i>valuesArray</i>»).</li>
+ </ol>
+ </li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-promise.prototype">
+ <h1><span class="secnum" id="sec-25.4.4.2"><a href="#sec-promise.prototype"
+ title="link to this section">25.4.4.2</a></span> Promise.prototype</h1>
+
+ <p>The initial value of <code>Promise.prototype</code> is the intrinsic object %PromisePrototype% (<a
+ href="#sec-properties-of-the-promise-prototype-object">25.4.5</a>).</p>
+
+ <p>This property has the attributes { [[Writable]]: <b>false</b>, [[Enumerable]]: <b>false</b>, [[Configurable]]:
+ <b>false</b> }.</p>
+ </section>
+
+ <section id="sec-promise.race">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.4.3"><a href="#sec-promise.race" title="link to this section">25.4.4.3</a></span>
+ Promise.race ( iterable )</h1>
+
+ <p>The <code>race</code> function returns a new promise which is settled in the same way as the first passed promise to
+ settle. It resolves all elements of the passed <span style="font-family: Times New Roman">iterable</span> to promises as
+ it runs this algorithm.</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>C</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-get-o-p">Get</a>(<i>C</i>, @@species).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>If <i>S</i> is neither <b>undefined</b> nor <b>null</b>, let <i>C</i> be <i>S</i>.</li>
+ <li>Let <i>promiseCapability</i> be <a href="#sec-newpromisecapability">NewPromiseCapability</a>(<i>C</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>promiseCapability</i>).</li>
+ <li>Let <i>iterator</i> be <a href="#sec-getiterator">GetIterator</a>(<i>iterable</i>).</li>
+ <li><a href="#sec-ifabruptrejectpromise">IfAbruptRejectPromise</a>(<i>iterator</i>, <i>promiseCapability</i>).</li>
+ <li>Let <i>iteratorRecord</i> be Record {[[iterator]]: <i>iterator</i>, [[done]]: <b>false</b>}.</li>
+ <li>Let <i>result</i> be <a href="#sec-performpromiseraceloop">PerformPromiseRaceLoop</a>(<i>iteratorRecord</i>,
+ <i>promiseCapability</i>, <i>C</i>).</li>
+ <li>If <i>result</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, then
+ <ol class="block">
+ <li>If <i>iteratorRecord</i>.[[done]] is <b>false</b>, let <i>result</i> be <a
+ href="#sec-iteratorclose">IteratorClose</a>(<i>iterator,result</i>).</li>
+ <li><a href="#sec-ifabruptrejectpromise">IfAbruptRejectPromise</a>(<i>result</i>, <i>promiseCapability</i>).</li>
+ </ol>
+ </li>
+ <li>Return <i>promiseCapability</i>.[[Promise]].</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE 1</span> If the <i>iterable</i> argument is empty or if none of the promises in
+ <i>iterable</i> ever settle then the pending promise returned by this method will never be settled</p>
+ </div>
+
+ <div class="note">
+ <p><span class="nh">NOTE 2</span> The <code>race</code> function expects its <b>this</b> value to be a constructor
+ function that supports the parameter conventions of the <code>Promise</code> constructor. It also expects that its
+ <b>this</b> value provides a <code>resolve</code> method.</p>
+ </div>
+ </div>
+
+ <section id="sec-performpromiseraceloop">
+ <h1><span class="secnum" id="sec-25.4.4.3.1"><a href="#sec-performpromiseraceloop"
+ title="link to this section">25.4.4.3.1</a></span> PerformPromiseRaceLoop( iteratorRecord, promiseCapability, C
+ )</h1>
+
+ <p>When the PerformPromiseRaceLoop abstract operation is called with arguments <var>iteratorRecord,
+ promiseCapability,</var> and <var>C</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Repeat
+ <ol class="block">
+ <li>Let <i>next</i> be <a href="#sec-iteratorstep">IteratorStep</a>(<i>iteratorRecord</i>.[[iterator]]).</li>
+ <li>If <i>next</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>next</i>).</li>
+ <li>If <i>next</i> is <b>false</b>, then
+ <ol class="block">
+ <li>Set <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li>Return <i>promiseCapability</i>.[[Promise]].</li>
+ </ol>
+ </li>
+ <li>Let <i>nextValue</i> be <a href="#sec-iteratorvalue">IteratorValue</a>(<i>next</i>).</li>
+ <li>If <i>nextValue</i> is an <a href="#sec-completion-record-specification-type">abrupt completion</a>, set
+ <i>iteratorRecord</i>.[[done]] to <b>true</b>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextValue</i>).</li>
+ <li>Let <i>nextPromise</i> be <a href="#sec-invoke">Invoke</a>(<i>C</i>, <code>"resolve"</code>,
+ «‍<i>nextValue</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>nextPromise</i>).</li>
+ <li>Let <i>result</i> be <a href="#sec-invoke">Invoke</a>(<i>nextPromise</i>, <code>"then"</code>,
+ «‍<i>promiseCapability</i>.[[Resolve]], <i>promiseCapability</i>.[[Reject]]»).</li>
+ </ol>
+ </li>
+ </ol>
+
+ <p><span class="marker">aa.	</span><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>result</i>).</p>
+ </section>
+ </section>
+
+ <section id="sec-promise.reject">
+ <h1><span class="secnum" id="sec-25.4.4.4"><a href="#sec-promise.reject" title="link to this section">25.4.4.4</a></span>
+ Promise.reject ( r )</h1>
+
+ <p>The <code>reject</code> function returns a new promise rejected with the passed argument.</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>C</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-get-o-p">Get</a>(<i>C</i>, @@species).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>If <i>S</i> is neither <b>undefined</b> nor <b>null</b>, let <i>C</i> be <i>S</i>.</li>
+ <li>Let <i>promiseCapability</i> be <a href="#sec-newpromisecapability">NewPromiseCapability</a>(<i>C</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>promiseCapability</i>).</li>
+ <li>Let <i>rejectResult</i> be <a href="#sec-call">Call</a>(<i>promiseCapability</i>.[[Reject]], <b>undefined</b>,
+ «<i>r</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>rejectResult</i>).</li>
+ <li>Return <i>promiseCapability</i>.[[Promise]].</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>reject</code> function requires that its <b>this</b> value to be a constructor
+ function that supports the parameter conventions of the <code>Promise</code> constructor.</p>
+ </div>
+ </section>
+
+ <section id="sec-promise.resolve">
+ <h1><span class="secnum" id="sec-25.4.4.5"><a href="#sec-promise.resolve" title="link to this section">25.4.4.5</a></span>
+ Promise.resolve ( x )</h1>
+
+ <p>The <code>resolve</code> function returns either a new promise resolved with the passed argument, or the argument
+ itself if the argument is a promise produced by this constructor.</p>
+
+ <ol class="proc">
+ <li>Let <i>C</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ispromise">IsPromise</a>(<i>x</i>) is <b>true</b>,
+ <ol class="block">
+ <li>Let <i>constructor</i> be the value of <i>x</i>'s [[PromiseConstructor]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <a href="#sec-samevalue">SameValue</a>(<i>constructor</i>, <i>C</i>) is <b>true</b>, return <i>x</i>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>C</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>S</i> be <a href="#sec-get-o-p">Get</a>(<i>C</i>, @@species).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>If <i>S</i> is neither <b>undefined</b> nor <b>null</b>, let <i>C</i> be <i>S</i>.</li>
+ <li>Let <i>promiseCapability</i> be <a href="#sec-newpromisecapability">NewPromiseCapability</a>(<i>C</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>promiseCapability</i>).</li>
+ <li>Let <i>resolveResult</i> be <a href="#sec-call">Call</a>(<i>promiseCapability</i>.[[Resolve]], <b>undefined</b>,
+ «<i>x</i>»).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resolveResult</i>).</li>
+ <li>Return <i>promiseCapability</i>.[[Promise]].</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>resolve</code> function requires that its <b>this</b> value to be a
+ constructor function that supports the parameter conventions of the <code>Promise</code> constructor.</p>
+ </div>
+ </section>
+
+ <section id="sec-get-promise-@@species">
+ <h1><span class="secnum" id="sec-25.4.4.6"><a href="#sec-get-promise-@@species"
+ title="link to this section">25.4.4.6</a></span> get Promise [ @@species ]</h1>
+
+ <p><code>Promise[@@species]</code> is an accessor property whose set accessor function is <span
+ class="value">undefined</span>. Its get accessor function performs the following steps:</p>
+
+ <ol class="proc">
+ <li>Return the <b>this</b> value.</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"get [Symbol.species]"</code>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> Promise prototype methods normally use their <code>this</code> object’s
+ constructor to create a derived object. However, a subclass constructor may over-ride that default behaviour by
+ redefining its @@species property.</p>
+ </div>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-promise-prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.5"><a href="#sec-properties-of-the-promise-prototype-object"
+ title="link to this section">25.4.5</a></span> Properties of the Promise Prototype Object</h1>
+
+ <p>The Promise prototype object is the intrinsic object %PromisePrototype%. The value of the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Promise prototype object is the intrinsic
+ object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>). The Promise prototype
+ object is an ordinary object. It does not have a [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> or any of the other internal slots of Promise
+ instances.</p>
+ </div>
+
+ <section id="sec-promise.prototype.catch">
+ <h1><span class="secnum" id="sec-25.4.5.1"><a href="#sec-promise.prototype.catch"
+ title="link to this section">25.4.5.1</a></span> Promise.prototype.catch ( onRejected )</h1>
+
+ <p>When the <code>catch</code> method is called with argument <var>onRejected</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>promise</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-invoke">Invoke</a>(<i>promise</i>, <code>"then"</code>, «‍<b>undefined</b>,
+ <i>onRejected</i>»).</li>
+ </ol>
+ </section>
+
+ <section id="sec-promise.prototype.constructor">
+ <h1><span class="secnum" id="sec-25.4.5.2"><a href="#sec-promise.prototype.constructor"
+ title="link to this section">25.4.5.2</a></span> Promise.prototype.constructor</h1>
+
+ <p>The initial value of <code>Promise.prototype.constructor</code> is the intrinsic object %Promise%.</p>
+ </section>
+
+ <section id="sec-promise.prototype.then">
+ <div class="front">
+ <h1><span class="secnum" id="sec-25.4.5.3"><a href="#sec-promise.prototype.then"
+ title="link to this section">25.4.5.3</a></span> Promise.prototype.then ( onFulfilled , onRejected )</h1>
+
+ <p>When the <code>then</code> method is called with arguments <var>onFulfilled</var> and <var>onRejected</var> the
+ following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>promise</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ispromise">IsPromise</a>(<i>promise</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>C</i> be <a href="#sec-speciesconstructor">SpeciesConstructor</a>(<i>promise</i>, %Promise%).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>C</i>).</li>
+ <li>Let <i>resultCapability</i> be <a href="#sec-newpromisecapability">NewPromiseCapability</a>(<i>C</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>resultCapability</i>).</li>
+ <li>Return <a href="#sec-performpromisethen">PerformPromiseThen</a>(<i>promise</i>, <i>onFulfilled</i>,
+ <i>onRejected</i>, <i>resultCapability</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-performpromisethen">
+ <h1><span class="secnum" id="sec-25.4.5.3.1"><a href="#sec-performpromisethen"
+ title="link to this section">25.4.5.3.1</a></span> PerformPromiseThen ( promise, onFulfilled, onRejected,
+ resultCapability )</h1>
+
+ <p>The abstract operation PerformPromiseThen performs the “then” operation on <var>promise</var> using
+ <var>onFulfilled</var> and <var>onRejected</var> as its settlement actions. The result is
+ <var>resultCapability</var>’s promise.</p>
+
+ <ol class="proc">
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <a href="#sec-ispromise">IsPromise</a>(<i>promise</i>) is
+ <b>true</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>resultCapability</i> is a PromiseCapability record.</li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>onFulfilled</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>onFulfilled</i> be <code>"Identity"</code>.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>onRejected</i>) is <b>false</b>, then
+ <ol class="block">
+ <li>Let <i>onRejected</i> be <code>"Thrower"</code>.</li>
+ </ol>
+ </li>
+ <li>Let <i>fulfillReaction</i> be the PromiseReaction { [[Capabilities]]: <i>resultCapability</i>, [[Handler]]:
+ <i>onFulfilled</i> }.</li>
+ <li>Let <i>rejectReaction</i> be the PromiseReaction { [[Capabilities]]: <i>resultCapability</i>, [[Handler]]:
+ <i>onRejected</i>}.</li>
+ <li>If the value of <i>promise</i>'s [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <code>"pending"</code>,
+ <ol class="block">
+ <li>Append <i>fulfillReaction</i> as the last element of the <a
+ href="#sec-list-and-record-specification-type">List</a> that is the value of <i>promise</i>'s
+ [[PromiseFulfillReactions]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Append <i>rejectReaction</i> as the last element of the <a
+ href="#sec-list-and-record-specification-type">List</a> that is the value of <i>promise</i>'s
+ [[PromiseRejectReactions]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Else if the value of <i>promise</i>'s [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <code>"fulfilled"</code>,
+ <ol class="block">
+ <li>Let <i>value</i> be the value of <i>promise</i>'s [[PromiseResult]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Perform <a href="#sec-enqueuejob">EnqueueJob</a>(<code>"PromiseJobs"</code>, <a
+ href="#sec-promisereactionjob">PromiseReactionJob</a>, «‍<i>fulfillReaction</i>,
+ <i>value</i>»).</li>
+ </ol>
+ </li>
+ <li>Else if the value of <i>promise</i>'s [[PromiseState]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> is <code>"rejected"</code>,
+ <ol class="block">
+ <li>Let <i>reason</i> be the value of <i>promise</i>'s [[PromiseResult]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Perform <a href="#sec-enqueuejob">EnqueueJob</a>(<code>"PromiseJobs"</code>, <a
+ href="#sec-promisereactionjob">PromiseReactionJob</a>, «‍<i>rejectReaction</i>,
+ <i>reason</i>»).</li>
+ </ol>
+ </li>
+ <li>Return <i>resultCapability</i>.[[Promise]].</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-promise.prototype-@@tostringtag">
+ <h1><span class="secnum" id="sec-25.4.5.4"><a href="#sec-promise.prototype-@@tostringtag"
+ title="link to this section">25.4.5.4</a></span> Promise.prototype [ @@toStringTag ]</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Promise</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-promise-instances">
+ <h1><span class="secnum" id="sec-25.4.6"><a href="#sec-properties-of-promise-instances"
+ title="link to this section">25.4.6</a></span> Properties of Promise Instances</h1>
+
+ <p>Promise instances are ordinary objects that inherit properties from the Promise prototype object (the intrinsic,
+ %PromisePrototype%). Promise instances are initially created with the internal slots described in <a href="#table-59">Table
+ 59</a>.</p>
+
+ <figure>
+ <figcaption><span id="table-59">Table 59</span> — Internal Slots of Promise Instances</figcaption>
+ <table class="real-table">
+ <tr>
+ <th style="border-bottom: 1px solid #000000; border-left: 1px solid #000000; border-top: 2px solid #000000">Internal Slot</th>
+ <th style="border-bottom: 1px solid #000000; border-left: 0px solid black; border-right: 1px solid #000000; border-top: 2px solid #000000">Description</th>
+ </tr>
+ <tr>
+ <td>[[PromiseState]]</td>
+ <td>A string value that governs how a promise will react to incoming calls to its <code>then</code> method. The possible values are: <b>undefined</b>, <code>"pending"</code><span style="font-family: Times New Roman">,</span> <code>"fulfilled"</code>, and <code>"rejected"</code><span style="font-family: Times New Roman">.</span></td>
+ </tr>
+ <tr>
+ <td>[[PromiseConstructor]]</td>
+ <td>The function object that was used to construct this promise. Checked by the <code>resolve</code> method of the <code>Promise</code> constructor.</td>
+ </tr>
+ <tr>
+ <td>[[PromiseResult]]</td>
+ <td>The value with which the promise has been fulfilled or rejected, if any. Only meaningful if <span style="font-family: Times New Roman">[[PromiseState]]</span> is not <code>"pending"</code>.</td>
+ </tr>
+ <tr>
+ <td>[[PromiseFulfillReactions]]</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of PromiseReaction records to be processed when/if the promise transitions from the <code>"pending"</code> state to the<code>"fulfilled"</code> state.</td>
+ </tr>
+ <tr>
+ <td>[[PromiseRejectReactions]]</td>
+ <td>A <a href="#sec-list-and-record-specification-type">List</a> of PromiseReaction records to be processed when/if the promise transitions from the <code>"pending"</code> state to the<code>"rejected"</code> state.</td>
+ </tr>
+ </table>
+ </figure>
+ </section>
+ </section>
+</section>
+
+<section id="sec-reflection">
+ <div class="front">
+ <h1><span class="secnum" id="sec-26"><a href="#sec-reflection" title="link to this section">26</a></span> Reflection</h1>
+ </div>
+
+ <section id="sec-reflect-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-26.1"><a href="#sec-reflect-object" title="link to this section">26.1</a></span> The
+ Reflect Object</h1>
+
+ <p>The Reflect object is the %Reflect% intrinsic object and the initial value of the <code>Reflect</code> property of the
+ global object.The Reflect object is an ordinary object.</p>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the Reflect
+ object is the intrinsic object %ObjectPrototype% (<a href="#sec-properties-of-the-object-prototype-object">19.1.3</a>).</p>
+
+ <p>The Reflect object is not a function object. It does not have a [[Construct]] internal method; it is not possible to use
+ the Reflect object as a constructor with the <code>new</code> operator. The Reflect object also does not have a [[Call]]
+ internal method; it is not possible to invoke the Reflect object as a function.</p>
+ </div>
+
+ <section id="sec-reflect.apply">
+ <h1><span class="secnum" id="sec-26.1.1"><a href="#sec-reflect.apply" title="link to this section">26.1.1</a></span>
+ Reflect.apply ( target, thisArgument, argumentsList )</h1>
+
+ <p>When the <code>apply</code> function is called with arguments <span style="font-family: Times New Roman"><i>target</i>,
+ <i>thisArgument</i></span>, and <var>argumentsList</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-iscallable">IsCallable</a>(<i>target</i>) is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>args</i> be <a href="#sec-createlistfromarraylike">CreateListFromArrayLike</a>(<i>argumentsList</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>args</i>).</li>
+ <li>Perform the <a href="#sec-preparefortailcall">PrepareForTailCall</a> abstract operation.</li>
+ <li>Return <a href="#sec-call">Call</a>(<i>target</i>, <i>thisArgument</i>, <i>args</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.construct">
+ <h1><span class="secnum" id="sec-26.1.2"><a href="#sec-reflect.construct" title="link to this section">26.1.2</a></span>
+ Reflect.construct ( target, argumentsList [, newTarget] )</h1>
+
+ <p>When the <code>construct</code> function is called with arguments <var>target</var>, <var>argumentsList</var>, and
+ <var>newTarget</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-isconstructor">IsConstructor</a>(<i>target</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <i>newTarget</i> is not present, let <i>newTarget</i> be <i>target</i>.</li>
+ <li>Else, if <a href="#sec-isconstructor">IsConstructor</a>(<i>newTarget</i>) is <b>false</b>, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>args</i> be <a href="#sec-createlistfromarraylike">CreateListFromArrayLike</a>(<i>argumentsList</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>args</i>).</li>
+ <li>Return <a href="#sec-construct">Construct</a>(<i>target</i>, <i>args</i>, <i>newTarget</i>).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>construct</code> function is <b>2</b>.</p>
+ </section>
+
+ <section id="sec-reflect.defineproperty">
+ <h1><span class="secnum" id="sec-26.1.3"><a href="#sec-reflect.defineproperty"
+ title="link to this section">26.1.3</a></span> Reflect.defineProperty ( target, propertyKey, attributes )</h1>
+
+ <p>When the <code>defineProperty</code> function is called with arguments <span style="font-family: Times New
+ Roman"><i>target</i>, <i>propertyKey</i></span>, and <var>attributes</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>Let <i>desc</i> be <a href="#sec-topropertydescriptor">ToPropertyDescriptor</a>(<i>attributes</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>Return <i>target.</i>[[DefineOwnProperty]](<i>key</i>, <i>desc</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.deleteproperty">
+ <h1><span class="secnum" id="sec-26.1.4"><a href="#sec-reflect.deleteproperty"
+ title="link to this section">26.1.4</a></span> Reflect.deleteProperty ( target, propertyKey )</h1>
+
+ <p>When the <code>deleteProperty</code> function is called with arguments <span style="font-family: Times New
+ Roman"><i>target</i> and <i>propertyKey</i></span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>Return <i>target.</i>[[Delete]](<i>key</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.enumerate">
+ <h1><span class="secnum" id="sec-26.1.5"><a href="#sec-reflect.enumerate" title="link to this section">26.1.5</a></span>
+ Reflect.enumerate ( target )</h1>
+
+ <p>When the <code>enumerate</code> function is called with argument <var>target</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>target.</i>[[Enumerate]]().</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.get">
+ <h1><span class="secnum" id="sec-26.1.6"><a href="#sec-reflect.get" title="link to this section">26.1.6</a></span>
+ Reflect.get ( target, propertyKey [ , receiver ])</h1>
+
+ <p>When the <code>get</code> function is called with arguments <span style="font-family: Times New Roman"><i>target</i>,
+ <i>propertyKey</i></span>, and <var>receiver</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>If <i>receiver</i> is not present, then
+ <ol class="block">
+ <li>Let <i>receiver</i> be <i>target</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>target.</i>[[Get]](<i>key</i>, <i>receiver</i>).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>get</code> function is <b>2</b>.</p>
+ </section>
+
+ <section id="sec-reflect.getownpropertydescriptor">
+ <h1><span class="secnum" id="sec-26.1.7"><a href="#sec-reflect.getownpropertydescriptor"
+ title="link to this section">26.1.7</a></span> Reflect.getOwnPropertyDescriptor ( target, propertyKey )</h1>
+
+ <p>When the <code>getOwnPropertyDescriptor</code> function is called with arguments <span style="font-family: Times New
+ Roman"><i>target</i> and <i>propertyKey</i></span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>Let <i>desc</i> be <i>target.</i>[[GetOwnProperty]](<i>key</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>desc</i>).</li>
+ <li>Return <a href="#sec-frompropertydescriptor">FromPropertyDescriptor</a>(<i>desc</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.getprototypeof">
+ <h1><span class="secnum" id="sec-26.1.8"><a href="#sec-reflect.getprototypeof"
+ title="link to this section">26.1.8</a></span> Reflect.getPrototypeOf ( target )</h1>
+
+ <p>When the <code>getPrototypeOf</code> function is called with argument <var>target</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>target.</i>[[GetPrototypeOf]]().</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.has">
+ <h1><span class="secnum" id="sec-26.1.9"><a href="#sec-reflect.has" title="link to this section">26.1.9</a></span>
+ Reflect.has ( target, propertyKey )</h1>
+
+ <p>When the <code>has</code> function is called with arguments <span style="font-family: Times New Roman"><i>target</i> and
+ <i>propertyKey</i></span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>Return <i>target.</i>[[HasProperty]](<i>key</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.isextensible">
+ <h1><span class="secnum" id="sec-26.1.10"><a href="#sec-reflect.isextensible"
+ title="link to this section">26.1.10</a></span> Reflect.isExtensible (target)</h1>
+
+ <p>When the <code>isExtensible</code> function is called with argument <var>target</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>target.</i>[[IsExtensible]]().</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.ownkeys">
+ <h1><span class="secnum" id="sec-26.1.11"><a href="#sec-reflect.ownkeys" title="link to this section">26.1.11</a></span>
+ Reflect.ownKeys ( target )</h1>
+
+ <p>When the <code>ownKeys</code> function is called with argument <var>target</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>keys</i> be <i>target.</i>[[OwnPropertyKeys]]().</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>keys</i>).</li>
+ <li>Return <a href="#sec-createarrayfromlist">CreateArrayFromList</a>(<i>keys</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.preventextensions">
+ <h1><span class="secnum" id="sec-26.1.12"><a href="#sec-reflect.preventextensions"
+ title="link to this section">26.1.12</a></span> Reflect.preventExtensions ( target )</h1>
+
+ <p>When the <code>preventExtensions</code> function is called with argument <var>target</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>target.</i>[[PreventExtensions]]().</li>
+ </ol>
+ </section>
+
+ <section id="sec-reflect.set">
+ <h1><span class="secnum" id="sec-26.1.13"><a href="#sec-reflect.set" title="link to this section">26.1.13</a></span>
+ Reflect.set ( target, propertyKey, V [ , receiver ] )</h1>
+
+ <p>When the <code>set</code> function is called with arguments <span style="font-family: Times New Roman"><i>target</i>,
+ <i>V</i>, <i>propertyKey</i></span>, and <var>receiver</var> the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Let <i>key</i> be <a href="#sec-topropertykey">ToPropertyKey</a>(<i>propertyKey</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>key</i>).</li>
+ <li>If <i>receiver</i> is not present, then
+ <ol class="block">
+ <li>Let <i>receiver</i> be <i>target</i>.</li>
+ </ol>
+ </li>
+ <li>Return <i>target.</i>[[Set]](<i>key</i>, <i>V</i>, <i>receiver</i>).</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>set</code> function is <b>3</b>.</p>
+ </section>
+
+ <section id="sec-reflect.setprototypeof">
+ <h1><span class="secnum" id="sec-26.1.14"><a href="#sec-reflect.setprototypeof"
+ title="link to this section">26.1.14</a></span> Reflect.setPrototypeOf ( target, proto )</h1>
+
+ <p>When the <code>setPrototypeOf</code> function is called with arguments <span style="font-family: Times New
+ Roman"><i>target</i> and <i>propertyKey</i></span>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>target</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>proto</i>) is not Object and <i>proto</i> is not
+ <b>null</b>, throw a <b>TypeError</b> exception</li>
+ <li>Return <i>target.</i>[[SetPrototypeOf]](<i>proto</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-proxy-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-26.2"><a href="#sec-proxy-objects" title="link to this section">26.2</a></span> Proxy
+ Objects</h1>
+ </div>
+
+ <section id="sec-proxy-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-26.2.1"><a href="#sec-proxy-constructor" title="link to this section">26.2.1</a></span>
+ The Proxy Constructor</h1>
+
+ <p>The Proxy constructor is the %Proxy% intrinsic object and the initial value of the <code>Proxy</code> property of the
+ global object. When called as a constructor it creates and initializes a new proxy exotic object. <code>Proxy</code> is
+ not intended to be called as a function and will throw an exception when called in that manner.</p>
+
+ <p>The <code>Proxy</code> constructor may be used as the value in an <code>extends</code> clause of a class definition.
+ Subclass constructors that intend to inherit the ability to create proxy exotic objects must include a <code>super</code>
+ call to the <code>Proxy</code> constructor.</p>
+ </div>
+
+ <section id="sec-proxy-target-handler">
+ <h1><span class="secnum" id="sec-26.2.1.1"><a href="#sec-proxy-target-handler"
+ title="link to this section">26.2.1.1</a></span> Proxy ( target, handler )</h1>
+
+ <p>When <code>Proxy</code> is called with arguments <var>target</var> and <var>handler</var> performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li>If NewTarget is <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <a href="#sec-proxycreate">ProxyCreate</a>(<i>target</i>, <i>handler</i>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-properties-of-the-proxy-constructor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-26.2.2"><a href="#sec-properties-of-the-proxy-constructor"
+ title="link to this section">26.2.2</a></span> Properties of the Proxy Constructor</h1>
+
+ <p>The value of the [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of the
+ <code>Proxy</code> constructor is the intrinsic object %FunctionPrototype% (<a
+ href="#sec-properties-of-the-function-prototype-object">19.2.3</a>).</p>
+
+ <p>The <code>Proxy</code> constructor does not have a <code>prototype</code> property because proxy exotic objects do not
+ have a [[Prototype]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> that requires
+ initialization.</p>
+
+ <p>Besides the <code>length</code> property (whose value is <b>2</b>), the <code>Proxy</code> constructor has the
+ following properties:</p>
+ </div>
+
+ <section id="sec-proxy.revocable">
+ <div class="front">
+ <h1><span class="secnum" id="sec-26.2.2.1"><a href="#sec-proxy.revocable"
+ title="link to this section">26.2.2.1</a></span> Proxy.revocable ( target, handler )</h1>
+
+ <p>The <code>Proxy.revocable</code> function is used to create a revocable Proxy object. When
+ <code>Proxy.revocable</code> is called with arguments <var>target</var> and <var>handler</var> the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>p</i> be <a href="#sec-proxycreate">ProxyCreate</a>(<i>target</i>, <i>handler</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>p</i>).</li>
+ <li>Let <i>revoker</i> be a new built-in function object as defined in <a
+ href="#sec-proxy-revocation-functions">26.2.2.1.1</a>.</li>
+ <li>Set the [[RevokableProxy]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ <i>revoker</i> to <i>p</i>.</li>
+ <li>Let <i>result</i> be <a href="#sec-objectcreate">ObjectCreate</a>(%ObjectPrototype%).</li>
+ <li>Perform <a href="#sec-createdataproperty">CreateDataProperty</a>(<i>result</i>, <code>"proxy"</code>,
+ <i>p</i>).</li>
+ <li>Perform <a href="#sec-createmethodproperty">CreateMethodProperty</a>(<i>result</i>, <code>"revoke"</code>,
+ <i>revoker</i>).</li>
+ <li>Return <i>result</i>.</li>
+ </ol>
+ </div>
+
+ <section id="sec-proxy-revocation-functions">
+ <h1><span class="secnum" id="sec-26.2.2.1.1"><a href="#sec-proxy-revocation-functions"
+ title="link to this section">26.2.2.1.1</a></span> Proxy Revocation Functions</h1>
+
+ <p>A Proxy revocation function is an anonymous function that has the ability to invalidate a specific Proxy object.</p>
+
+ <p>Each Proxy revocation function has a [[RevokableProxy]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</p>
+
+ <p>When a Proxy revocation function, <var>F</var>, is called the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>p</i> be the value of <i>F</i>’s [[RevokableProxy]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>If <i>p</i> is <b>null</b>, return <b>undefined</b>.</li>
+ <li>Set the value of <i>F</i>’s [[RevokableProxy]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> to <b>null</b>.</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>p</i> is a Proxy object.</li>
+ <li>Set the [[ProxyTarget]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>p</i> to
+ <b>null</b>.</li>
+ <li>Set the [[ProxyHandler]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of <i>p</i>
+ to <b>null</b>.</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-module-namespace-objects">
+ <div class="front">
+ <h1><span class="secnum" id="sec-26.3"><a href="#sec-module-namespace-objects" title="link to this section">26.3</a></span>
+ Module Namespace Objects</h1>
+
+ <p>A Module Namespace Object is a module namespace exotic object that provides runtime property-based access to a
+ module’s exported bindings. There is no constructor function for Module Namespace Objects. Instead, such an object is
+ created for each module that is imported by an <span class="nt">ImportDeclaration</span> that includes a <span
+ class="nt">NameSpaceImport</span> (See <a href="#sec-imports">15.2.2</a>).</p>
+
+ <p>In addition to the properties specified in <a href="#sec-imports">15.2.2</a> each Module Namespace Object has the own
+ following properties:</p>
+ </div>
+
+ <section id="sec-@@tostringtag">
+ <h1><span class="secnum" id="sec-26.3.1"><a href="#sec-@@tostringtag" title="link to this section">26.3.1</a></span>
+ @@toStringTag</h1>
+
+ <p>The initial value of the @@toStringTag property is the string value <b>"<code>Module</code>"</b>.</p>
+
+ <p>This property has the attributes { [[Writable]]: <span class="value">false</span>, [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }.</p>
+ </section>
+
+ <section id="sec-@@iterator">
+ <h1><span class="secnum" id="sec-26.3.2"><a href="#sec-@@iterator" title="link to this section">26.3.2</a></span> [
+ @@iterator ] ( )</h1>
+
+ <p>The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>N</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>N</i>) is not Object, throw a <b>TypeError</b>
+ exception.</li>
+ <li>Return <i>N</i>.[[Enumerate]]().</li>
+ </ol>
+
+ <p>The value of the <code>name</code> property of this function is <code>"[Symbol.iterator]"</code>.</p>
+ </section>
+ </section>
+</section>
+
+<section id="sec-grammar-summary">
+ <div class="front">
+ <h1><span class="secnum" id="sec-A"><a href="#sec-grammar-summary" title="link to this section">Annex A</a></span> <span
+ class="section-status">(informative)</span> Grammar Summary</h1>
+ </div>
+
+ <section id="sec-lexical-grammar">
+ <h1><span class="secnum" id="sec-A.1"><a href="#sec-lexical-grammar" title="link to this section">A.1</a></span> Lexical
+ Grammar</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-source-text">See 10.1</a></div>
+ <div class="lhs"><span class="nt">SourceCharacter</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="gprose">any Unicode code point</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-lexical-grammar">See clause 11</a></div>
+ <div class="lhs"><span class="nt">InputElementDiv</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">DivPunctuator</span></div>
+ <div class="rhs"><span class="nt">RightBracePunctuator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-lexical-grammar">See clause 11</a></div>
+ <div class="lhs"><span class="nt">InputElementRegExp</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">RightBracePunctuator</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-lexical-grammar">See clause 11</a></div>
+ <div class="lhs"><span class="nt">InputElementRegExpOrTemplateTail</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateSubstitutionTail</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-lexical-grammar">See clause 11</a></div>
+ <div class="lhs"><span class="nt">InputElementTemplateTail</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ <div class="rhs"><span class="nt">Comment</span></div>
+ <div class="rhs"><span class="nt">CommonToken</span></div>
+ <div class="rhs"><span class="nt">DivPunctuator</span></div>
+ <div class="rhs"><span class="nt">TemplateSubstitutionTail</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-white-space">See 11.2</a></div>
+ <div class="lhs"><span class="nt">WhiteSpace</span> <span class="geq">::</span> </div>
+ <div class="rhs"><TAB></div>
+ <div class="rhs"><VT></div>
+ <div class="rhs"><FF></div>
+ <div class="rhs"><SP></div>
+ <div class="rhs"><NBSP></div>
+ <div class="rhs"><ZWNBSP></div>
+ <div class="rhs"><USP></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-line-terminators">See 11.3</a></div>
+ <div class="lhs"><span class="nt">LineTerminator</span> <span class="geq">::</span> </div>
+ <div class="rhs"><LF></div>
+ <div class="rhs"><CR></div>
+ <div class="rhs"><LS></div>
+ <div class="rhs"><PS></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-line-terminators">See 11.3</a></div>
+ <div class="lhs"><span class="nt">LineTerminatorSequence</span> <span class="geq">::</span> </div>
+ <div class="rhs"><LF></div>
+ <div class="rhs"><CR> <span class="grhsannot">[lookahead ≠ <LF> ]</span></div>
+ <div class="rhs"><LS></div>
+ <div class="rhs"><PS></div>
+ <div class="rhs"><CR> <LF></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">Comment</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">MultiLineComment</span></div>
+ <div class="rhs"><span class="nt">SingleLineComment</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">MultiLineComment</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">/*</code> <span class="nt">MultiLineCommentChars</span><sub>opt</sub> <code class="t">*/</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">MultiLineCommentChars</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">MultiLineNotAsteriskChar</span> <span class="nt">MultiLineCommentChars</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">PostAsteriskCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">PostAsteriskCommentChars</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">MultiLineNotForwardSlashOrAsteriskChar</span> <span class="nt">MultiLineCommentChars</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">PostAsteriskCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">MultiLineNotAsteriskChar</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <code class="t">*</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">MultiLineNotForwardSlashOrAsteriskChar</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">/</code> <span class="grhsmod">or</span> <code class="t">*</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">SingleLineComment</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">//</code> <span class="nt">SingleLineCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">SingleLineCommentChars</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SingleLineCommentChar</span> <span class="nt">SingleLineCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comments">See 11.4</a></div>
+ <div class="lhs"><span class="nt">SingleLineCommentChar</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tokens">See 11.5</a></div>
+ <div class="lhs"><span class="nt">CommonToken</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">Punctuator</span></div>
+ <div class="rhs"><span class="nt">NumericLiteral</span></div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ <div class="rhs"><span class="nt">Template</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-names-and-keywords">See 11.6</a></div>
+ <div class="lhs"><span class="nt">IdentifierName</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">IdentifierStart</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <span class="nt">IdentifierPart</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-names-and-keywords">See 11.6</a></div>
+ <div class="lhs"><span class="nt">IdentifierStart</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">UnicodeIDStart</span></div>
+ <div class="rhs"><code class="t">$</code></div>
+ <div class="rhs"><code class="t">_</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">UnicodeEscapeSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-names-and-keywords">See 11.6</a></div>
+ <div class="lhs"><span class="nt">IdentifierPart</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">UnicodeIDContinue</span></div>
+ <div class="rhs"><code class="t">$</code></div>
+ <div class="rhs"><code class="t">_</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">UnicodeEscapeSequence</span></div>
+ <div class="rhs"><ZWNJ></div>
+ <div class="rhs"><ZWJ></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-names-and-keywords">See 11.6</a></div>
+ <div class="lhs"><span class="nt">UnicodeIDStart</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="gprose">any Unicode code point with the Unicode property “ID_Start” or “Other_ID_Start”</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-names-and-keywords">See 11.6</a></div>
+ <div class="lhs"><span class="nt">UnicodeIDContinue</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="gprose">any Unicode code point with the Unicode property “ID_Continue”, “Other_ID_Continue”, or “Other_ID_Start”</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-reserved-words">See 11.6.2</a></div>
+ <div class="lhs"><span class="nt">ReservedWord</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">Keyword</span></div>
+ <div class="rhs"><span class="nt">FutureReservedWord</span></div>
+ <div class="rhs"><span class="nt">NullLiteral</span></div>
+ <div class="rhs"><span class="nt">BooleanLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-keywords">See 11.6.2.1</a></div>
+ <div class="lhs"><span class="nt">Keyword</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ </div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>break</code></td>
+ <td><code>do</code></td>
+ <td><code>in</code></td>
+ <td><code>typeof</code></td>
+ </tr>
+ <tr>
+ <td><code>case</code></td>
+ <td><code>else</code></td>
+ <td><code>instanceof</code></td>
+ <td><code>var</code></td>
+ </tr>
+ <tr>
+ <td><code>catch</code></td>
+ <td><code>export</code></td>
+ <td><code>new</code></td>
+ <td><code>void</code></td>
+ </tr>
+ <tr>
+ <td><code>class</code></td>
+ <td><code>extends</code></td>
+ <td><code>return</code></td>
+ <td><code>while</code></td>
+ </tr>
+ <tr>
+ <td><code>const</code></td>
+ <td><code>finally</code></td>
+ <td><code>super</code></td>
+ <td><code>with</code></td>
+ </tr>
+ <tr>
+ <td><code>continue</code></td>
+ <td><code>for</code></td>
+ <td><code>switch</code></td>
+ <td><code>yield</code></td>
+ </tr>
+ <tr>
+ <td><code>debugger</code></td>
+ <td><code>function</code></td>
+ <td><code>this</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>default</code></td>
+ <td><code>if</code></td>
+ <td><code>throw</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>delete</code></td>
+ <td><code>import</code></td>
+ <td><code>try</code></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-future-reserved-words">See 11.6.2.2</a></div>
+ <div class="lhs"><span class="nt">FutureReservedWord</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">enum</code></div>
+ <div class="rhs"><code class="t">await</code></div>
+ </div>
+
+ <p><code>await</code> is only treated as a <span class="nt">FutureReservedWord</span> when <span class="nt">Module</span> is
+ the goal symbol of the syntactic grammar.</p>
+
+ <p>The following tokens are also considered to be <span class="nt">FutureReservedWords</span> when parsing <a
+ href="#sec-strict-mode-code">strict mode code</a> (<a href="#sec-strict-mode-code">see 10.2.1</a>).</p>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>implements</code></td>
+ <td><code>package</code></td>
+ <td><code>protected</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>interface</code></td>
+ <td><code>private</code></td>
+ <td><code>public</code></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-punctuators">See 11.7</a></div>
+ <div class="lhs"><span class="nt">Punctuator</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ </div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>{</code></td>
+ <td><code>}</code></td>
+ <td><code>(</code></td>
+ <td><code>)</code></td>
+ <td><code>[</code></td>
+ <td><code>]</code></td>
+ </tr>
+ <tr>
+ <td><code>.</code></td>
+ <td><code>;</code></td>
+ <td><code>,</code></td>
+ <td><code><</code></td>
+ <td><code>></code></td>
+ <td><code><=</code></td>
+ </tr>
+ <tr>
+ <td><code>>=</code></td>
+ <td><code>==</code></td>
+ <td><code>!=</code></td>
+ <td><code>===</code></td>
+ <td><code>!==</code></td>
+ <td></td>
+ </tr>
+ <tr>
+ <td><code>+</code></td>
+ <td><code>-</code></td>
+ <td><code>*</code></td>
+ <td><code>%</code></td>
+ <td><code>++</code></td>
+ <td><code>--</code></td>
+ </tr>
+ <tr>
+ <td><code><<</code></td>
+ <td><code>>></code></td>
+ <td><code>>>></code></td>
+ <td><code>&</code></td>
+ <td><code>|</code></td>
+ <td><code>^</code></td>
+ </tr>
+ <tr>
+ <td><code>!</code></td>
+ <td><code>~</code></td>
+ <td><code>&&</code></td>
+ <td><code>||</code></td>
+ <td><code>?</code></td>
+ <td><code>:</code></td>
+ </tr>
+ <tr>
+ <td><code>=</code></td>
+ <td><code>+=</code></td>
+ <td><code>-=</code></td>
+ <td><code>*=</code></td>
+ <td><code>%=</code></td>
+ <td><code><<=</code></td>
+ </tr>
+ <tr>
+ <td><code>>>=</code></td>
+ <td><code>>>>=</code></td>
+ <td><code>&=</code></td>
+ <td><code>|=</code></td>
+ <td><code>^=</code></td>
+ <td><code>=></code></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-punctuators">See 11.7</a></div>
+ <div class="lhs"><span class="nt">DivPunctuator</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ </div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>/</code></td>
+ <td><code>/=</code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-punctuators">See 11.7</a></div>
+ <div class="lhs"><span class="nt">RightBracePunctuator</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ </div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>}</code></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ <td></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-null-literals">See 11.8.1</a></div>
+ <div class="lhs"><span class="nt">NullLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">null</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-boolean-literals">See 11.8.2</a></div>
+ <div class="lhs"><span class="nt">BooleanLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">true</code></div>
+ <div class="rhs"><code class="t">false</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">NumericLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DecimalLiteral</span></div>
+ <div class="rhs"><span class="nt">BinaryIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">OctalIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">HexIntegerLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">DecimalLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DecimalIntegerLiteral</span> <code class="t">.</code> <span class="nt">DecimalDigits</span><sub>opt</sub> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">.</code> <span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">DecimalIntegerLiteral</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">DecimalIntegerLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">0</code></div>
+ <div class="rhs"><span class="nt">NonZeroDigit</span> <span class="nt">DecimalDigits</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">DecimalDigits</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <span class="nt">DecimalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">DecimalDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">NonZeroDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">ExponentPart</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">ExponentIndicator</span> <span class="nt">SignedInteger</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">ExponentIndicator</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">e</code> <code class="t">E</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">SignedInteger</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">DecimalDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">BinaryIntegerLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">0b</code> <span class="nt">BinaryDigits</span></div>
+ <div class="rhs"><code class="t">0B</code> <span class="nt">BinaryDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">BinaryDigits</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">BinaryDigit</span></div>
+ <div class="rhs"><span class="nt">BinaryDigits</span> <span class="nt">BinaryDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">BinaryDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">OctalIntegerLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">0o</code> <span class="nt">OctalDigits</span></div>
+ <div class="rhs"><code class="t">0O</code> <span class="nt">OctalDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">OctalDigits</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">OctalDigit</span></div>
+ <div class="rhs"><span class="nt">OctalDigits</span> <span class="nt">OctalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">OctalDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">HexIntegerLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">0x</code> <span class="nt">HexDigits</span></div>
+ <div class="rhs"><code class="t">0X</code> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">HexDigits</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">HexDigit</span></div>
+ <div class="rhs"><span class="nt">HexDigits</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-numeric-literals">See 11.8.3</a></div>
+ <div class="lhs"><span class="nt">HexDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code> <code class="t">a</code> <code class="t">b</code> <code class="t">c</code> <code class="t">d</code> <code class="t">e</code> <code class="t">f</code> <code class="t">A</code> <code class="t">B</code> <code class="t">C</code> <code class="t">D</code> <code class="t">E</code> <code class="t">F</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">StringLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">"</code> <span class="nt">DoubleStringCharacters</span><sub>opt</sub> <code class="t">"</code></div>
+ <div class="rhs"><code class="t">'</code> <span class="nt">SingleStringCharacters</span><sub>opt</sub> <code class="t">'</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">DoubleStringCharacters</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DoubleStringCharacter</span> <span class="nt">DoubleStringCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">SingleStringCharacters</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SingleStringCharacter</span> <span class="nt">SingleStringCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">DoubleStringCharacter</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">"</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">EscapeSequence</span></div>
+ <div class="rhs"><span class="nt">LineContinuation</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">SingleStringCharacter</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">'</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">EscapeSequence</span></div>
+ <div class="rhs"><span class="nt">LineContinuation</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">LineContinuation</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">LineTerminatorSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">EscapeSequence</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">CharacterEscapeSequence</span></div>
+ <div class="rhs"><code class="t">0</code> <span class="grhsannot">[lookahead ∉ <span class="nt">DecimalDigit</span>]</span></div>
+ <div class="rhs"><span class="nt">HexEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">UnicodeEscapeSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">CharacterEscapeSequence</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SingleEscapeCharacter</span></div>
+ <div class="rhs"><span class="nt">NonEscapeCharacter</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">SingleEscapeCharacter</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">'</code> <code class="t">"</code> <code class="t">\</code> <code class="t">b</code> <code class="t">f</code> <code class="t">n</code> <code class="t">r</code> <code class="t">t</code> <code class="t">v</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">NonEscapeCharacter</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <span class="nt">EscapeCharacter</span> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">EscapeCharacter</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SingleEscapeCharacter</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><code class="t">x</code></div>
+ <div class="rhs"><code class="t">u</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">HexEscapeSequence</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">x</code> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">UnicodeEscapeSequence</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">u</code> <span class="nt">Hex4Digits</span></div>
+ <div class="rhs"><code class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-string-literals">See 11.8.4</a></div>
+ <div class="lhs"><span class="nt">Hex4Digits</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionLiteral</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">/</code> <span class="nt">RegularExpressionBody</span> <code class="t">/</code> <span class="nt">RegularExpressionFlags</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionBody</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">RegularExpressionFirstChar</span> <span class="nt">RegularExpressionChars</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionChars</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionChars</span> <span class="nt">RegularExpressionChar</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionFirstChar</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="grhsmod">but not one of</span> <code class="t">*</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">/</code> <span class="grhsmod">or</span> <code class="t">[</code></div>
+ <div class="rhs"><span class="nt">RegularExpressionBackslashSequence</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionClass</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionChar</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">/</code> <span class="grhsmod">or</span> <code class="t">[</code></div>
+ <div class="rhs"><span class="nt">RegularExpressionBackslashSequence</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionClass</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionBackslashSequence</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">RegularExpressionNonTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionClass</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">RegularExpressionClassChars</span> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionClassChars</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionClassChars</span> <span class="nt">RegularExpressionClassChar</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionClassChar</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">RegularExpressionNonTerminator</span> <span class="grhsmod">but not one of</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">\</code></div>
+ <div class="rhs"><span class="nt">RegularExpressionBackslashSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-literals-regular-expression-literals">See 11.8.5</a></div>
+ <div class="lhs"><span class="nt">RegularExpressionFlags</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionFlags</span> <span class="nt">IdentifierPart</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">Template</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">NoSubstitutionTemplate</span></div>
+ <div class="rhs"><span class="nt">TemplateHead</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">NoSubstitutionTemplate</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">`</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">`</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">TemplateHead</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">`</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">${</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">TemplateSubstitutionTail</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">TemplateMiddle</span></div>
+ <div class="rhs"><span class="nt">TemplateTail</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">TemplateMiddle</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">}</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">${</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">TemplateTail</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">}</code> <span class="nt">TemplateCharacters</span><sub>opt</sub> <code class="t">`</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">TemplateCharacters</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">TemplateCharacter</span> <span class="nt">TemplateCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literal-lexical-components">See 11.8.6</a></div>
+ <div class="lhs"><span class="nt">TemplateCharacter</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">$</code> <span class="grhsannot">[lookahead ≠ { ]</span></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">EscapeSequence</span></div>
+ <div class="rhs"><span class="nt">LineContinuation</span></div>
+ <div class="rhs"><span class="nt">LineTerminatorSequence</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">`</code> <span class="grhsmod">or</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">$</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ </div>
+ </section>
+
+ <section id="sec-expressions">
+ <h1><span class="secnum" id="sec-A.2"><a href="#sec-expressions" title="link to this section">A.2</a></span> Expressions</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-identifiers">See 12.1</a></div>
+ <div class="lhs"><span class="nt">IdentifierReference</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">Identifier</span></div>
+ <div class="rhs"><span class="grhsannot">[~Yield]</span> <code class="t">yield</code></div>
+ </div>
+
+ <p><span class="nt">BindingIdentifier</span><sub>[Yield]</sub> <span class="value">:</span> 	See <a
+ href="#sec-identifiers">12.1</a></p>
+
+ <p><span style="font-family: Times New Roman"><i>Identifier<br></i></span>[~Yield] <code>yield</code></p>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-identifiers">See 12.1</a></div>
+ <div class="lhs"><span class="nt">LabelIdentifier</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">Identifier</span></div>
+ <div class="rhs"><span class="grhsannot">[~Yield]</span> <code class="t">yield</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-identifiers">See 12.1</a></div>
+ <div class="lhs"><span class="nt">Identifier</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <span class="grhsmod">but not</span> <span class="nt">ReservedWord</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-primary-expression">See 12.2</a></div>
+ <div class="lhs"><span class="nt">PrimaryExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">this</code></div>
+ <div class="rhs"><span class="nt">IdentifierReference</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">Literal</span></div>
+ <div class="rhs"><span class="nt">ArrayLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ObjectLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">FunctionExpression</span></div>
+ <div class="rhs"><span class="nt">ClassExpression</span></div>
+ <div class="rhs"><span class="nt">GeneratorExpression</span></div>
+ <div class="rhs"><span class="nt">RegularExpressionLiteral</span></div>
+ <div class="rhs"><span class="nt">TemplateLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-primary-expression">See 12.2</a></div>
+ <div class="lhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">,</code> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">)</code></div>
+ </div>
+
+ <p>When processing the production</p>
+
+ <p><span class="nt">PrimaryExpression</span><sub>[Yield]</sub> <b>:</b> <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub><span style="font-family: Times New
+ Roman"><i><br></i></span>the interpretation of <span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span> is
+ refined using the following grammar:</p>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-primary-expression">See 12.2</a></div>
+ <div class="lhs"><span class="nt">ParenthesizedExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-primary-expression-literals">See 12.2.3</a></div>
+ <div class="lhs"><span class="nt">Literal</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">NullLiteral</span></div>
+ <div class="rhs"><span class="nt">BooleanLiteral</span></div>
+ <div class="rhs"><span class="nt">NumericLiteral</span></div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-array-initializer">See 12.2.4</a></div>
+ <div class="lhs"><span class="nt">ArrayLiteral</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-array-initializer">See 12.2.4</a></div>
+ <div class="lhs"><span class="nt">ElementList</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">Elision</span><sub>opt</sub> <span class="nt">SpreadElement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ElementList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">SpreadElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-array-initializer">See 12.2.4</a></div>
+ <div class="lhs"><span class="nt">Elision</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">,</code></div>
+ <div class="rhs"><span class="nt">Elision</span> <code class="t">,</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-array-initializer">See 12.2.4</a></div>
+ <div class="lhs"><span class="nt">SpreadElement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">...</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">ObjectLiteral</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">PropertyDefinitionList</span><sub>[?Yield]</sub> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">PropertyDefinitionList</span><sub>[?Yield]</sub> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">PropertyDefinitionList</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">PropertyDefinition</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">PropertyDefinitionList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">PropertyDefinition</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">PropertyDefinition</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">IdentifierReference</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CoverInitializedName</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">:</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MethodDefinition</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">PropertyName</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LiteralPropertyName</span></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">ComputedPropertyName</span></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">ComputedPropertyName</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">LiteralPropertyName</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ <div class="rhs"><span class="nt">NumericLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">ComputedPropertyName</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">CoverInitializedName</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">IdentifierReference</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-object-initializer">See 12.2.5</a></div>
+ <div class="lhs"><span class="nt">Initializer</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">=</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literals">See 12.2.8</a></div>
+ <div class="lhs"><span class="nt">TemplateLiteral</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">NoSubstitutionTemplate</span></div>
+ <div class="rhs"><span class="nt">TemplateHead</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <span class="nt">TemplateSpans</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literals">See 12.2.8</a></div>
+ <div class="lhs"><span class="nt">TemplateSpans</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">TemplateTail</span></div>
+ <div class="rhs"><span class="nt">TemplateMiddleList</span><sub>[?Yield]</sub> <span class="nt">TemplateTail</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-template-literals">See 12.2.8</a></div>
+ <div class="lhs"><span class="nt">TemplateMiddleList</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">TemplateMiddle</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">TemplateMiddleList</span><sub>[?Yield]</sub> <span class="nt">TemplateMiddle</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">MemberExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">PrimaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <code class="t">[</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <span class="nt">TemplateLiteral</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">SuperProperty</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MetaProperty</span></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">MemberExpression</span><sub>[?Yield]</sub> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">SuperProperty</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">super</code> <code class="t">[</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">super</code> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">MetaProperty</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">NewTarget</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">NewTarget</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">new</code> <code class="t">.</code> <code class="t">target</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">NewExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">new</code> <span class="nt">NewExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">CallExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">MemberExpression</span><sub>[?Yield]</sub> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">SuperCall</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <code class="t">[</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">]</code></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <code class="t">.</code> <span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub> <span class="nt">TemplateLiteral</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">SuperCall</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">super</code> <span class="nt">Arguments</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">Arguments</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">(</code> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">ArgumentList</span><sub>[?Yield]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">ArgumentList</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><code class="t">...</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ArgumentList</span><sub>[?Yield]</sub> <code class="t">,</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ArgumentList</span><sub>[?Yield]</sub> <code class="t">,</code> <code class="t">...</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-left-hand-side-expressions">See 12.3</a></div>
+ <div class="lhs"><span class="nt">LeftHandSideExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">NewExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CallExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-postfix-expressions">See 12.4</a></div>
+ <div class="lhs"><span class="nt">PostfixExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">++</code></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">--</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-unary-operators">See 12.5</a></div>
+ <div class="lhs"><span class="nt">UnaryExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">PostfixExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">delete</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">void</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">typeof</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">++</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">--</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">~</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">!</code> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-multiplicative-operators">See 12.6</a></div>
+ <div class="lhs"><span class="nt">MultiplicativeExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub> <span class="nt">MultiplicativeOperator</span> <span class="nt">UnaryExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-multiplicative-operators">See 12.6</a></div>
+ <div class="lhs"><span class="nt">MultiplicativeOperator</span> <span class="geq">:</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">*</code> <code class="t">/</code> <code class="t">%</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-additive-operators">See 12.7</a></div>
+ <div class="lhs"><span class="nt">AdditiveExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span><sub>[?Yield]</sub> <code class="t">+</code> <span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span><sub>[?Yield]</sub> <code class="t">-</code> <span class="nt">MultiplicativeExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-bitwise-shift-operators">See 12.8</a></div>
+ <div class="lhs"><span class="nt">ShiftExpression</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub> <code class="t"><<</code> <span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub> <code class="t">>></code> <span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub> <code class="t">>>></code> <span class="nt">AdditiveExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-relational-operators">See 12.9</a></div>
+ <div class="lhs"><span class="nt">RelationalExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t"><</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t">></code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t"><=</code> <span class="nt">ShiftExpression</span><sub>[? Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t">>=</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub> <code class="t">instanceof</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+In]</span> <span class="nt">RelationalExpression</span><sub>[In, ?Yield]</sub> <code class="t">in</code> <span class="nt">ShiftExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-equality-operators">See 12.10</a></div>
+ <div class="lhs"><span class="nt">EqualityExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">==</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">!=</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">===</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub> <code class="t">!==</code> <span class="nt">RelationalExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-binary-bitwise-operators">See 12.11</a></div>
+ <div class="lhs"><span class="nt">BitwiseANDExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BitwiseANDExpression</span><sub>[?In, ?Yield]</sub> <code class="t">&</code> <span class="nt">EqualityExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-binary-bitwise-operators">See 12.11</a></div>
+ <div class="lhs"><span class="nt">BitwiseXORExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BitwiseANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BitwiseXORExpression</span><sub>[?In, ?Yield]</sub> <code class="t">^</code> <span class="nt">BitwiseANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-binary-bitwise-operators">See 12.11</a></div>
+ <div class="lhs"><span class="nt">BitwiseORExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BitwiseXORExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BitwiseORExpression</span><sub>[?In, ?Yield]</sub> <code class="t">|</code> <span class="nt">BitwiseXORExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-binary-logical-operators">See 12.12</a></div>
+ <div class="lhs"><span class="nt">LogicalANDExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BitwiseORExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LogicalANDExpression</span><sub>[?In, ?Yield]</sub> <code class="t">&&</code> <span class="nt">BitwiseORExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-binary-logical-operators">See 12.12</a></div>
+ <div class="lhs"><span class="nt">LogicalORExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LogicalANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LogicalORExpression</span><sub>[?In, ?Yield]</sub> <code class="t">||</code> <span class="nt">LogicalANDExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-conditional-operator">See 12.13</a></div>
+ <div class="lhs"><span class="nt">ConditionalExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LogicalORExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LogicalORExpression</span><sub>[?In,?Yield]</sub> <code class="t">?</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">:</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-assignment-operators">See 12.14</a></div>
+ <div class="lhs"><span class="nt">AssignmentExpression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ConditionalExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+Yield]</span> <span class="nt">YieldExpression</span><sub>[?In]</sub></div>
+ <div class="rhs"><span class="nt">ArrowFunction</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <code class="t">=</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <span class="nt">AssignmentOperator</span> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-assignment-operators">See 12.14</a></div>
+ <div class="lhs"><span class="nt">AssignmentOperator</span> <span class="geq">:</span> <span class="grhsmod">one of</span> </div>
+ </div>
+
+ <figure>
+ <table class="lightweight-table">
+ <tr>
+ <td><code>*=</code></td>
+ <td><code>/=</code></td>
+ <td><code>%=</code></td>
+ <td><code>+=</code></td>
+ <td><code>-=</code></td>
+ <td><code><<=</code></td>
+ <td><code>>>=</code></td>
+ <td><code>>>>=</code></td>
+ <td><code>&=</code></td>
+ <td><code>^=</code></td>
+ <td><code>|=</code></td>
+ </tr>
+ </table>
+ </figure>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-comma-operator">See 12.15</a></div>
+ <div class="lhs"><span class="nt">Expression</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">Expression</span><sub>[?In, ?Yield]</sub> <code class="t">,</code> <span class="nt">AssignmentExpression</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+ </section>
+
+ <section id="sec-statements">
+ <h1><span class="secnum" id="sec-A.3"><a href="#sec-statements" title="link to this section">A.3</a></span> Statements</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-statements-and-declarations">See clause 13</a></div>
+ <div class="lhs"><span class="nt">Statement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BlockStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">VariableStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">EmptyStatement</span></div>
+ <div class="rhs"><span class="nt">ExpressionStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">IfStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">BreakableStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">ContinueStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BreakStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+Return]</span> <span class="nt">ReturnStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">WithStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">LabelledStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">ThrowStatement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">TryStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">DebuggerStatement</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-statements-and-declarations">See clause 13</a></div>
+ <div class="lhs"><span class="nt">Declaration</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">HoistableDeclaration</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ClassDeclaration</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">LexicalDeclaration</span><sub>[In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-statements-and-declarations">See clause 13</a></div>
+ <div class="lhs"><span class="nt">HoistableDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">FunctionDeclaration</span><sub>[?Yield,?Default]</sub></div>
+ <div class="rhs"><span class="nt">GeneratorDeclaration</span><sub>[?Yield, ?Default]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-ecmascript-language-statements-and-declarations">See clause 13</a></div>
+ <div class="lhs"><span class="nt">BreakableStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">IterationStatement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">SwitchStatement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-block">See 13.1</a></div>
+ <div class="lhs"><span class="nt">BlockStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">Block</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-block">See 13.1</a></div>
+ <div class="lhs"><span class="nt">Block</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-block">See 13.1</a></div>
+ <div class="lhs"><span class="nt">StatementList</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">StatementListItem</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub> <span class="nt">StatementListItem</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-block">See 13.1</a></div>
+ <div class="lhs"><span class="nt">StatementListItem</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">Declaration</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-let-and-const-declarations">See 13.2.1</a></div>
+ <div class="lhs"><span class="nt">LexicalDeclaration</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LetOrConst</span> <span class="nt">BindingList</span><sub>[?In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-let-and-const-declarations">See 13.2.1</a></div>
+ <div class="lhs"><span class="nt">LetOrConst</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">let</code></div>
+ <div class="rhs"><code class="t">const</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-let-and-const-declarations">See 13.2.1</a></div>
+ <div class="lhs"><span class="nt">BindingList</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LexicalBinding</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BindingList</span><sub>[?In, ?Yield]</sub> <code class="t">,</code> <span class="nt">LexicalBinding</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-let-and-const-declarations">See 13.2.1</a></div>
+ <div class="lhs"><span class="nt">LexicalBinding</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-variable-statement">See 13.2.2</a></div>
+ <div class="lhs"><span class="nt">VariableStatement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">var</code> <span class="nt">VariableDeclarationList</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-variable-statement">See 13.2.2</a></div>
+ <div class="lhs"><span class="nt">VariableDeclarationList</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">VariableDeclaration</span><sub>[?In, ?Yield]</sub></div>
+ <div class="rhs"><span class="nt">VariableDeclarationList</span><sub>[?In, ?Yield]</sub> <code class="t">,</code> <span class="nt">VariableDeclaration</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-variable-statement">See 13.2.2</a></div>
+ <div class="lhs"><span class="nt">VariableDeclaration</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[?In, ?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">BindingPattern</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ObjectBindingPattern</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">ArrayBindingPattern</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">ObjectBindingPattern</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">BindingPropertyList</span><sub>[?Yield,?GeneratorParameter]</sub> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">BindingPropertyList</span><sub>[?Yield,?GeneratorParameter]</sub> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">ArrayBindingPattern</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span><sub>[?Yield, ?GeneratorParameter]</sub><sub>opt</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">BindingElementList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <span class="nt">BindingElementList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingRestElement</span><sub>[?Yield, ?GeneratorParameter]</sub><sub>opt</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">BindingPropertyList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingProperty</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">BindingPropertyList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">BindingProperty</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">BindingElementList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingElisionElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">BindingElementList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">BindingElisionElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">BindingElisionElement</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">Elision</span><sub>opt</sub> <span class="nt">BindingElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">BindingProperty</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">SingleNameBinding</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">PropertyName</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">:</code> <span class="nt">BindingElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">BindingElement</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">SingleNameBinding</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">BindingPattern</span><sub>[?Yield,GeneratorParameter]</sub> <span class="nt">Initializer</span><sub>[In]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">BindingPattern</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In, ?Yield]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">SingleNameBinding</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">BindingIdentifier</span><sub>[Yield]</sub> <span class="nt">Initializer</span><sub>[In]</sub><sub>opt</sub></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">Initializer</span><sub>[In, ?Yield]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-destructuring-binding-patterns">See 13.2.3</a></div>
+ <div class="lhs"><span class="nt">BindingRestElement</span><sub>[Yield, GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <code class="t">...</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-empty-statement">See 13.3</a></div>
+ <div class="lhs"><span class="nt">EmptyStatement</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-expression-statement">See 13.4</a></div>
+ <div class="lhs"><span class="nt">ExpressionStatement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="grhsannot">[lookahead ∉ {<code class="t">{</code>, <code class="t">function</code>, <code class="t">class</code>, <code class="t">let [</code>}]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-if-statement">See 13.5</a></div>
+ <div class="lhs"><span class="nt">IfStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub> <code class="t">else</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-iteration-statements">See 13.6</a></div>
+ <div class="lhs"><span class="nt">IterationStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">do</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub> <code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <code class="t">;</code><sub>opt</sub></div>
+ <div class="rhs"><code class="t">while</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="grhsannot">[lookahead ∉ {<code class="t">let [</code>}]</span> <span class="nt">Expression</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">VariableDeclarationList</span><sub>[?Yield]</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LexicalDeclaration</span><sub>[?Yield]</sub> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">;</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub><sub>opt</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="grhsannot">[lookahead ∉ {<code class="t">let [</code>}]</span> <span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <code class="t">in</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span><sub>[?Yield]</sub> <code class="t">in</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span><sub>[?Yield]</sub> <code class="t">in</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub> <code class="t">of</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <code class="t">var</code> <span class="nt">ForBinding</span><sub>[?Yield]</sub> <code class="t">of</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">for</code> <code class="t">(</code> <span class="nt">ForDeclaration</span><sub>[?Yield]</sub> <code class="t">of</code> <span class="nt">AssignmentExpression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-iteration-statements">See 13.6</a></div>
+ <div class="lhs"><span class="nt">ForDeclaration</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LetOrConst</span> <span class="nt">ForBinding</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-iteration-statements">See 13.6</a></div>
+ <div class="lhs"><span class="nt">ForBinding</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-continue-statement">See 13.7</a></div>
+ <div class="lhs"><span class="nt">ContinueStatement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">continue</code> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">continue</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-break-statement">See 13.8</a></div>
+ <div class="lhs"><span class="nt">BreakStatement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">break</code> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">break</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-return-statement">See 13.9</a></div>
+ <div class="lhs"><span class="nt">ReturnStatement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">return</code> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">return</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-with-statement">See 13.10</a></div>
+ <div class="lhs"><span class="nt">WithStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">with</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-switch-statement">See 13.11</a></div>
+ <div class="lhs"><span class="nt">SwitchStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">switch</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">CaseBlock</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-switch-statement">See 13.11</a></div>
+ <div class="lhs"><span class="nt">CaseBlock</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <span class="nt">DefaultClause</span><sub>[?Yield, ?Return]</sub> <span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub><sub>opt</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-switch-statement">See 13.11</a></div>
+ <div class="lhs"><span class="nt">CaseClauses</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">CaseClause</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">CaseClauses</span><sub>[?Yield, ?Return]</sub> <span class="nt">CaseClause</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-switch-statement">See 13.11</a></div>
+ <div class="lhs"><span class="nt">CaseClause</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">case</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">:</code> <span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-switch-statement">See 13.11</a></div>
+ <div class="lhs"><span class="nt">DefaultClause</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">default</code> <code class="t">:</code> <span class="nt">StatementList</span><sub>[?Yield, ?Return]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-labelled-statements">See 13.12</a></div>
+ <div class="lhs"><span class="nt">LabelledStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">LabelIdentifier</span><sub>[?Yield]</sub> <code class="t">:</code> <span class="nt">LabelledItem</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-labelled-statements">See 13.12</a></div>
+ <div class="lhs"><span class="nt">LabelledItem</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-throw-statement">See 13.13</a></div>
+ <div class="lhs"><span class="nt">ThrowStatement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">throw</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-try-statement">See 13.14</a></div>
+ <div class="lhs"><span class="nt">TryStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">try</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub> <span class="nt">Catch</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">try</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub> <span class="nt">Finally</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">try</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub> <span class="nt">Catch</span><sub>[?Yield, ?Return]</sub> <span class="nt">Finally</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-try-statement">See 13.14</a></div>
+ <div class="lhs"><span class="nt">Catch</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span><sub>[?Yield]</sub> <code class="t">)</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-try-statement">See 13.14</a></div>
+ <div class="lhs"><span class="nt">Finally</span><sub>[Yield, Return]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">finally</code> <span class="nt">Block</span><sub>[?Yield, ?Return]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-try-statement">See 13.14</a></div>
+ <div class="lhs"><span class="nt">CatchParameter</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">BindingPattern</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-debugger-statement">See 13.15</a></div>
+ <div class="lhs"><span class="nt">DebuggerStatement</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">debugger</code> <code class="t">;</code></div>
+ </div>
+ </section>
+
+ <section id="sec-functions-and-classes">
+ <h1><span class="secnum" id="sec-A.4"><a href="#sec-functions-and-classes" title="link to this section">A.4</a></span>
+ Functions and Classes</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FunctionDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">function</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><span class="grhsannot">[+Default]</span> <code class="t">function</code> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FunctionExpression</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">function</code> <span class="nt">BindingIdentifier</span><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">StrictFormalParameters</span><sub>[Yield, GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">FormalParameters</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">FormalParameterList</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FormalParameterList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">FunctionRestParameter</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">FormalsList</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">FormalsList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">FunctionRestParameter</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FormalsList</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">FormalParameter</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ <div class="rhs"><span class="nt">FormalsList</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">,</code> <span class="nt">FormalParameter</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FunctionRestParameter</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingRestElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FormalParameter</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingElement</span><sub>[?Yield, ?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FunctionBody</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">FunctionStatementList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-function-definitions">See 14.1</a></div>
+ <div class="lhs"><span class="nt">FunctionStatementList</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">StatementList</span><sub>[?Yield, Return]</sub><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-arrow-function-definitions">See 14.2</a></div>
+ <div class="lhs"><span class="nt">ArrowFunction</span><sub>[In, Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ArrowParameters</span><sub>[?Yield]</sub> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">=></code> <span class="nt">ConciseBody</span><sub>[?In]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-arrow-function-definitions">See 14.2</a></div>
+ <div class="lhs"><span class="nt">ArrowParameters</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-arrow-function-definitions">See 14.2</a></div>
+ <div class="lhs"><span class="nt">ConciseBody</span><sub>[In]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="grhsannot">[lookahead ≠ { ]</span> <span class="nt">AssignmentExpression</span><sub>[?In]</sub></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <p>When the production</p>
+
+ <p><span class="nt">ArrowParameters</span><sub>[Yield]</sub> <b>:</b> <span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span><sub>[?Yield]</sub></p>
+
+ <p>is recognized the following grammar is used to refine the interpretation of <span class="prod"><span
+ class="nt">CoverParenthesizedExpressionAndArrowParameterList</span> <span class="geq">:</span></span></p>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-arrow-function-definitions">See 14.2</a></div>
+ <div class="lhs"><span class="nt">ArrowFormalParameters</span><sub>[Yield, GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">StrictFormalParameters</span><sub>[?Yield, ?GeneratorParameter]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-method-definitions">See 14.3</a></div>
+ <div class="lhs"><span class="nt">MethodDefinition</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">StrictFormalParameters</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><span class="nt">GeneratorMethod</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">get</code> <span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">set</code> <span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">PropertySetParameterList</span> <code class="t">)</code> <code class="t">{</code> <span class="nt">FunctionBody</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-method-definitions">See 14.3</a></div>
+ <div class="lhs"><span class="nt">PropertySetParameterList</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">FormalParameter</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-generator-function-definitions">See 14.4</a></div>
+ <div class="lhs"><span class="nt">GeneratorMethod</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">PropertyName</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">StrictFormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-generator-function-definitions">See 14.4</a></div>
+ <div class="lhs"><span class="nt">GeneratorDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <code class="t">(</code> <span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ <div class="rhs"><span class="grhsannot">[+Default]</span> <code class="t">function</code> <code class="t">*</code> <code class="t">(</code> <span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-generator-function-definitions">See 14.4</a></div>
+ <div class="lhs"><span class="nt">GeneratorExpression</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">function</code> <code class="t">*</code> <span class="nt">BindingIdentifier</span><sub>[Yield]</sub><sub>opt</sub> <code class="t">(</code> <span class="nt">FormalParameters</span><sub>[Yield,GeneratorParameter]</sub> <code class="t">)</code> <code class="t">{</code> <span class="nt">GeneratorBody</span><sub>[Yield]</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-generator-function-definitions">See 14.4</a></div>
+ <div class="lhs"><span class="nt">GeneratorBody</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">FunctionBody</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-generator-function-definitions">See 14.4</a></div>
+ <div class="lhs"><span class="nt">YieldExpression</span><sub>[In]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">yield</code></div>
+ <div class="rhs"><code class="t">yield</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <span class="nt">AssignmentExpression</span><sub>[?In, Yield]</sub></div>
+ <div class="rhs"><code class="t">yield</code> <span class="grhsannot">[no <span class="nt">LineTerminator</span> here]</span> <code class="t">*</code> <span class="nt">AssignmentExpression</span><sub>[?In, Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-class-definitions">See 14.5</a></div>
+ <div class="lhs"><span class="nt">ClassDeclaration</span><sub>[Yield, Default]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">class</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub> <span class="nt">ClassTail</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+Default]</span> <code class="t">class</code> <span class="nt">ClassTail</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-class-definitions">See 14.5</a></div>
+ <div class="lhs"><span class="nt">ClassExpression</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">class</code> <span class="nt">BindingIdentifier</span><sub>[?Yield]</sub><sub>opt</sub> <span class="nt">ClassTail</span><sub>[?Yield,?GeneratorParameter]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-class-definitions">See 14.5</a></div>
+ <div class="lhs"><span class="nt">ClassTail</span><sub>[Yield,GeneratorParameter]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="grhsannot">[~GeneratorParameter]</span> <span class="nt">ClassHeritage</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">{</code> <span class="nt">ClassBody</span><sub>[?Yield]</sub><sub>opt</sub> <code class="t">}</code></div>
+ <div class="rhs"><span class="grhsannot">[+GeneratorParameter]</span> <span class="nt">ClassHeritage</span><sub>opt</sub> <code class="t">{</code> <span class="nt">ClassBody</span><sub>opt</sub> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-class-definitions">See 14.5</a></div>
+ <div class="lhs"><span class="nt">ClassHeritage</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">extends</code> <span class="nt">LeftHandSideExpression</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-class-definitions">See 14.5</a></div>
+ <div class="lhs"><span class="nt">ClassBody</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ClassElementList</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-class-definitions">See 14.5</a></div>
+ <div class="lhs"><span class="nt">ClassElementList</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ClassElement</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><span class="nt">ClassElementList</span><sub>[?Yield]</sub> <span class="nt">ClassElement</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-class-definitions">See 14.5</a></div>
+ <div class="lhs"><span class="nt">ClassElement</span><sub>[Yield]</sub> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">MethodDefinition</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">static</code> <span class="nt">MethodDefinition</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">;</code></div>
+ </div>
+ </section>
+
+ <section id="sec-scripts-and-modules">
+ <h1><span class="secnum" id="sec-A.5"><a href="#sec-scripts-and-modules" title="link to this section">A.5</a></span> Scripts
+ and Modules</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-scripts">See 15.1</a></div>
+ <div class="lhs"><span class="nt">Script</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ScriptBody</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-scripts">See 15.1</a></div>
+ <div class="lhs"><span class="nt">ScriptBody</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">StatementList</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-modules">See 15.2</a></div>
+ <div class="lhs"><span class="nt">Module</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ModuleBody</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-modules">See 15.2</a></div>
+ <div class="lhs"><span class="nt">ModuleBody</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ModuleItemList</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-modules">See 15.2</a></div>
+ <div class="lhs"><span class="nt">ModuleItemList</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ModuleItem</span></div>
+ <div class="rhs"><span class="nt">ModuleItemList</span> <span class="nt">ModuleItem</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-modules">See 15.2</a></div>
+ <div class="lhs"><span class="nt">ModuleItem</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ImportDeclaration</span></div>
+ <div class="rhs"><span class="nt">ExportDeclaration</span></div>
+ <div class="rhs"><span class="nt">StatementListItem</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">ImportDeclaration</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">import</code> <span class="nt">ImportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">import</code> <span class="nt">ModuleSpecifier</span> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">ImportClause</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ImportedDefaultBinding</span></div>
+ <div class="rhs"><span class="nt">NameSpaceImport</span></div>
+ <div class="rhs"><span class="nt">NamedImports</span></div>
+ <div class="rhs"><span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NameSpaceImport</span></div>
+ <div class="rhs"><span class="nt">ImportedDefaultBinding</span> <code class="t">,</code> <span class="nt">NamedImports</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">ImportedDefaultBinding</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ImportedBinding</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">NameSpaceImport</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">*</code> <code class="t">as</code> <span class="nt">ImportedBinding</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">NamedImports</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ImportsList</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ImportsList</span> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">FromClause</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">from</code> <span class="nt">ModuleSpecifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">ImportsList</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ImportSpecifier</span></div>
+ <div class="rhs"><span class="nt">ImportsList</span> <code class="t">,</code> <span class="nt">ImportSpecifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">ImportSpecifier</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ImportedBinding</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">ImportedBinding</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">ModuleSpecifier</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">StringLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-imports">See 15.2.2</a></div>
+ <div class="lhs"><span class="nt">ImportedBinding</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">BindingIdentifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-exports">See 15.2.3</a></div>
+ <div class="lhs"><span class="nt">ExportDeclaration</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">export</code> <code class="t">*</code> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <span class="nt">FromClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">ExportClause</span> <code class="t">;</code></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">VariableStatement</span></div>
+ <div class="rhs"><code class="t">export</code> <span class="nt">Declaration</span></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">HoistableDeclaration</span><sub>[Default]</sub></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="nt">ClassDeclaration</span><sub>[Default]</sub></div>
+ <div class="rhs"><code class="t">export</code> <code class="t">default</code> <span class="grhsannot">[lookahead ∉ {<code class="t">function</code>, <code class="t">class</code>}]</span> <span class="nt">AssignmentExpression</span><sub>[In]</sub> <code class="t">;</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-exports">See 15.2.3</a></div>
+ <div class="lhs"><span class="nt">ExportClause</span> <span class="geq">:</span> </div>
+ <div class="rhs"><code class="t">{</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ExportsList</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">ExportsList</span> <code class="t">,</code> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-exports">See 15.2.3</a></div>
+ <div class="lhs"><span class="nt">ExportsList</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">ExportSpecifier</span></div>
+ <div class="rhs"><span class="nt">ExportsList</span> <code class="t">,</code> <span class="nt">ExportSpecifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-exports">See 15.2.3</a></div>
+ <div class="lhs"><span class="nt">ExportSpecifier</span> <span class="geq">:</span> </div>
+ <div class="rhs"><span class="nt">IdentifierName</span></div>
+ <div class="rhs"><span class="nt">IdentifierName</span> <code class="t">as</code> <span class="nt">IdentifierName</span></div>
+ </div>
+ </section>
+
+ <section id="sec-number-conversions">
+ <h1><span class="secnum" id="sec-A.6"><a href="#sec-number-conversions" title="link to this section">A.6</a></span> Number
+ Conversions</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">StringNumericLiteral</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">StrWhiteSpace</span><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">StrWhiteSpace</span><sub>opt</sub> <span class="nt">StrNumericLiteral</span> <span class="nt">StrWhiteSpace</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">StrWhiteSpace</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">StrWhiteSpaceChar</span> <span class="nt">StrWhiteSpace</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">StrWhiteSpaceChar</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">WhiteSpace</span></div>
+ <div class="rhs"><span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">StrNumericLiteral</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">StrDecimalLiteral</span></div>
+ <div class="rhs"><span class="nt">BinaryIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">OctalIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">HexIntegerLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">StrDecimalLiteral</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">StrUnsignedDecimalLiteral</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">StrUnsignedDecimalLiteral</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">StrUnsignedDecimalLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">StrUnsignedDecimalLiteral</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">Infinity</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <code class="t">.</code> <span class="nt">DecimalDigits</span><sub>opt</sub> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">.</code> <span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <span class="nt">ExponentPart</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">DecimalDigits</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><span class="nt">DecimalDigits</span> <span class="nt">DecimalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">DecimalDigit</span> <span class="geq">:::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">ExponentPart</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">ExponentIndicator</span> <span class="nt">SignedInteger</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">ExponentIndicator</span> <span class="geq">:::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">e</code> <code class="t">E</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">SignedInteger</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">+</code> <span class="nt">DecimalDigits</span></div>
+ <div class="rhs"><code class="t">-</code> <span class="nt">DecimalDigits</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">HexIntegerLiteral</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><code class="t">0x</code> <span class="nt">HexDigit</span></div>
+ <div class="rhs"><code class="t">0X</code> <span class="nt">HexDigit</span></div>
+ <div class="rhs"><span class="nt">HexIntegerLiteral</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-tonumber-applied-to-the-string-type">See 7.1.3.1</a></div>
+ <div class="lhs"><span class="nt">HexDigit</span> <span class="geq">:::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code> <code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code> <code class="t">8</code> <code class="t">9</code> <code class="t">a</code> <code class="t">b</code> <code class="t">c</code> <code class="t">d</code> <code class="t">e</code> <code class="t">f</code> <code class="t">A</code> <code class="t">B</code> <code class="t">C</code> <code class="t">D</code> <code class="t">E</code> <code class="t">F</code></div>
+ </div>
+
+ <p>All grammar symbols not explicitly defined by the <span class="nt">StringNumericLiteral</span> grammar have the definitions
+ used in the Lexical Grammar for numeric literals (<a href="#sec-literals-numeric-literals">11.8.3</a>)</p>
+ </section>
+
+ <section id="sec-universal-resource-identifier-character-classes">
+ <h1><span class="secnum" id="sec-A.7"><a href="#sec-universal-resource-identifier-character-classes"
+ title="link to this section">A.7</a></span> Universal Resource Identifier Character Classes</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uri</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">uriCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uriCharacters</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">uriCharacter</span> <span class="nt">uriCharacters</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uriCharacter</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">uriReserved</span></div>
+ <div class="rhs"><span class="nt">uriUnescaped</span></div>
+ <div class="rhs"><span class="nt">uriEscaped</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uriReserved</span> <span class="geq">:::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">;</code> <code class="t">/</code> <code class="t">?</code> <code class="t">:</code> <code class="t">@</code> <code class="t">&</code> <code class="t">=</code> <code class="t">+</code> <code class="t">$</code> <code class="t">,</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uriUnescaped</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><span class="nt">uriAlpha</span></div>
+ <div class="rhs"><span class="nt">DecimalDigit</span></div>
+ <div class="rhs"><span class="nt">uriMark</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uriEscaped</span> <span class="geq">:::</span> </div>
+ <div class="rhs"><code class="t">%</code> <span class="nt">HexDigit</span> <span class="nt">HexDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uriAlpha</span> <span class="geq">:::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">a</code> <code class="t">b</code> <code class="t">c</code> <code class="t">d</code> <code class="t">e</code> <code class="t">f</code> <code class="t">g</code> <code class="t">h</code> <code class="t">i</code> <code class="t">j</code> <code class="t">k</code> <code class="t">l</code> <code class="t">m</code> <code class="t">n</code> <code class="t">o</code> <code class="t">p</code> <code class="t">q</code> <code class="t">r</code> <code class="t">s</code> <code class="t">t</code> <code class="t">u</code> <code class="t">v</code> <code class="t">w</code> <code class="t">x</code> <code class="t">y</code> <code class="t">z</code></div>
+ <div class="rhs"><code class="t">A</code> <code class="t">B</code> <code class="t">C</code> <code class="t">D</code> <code class="t">E</code> <code class="t">F</code> <code class="t">G</code> <code class="t">H</code> <code class="t">I</code> <code class="t">J</code> <code class="t">K</code> <code class="t">L</code> <code class="t">M</code> <code class="t">N</code> <code class="t">O</code> <code class="t">P</code> <code class="t">Q</code> <code class="t">R</code> <code class="t">S</code> <code class="t">T</code> <code class="t">U</code> <code class="t">V</code> <code class="t">W</code> <code class="t">X</code> <code class="t">Y</code> <code class="t">Z</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-uri-syntax-and-semantics">See 18.2.6.1</a></div>
+ <div class="lhs"><span class="nt">uriMark</span> <span class="geq">:::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">-</code> <code class="t">_</code> <code class="t">.</code> <code class="t">!</code> <code class="t">~</code> <code class="t">*</code> <code class="t">'</code> <code class="t">(</code> <code class="t">)</code></div>
+ </div>
+ </section>
+
+ <section id="sec-regular-expressions">
+ <h1><span class="secnum" id="sec-A.8"><a href="#sec-regular-expressions" title="link to this section">A.8</a></span> Regular
+ Expressions</h1>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">Pattern</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">Disjunction</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">Disjunction</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">Alternative</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">Alternative</span><sub>[?U]</sub> <code class="t">|</code> <span class="nt">Disjunction</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">Alternative</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">Alternative</span><sub>[?U]</sub> <span class="nt">Term</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">Term</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">Assertion</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">Atom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">Atom</span><sub>[?U]</sub> <span class="nt">Quantifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">Assertion</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">^</code></div>
+ <div class="rhs"><code class="t">$</code></div>
+ <div class="rhs"><code class="t">\</code> <code class="t">b</code></div>
+ <div class="rhs"><code class="t">\</code> <code class="t">B</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">=</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">!</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">Quantifier</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">QuantifierPrefix</span></div>
+ <div class="rhs"><span class="nt">QuantifierPrefix</span> <code class="t">?</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">QuantifierPrefix</span> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">*</code></div>
+ <div class="rhs"><code class="t">+</code></div>
+ <div class="rhs"><code class="t">?</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">,</code> <code class="t">}</code></div>
+ <div class="rhs"><code class="t">{</code> <span class="nt">DecimalDigits</span> <code class="t">,</code> <span class="nt">DecimalDigits</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">Atom</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">PatternCharacter</span></div>
+ <div class="rhs"><code class="t">.</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">AtomEscape</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">CharacterClass</span><sub>[?U]</sub></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">:</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">SyntaxCharacter</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">^</code> <code class="t">$</code> <code class="t">\</code> <code class="t">.</code> <code class="t">*</code> <code class="t">+</code> <code class="t">?</code> <code class="t">(</code> <code class="t">)</code> <code class="t">[</code> <code class="t">]</code> <code class="t">{</code> <code class="t">}</code> <code class="t">|</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">PatternCharacter</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">SyntaxCharacter</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">AtomEscape</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DecimalEscape</span></div>
+ <div class="rhs"><span class="nt">CharacterEscape</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">CharacterClassEscape</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">CharacterEscape</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">ControlEscape</span></div>
+ <div class="rhs"><code class="t">c</code> <span class="nt">ControlLetter</span></div>
+ <div class="rhs"><span class="nt">HexEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">RegExpUnicodeEscapeSequence</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">IdentityEscape</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">ControlEscape</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">f</code> <code class="t">n</code> <code class="t">r</code> <code class="t">t</code> <code class="t">v</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">ControlLetter</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">a</code> <code class="t">b</code> <code class="t">c</code> <code class="t">d</code> <code class="t">e</code> <code class="t">f</code> <code class="t">g</code> <code class="t">h</code> <code class="t">i</code> <code class="t">j</code> <code class="t">k</code> <code class="t">l</code> <code class="t">m</code> <code class="t">n</code> <code class="t">o</code> <code class="t">p</code> <code class="t">q</code> <code class="t">r</code> <code class="t">s</code> <code class="t">t</code> <code class="t">u</code> <code class="t">v</code> <code class="t">w</code> <code class="t">x</code> <code class="t">y</code> <code class="t">z</code></div>
+ <div class="rhs"><code class="t">A</code> <code class="t">B</code> <code class="t">C</code> <code class="t">D</code> <code class="t">E</code> <code class="t">F</code> <code class="t">G</code> <code class="t">H</code> <code class="t">I</code> <code class="t">J</code> <code class="t">K</code> <code class="t">L</code> <code class="t">M</code> <code class="t">N</code> <code class="t">O</code> <code class="t">P</code> <code class="t">Q</code> <code class="t">R</code> <code class="t">S</code> <code class="t">T</code> <code class="t">U</code> <code class="t">V</code> <code class="t">W</code> <code class="t">X</code> <code class="t">Y</code> <code class="t">Z</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">RegExpUnicodeEscapeSequence</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">u</code> <span class="nt">LeadSurrogate</span> <code class="t">\u</code> <span class="nt">TrailSurrogate</span></div>
+ <div class="rhs"><code class="t">u</code> <span class="nt">Hex4Digits</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">u{</code> <span class="nt">HexDigits</span> <code class="t">}</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">LeadSurrogate</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">Hex4Digits</span> <span class="grhsannot">[match only if the SV of <span class="nt">Hex4Digits</span> is in the inclusive range 0xD800 to 0xDBFF]</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">TrailSurrogate</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">Hex4Digits</span> <span class="grhsannot">[match only if the SV of <span class="nt">Hex4Digits</span> is in the inclusive range 0xDC00 to 0xDFFF]</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">IdentityEscape</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">SyntaxCharacter</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <span class="nt">UnicodeIDContinue</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">DecimalEscape</span> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DecimalIntegerLiteral</span> <span class="grhsannot">[lookahead ∉ <span class="nt">DecimalDigit</span>]</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">CharacterClassEscape</span> <span class="geq">::</span> <span class="grhsmod">one of</span> </div>
+ <div class="rhs"><code class="t">d</code> <code class="t">D</code> <code class="t">s</code> <code class="t">S</code> <code class="t">w</code> <code class="t">W</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">CharacterClass</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">[</code> <span class="grhsannot">[lookahead ∉ {<code class="t">^</code>}]</span> <span class="nt">ClassRanges</span><sub>[?U]</sub> <code class="t">]</code></div>
+ <div class="rhs"><code class="t">[</code> <code class="t">^</code> <span class="nt">ClassRanges</span><sub>[?U]</sub> <code class="t">]</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">ClassRanges</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="grhsannot">[empty]</span></div>
+ <div class="rhs"><span class="nt">NonemptyClassRanges</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">NonemptyClassRanges</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub> <span class="nt">NonemptyClassRangesNoDash</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub> <code class="t">-</code> <span class="nt">ClassAtom</span><sub>[?U]</sub> <span class="nt">ClassRanges</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">NonemptyClassRangesNoDash</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub> <span class="nt">NonemptyClassRangesNoDash</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub> <code class="t">-</code> <span class="nt">ClassAtom</span><sub>[?U]</sub> <span class="nt">ClassRanges</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">ClassAtom</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><code class="t">-</code></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">ClassAtomNoDash</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">-</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">ClassEscape</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="gsumxref"><a href="#sec-patterns">See 21.2.1</a></div>
+ <div class="lhs"><span class="nt">ClassEscape</span><sub>[U]</sub> <span class="geq">::</span> </div>
+ <div class="rhs"><span class="nt">DecimalEscape</span></div>
+ <div class="rhs"><code class="t">b</code></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">-</code></div>
+ <div class="rhs"><span class="nt">CharacterEscape</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">CharacterClassEscape</span></div>
+ </div>
+ </section>
+</section>
+
+<section id="sec-additional-ecmascript-features-for-web-browsers">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B"><a href="#sec-additional-ecmascript-features-for-web-browsers"
+ title="link to this section">Annex B</a></span> <span class="section-status">(normative)</span> Additional ECMAScript
+ Features for Web Browsers</h1>
+
+ <p>The ECMAScript language syntax and semantics defined in this annex are required when the ECMAScript host is a web browser.
+ The content of this annex is normative but optional if the ECMAScript host is not a web browser.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> This annex describes various legacy features and other characteristics of web browser based
+ ECMAScript implementations. All of the language features and behaviours specified in this annex have one or more undesirable
+ characteristics and in the absence of legacy usage would be removed from this specification. However, the usage of these
+ features by large numbers of existing web pages means that web browsers must continue to support them. The specifications in
+ this annex defined the requirements for interoperable implementations of these legacy features.</p>
+
+ <p>These features are not considered part of the core ECMAScript language. Programmers should not use or assume the
+ existence of these features and behaviours when writing new ECMAScript code. ECMAScript implementations are discouraged from
+ implementing these features unless the implementation is part of a web browser or is required to run the same legacy
+ ECMAScript code that web browsers encounter.</p>
+ </div>
+ </div>
+
+ <section id="sec-additional-syntax">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.1"><a href="#sec-additional-syntax" title="link to this section">B.1</a></span>
+ Additional Syntax</h1>
+ </div>
+
+ <section id="sec-additional-syntax-numeric-literals">
+ <h1><span class="secnum" id="sec-B.1.1"><a href="#sec-additional-syntax-numeric-literals"
+ title="link to this section">B.1.1</a></span> Numeric Literals</h1>
+
+ <p>The syntax and semantics of <a href="#sec-literals-numeric-literals">11.8.3</a> is extended as follows except that this
+ extension is not allowed for <a href="#sec-strict-mode-code">strict mode code</a>:</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NumericLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">DecimalLiteral</span></div>
+ <div class="rhs"><span class="nt">BinaryIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">OctalIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">HexIntegerLiteral</span></div>
+ <div class="rhs"><span class="nt">LegacyOctalIntegerLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LegacyOctalIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0</code> <span class="nt">OctalDigit</span></div>
+ <div class="rhs"><span class="nt">LegacyOctalIntegerLiteral</span> <span class="nt">OctalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">DecimalIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0</code></div>
+ <div class="rhs"><span class="nt">NonZeroDigit</span> <span class="nt">DecimalDigits</span><sub>opt</sub></div>
+ <div class="rhs"><span class="nt">NonOctalDecimalIntegerLiteral</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonOctalDecimalIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0</code> <span class="nt">NonOctalDigit</span></div>
+ <div class="rhs"><span class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> <span class="nt">NonOctalDigit</span></div>
+ <div class="rhs"><span class="nt">NonOctalDecimalIntegerLiteral</span> <span class="nt">DecimalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">0</code> <span class="nt">OctalDigit</span></div>
+ <div class="rhs"><span class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> <span class="nt">OctalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonOctalDigit</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">8</code> <code class="t">9</code></div>
+ </div>
+
+ <p><span class="marker">B.1.1.1	</span><b>Static Semantics</b></p>
+
+ <ul>
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">LegacyOctalIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0</code> <span class="nt">OctalDigit</span></span> is the MV of <span class="nt">OctalDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">LegacyOctalIntegerLiteral</span> <span class="geq">::</span> <span
+ class="nt">LegacyOctalIntegerLiteral</span> <span class="nt">OctalDigit</span></span> is (the MV of <span
+ class="nt">LegacyOctalIntegerLiteral</span> times 8) plus the MV of <span class="nt">OctalDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">DecimalIntegerLiteral</span> <span class="geq">::</span> <span
+ class="nt">NonOctalDecimalIntegerLiteral</span></span> is the MV of <span
+ class="nt">NonOctalDecimalIntegerLiteral</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NonOctalDecimalIntegerLiteral</span> <span class="geq">::</span> <code
+ class="t">0</code> <span class="nt">NonOctalDigit</span></span> is the MV of <span class="nt">NonOctalDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NonOctalDecimalIntegerLiteral</span> <span class="geq">::</span> <span
+ class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> <span class="nt">NonOctalDigit</span></span> is (the MV of <span
+ class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> times 10) plus the MV of <span
+ class="nt">NonOctalDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NonOctalDecimalIntegerLiteral</span> <span class="geq">::</span> <span
+ class="nt">NonOctalDecimalIntegerLiteral</span> <span class="nt">DecimalDigit</span></span> is (the MV of <span
+ class="nt">NonOctalDecimalIntegerLiteral</span> times 10) plus the MV of <span class="nt">DecimalDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> <span class="geq">::</span>
+ <code class="t">0</code> <span class="nt">OctalDigit</span></span> is the MV of <span class="nt">OctalDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> <span class="geq">::</span>
+ <span class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> <span class="nt">OctalDigit</span></span> is (the MV of
+ <span class="nt">LegacyOctalLikeDecimalIntegerLiteral</span> times 10) plus the MV of <span
+ class="nt">OctalDigit</span>.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NonOctalDigit</span> <span class="geq">::</span> <code
+ class="t">8</code></span> is 8.</p>
+ </li>
+
+ <li>
+ <p>The MV of <span class="prod"><span class="nt">NonOctalDigit</span> <span class="geq">::</span> <code
+ class="t">9</code></span> is 9.</p>
+ </li>
+ </ul>
+ </section>
+
+ <section id="sec-additional-syntax-string-literals">
+ <h1><span class="secnum" id="sec-B.1.2"><a href="#sec-additional-syntax-string-literals"
+ title="link to this section">B.1.2</a></span> String Literals</h1>
+
+ <p>The syntax and semantics of <a href="#sec-literals-string-literals">11.8.4</a> is extended as follows except that this
+ extension is not allowed for <a href="#sec-strict-mode-code">strict mode code</a>:</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">EscapeSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">CharacterEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">LegacyOctalEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">HexEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">UnicodeEscapeSequence</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">LegacyOctalEscapeSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">OctalDigit</span> <span class="grhsannot">[lookahead ∉ <span class="nt">OctalDigit</span>]</span></div>
+ <div class="rhs"><span class="nt">ZeroToThree</span> <span class="nt">OctalDigit</span> <span class="grhsannot">[lookahead ∉ <span class="nt">OctalDigit</span>]</span></div>
+ <div class="rhs"><span class="nt">FourToSeven</span> <span class="nt">OctalDigit</span></div>
+ <div class="rhs"><span class="nt">ZeroToThree</span> <span class="nt">OctalDigit</span> <span class="nt">OctalDigit</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ZeroToThree</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">0</code> <code class="t">1</code> <code class="t">2</code> <code class="t">3</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FourToSeven</span> <span class="geq">::</span> <span class="grhsmod">one of</span></div>
+ <div class="rhs"><code class="t">4</code> <code class="t">5</code> <code class="t">6</code> <code class="t">7</code></div>
+ </div>
+
+ <p>This definition of <span class="nt">EscapeSequence</span> is not used in strict mode or when parsing <span
+ class="nt">TemplateCharacter</span> (<a href="#sec-template-literal-lexical-components">11.8.6</a>).</p>
+
+ <p><span class="marker">B.1.2.1	</span><b>Static Semantics</b></p>
+
+ <ul>
+ <li>The SV of <span class="prod"><span class="nt">EscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">LegacyOctalEscapeSequence</span></span> is the SV of the <i>LegacyOctalEscapeSequence</i>.</li>
+ <li>The SV of <span class="prod"><span class="nt">LegacyOctalEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">OctalDigit</span></span> is the code unit whose value is the MV of the <i>OctalDigit</i>.</li>
+ <li>The SV of <span class="prod"><span class="nt">LegacyOctalEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">ZeroToThree</span> <span class="nt">OctalDigit</span></span> is the code unit whose value is (8 times the
+ MV of the <i>ZeroToThree</i>) plus the MV of the <i>OctalDigit</i>.</li>
+ <li>The SV of <span class="prod"><span class="nt">LegacyOctalEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">FourToSeven</span> <span class="nt">OctalDigit</span></span> is the code unit whose value is (8 times the
+ MV of the <i>FourToSeven</i>) plus the MV of the <i>OctalDigit</i>.</li>
+ <li>The SV of <span class="prod"><span class="nt">LegacyOctalEscapeSequence</span> <span class="geq">::</span> <span
+ class="nt">ZeroToThree</span> <span class="nt">OctalDigit</span> <span class="nt">OctalDigit</span></span> is the code
+ unit whose value is (64 (that is, 8<sup>2</sup>) times the MV of the <i>ZeroToThree</i>) plus (8 times the MV of the
+ first <i>OctalDigit</i>) plus the MV of the second <i>OctalDigit</i>.</li>
+ <li>The MV of <span class="prod"><span class="nt">ZeroToThree</span> <span class="geq">::</span> <code
+ class="t">0</code></span> is 0.</li>
+ <li>The MV of <span class="prod"><span class="nt">ZeroToThree</span> <span class="geq">::</span> <code
+ class="t">1</code></span> is 1.</li>
+ <li>The MV of <span class="prod"><span class="nt">ZeroToThree</span> <span class="geq">::</span> <code
+ class="t">2</code></span> is 2.</li>
+ <li>The MV of <span class="prod"><span class="nt">ZeroToThree</span> <span class="geq">::</span> <code
+ class="t">3</code></span> is 3.</li>
+ <li>The MV of <span class="prod"><span class="nt">FourToSeven</span> <span class="geq">::</span> <code
+ class="t">4</code></span> is 4.</li>
+ <li>The MV of <span class="prod"><span class="nt">FourToSeven</span> <span class="geq">::</span> <code
+ class="t">5</code></span> is 5.</li>
+ <li>The MV of <span class="prod"><span class="nt">FourToSeven</span> <span class="geq">::</span> <code
+ class="t">6</code></span> is 6.</li>
+ <li>The MV of <span class="prod"><span class="nt">FourToSeven</span> <span class="geq">::</span> <code
+ class="t">7</code></span> is 7.</li>
+ </ul>
+ </section>
+
+ <section id="sec-html-like-comments">
+ <h1><span class="secnum" id="sec-B.1.3"><a href="#sec-html-like-comments" title="link to this section">B.1.3</a></span>
+ HTML-like Comments</h1>
+
+ <p>The syntax and semantics of <a href="#sec-comments">11.4</a> is extended as follows except that this extension is not
+ allowed within module code:</p>
+
+ <h2>Syntax</h2>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Comment</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">MultiLineComment</span></div>
+ <div class="rhs"><span class="nt">SingleLineComment</span></div>
+ <div class="rhs"><span class="nt">SingleLineHTMLOpenComment</span></div>
+ <div class="rhs"><span class="nt">SingleLineHTMLCloseComment</span></div>
+ <div class="rhs"><span class="nt">SingleLineDelimitedComment</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">MultiLineComment</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">/*</code> <span class="nt">FirstCommentLine</span><sub>opt</sub> <span class="nt">LineTerminator</span> <span class="nt">MultiLineCommentChars</span><sub>opt</sub> <code class="t">*/</code> <span class="nt">HTMLCloseComment</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">FirstCommentLine</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleLineDelimitedCommentChars</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineHTMLOpenComment</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t"><!--</code> <span class="nt">SingleLineCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineHTMLCloseComment</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">LineTerminatorSequence</span> <span class="nt">HTMLCloseComment</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineDelimitedComment</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">/*</code> <span class="nt">SingleLineDelimitedCommentChars</span><sub>opt</sub> <code class="t">*/</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">HTMLCloseComment</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">WhiteSpaceSequence</span><sub>opt</sub> <span class="nt">SingleLineDelimitedCommentSequence</span><sub>opt</sub> <code class="t">--></code> <span class="nt">SingleLineCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineDelimitedCommentChars</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleLineNotAsteriskChar</span> <span class="nt">SingleLineDelimitedCommentChars</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">SingleLinePostAsteriskCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineNotAsteriskChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">*</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLinePostAsteriskCommentChars</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleLineNotForwardSlashOrAsteriskChar</span> <span class="nt">SingleLineDelimitedCommentChars</span><sub>opt</sub></div>
+ <div class="rhs"><code class="t">*</code> <span class="nt">SingleLinePostAsteriskCommentChars</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineNotForwardSlashOrAsteriskChar</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">/</code> <span class="grhsmod">or</span> <code class="t">*</code> <span class="grhsmod">or</span> <span class="nt">LineTerminator</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">WhiteSpaceSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">WhiteSpace</span> <span class="nt">WhiteSpaceSequence</span><sub>opt</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">SingleLineDelimitedCommentSequence</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SingleLineDelimitedComment</span> <span class="nt">WhiteSpaceSequence</span><sub>opt</sub> <span class="nt">SingleLineDelimitedCommentSequence</span><sub>opt</sub></div>
+ </div>
+
+ <p>Similar to a <span class="nt">MultiLineComment</span> that contains a line terminator code point, a <span
+ class="nt">SingleLineHTMLCloseComment</span> is considered to be a <span class="nt">LineTerminator</span> for purposes of
+ parsing by the syntactic grammar.</p>
+ </section>
+
+ <section id="sec-regular-expressions-patterns">
+ <h1><span class="secnum" id="sec-B.1.4"><a href="#sec-regular-expressions-patterns"
+ title="link to this section">B.1.4</a></span> Regular Expressions Patterns</h1>
+
+ <p>The syntax of <a href="#sec-patterns">21.2.1</a> is modified and extended as follows. These changes introduce ambiguities
+ that are broken by the ordering of grammar productions and by contextual information. When parsing using the following
+ grammar, each alternative is considered only if previous production alternatives do not match.</p>
+
+ <p>This alternative pattern grammar and semantics only changes the syntax and semantics of BMP patterns. The following
+ grammar extensions include productions parameterized with the [U] parameter. However, none of these extensions change the
+ syntax of Unicode patterns recognized when parsing with the [U] parameter present on the goal symbol.</p>
+
+ <p><b>Syntax</b></p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Term</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">ExtendedTerm</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">Assertion</span><sub>[U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">Atom</span><sub>[U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">Atom</span><sub>[U]</sub> <span class="nt">Quantifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ExtendedTerm</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">Assertion</span></div>
+ <div class="rhs"><span class="nt">AtomNoBrace</span> <span class="nt">Quantifier</span></div>
+ <div class="rhs"><span class="nt">Atom</span></div>
+ <div class="rhs"><span class="nt">QuantifiableAssertion</span> <span class="nt">Quantifier</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AtomNoBrace</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">PatternCharacterNoBrace</span></div>
+ <div class="rhs"><code class="t">.</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">AtomEscape</span></div>
+ <div class="rhs"><span class="nt">CharacterClass</span></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Disjunction</span> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">:</code> <span class="nt">Disjunction</span> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Atom</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">PatternCharacter</span></div>
+ <div class="rhs"><code class="t">.</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">AtomEscape</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">CharacterClass</span><sub>[?U]</sub></div>
+ <div class="rhs"><code class="t">(</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">:</code> <span class="nt">Disjunction</span><sub>[?U]</sub> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PatternCharacterNoBrace</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span></div>
+ <div class="rhs"><code class="t">^</code> <code class="t">$</code> <code class="t">\</code> <code class="t">.</code> <code class="t">*</code> <code class="t">+</code> <code class="t">?</code> <code class="t">(</code> <code class="t">)</code> <code class="t">[</code> <code class="t">]</code> <code class="t">{</code> <code class="t">}</code> <code class="t">|</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">PatternCharacter</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span></div>
+ <div class="rhs"><code class="t">^</code> <code class="t">$</code> <code class="t">\</code> <code class="t">.</code> <code class="t">*</code> <code class="t">+</code> <code class="t">?</code> <code class="t">(</code> <code class="t">)</code> <code class="t">[</code> <code class="t">]</code> <code class="t">|</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">QuantifiableAssertion</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">=</code> <span class="nt">Disjunction</span> <code class="t">)</code></div>
+ <div class="rhs"><code class="t">(</code> <code class="t">?</code> <code class="t">!</code> <span class="nt">Disjunction</span> <code class="t">)</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">Assertion</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">^</code></div>
+ <div class="rhs"><code class="t">$</code></div>
+ <div class="rhs"><code class="t">\</code> <code class="t">b</code></div>
+ <div class="rhs"><code class="t">\</code> <code class="t">B</code></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">(</code> <code class="t">?</code> <code class="t">=</code> <span class="nt">Disjunction</span><sub>[U]</sub> <code class="t">)</code></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <code class="t">(</code> <code class="t">?</code> <code class="t">!</code> <span class="nt">Disjunction</span><sub>[U]</sub> <code class="t">)</code></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">QuantifiableAssertion</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">AtomEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">DecimalEscape</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">CharacterEscape</span><sub>[U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">CharacterClassEscape</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">DecimalEscape</span> <code class="t">but</code> <code class="t">only</code> <code class="t">if</code> <code class="t">the</code> <code class="t">integer</code> <code class="t">value</code> <code class="t">of</code> <span class="nt">DecimalEscape</span> <code class="t">is</code> <code class="t"><=</code> <span class="nt">NCapturingParens</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">CharacterClassEscape</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">CharacterEscape</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">CharacterEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">ControlEscape</span></div>
+ <div class="rhs"><code class="t">c</code> <span class="nt">ControlLetter</span></div>
+ <div class="rhs"><span class="nt">HexEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">RegExpUnicodeEscapeSequence</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">LegacyOctalEscapeSequence</span></div>
+ <div class="rhs"><span class="nt">IdentityEscape</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IdentityEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">SyntaxCharacter</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">SourceCharacter</span> <span class="grhsmod">but not</span> <code class="t">c</code></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonemptyClassRanges</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub> <span class="nt">NonemptyClassRangesNoDash</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">ClassAtom</span><sub>[U]</sub> <code class="t">-</code> <span class="nt">ClassAtom</span><sub>[U]</sub> <span class="nt">ClassRanges</span><sub>[U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">ClassAtomInRange</span> <code class="t">-</code> <span class="nt">ClassAtomInRange</span> <span class="nt">ClassRanges</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">NonemptyClassRangesNoDash</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">ClassAtom</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub> <span class="nt">NonemptyClassRangesNoDash</span><sub>[?U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">ClassAtomNoDash</span><sub>[U]</sub> <code class="t">-</code> <span class="nt">ClassAtom</span><sub>[U]</sub> <span class="nt">ClassRanges</span><sub>[U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">ClassAtomNoDashInRange</span> <code class="t">-</code> <span class="nt">ClassAtomInRange</span> <span class="nt">ClassRanges</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassAtom</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">-</code></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDash</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassAtomNoDash</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">-</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">ClassEscape</span><sub>[?U]</sub></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassAtomInRange</span> <span class="geq">::</span></div>
+ <div class="rhs"><code class="t">-</code></div>
+ <div class="rhs"><span class="nt">ClassAtomNoDashInRange</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassAtomNoDashInRange</span> <span class="geq">::</span></div>
+ <div class="rhs"><span class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span class="grhsmod">or</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">-</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">ClassEscape</span> <code class="t">but</code> <code class="t">only</code> <code class="t">if</code> <span class="nt">ClassEscape</span> <code class="t">evaluates</code> <code class="t">to</code> <code class="t">a</code> <span class="nt">CharSet</span> <code class="t">with</code> <code class="t">exactly</code> <code class="t">one</code> <code class="t">character</code></div>
+ <div class="rhs"><code class="t">\</code> <span class="nt">IdentityEscape</span></div>
+ </div>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">ClassEscape</span><sub>[U]</sub> <span class="geq">::</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">DecimalEscape</span></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">CharacterEscape</span><sub>[U]</sub></div>
+ <div class="rhs"><span class="grhsannot">[+U]</span> <span class="nt">CharacterClassEscape</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">DecimalEscape</span></div>
+ <div class="rhs"><code class="t">b</code></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">CharacterClassEscape</span></div>
+ <div class="rhs"><span class="grhsannot">[~U]</span> <span class="nt">CharacterEscape</span></div>
+ </div>
+
+ <p><span class="marker">B.1.4.1	</span><b>Pattern Semantics</b></p>
+
+ <p>The semantics of <a href="#sec-pattern-semantics">21.2.2</a> is extended as follows:</p>
+
+ <p>Within <a href="#sec-term">21.2.2.5</a> reference to “<span class="prod"><span class="nt">Atom</span> <span
+ class="geq">::</span> <code class="t">(</code> <span class="nt">Disjunction</span> <code class="t">)</code></span> ”
+ are to be interpreted as meaning “<span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <code
+ class="t">(</code> <span class="nt">Disjunction</span> <code class="t">)</code></span> or <span class="prod"><span
+ class="nt">AtomNoBrace</span> <span class="geq">::</span> <code class="t">(</code> <span class="nt">Disjunction</span> <code
+ class="t">)</code></span> ”.</p>
+
+ <p>Term (<a href="#sec-term">21.2.2.5</a>) includes the following additional evaluation rule:</p>
+
+ <p>The production <span class="prod"><span class="nt">Term</span> <span class="geq">::</span> <span
+ class="nt">QuantifiableAssertion</span> <span class="nt">Quantifier</span></span> evaluates the same as the production <span
+ class="prod"><span class="nt">Term</span> <span class="geq">::</span> <span class="nt">Atom</span> <span
+ class="nt">Quantifier</span></span> but with <span class="nt">QuantifiableAssertion</span> substituted for <span
+ style="font-family: Times New Roman"><i>Atom</i>.</span></p>
+
+ <p>Atom (<a href="#sec-atom">21.2.2.8</a>) evaluation rules for the <span class="nt">Atom</span> productions except for
+ <span class="prod"><span class="nt">Atom</span> <span class="geq">::</span> <span class="nt">PatternCharacter</span></span>
+ are also used for the <span class="nt">AtomNoBrace</span> productions, but with <span class="nt">AtomNoBrace</span>
+ substituted for <span style="font-family: Times New Roman"><i>Atom</i>.</span> The following evaluation rule is also
+ added:</p>
+
+ <p>The production <span class="prod"><span class="nt">AtomNoBrace</span> <span class="geq">::</span> <span
+ class="nt">PatternCharacterNoBrace</span></span> evaluates as follows:</p>
+
+ <ol class="proc">
+ <li>Let <i>ch</i> be the character represented by <i>PatternCharacterNoBrace</i>.</li>
+ <li>Let <i>A</i> be a one-element CharSet containing the character <i>ch</i>.</li>
+ <li><a href="#sec-call">Call</a> CharacterSetMatcher(<i>A</i>, <b>false</b>) and return its Matcher result.</li>
+ </ol>
+
+ <p>CharacterEscape (<a href="#sec-characterescape">21.2.2.10</a>) includes the following additional evaluation rule:</p>
+
+ <p>The production <span class="prod"><span class="nt">CharacterEscape</span> <span class="geq">::</span> <span
+ class="nt">LegacyOctalEscapeSequence</span></span> evaluates by evaluating the SV of the <span
+ class="nt">LegacyOctalEscapeSequence</span> (<a href="#sec-additional-syntax-string-literals">see B.1.2</a>) and returning
+ its character result.</p>
+
+ <p>ClassAtom (<a href="#sec-classatom">21.2.2.17</a>) includes the following additional evaluation rules:</p>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtomInRange</span> <span class="geq">::</span> <code
+ class="t">-</code></span> evaluates by returning the CharSet containing the one character <code>-</code>.</p>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtomInRange</span> <span class="geq">::</span> <span
+ class="nt">ClassAtomNoDashInRange</span></span> evaluates by evaluating <span class="nt">ClassAtomNoDashInRange</span> to
+ obtain a CharSet and returning that CharSet.</p>
+
+ <p>ClassAtomNoDash (<a href="#sec-classatomnodash">21.2.2.18</a>) includes the following additional evaluation rules:</p>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtomNoDashInRange</span> <span class="geq">::</span> <span
+ class="nt">SourceCharacter</span> <span class="grhsmod">but not one of</span> <code class="t">\</code> <span
+ class="grhsmod">or</span> <code class="t">]</code> <span class="grhsmod">or</span> <code class="t">-</code></span> evaluates
+ by returning a one-element CharSet containing the character represented by <span class="nt">SourceCharacter</span>.</p>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtomNoDashInRange</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">ClassEscape</span></span> but only if…, evaluates by evaluating <span
+ class="nt">ClassEscape</span> to obtain a CharSet and returning that CharSet.</p>
+
+ <p>The production <span class="prod"><span class="nt">ClassAtomNoDashInRange</span> <span class="geq">::</span> <code
+ class="t">\</code> <span class="nt">IdentityEscape</span></span> evaluates by returning the character represented by <span
+ class="nt">IdentityEscape</span>.</p>
+ </section>
+ </section>
+
+ <section id="sec-additional-built-in-properties">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2"><a href="#sec-additional-built-in-properties"
+ title="link to this section">B.2</a></span> Additional Built-in Properties</h1>
+
+ <p>When the ECMAScript host is a web browser the following additional properties of the standard built-in objects are
+ defined.</p>
+ </div>
+
+ <section id="sec-additional-properties-of-the-global-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2.1"><a href="#sec-additional-properties-of-the-global-object"
+ title="link to this section">B.2.1</a></span> Additional Properties of the Global Object</h1>
+ </div>
+
+ <section id="sec-escape-string">
+ <h1><span class="secnum" id="sec-B.2.1.1"><a href="#sec-escape-string" title="link to this section">B.2.1.1</a></span>
+ escape (string)</h1>
+
+ <p>The <code>escape</code> function is a property of the global object. It computes a new version of a String value in
+ which certain code units have been replaced by a hexadecimal escape sequence.</p>
+
+ <p>For those code units being replaced whose value is <code>0x00FF</code> or less, a two-digit escape sequence of the form
+ <code>%</code><i>xx</i> is used. For those characters being replaced whose code unit value is greater than
+ <code>0x00FF</code>, a four-digit escape sequence of the form <code>%u</code><i>xxxx</i> is used.</p>
+
+ <p>When the <code>escape</code> function is called with one argument <var>string</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>string</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>string</i>).</li>
+ <li>Let <i>length</i> be the number of code units in <i>string</i>.</li>
+ <li>Let <i>R</i> be the empty string.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> < <i>length</i>,
+ <ol class="block">
+ <li>Let <i>char</i> be the code unit (represented as a 16-bit unsigned integer) at index <i>k</i> within
+ <i>string</i>.</li>
+ <li>If <i>char</i> is the code unit of one of the 69 nonblank code units
+ in<br><b>"<code>ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@*_+-./</code>"</b>, then
+ <ol class="block">
+ <li>Let <i>S</i> be a String containing the single code unit <i>char</i>.</li>
+ </ol>
+ </li>
+ <li>Else if <i>char</i> ≥ 256, then
+ <ol class="block">
+ <li>Let <i>S</i> be a String containing six code units <b>"<code>%u</code></b><i>wxyz</i><b>"</b> where
+ <i>wxyz</i> are the code units of the four hexadecimal digits encoding the value of <i>char</i>.</li>
+ </ol>
+ </li>
+ <li>Else, <i>char</i> < 256
+ <ol class="block">
+ <li>Let <i>S</i> be a String containing three code units <b>"<code>%</code></b><i>xy</i><b>"</b> where <i>xy</i>
+ are the code units of two hexadecimal digits encoding the value of <i>char</i>.</li>
+ </ol>
+ </li>
+ <li>Let <i>R</i> be a new String value computed by concatenating the previous value of <i>R</i> and <i>S</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>R</i>.</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The encoding is partly based on the encoding described in RFC 1738, but the entire
+ encoding specified in this standard is described above without regard to the contents of RFC 1738. This encoding does
+ not reflect changes to RFC 1738 made by RFC 3986.</p>
+ </div>
+ </section>
+
+ <section id="sec-unescape-string">
+ <h1><span class="secnum" id="sec-B.2.1.2"><a href="#sec-unescape-string" title="link to this section">B.2.1.2</a></span>
+ unescape (string)</h1>
+
+ <p>The <code>unescape</code> function is a property of the global object. It computes a new version of a String value in
+ which each escape sequence of the sort that might be introduced by the <code>escape</code> function is replaced with the
+ code unit that it represents.</p>
+
+ <p>When the <code>unescape</code> function is called with one argument <var>string</var>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>string</i> be <a href="#sec-tostring">ToString</a>(<i>string</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>string</i>).</li>
+ <li>Let <i>length</i> be the number of code units in <i>string</i>.</li>
+ <li>Let <i>R</i> be the empty String.</li>
+ <li>Let <i>k</i> be 0.</li>
+ <li>Repeat, while <i>k</i> ≠ <i>length</i>
+ <ol class="block">
+ <li>Let <i>c</i> be the code unit at index <i>k</i> within <i>string</i>.</li>
+ <li>If <i>c</i> is <code>%</code>,
+ <ol class="block">
+ <li>If <i>k</i> ≤ <i>length</i>−6 and the code unit at index <i>k</i>+1 within <i>string</i> is
+ <code>u</code> and the four code units at indices <i>k</i>+2, <i>k</i>+3, <i>k</i>+4, and <i>k</i>+5 within
+ <i>string</i> are all hexadecimal digits, then
+ <ol class="block">
+ <li>Let <i>c</i> be the code unit whose value is the integer represented by the four hexadecimal digits at
+ indices <i>k</i>+2, <i>k</i>+3, <i>k</i>+4, and <i>k</i>+5 within <i>string</i>.</li>
+ <li>Increase <i>k</i> by 5.</li>
+ </ol>
+ </li>
+ <li>Else if <i>k</i> ≤ <i>length</i>−3 and the two code units at indices <i>k</i>+1 and <i>k</i>+2
+ within <i>string</i> are both hexadecimal digits, then
+ <ol class="block">
+ <li>Let <i>c</i> be the code unit whose value is the integer represented by two zeroes plus the two
+ hexadecimal digits at indices <i>k</i>+1 and <i>k</i>+2 within <i>string</i>.</li>
+ <li>Increase <i>k</i> by 2.</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>R</i> be a new String value computed by concatenating the previous value of <i>R</i> and <i>c</i>.</li>
+ <li>Increase <i>k</i> by 1.</li>
+ </ol>
+ </li>
+ <li>Return <i>R</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-additional-properties-of-the-object.prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2.2"><a href="#sec-additional-properties-of-the-object.prototype-object"
+ title="link to this section">B.2.2</a></span> Additional Properties of the Object.prototype Object</h1>
+ </div>
+
+ <section id="sec-object.prototype.__proto__">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2.2.1"><a href="#sec-object.prototype.__proto__"
+ title="link to this section">B.2.2.1</a></span> Object.prototype.__proto__</h1>
+
+ <p>Object.prototype.__proto__ is an accessor property with attributes { [[Enumerable]]: <span
+ class="value">false</span>, [[Configurable]]: <span class="value">true</span> }. The [[Get]] and [[Set]] attributes are
+ defined as follows</p>
+ </div>
+
+ <section id="sec-get-object.prototype.__proto__">
+ <h1><span class="secnum" id="sec-B.2.2.1.1"><a href="#sec-get-object.prototype.__proto__"
+ title="link to this section">B.2.2.1.1</a></span> get Object.prototype.__proto__</h1>
+
+ <p>The value of the [[Get]] attribute is a built-in function that requires no arguments. It performs the following
+ steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-toobject">ToObject</a>(<b>this</b> value).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>Return <i>O</i>.[[GetPrototypeOf]]().</li>
+ </ol>
+ </section>
+
+ <section id="sec-set-object.prototype.__proto__">
+ <h1><span class="secnum" id="sec-B.2.2.1.2"><a href="#sec-set-object.prototype.__proto__"
+ title="link to this section">B.2.2.1.2</a></span> set Object.prototype.__proto__</h1>
+
+ <p>The value of the [[Set]] attribute is a built-in function that takes an argument <var>proto</var>. It performs the
+ following steps:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value)<i>.</i></li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>O</i>).</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>proto</i>) is neither Object nor Null, return
+ <b>undefined</b>.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object, return <b>undefined</b>.</li>
+ <li>Let <i>status</i> be <i>O</i>.[[SetPrototypeOf]](<i>proto</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>status</i>).</li>
+ <li>If <i>status</i> is <b>false</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Return <b>undefined</b>.</li>
+ </ol>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-additional-properties-of-the-string.prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2.3"><a href="#sec-additional-properties-of-the-string.prototype-object"
+ title="link to this section">B.2.3</a></span> Additional Properties of the String.prototype Object</h1>
+ </div>
+
+ <section id="sec-string.prototype.substr">
+ <h1><span class="secnum" id="sec-B.2.3.1"><a href="#sec-string.prototype.substr"
+ title="link to this section">B.2.3.1</a></span> String.prototype.substr (start, length)</h1>
+
+ <p>The <code>substr</code> method takes two arguments, <var>start</var> and <var>length</var>, and returns a substring of
+ the result of converting the <b>this</b> object to a String, starting from index <var>start</var> and running for
+ <var>length</var> code units (or through the end of the String if <var>length</var> is <b>undefined</b>). If
+ <var>start</var> is negative, it is treated as <span style="font-family: Times New
+ Roman">(<i>sourceLength</i>+<i>start</i>)</span> where <var>sourceLength</var> is the length of the String. The result is
+ a String value, not a String object. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<b>this</b> value).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>O</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>intStart</i> be <a href="#sec-tointeger">ToInteger</a>(<i>start</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>intStart</i>).</li>
+ <li>If <i>length</i> is <b>undefined</b>, let <i>end</i> be <b>+∞</b>; otherwise let <i>end</i> be <a
+ href="#sec-tointeger">ToInteger</a>(<i>length</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>end</i>).</li>
+ <li>Let <i>size</i> be the number of code units in <i>S</i>.</li>
+ <li>If <i>intStart</i> < 0, let <i>intStart</i> be max(<i>size</i> + <i>intStart</i>,0).</li>
+ <li>Let <i>resultLength</i> be min(max(<i>end</i>,0), <i>size</i> – <i>intStart</i>).</li>
+ <li>If <i>resultLength</i> ≤ 0, return the empty String <code>""</code>.</li>
+ <li>Return a String containing <i>resultLength</i> consecutive code units from <i>S</i> beginning with the code unit at
+ index <i>intStart</i>.</li>
+ </ol>
+
+ <p>The <code>length</code> property of the <code>substr</code> method is <b>2</b>.</p>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>substr</code> function is intentionally generic; it does not require that its
+ <b>this</b> value be a String object. Therefore it can be transferred to other kinds of objects for use as a method.</p>
+ </div>
+ </section>
+
+ <section id="sec-string.prototype.anchor">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2.3.2"><a href="#sec-string.prototype.anchor"
+ title="link to this section">B.2.3.2</a></span> String.prototype.anchor ( name )</h1>
+
+ <p>When the <b>anchor</b> method is called with argument <var>name</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"a"</code>, <code>"name"</code>,
+ <i>name</i>).</li>
+ </ol>
+ </div>
+
+ <section id="sec-createhtml">
+ <h1><span class="secnum" id="sec-B.2.3.2.1"><a href="#sec-createhtml" title="link to this section">B.2.3.2.1</a></span>
+ Runtime Semantics: CreateHTML ( string, tag, attribute, value )</h1>
+
+ <p>The abstract operation <span style="font-family: Times New Roman">CreateHTML</span> is called with arguments
+ <var>string, tag</var>, <var>attribute</var>, and <span style="font-family: Times New Roman"><i>value</i>.</span> The
+ arguments <var>tag</var> and <var>attribute</var> must be string values. The following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>str</i> be <a href="#sec-requireobjectcoercible">RequireObjectCoercible</a>(<i>string</i>).</li>
+ <li>Let <i>S</i> be <a href="#sec-tostring">ToString</a>(<i>str</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>S</i>).</li>
+ <li>Let <i>p1</i> be the string value that is the concatenation of <code>"<"</code> and <i>tag</i>.</li>
+ <li>If <i>attribute</i> is not the empty String, then
+ <ol class="block">
+ <li>Let <i>V</i> be <a href="#sec-tostring">ToString</a>(<i>value</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>V</i>).</li>
+ <li>Let <i>escapedV</i> be the string value that is the same as <i>V</i> except that each occurrence of the code
+ unit 0x0022 (QUOTATION MARK) in <i>V</i> has been replaced with the six code unit sequence
+ <code>"&quot;"</code>.</li>
+ <li>Let <i>p1</i> be the string value that is the concatenation of the following string values:
+ <ul>
+ <li>The string value of <i>p1</i></li>
+ <li>Code unit 0x0020 (SPACE)</li>
+ <li>The string value of <i>attribute</i></li>
+ <li>Code unit 0x003D (EQUALS SIGN)</li>
+ <li>Code unit 0x0022 (QUOTATION MARK)</li>
+ <li>The string value of <i>escapedV</i></li>
+ <li>Code unit 0x0022 (QUOTATION MARK)</li>
+ </ul>
+ </li>
+ </ol>
+ </li>
+ <li>Let <i>p2</i> be the string value that is the concatenation of <i>p1</i> and <code>">"</code>.</li>
+ <li>Let <i>p3</i> be the string value that is the concatenation of <i>p2</i> and <i>S</i>.</li>
+ <li>Let <i>p4</i> be the string value that is the concatenation of <i>p3</i>, <code>"</"</code>, <i>tag</i>, and
+ <code>">"</code>.</li>
+ <li>Return <i>p4</i>.</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-string.prototype.big">
+ <h1><span class="secnum" id="sec-B.2.3.3"><a href="#sec-string.prototype.big"
+ title="link to this section">B.2.3.3</a></span> String.prototype.big ()</h1>
+
+ <p>When the <b>big</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"big"</code>, <code>""</code>,
+ <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.blink">
+ <h1><span class="secnum" id="sec-B.2.3.4"><a href="#sec-string.prototype.blink"
+ title="link to this section">B.2.3.4</a></span> String.prototype.blink ()</h1>
+
+ <p>When the <b>blink</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"blink"</code>, <code>""</code>,
+ <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.bold">
+ <h1><span class="secnum" id="sec-B.2.3.5"><a href="#sec-string.prototype.bold"
+ title="link to this section">B.2.3.5</a></span> String.prototype.bold ()</h1>
+
+ <p>When the <b>bold</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"b"</code>, <code>""</code>, <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.fixed">
+ <h1><span class="secnum" id="sec-B.2.3.6"><a href="#sec-string.prototype.fixed"
+ title="link to this section">B.2.3.6</a></span> String.prototype.fixed ()</h1>
+
+ <p>When the <b>fixed</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"tt"</code>, <code>""</code>, <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.fontcolor">
+ <h1><span class="secnum" id="sec-B.2.3.7"><a href="#sec-string.prototype.fontcolor"
+ title="link to this section">B.2.3.7</a></span> String.prototype.fontcolor ( color )</h1>
+
+ <p>When the <b>fontcolor</b> method is called with argument <var>color</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"font"</code>, <code>"color"</code>,
+ <i>color</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.fontsize">
+ <h1><span class="secnum" id="sec-B.2.3.8"><a href="#sec-string.prototype.fontsize"
+ title="link to this section">B.2.3.8</a></span> String.prototype.fontsize ( size )</h1>
+
+ <p>When the <b>fontsize</b> method is called with argument <var>size</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"font"</code>, <code>"size"</code>,
+ <i>size</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.italics">
+ <h1><span class="secnum" id="sec-B.2.3.9"><a href="#sec-string.prototype.italics"
+ title="link to this section">B.2.3.9</a></span> String.prototype.italics ()</h1>
+
+ <p>When the <b>italics</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"i"</code>, <code>""</code>, <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.link">
+ <h1><span class="secnum" id="sec-B.2.3.10"><a href="#sec-string.prototype.link"
+ title="link to this section">B.2.3.10</a></span> String.prototype.link ( url )</h1>
+
+ <p>When the <b>link</b> method is called with argument <var>url</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"a"</code>, <code>"href"</code>, <i>url</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.small">
+ <h1><span class="secnum" id="sec-B.2.3.11"><a href="#sec-string.prototype.small"
+ title="link to this section">B.2.3.11</a></span> String.prototype.small ()</h1>
+
+ <p>When the <b>small</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"small"</code>, <code>""</code>,
+ <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.strike">
+ <h1><span class="secnum" id="sec-B.2.3.12"><a href="#sec-string.prototype.strike"
+ title="link to this section">B.2.3.12</a></span> String.prototype.strike ()</h1>
+
+ <p>When the <b>strike</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"strike"</code>, <code>""</code>,
+ <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.sub">
+ <h1><span class="secnum" id="sec-B.2.3.13"><a href="#sec-string.prototype.sub"
+ title="link to this section">B.2.3.13</a></span> String.prototype.sub ()</h1>
+
+ <p>When the <b>sub</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"sub"</code>, <code>""</code>,
+ <code>""</code>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-string.prototype.sup">
+ <h1><span class="secnum" id="sec-B.2.3.14"><a href="#sec-string.prototype.sup"
+ title="link to this section">B.2.3.14</a></span> String.prototype.sup ()</h1>
+
+ <p>When the <b>sup</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>S</i> be the <b>this</b> value.</li>
+ <li>Return <a href="#sec-createhtml">CreateHTML</a>(<i>S</i>, <code>"sup"</code>, <code>""</code>,
+ <code>""</code>).</li>
+ </ol>
+ </section>
+ </section>
+
+ <section id="sec-additional-properties-of-the-date.prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2.4"><a href="#sec-additional-properties-of-the-date.prototype-object"
+ title="link to this section">B.2.4</a></span> Additional Properties of the Date.prototype Object</h1>
+ </div>
+
+ <section id="sec-date.prototype.getyear">
+ <h1><span class="secnum" id="sec-B.2.4.1"><a href="#sec-date.prototype.getyear"
+ title="link to this section">B.2.4.1</a></span> Date.prototype.getYear ( )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>getFullYear</code> method is preferred for nearly all purposes, because it
+ avoids the “year 2000 problem.”</p>
+ </div>
+
+ <p>When the <b>getYear</b> method is called with no arguments, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, return <b>NaN</b>.</li>
+ <li>Return <a href="#sec-year-number">YearFromTime</a>(<a href="#sec-local-time">LocalTime</a>(<i>t</i>)) −
+ 1900.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.setyear">
+ <h1><span class="secnum" id="sec-B.2.4.2"><a href="#sec-date.prototype.setyear"
+ title="link to this section">B.2.4.2</a></span> Date.prototype.setYear (year)</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>setFullYear</code> method is preferred for nearly all purposes, because it
+ avoids the “year 2000 problem.”</p>
+ </div>
+
+ <p>When the <b>setYear</b> method is called with one argument <var>year</var>, the following steps are taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>t</i> be <a href="#sec-properties-of-the-date-prototype-object">this time value</a>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>t</i>).</li>
+ <li>If <i>t</i> is <b>NaN</b>, let <i>t</i> be <b>+0</b>; otherwise, let <i>t</i> be <a
+ href="#sec-local-time">LocalTime</a>(<i>t</i>).</li>
+ <li>Let <i>y</i> be <a href="#sec-tonumber">ToNumber</a>(<i>year</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>y</i>).</li>
+ <li>If <i>y</i> is <b>NaN</b>, set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal
+ slot</a> of this Date object to <b>NaN</b> and return <b>NaN</b>.</li>
+ <li>If <i>y</i> is not <b>NaN</b> and 0 ≤ <a href="#sec-tointeger">ToInteger</a>(<i>y</i>) ≤ 99, let <i>yyyy</i>
+ be <a href="#sec-tointeger">ToInteger</a>(<i>y</i>) + 1900.</li>
+ <li>Else, let <i>yyyy</i> be <i>y</i>.</li>
+ <li>Let <i>d</i> be <a href="#sec-makeday">MakeDay</a>(<i>yyyy</i>, <a
+ href="#sec-month-number">MonthFromTime</a>(<i>t</i>), <a href="#sec-date-number">DateFromTime</a>(<i>t</i>)).</li>
+ <li>Let <i>date</i> be <a href="#sec-local-time">UTC</a>(<a href="#sec-makedate">MakeDate</a>(<i>d</i>, <a
+ href="#sec-day-number-and-time-within-day">TimeWithinDay</a>(<i>t</i>))).</li>
+ <li>Set the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of this Date
+ object to <a href="#sec-timeclip">TimeClip</a>(<i>date</i>).</li>
+ <li>Return the value of the [[DateValue]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of
+ this Date object.</li>
+ </ol>
+ </section>
+
+ <section id="sec-date.prototype.togmtstring">
+ <h1><span class="secnum" id="sec-B.2.4.3"><a href="#sec-date.prototype.togmtstring"
+ title="link to this section">B.2.4.3</a></span> Date.prototype.toGMTString ( )</h1>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The property <code>toUTCString</code> is preferred. The <code>toGMTString</code>
+ property is provided principally for compatibility with old code. It is recommended that the <code>toUTCString</code>
+ property be used in new ECMAScript code.</p>
+ </div>
+
+ <p>The Function object that is the initial value of <code>Date.prototype.toGMTString</code> is the same Function object
+ that is the initial value of <code><a href="#sec-date.prototype.toutcstring">Date.prototype.toUTCString</a></code>.</p>
+ </section>
+ </section>
+
+ <section id="sec-additional-properties-of-the-regexp.prototype-object">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.2.5"><a href="#sec-additional-properties-of-the-regexp.prototype-object"
+ title="link to this section">B.2.5</a></span> Additional Properties of the RegExp.prototype Object</h1>
+ </div>
+
+ <section id="sec-regexp.prototype.compile">
+ <h1><span class="secnum" id="sec-B.2.5.1"><a href="#sec-regexp.prototype.compile"
+ title="link to this section">B.2.5.1</a></span> RegExp.prototype.compile (pattern, flags )</h1>
+
+ <p>When the <b>compile</b> method is called with arguments <i>pattern</i> and <i>flags</i>, the following steps are
+ taken:</p>
+
+ <ol class="proc">
+ <li>Let <i>O</i> be the <b>this</b> value.</li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is not Object or <a
+ href="#sec-ecmascript-data-types-and-values">Type</a>(<i>O</i>) is Object and <i>O</i> does not have a
+ [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li>Throw a <b>TypeError</b> exception.</li>
+ </ol>
+ </li>
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>pattern</i>) is Object and <i>pattern</i> has a
+ [[RegExpMatcher]] <a href="#sec-object-internal-methods-and-internal-slots">internal slot</a>, then
+ <ol class="block">
+ <li>If <i>flags</i> is not <b>undefined</b>, throw a <b>TypeError</b> exception.</li>
+ <li>Let <i>P</i> be the value of <i>pattern’s</i> [[OriginalSource]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ <li>Let <i>F</i> be the value of <i>pattern’s</i> [[OriginalFlags]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a>.</li>
+ </ol>
+ </li>
+ <li>Else,
+ <ol class="block">
+ <li>Let <i>P</i> be <i>pattern</i>.</li>
+ <li>Let <i>F</i> be <i>flags</i>.</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-regexpinitialize">RegExpInitialize</a>(<i>O,</i> <i>P</i>, <i>F</i>).</li>
+ </ol>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <code>compile</code> method completely reinitializes the <b>this</b> object RegExp
+ with a new pattern and flags. An implementation may interpret use of this method as an assertion that the resulting
+ RegExp object will be used multiple times and hence is a candidate for extra optimization.</p>
+ </div>
+ </section>
+ </section>
+ </section>
+
+ <section id="sec-other-additional-features">
+ <div class="front">
+ <h1><span class="secnum" id="sec-B.3"><a href="#sec-other-additional-features" title="link to this section">B.3</a></span>
+ Other Additional Features</h1>
+ </div>
+
+ <section id="sec-__proto__-property-names-in-object-initializers">
+ <h1><span class="secnum" id="sec-B.3.1"><a href="#sec-__proto__-property-names-in-object-initializers"
+ title="link to this section">B.3.1</a></span> __proto__ Property Names in Object Initializers</h1>
+
+ <p>The following Early Error rule is added to those in <a
+ href="#sec-object-initializer-static-semantics-early-errors">12.2.5.1</a>:</p>
+
+ <div class="gp prod"><span class="nt">ObjectLiteral</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">PropertyDefinitionList</span> <code class="t">}</code></div>
+
+ <p>and</p>
+
+ <div class="gp prod"><span class="nt">ObjectLiteral</span> <span class="geq">:</span> <code class="t">{</code> <span class="nt">PropertyDefinitionList</span> <code class="t">,</code> <code class="t">}</code></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if <span style="font-family: Times New Roman">PropertyNameList</span> of <span
+ class="nt">PropertyDefinitionList</span> contains any duplicate entries for <code>"__proto__"</code> and at least two of
+ those entries were obtained from productions of the form <span class="prod"><span class="nt">PropertyDefinition</span>
+ <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span
+ class="nt">AssignmentExpression</span></span> .</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <a href="#sec-list-and-record-specification-type">List</a> returned by
+ PropertyNameList does not include string literal property names defined as using a <i>ComputedPropertyName.</i></p>
+ </div>
+
+ <p>In <a href="#sec-object-initializer-runtime-semantics-propertydefinitionevaluation">12.2.5.9</a> the
+ PropertyDefinitionEvaluation algorithm for the production<br><span class="prod"><span class="nt">PropertyDefinition</span>
+ <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span
+ class="nt">AssignmentExpression</span></span><br>is replaced with the following definition:</p>
+
+ <div class="gp prod"><span class="nt">PropertyDefinition</span> <span class="geq">:</span> <span class="nt">PropertyName</span> <code class="t">:</code> <span class="nt">AssignmentExpression</span></div>
+ <ol class="proc">
+ <li>Let <i>propKey</i> be the result of evaluating <i>PropertyName</i>.</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propKey</i>).</li>
+ <li>Let <i>exprValueRef</i> be the result of evaluating <i>AssignmentExpression</i>.</li>
+ <li>Let <i>propValue</i> be <a href="#sec-getvalue">GetValue</a>(<i>exprValueRef</i>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>propValue</i>).</li>
+ <li>If <i>propKey</i> is the string value <code>"__proto__"</code> and if IsComputedPropertyKey(<i>propKey</i>) is
+ <b>false</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-ecmascript-data-types-and-values">Type</a>(<i>propValue</i>) is either Object or Null, then
+ <ol class="block">
+ <li>Return <i>object</i>.[[SetPrototypeOf]](<i>propValue</i>).</li>
+ </ol>
+ </li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </li>
+ <li>If IsFunctionDefinition of <i>AssignmentExpression</i> is <b>true</b>, then
+ <ol class="block">
+ <li>If <a href="#sec-isanonymousfunctiondefinition">IsAnonymousFunctionDefinition</a>(<i>AssignmentExpression)</i> is
+ <b>true</b>, then
+ <ol class="block">
+ <li>Let <i>hasNameProperty</i> be <a href="#sec-hasownproperty">HasOwnProperty</a>(<i>propValue</i>,
+ <code>"name"</code>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>hasNameProperty</i>).</li>
+ <li>If <i>hasNameProperty</i> is <b>false</b>, perform <a
+ href="#sec-setfunctionname">SetFunctionName</a>(<i>propValue</i>, <i>propKey</i>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>enumerable</i> is <b>true</b>.</li>
+ <li>Return <a href="#sec-createdatapropertyorthrow">CreateDataPropertyOrThrow</a>(<i>object</i>, <i>propKey</i>,
+ <i>propValue</i>).</li>
+ </ol>
+ </section>
+
+ <section id="sec-labelled-function-declarations">
+ <h1><span class="secnum" id="sec-B.3.2"><a href="#sec-labelled-function-declarations"
+ title="link to this section">B.3.2</a></span> Labelled Function Declarations</h1>
+
+ <p>Prior to the Sixth Edition, the ECMAScript specification <span class="nt">LabelledStatement</span> did not allow for the
+ association of a statement label with a <span class="nt">FunctionDeclaration</span>. However, a labelled <span
+ class="nt">FunctionDeclaration</span> was an allowable extension for non-<a href="#sec-strict-mode-code">strict mode
+ code</a> and most browser-hosted ECMAScript implementations supported that extension. In the Sixth Edition, the grammar
+ productions for <span class="nt">LabelledStatement</span> permits use of <span class="nt">FunctionDeclaration</span> as a
+ <span class="nt">LabelledItem</span> but <a href="#sec-labelled-statements-static-semantics-early-errors">13.12.1</a>
+ includes an Early Error rule that produces a Syntax Error if that occurs. For web browser compatibility, that rule is
+ modified with the addition of the underlined text:</p>
+
+ <div class="gp prod"><span class="nt">LabelledItem</span> <span class="geq">:</span> <span class="nt">FunctionDeclaration</span></div>
+ <ul>
+ <li>It is a Syntax Error if any strict mode source code matches this rule.</li>
+ </ul>
+ </section>
+
+ <section id="sec-block-level-function-declarations-web-legacy-compatibility-semantics">
+ <h1><span class="secnum" id="sec-B.3.3"><a href="#sec-block-level-function-declarations-web-legacy-compatibility-semantics"
+ title="link to this section">B.3.3</a></span> Block-Level Function Declarations Web Legacy Compatibility Semantics</h1>
+
+ <p>Prior to the Sixth Edition, the ECMAScript specification did not define the occurrence of a <span
+ class="nt">FunctionDeclaration</span> as an element of a <span class="nt">Block</span> statement’s <span
+ class="nt">StatementList</span>. However, support for that form of <span class="nt">FunctionDeclaration</span> was an
+ allowable extension and most browser-hosted ECMAScript implementations permitted them. Unfortunately, the semantics of such
+ declarations differ among those implementations. Because of these semantic differences, existing web ECMAScript code that
+ uses <span class="nt">Block</span> level function declarations is only portable among browser implementation if the usage
+ only depends upon the semantic intersection of all of the browser implementations for such declarations. The following are
+ the use cases that fall within that intersection semantics:</p>
+
+ <ol class="proc">
+ <li>A function is declared and only referenced within a single block
+ <ul>
+ <li>
+ <p>A function declaration with the name <var>f</var> is declared exactly once within the function code of an
+ enclosing function <var>g</var> and that declaration is nested within a <span class="nt">Block</span>.</p>
+ </li>
+
+ <li>
+ <p>No other declaration of <var>f</var> that is not a <code>var</code> declaration occurs within the function code
+ of <var>g</var></p>
+ </li>
+
+ <li>
+ <p>All references to <var>f</var> occur within the <span class="nt">StatementList</span> of the <span
+ class="nt">Block</span> containing the declaration of <var>f</var>.</p>
+ </li>
+ </ul>
+ </li>
+ <li>A function is declared and possibly used within a single <span class="nt">Block</span> but also referenced by an inner
+ function definition that is not contained within that same <span class="nt">Block</span>.
+ <ul>
+ <li>
+ <p>A function declaration with the name <var>f</var> is declared exactly once within the function code of an
+ enclosing function <var>g</var> and that declaration is nested within a <span class="nt">Block</span>.</p>
+ </li>
+
+ <li>
+ <p>No other declaration of <var>f</var> that is not a <code>var</code> declaration occurs within the function code
+ of <var>g</var></p>
+ </li>
+
+ <li>
+ <p>References to <var>f</var> may occur within the <span class="nt">StatementList</span> of the <span
+ class="nt">Block</span> containing the declaration of <var>f</var>.</p>
+ </li>
+
+ <li>
+ <p>References to <var>f</var> occur within the function code of <var>g</var> that lexically follows the <span
+ class="nt">Block</span> containing the declaration of <var>f</var>.</p>
+ </li>
+ </ul>
+ </li>
+ <li>A function is declared and possibly used within a single block but also referenced within subsequent blocks.
+ <ul>
+ <li>
+ <p>A function declaration with the name <var>f</var> is declared exactly once within the function code of an
+ enclosing function <var>g</var> and that declaration is nested within a <span class="nt">Block</span>.</p>
+ </li>
+
+ <li>
+ <p>No other declaration of <var>f</var> that is not a <code>var</code> declaration occurs within the function code
+ of <var>g</var></p>
+ </li>
+
+ <li>
+ <p>References to <var>f</var> may occur within the <span class="nt">StatementList</span> of the <span
+ class="nt">Block</span> containing the declaration of <var>f</var>.</p>
+ </li>
+
+ <li>
+ <p>References to <var>f</var> occur within another function <var>h</var> that is nested within <var>g</var> and no
+ other declaration of <var>f</var> shadows the references to <var>f</var> from within <var>h</var>.</p>
+ </li>
+
+ <li>
+ <p>All invocations of <i>h</i> occur after the declaration of <i>f</i> has been evaluated.</p>
+ </li>
+ </ul>
+ </li>
+ </ol>
+
+ <p>The first use case is interoperable with the semantics of <span class="nt">Block</span> level function declarations
+ provided by ECMA-262 Edition 6. Any pre-existing ECMAScript code that employees that use case will operate using the Block
+ level function declarations semantics defined by clauses 9, 13, and 14 of this specification.</p>
+
+ <p>Sixth edition interoperability for the second and third use cases requires the following extensions to the <a
+ href="#sec-ordinary-and-exotic-objects-behaviours">clause 9</a> and <a
+ href="#sec-ecmascript-language-functions-and-classes">clause 14</a> semantics. During <a
+ href="#sec-functiondeclarationinstantiation">FunctionDeclarationInstantiation</a> (<a
+ href="#sec-functiondeclarationinstantiation">9.2.13</a>) the following steps are performed in place of step 29:</p>
+
+ <ol class="proc">
+ <li>If <i>strict</i> is <b>false</b>, then
+ <ol class="block">
+ <li>For each <i>FunctionDeclaration</i> <i>f</i> in <i>varDeclarations</i> that is directly contained in the
+ <i>StatementList</i> of a <i>Block</i>, <i>CaseClause</i>, or <i>DefaultClause,</i>
+ <ol class="block">
+ <li>Let <i>F</i> be StringValue of the <i>BindingIdentifier</i> of <i>FunctionDeclaration</i> <i>f</i>.</li>
+ <li>If replacing the <i>FunctionDeclaration</i> <i>f</i> with a <i>VariableStatement</i> that has <i>F</i> as a
+ <i>BindingIdentifier</i> would not produce any Early Errors for <i>func</i> and <i>F</i> is not an element of
+ BoundNames of <i>argumentsList</i>, then
+ <ol class="block">
+ <li><span style="font-family: sans-serif">NOTE	A var binding for</span> <i>F</i> <span style="font-family:
+ sans-serif">is only instantiated here if it is neither a VarDeclaredName, the name of a formal parameter,
+ or another</span> <i>FunctionDeclarations</i>.</li>
+ <li>If <i>instantiatedVarNames</i> does not contain <i>F</i>, then
+ <ol class="block">
+ <li>Let <i>status</i> be <i>varEnvRec.</i>CreateMutableBinding(<i>F</i>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Perform <i>varEnvRec.</i>InitializeBinding(<i>F</i>, <b>undefined</b>).</li>
+ <li>Append <i>F</i> to <i>instantiatedVarNames</i>.</li>
+ </ol>
+ </li>
+ <li>When the <i>FunctionDeclaration</i> <i>f</i> is evaluated, perform the following steps in place of the
+ <i>FunctionDeclaration</i> Evaluation algorithm provided in <a
+ href="#sec-function-definitions-runtime-semantics-evaluation">14.1.21</a>:
+ <ol class="nested proc">
+ <li>Let <i>fenv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">VariableEnvironment</a>.</li>
+ <li>Let <i>benv</i> be <a href="#sec-execution-contexts">the running execution context</a>’s <a
+ href="#sec-execution-contexts">LexicalEnvironment</a>.</li>
+ <li>Let <i>fobj</i> be <i>benv</i>.GetBindingValue(<i>F</i>, <b>false</b>).</li>
+ <li><a href="#sec-returnifabrupt">ReturnIfAbrupt</a>(<i>fobj</i>).</li>
+ <li>Let <i>status</i> be <i>fenv</i>.SetMutableBinding(<i>F</i>, <i>fobj</i>, <b>false</b>).</li>
+ <li><a href="#sec-algorithm-conventions">Assert</a>: <i>status</i> is never an <a
+ href="#sec-completion-record-specification-type">abrupt completion</a>.</li>
+ <li>Return <a href="#sec-normalcompletion">NormalCompletion</a>(<span style="font-family:
+ sans-serif">empty</span>).</li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+ </li>
+ </ol>
+
+ <p>If an ECMAScript implementation has a mechanism for reporting diagnostic warning messages, a warning should be produced
+ for each function whose function code contains a <i>FunctionDeclaration</i> for which steps 2.b.i.1-3 will be performed.</p>
+ </section>
+
+ <section id="sec-functiondeclarations-in-ifstatement-statement-clauses">
+ <h1><span class="secnum" id="sec-B.3.4"><a href="#sec-functiondeclarations-in-ifstatement-statement-clauses"
+ title="link to this section">B.3.4</a></span> FunctionDeclarations in IfStatement Statement Clauses</h1>
+
+ <p>The following rules for <span class="nt">IfStatement</span> augment those in <a href="#sec-if-statement">13.5</a>:</p>
+
+ <div class="gp">
+ <div class="lhs"><span class="nt">IfStatement</span><sub>[Yield, Return]</sub> <span class="geq">:</span></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub> <code class="t">else</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">Statement</span><sub>[?Yield, ?Return]</sub> <code class="t">else</code> <span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub> <code class="t">else</code> <span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub></div>
+ <div class="rhs"><code class="t">if</code> <code class="t">(</code> <span class="nt">Expression</span><sub>[In, ?Yield]</sub> <code class="t">)</code> <span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub></div>
+ </div>
+
+ <p>The above rules are only applied when parsing non-<a href="#sec-strict-mode-code">strict mode code</a>. If any non-<a
+ href="#sec-strict-mode-code">strict code</a> is match by one of these rules subsequent processing of that code takes places
+ as if each matching occurrence of <span class="nt">FunctionDeclaration</span><sub>[?Yield]</sub> was the sole <span
+ class="nt">StatementListItem</span> of a <span class="nt">BlockStatement</span> occupying that position in the source code.
+ The semantics of such a synthetic <span class="nt">BlockStatement</span> includes the web legacy compatibility semantics
+ specified in <a href="#sec-block-level-function-declarations-web-legacy-compatibility-semantics">B.3.3</a>.</p>
+ </section>
+
+ <section id="sec-variablestatements-in-catch-blocks">
+ <h1><span class="secnum" id="sec-B.3.5"><a href="#sec-variablestatements-in-catch-blocks"
+ title="link to this section">B.3.5</a></span> VariableStatements in Catch blocks</h1>
+
+ <p>The content of <a href="#sec-try-statement-static-semantics-early-errors">subclause 13.14.1</a> is replaced with the
+ following:</p>
+
+ <div class="gp prod"><span class="nt">Catch</span> <span class="geq">:</span> <code class="t">catch</code> <code class="t">(</code> <span class="nt">CatchParameter</span> <code class="t">)</code> <span class="nt">Block</span></div>
+ <ul>
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <span class="nt">CatchParameter</span> also occurs in the
+ LexicallyDeclaredNames of <span class="nt">Block</span>.</p>
+ </li>
+
+ <li>
+ <p>It is a Syntax Error if any element of the BoundNames of <span class="nt">CatchParameter</span> also occurs in the
+ VarDeclaredNames of <var>Block, unless that element is only bound by a VariableStatement or</var> <var>the
+ VariableDeclarationList of a for statement, or the ForBinding of a for-in statement</var>.</p>
+ </li>
+ </ul>
+
+ <div class="note">
+ <p><span class="nh">NOTE</span> The <i>Block</i> of a <i>Catch</i> clause may contain <code>var</code> declarations that
+ bind a name that is also bound by the <i>CatchParameter</i>. At runtime, such bindings are instantiated in the
+ VariableDeclarationEnvironment. They do not shadow the same-named bindings introduced by the <i>CatchParameter</i> and
+ hence the <i>Initializer</i> for such <code>var</code> declarations will assign to the corresponding catch parameter
+ rather than the <code>var</code> binding. The relaxation of the normal static semantic rule does not apply to names only
+ bound by for-of statements.</p>
+ </div>
+
+ <p>This modified behaviour also applies to <code>var</code> declarations introduced by direct evals contained within the
+ <span class="nt">Block</span> of a <span class="nt">Catch</span> clause. This change is accomplish by modify the algorithm
+ of <a href="#sec-evaldeclarationinstantiation">18.2.1.2</a> as follows:</p>
+
+ <p>Step 6.d.ii is replaced by:</p>
+
+ <ol class="proc">
+ <li>If <i>thisEnvRec</i> is neither an <a href="#sec-object-environment-records">object environment record</a> nor the
+ environment record for a <i>Catch</i> clause, then</li>
+ </ol>
+
+ <p>Step 6.d.ii.2 is replaced by:</p>
+
+ <ol class="proc">
+ <li>For each <i>name</i> in <i>varNames</i> that is <i>only bound by a VariableStatement</i> <i>or the
+ VariableDeclarationList</i> <i>of a for statement, or the</i> <i>ForBinding</i> <i>of a for-in statement</i>, do</li>
+ </ol>
+ </section>
+ </section>
+</section>
+
+<section id="sec-strict-mode-of-ecmascript">
+ <h1><span class="secnum" id="sec-C"><a href="#sec-strict-mode-of-ecmascript"
+ title="link to this section">Annex C</a></span> <span class="section-status">(informative)</span> The Strict Mode of
+ ECMAScript</h1>
+
+ <p><b>The strict mode restriction and exceptions</b></p>
+
+ <ul>
+ <li>
+ <p>"<code>implements</code>", "<code>interface</code>", "<code>let</code>", "<code>package</code>", "<code>private</code>",
+ "<code>protected</code>", "<code>public</code>", "<code>static</code>", and "<code>yield</code>" are reserved words within
+ <a href="#sec-strict-mode-code">strict mode code</a>. (<a href="#sec-reserved-words">11.6.2</a>).</p>
+ </li>
+
+ <li>
+ <p>A conforming implementation, when processing <a href="#sec-strict-mode-code">strict mode code</a>, may not extend the
+ syntax of <i>NumericLiteral</i> (<a href="#sec-literals-numeric-literals">11.8.3</a>) to include
+ <i>LegacyOctalIntegerLiteral</i> as described in <a href="#sec-additional-syntax-numeric-literals">B.1.1</a>.</p>
+ </li>
+
+ <li>
+ <p>A conforming implementation, when processing <a href="#sec-strict-mode-code">strict mode code</a> (<a
+ href="#sec-strict-mode-code">see 10.2.1</a>), may not extend the syntax of <i>EscapeSequence</i> to include
+ <i>LegacyOctalEscapeSequence</i> as described in <a href="#sec-additional-syntax-string-literals">B.1.2</a>.</p>
+ </li>
+
+ <li>
+ <p>Assignment to an undeclared identifier or otherwise unresolvable reference does not create a property in the global
+ object. When a simple assignment occurs within <a href="#sec-strict-mode-code">strict mode code</a>, its <i>LeftHandSide</i>
+ must not evaluate to an <a href="#sec-reference-specification-type">unresolvable Reference</a>. If it does a
+ <b>ReferenceError</b> exception is thrown (<a href="#sec-putvalue">6.2.3.2</a>). The <i>LeftHandSide</i> also may not be a
+ reference to a data property with the attribute value {[[Writable]]:<b>false</b>}, to an accessor property with the
+ attribute value {[[Set]]:<b>undefined</b>}, nor to a non-existent property of an object whose [[Extensible]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> has the value <b>false</b>. In these cases a
+ <code>TypeError</code> exception is thrown (<a href="#sec-assignment-operators">12.14</a>).</p>
+ </li>
+
+ <li>
+ <p>The identifier <code>eval</code> or <code>arguments</code> may not appear as the <i>LeftHandSideExpression</i> of an
+ Assignment operator (<a href="#sec-assignment-operators">12.14</a>) or of a <i>PostfixExpression</i> (<a
+ href="#sec-assignment-operators">12.14</a>) or as the <i>UnaryExpression</i> operated upon by a Prefix Increment (<a
+ href="#sec-prefix-increment-operator">12.5.7</a>) or a Prefix Decrement (<a
+ href="#sec-prefix-decrement-operator">12.5.8</a>) operator.</p>
+ </li>
+
+ <li>
+ <p>Arguments objects for strict mode functions define non-configurable accessor properties named "<code>caller</code>" and
+ "<code>callee</code>" which throw a <b>TypeError</b> exception on access (<a
+ href="#sec-addrestrictedfunctionproperties">9.2.8</a>).</p>
+ </li>
+
+ <li>
+ <p>Arguments objects for strict mode functions do not dynamically share their array indexed property values with the
+ corresponding formal parameter bindings of their functions. (<a href="#sec-arguments-exotic-objects">9.4.4</a>).</p>
+ </li>
+
+ <li>
+ <p>For strict mode functions, if an arguments object is created the binding of the local identifier <code>arguments</code>
+ to the arguments object is immutable and hence may not be the target of an assignment expression. (<a
+ href="#sec-functiondeclarationinstantiation">9.2.13</a>).</p>
+ </li>
+
+ <li>
+ <p>It is a <b>SyntaxError</b> if the <i>IdentifierName</i> <code>eval</code> or the <i>IdentifierName</i>
+ <code>arguments</code> occurs as a <span class="nt">BindingIdentifier</span> within <a href="#sec-strict-mode-code">strict
+ mode code</a> (<a href="#sec-identifiers-static-semantics-early-errors">12.1.1</a>).</p>
+ </li>
+
+ <li>
+ <p>Strict mode eval code cannot instantiate variables or functions in the variable environment of the caller to eval.
+ Instead, a new variable environment is created and that environment is used for declaration binding instantiation for the
+ eval code (<a href="#sec-eval-x">18.2.1</a>).</p>
+ </li>
+
+ <li>
+ <p>If <b>this</b> is evaluated within <a href="#sec-strict-mode-code">strict mode code</a>, then the <b>this</b> value is
+ not coerced to an object. A <b>this</b> value of <b>null</b> or <b>undefined</b> is not converted to the global object and
+ primitive values are not converted to wrapper objects. The <b>this</b> value passed via a function call (including calls
+ made using <code><a href="#sec-function.prototype.apply">Function.prototype.apply</a></code> and <b><code><a
+ href="#sec-function.prototype.call">Function.prototype.call</a></code>)</b> do not coerce the passed this value to an object
+ (<a href="#sec-getthisenvironment">8.3.2</a>, <a href="#sec-this-keyword">12.2.1</a>, <a
+ href="#sec-function.prototype.apply">19.2.3.1</a>, <a href="#sec-function.prototype.call">19.2.3.3</a>).</p>
+ </li>
+
+ <li>
+ <p>When a <code>delete</code> operator occurs within <a href="#sec-strict-mode-code">strict mode code</a>, a
+ <b>SyntaxError</b> is thrown if its <i>UnaryExpression</i> is a direct reference to a variable, function argument, or
+ function name (<a href="#sec-delete-operator">12.5.4</a>).</p>
+ </li>
+
+ <li>
+ <p>When a <code>delete</code> operator occurs within <a href="#sec-strict-mode-code">strict mode code</a>, a
+ <b>TypeError</b> is thrown if the property to be deleted has the attribute { [[Configurable]]:<b>false</b> } (<a
+ href="#sec-delete-operator">12.5.4</a>).</p>
+ </li>
+
+ <li>
+ <p>Strict mode code may not include a <i>WithStatement</i>. The occurrence of a <i>WithStatement</i> in such a context is a
+ <b>SyntaxError</b> (<a href="#sec-with-statement">13.10</a>).</p>
+ </li>
+
+ <li>
+ <p>It is a <b>SyntaxError</b> if a <i>TryStatement</i> with a <i>Catch</i> occurs within <a
+ href="#sec-strict-mode-code">strict code</a> and the <i>Identifier</i> of the <i>Catch</i> production is <code>eval</code>
+ or <code>arguments</code> (<a href="#sec-try-statement">13.14</a>)</p>
+ </li>
+
+ <li>
+ <p>It is a <b>SyntaxError</b> if the same <span class="nt">BindingIdentifier</span> appears more than once in the <span
+ class="nt">FormalParameters</span> of a strict mode function. An attempt to create such a function using a
+ <code>Function</code> or <code>Generator</code> constructor is a <b>SyntaxError</b> (<a
+ href="#sec-function-definitions-static-semantics-early-errors">14.1.2</a>, <a href="#sec-function-constructor">19.2.1</a>,
+ <a href="#sec-generatorfunction-constructor">25.2.1</a>).</p>
+ </li>
+
+ <li>
+ <p>An implementation may not extend, beyond that defined in this specification, the meanings within strict mode functions of
+ properties named <code>caller</code> or <code>arguments</code> of function instances. ECMAScript code may not create or
+ modify properties with these names on function objects that correspond to strict mode functions (<a
+ href="#sec-ecmascript-function-objects-getownproperty-p">9.2.1</a>, <a href="#sec-arguments-exotic-objects">9.4.4</a>).</p>
+ </li>
+ </ul>
+</section>
+
+<section id="sec-corrections-and-clarifications-in-edition-6-with-possible-compatibility-impact">
+ <h1><span class="secnum" id="sec-D"><a
+ href="#sec-corrections-and-clarifications-in-edition-6-with-possible-compatibility-impact"
+ title="link to this section">Annex D</a></span> <span class="section-status">(informative)</span> Corrections and
+ Clarifications in Edition 6 with Possible Compatibility Impact</h1>
+
+ <p><a href="#sec-candeclareglobalvar">8.1.1.4.15</a>-<a href="#sec-createglobalfunctionbinding">8.1.1.4.18</a> Edition 5 and <a
+ href="#sec-syntactic-and-lexical-grammars">5.1</a> used a property existence test to determine whether a global object property
+ corresponding to a new global declaration already existed. Edition 6 uses an own property existence test. This corresponds to
+ what has been most commonly implemented by web browsers.</p>
+
+ <p><a href="#sec-array-exotic-objects-defineownproperty-p-desc">9.4.2.1</a>: The 5<sup>th</sup> Edition moved the capture of the
+ current array length prior to the integer conversion of the array index or new length value. However, the captured length value
+ could become invalid if the conversion process has the side-effect of changing the array length. The 6<sup>th</sup> Edition
+ specifies that the current array length must be captured after the possible occurrence of such side-effects.</p>
+
+ <p><a href="#sec-timeclip">20.3.1.14</a>: Previous editions permitted the <a href="#sec-timeclip">TimeClip</a> abstract
+ operation to return either +0 or <b>−</b>0 as the representation of a 0 <a href="#sec-time-values-and-time-range">time
+ value</a>. The 6<sup>th</sup> Edition specifies that +0 always returned. This means that for the 6<sup>th</sup> Edition the <a
+ href="#sec-time-values-and-time-range">time value</a> of a Date object is never observably <b>−</b>0 and methods that
+ return time values never return <b>−</b>0.</p>
+
+ <p><a href="#sec-date-time-string-format">20.3.1.15</a>: If a time zone offset is not present, the local time zone is used.
+ Edition 5.1 incorrectly stated that a missing time zone should be interpreted as “<code>z</code>”.</p>
+
+ <p><a href="#sec-date.prototype.toisostring">20.3.4.36</a>: If the year cannot be represented using the Date Time String Format
+ specified in <a href="#sec-date-time-string-format">20.3.1.15</a> a RangeError exception is thrown. Previous editions did not
+ specify the behaviour for that case.</p>
+
+ <p><a href="#sec-date.prototype.tostring">20.3.4.41</a>: Previous editions did not specify the value returned by <a
+ href="#sec-date.prototype.tostring">Date.prototype.toString</a> when <a href="#sec-properties-of-the-date-prototype-object">this
+ time value</a> is NaN. The 6<sup>th</sup> Edition specifies the result to be the String value is <code>"Invalid
+ Date".</code></p>
+
+ <p><a href="#sec-regexp-pattern-flags">21.2.3.1</a>, <a href="#sec-escaperegexppattern">21.2.3.2.4</a>: Any LineTerminator code
+ points in the value of the <code>source</code> property of an RegExp instance must be expressed using an escape sequence.
+ Edition 5.1 only required the escaping of <code>"/"</code>.</p>
+
+ <p><a href="#sec-regexp.prototype-@@match">21.2.5.6</a>, <a href="#sec-regexp.prototype-@@replace">21.2.5.8</a>: In previous
+ editions, the specifications for <code><a href="#sec-string.prototype.match">String.prototype.match</a></code> and <code><a
+ href="#sec-string.prototype.replace">String.prototype.replace</a></code> was incorrect for cases where the pattern argument was
+ a RegExp value whose <code>global</code> is flag set. The previous specifications stated that for each attempt to match the
+ pattern, if <code>lastIndex</code> did not change it should be incremented by 1. The correct behaviour is that
+ <code>lastIndex</code> should be incremented by one only if the pattern matched the empty string.</p>
+
+ <p><a href="#sec-array.prototype.sort">22.1.3.24</a>, <a href="#sec-sortcompare">22.1.3.24.1</a>: Previous editions did not
+ specify how a <b>NaN</b> value returned by a <var>comparefn</var> was interpreted by <code><a
+ href="#sec-array.prototype.sort">Array.prototype.sort</a></code>. Edition 6 specifies that such as value is treated as if +0 was
+ returned from the <var>comparefn</var>. Edition 6 also specifies that <a href="#sec-tonumber">ToNumber</a> is applied to the
+ result returned by a <span style="font-family: Times New Roman"><i>comparefn</i>.</span> In previous editions, the effect of a
+ <var>comparefn</var> result that is not a Number value was implementation dependent. In practice, implementations call <a
+ href="#sec-tonumber">ToNumber</a>.</p>
+</section>
+
+<section id="sec-additions-and-changes-that-introduce-incompatibilities-with-prior-editions">
+ <h1><span class="secnum" id="sec-E"><a href="#sec-additions-and-changes-that-introduce-incompatibilities-with-prior-editions"
+ title="link to this section">Annex E</a></span> <span class="section-status">(informative)</span> Additions and Changes
+ That Introduce Incompatibilities with Prior Editions</h1>
+
+ <p><a href="#sec-tonumber-applied-to-the-string-type">7.1.3.1</a>: In Edition 6, <a href="#sec-tonumber">ToNumber</a> applied to
+ a String value now recognizes and converts <span class="nt">BinaryIntegerLiteral</span> and <span
+ class="nt">OctalIntegerLIteral</span> numeric strings. In previous editions such strings were converted to <span
+ class="value">NaN</span>,</p>
+
+ <p><a href="#sec-reference-specification-type">6.2.3</a>: In Edition 6, Function calls are not allowed to return a <a
+ href="#sec-reference-specification-type">Reference</a> value.</p>
+
+ <p><a href="#sec-object-initializer-static-semantics-early-errors">12.2.5.1</a>: In Edition 6, it is no longer an early error to
+ have duplicate property names in Object Initializers.</p>
+
+ <p><a href="#sec-assignment-operators-static-semantics-early-errors">12.14.1</a>: In Edition 6, <a
+ href="#sec-strict-mode-code">strict mode code</a> containing an assignment to an immutable binding such as the function name of
+ a <span class="nt">FunctionExpression</span> does not produce an early error. Instead it produces a runtime error.</p>
+
+ <p><a href="#sec-expression-statement">13.4</a>: In Edition 6, a <span class="nt">StatementListItem</span> beginning with the
+ token <code>let</code> followed by the token <code>[</code> is the start of a <span class="nt">LexicalDeclaration</span>. In
+ previous editions such a sequence would be the start of an <span class="nt">ExpressionStatement</span>.</p>
+
+ <p><a href="#sec-iteration-statements">13.6</a>: In Edition 6, a terminating semi-colon is no longer required at the end of a
+ do-while statement.</p>
+
+ <p><a href="#sec-iteration-statements">13.6</a>: Prior to Edition 6, an initialization expression could appear as part of the
+ <i>VariableDeclaration</i> that precedes the <code>in</code> keyword. The value of that expression was always discarded. In
+ Edition 6, the <i>ForBind</i> in that same position does not allow the occurrence of such an initializer.</p>
+
+ <p><a href="#sec-try-statement">13.14</a>: In Edition 6, it is an early error for a <span class="nt">Catch</span> clause to
+ contained a <code>var</code> declaration for the same <span class="nt">Identifier</span> that appears as the <span
+ class="nt">Catch</span> clause parameter. In previous editions, such a variable declaration would be instantiated in the
+ enclosing variable environment but the declaration’s <span class="nt">Initializer</span> value would be assigned to the
+ <span class="nt">Catch</span> parameter.</p>
+
+ <p><a href="#sec-runtime-semantics-definemethod">14.3.9</a> In Edition 6, the function objects that are created as the values of
+ the [[Get]] or [[Set]] attribute of accessor properties in an <span class="nt">ObjectLiteral</span> are not constructor
+ functions and they do not have a <code>prototype</code> own property. In Edition 5, they were constructors and had a
+ <code>prototype</code> property.</p>
+
+ <p><a href="#sec-object.freeze">19.1.2.5</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.freeze">Object.freeze</a></code> is not an object it is treated as if it was a non-extensible ordinary object
+ with no own properties. In Edition 5, a non-object argument always causes a <span class="value">TypeError</span> to be
+ thrown.</p>
+
+ <p><a href="#sec-object.getownpropertydescriptor">19.1.2.6</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.getownpropertydescriptor">Object.getOwnPropertyDescriptor</a></code> is not an object an attempt is make to
+ coerce the argument using <a href="#sec-toobject">ToObject</a>. If the coercion is successful the result is used in place of the
+ original argument value. In Edition 5, a non-object argument always causes a <span class="value">TypeError</span> to be
+ thrown.</p>
+
+ <p><a href="#sec-object.getownpropertynames">19.1.2.7</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.getownpropertynames">Object.getOwnPropertyNames</a></code> is not an object an attempt is make to coerce the
+ argument using <a href="#sec-toobject">ToObject</a>. If the coercion is successful the result is used in place of the original
+ argument value. In Edition 5, a non-object argument always causes a <span class="value">TypeError</span> to be thrown.</p>
+
+ <p><a href="#sec-object.getprototypeof">19.1.2.9</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.getprototypeof">Object.getPrototypeOf</a></code> is not an object an attempt is make to coerce the argument
+ using <a href="#sec-toobject">ToObject</a>. If the coercion is successful the result is used in place of the original argument
+ value. In Edition 5, a non-object argument always causes a <b>TypeError</b> to be thrown.</p>
+
+ <p><a href="#sec-object.isextensible">19.1.2.11</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.isextensible">Object.isExtensible</a></code> is not an object it is treated as if it was a non-extensible
+ ordinary object with no own properties. In Edition 5, a non-object argument always causes a <span class="value">TypeError</span>
+ to be thrown.</p>
+
+ <p><a href="#sec-object.isfrozen">19.1.2.12</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.isfrozen">Object.isFrozen</a></code> is not an object it is treated as if it was a non-extensible ordinary
+ object with no own properties. In Edition 5, a non-object argument always causes a <span class="value">TypeError</span> to be
+ thrown.</p>
+
+ <p><a href="#sec-object.issealed">19.1.2.13</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.issealed">Object.isSealed</a></code> is not an object it is treated as if it was a non-extensible ordinary
+ object with no own properties. In Edition 5, a non-object argument always causes a <span class="value">TypeError</span> to be
+ thrown.</p>
+
+ <p><a href="#sec-object.keys">19.1.2.14</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.keys">Object.keys</a></code> is not an object an attempt is made to coerce the argument using <a
+ href="#sec-toobject">ToObject</a>. If the coercion is successful the result is used in place of the original argument value. In
+ Edition 5, a non-object argument always causes a <span class="value">TypeError</span> to be thrown.</p>
+
+ <p><a href="#sec-object.preventextensions">19.1.2.15</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.preventextensions">Object.preventExtensions</a></code> is not an object it is treated as if it was a
+ non-extensible ordinary object with no own properties. In Edition 5, a non-object argument always causes a <span
+ class="value">TypeError</span> to be thrown.</p>
+
+ <p><a href="#sec-object.seal">19.1.2.17</a>: In Edition 6, if the argument to <code><a
+ href="#sec-object.seal">Object.seal</a></code> is not an object it is treated as if it was a non-extensible ordinary object with
+ no own properties. In Edition 5, a non-object argument always causes a <span class="value">TypeError</span> to be thrown.</p>
+
+ <p><a href="#sec-function-instances-length">19.2.4.1</a>: In Edition 6, the <code>length</code> property of function instances
+ is configurable. In previous editions it was non-configurable.</p>
+
+ <p><a href="#sec-properties-of-the-boolean-prototype-object">19.3.3</a>: In Edition 6, the Boolean prototype object is not a
+ Boolean instance. In previous editions it was a Boolean instance whose Boolean value was <b>false</b>.</p>
+
+ <p><a href="#sec-properties-of-the-nativeerror-constructors">19.5.6.2</a>: In Edition 6, the [[Prototype]] <a
+ href="#sec-object-internal-methods-and-internal-slots">internal slot</a> of a <i>NativeError</i> constructor is the Error
+ constructor. In previous editions it was the Function prototype object.</p>
+
+ <p><a href="#sec-properties-of-the-number-prototype-object">20.1.3</a> In Edition 6, the Number prototype object is not a Number
+ instance. In previous editions it was a Number instance whose number value was +0.</p>
+
+ <p><a href="#sec-properties-of-the-date-prototype-object">20.3.4</a> In Edition 6, the Date prototype object is not a Date
+ instance. In previous editions it was a Date instance whose TimeValue was NaN.</p>
+
+ <p><a href="#sec-string.prototype.localecompare">21.1.3.10</a> In Edition 6, the <code><a
+ href="#sec-string.prototype.localecompare">String.prototype.localeCompare</a></code> function must treat Strings that are
+ canonically equivalent according to the Unicode standard as being identical. In previous editions implementations were permitted
+ to ignore canonical equivalence and could instead use a bit-wise comparison.</p>
+
+ <p><a href="#sec-properties-of-the-string-prototype-object">21.1.3</a> In Edition 6, the String prototype object is not a String
+ instance. In previous editions it was a String instance whose String value was the empty string.</p>
+
+ <p><a href="#sec-string.prototype.tolowercase">21.1.3.22</a> and <a href="#sec-string.prototype.touppercase">21.1.3.24</a> In
+ Edition 6, lowercase/upper conversion processing operates on code points. In previous editions such the conversion processing
+ was only applied to individual code units. The only affected code points are those in the Deseret block of Unicode</p>
+
+ <p><a href="#sec-string.prototype.trim">21.1.3.25</a> In Edition 6, the <code><a
+ href="#sec-string.prototype.trim">String.prototype.trim</a></code> method is defined to recognize white space code points that
+ may exists outside of the Unicode BMP. However, as of Unicode 6.1 no such code points are defined. In previous editions such
+ code points would not have been recognized as white space.</p>
+
+ <p><a href="#sec-regexp-pattern-flags">21.2.3.1</a> In Edition 6, If the <var>pattern</var> argument is a RegExp instance and
+ the <var>flags</var> argument is not <span class="value">undefined</span>, a new RegExp instance is created just like
+ <var>pattern</var> except that <var>pattern’s</var> flags are replaced by the argument <var>flags</var>. In previous
+ editions a <b>TypeError</b> exception was thrown when <var>pattern</var> was a RegExp instance and <var>flags</var> was not
+ <span class="value">undefined</span>.</p>
+
+ <p><a href="#sec-properties-of-the-regexp-prototype-object">21.2.5</a> In Edition 6, the RegExp prototype object is not a RegExp
+ instance. In previous editions it was a RegExp instance whose pattern is the empty string.</p>
+
+ <p><a href="#sec-properties-of-the-regexp-prototype-object">21.2.5</a> In Edition 6, <code>source</code>, <code>global</code>,
+ <code>ignoreCase</code>, and <code>multiline</code> are accessor properties defined on the RegExp prototype object. In previous
+ editions they were data properties defined on RegExp instances.</p>
+</section>
+
+<section>
+ <h1>Bibliography</h1>
+
+ <p><span class="marker">[1]	</span><i>IANA Time Zone Database</i> at <<span style="font-family:
+ sans-serif">http://www.iana.org/time-zones</span>></p>
+
+ <p><span class="marker">[2]	</span>ISO 8601:2004(E) <i>Data elements and interchange formats – Information
+ interchange</i> <span style="font-family: Times New Roman">—</span> <i>Representation of dates and times</i></p>
+
+ <p><span class="marker">[3]	</span>RFC 1738 “Uniform Resource Locators (URL)”, available at
+ <http://tools.ietf.org/html/rfc1738></p>
+
+ <p><span class="marker">[4]	</span>RFC 2396 “Uniform Resource Identifiers (URI): Generic Syntax”, available at
+ <http://tools.ietf.org/html/rfc2396></p>
+
+ <p><span class="marker">[5]	</span>RFC 3629 “UTF-8, a transformation format of ISO 10646”, available at
+ <http://tools.ietf.org/html/rfc3629></p>
+
+ <p><span class="marker">[6]	</span>RFC 4627 “The application/json Media Type for JavaScript Object Notation
+ (JSON)” , available at <http://tools.ietf.org/html/rfc4627></p>
+
+ <p><span class="marker">[7]	</span>Unicode Inc. (2002), Unicode Technical Note #5: Canonical Equivalence in Applications,
+ available at <http://www.unicode.org/notes/tn5/></p>
+
+ <p><span class="marker">[8]	</span>Unicode Inc. (2002), Unicode Technical Standard #10: Unicode Collation Algorithm version
+ 5.1.0, or successor, available at <http://www.unicode.org/reports/tr10/></p>
+
+ <p></p>
+</section>
+</body>
+</html>
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