1 # Build Cache wrapper for minifying JavaScript files
7 The `min_js_cache` package exports a single constructor
9 which must be called with the `new` operator. The resulting cache object stores
10 the `utf-8`-encoded text of JavaScript files loaded from disk and minified.
12 See the `build_cache`, `disk_build`, and `uglify-es` packages for more
13 information. The `MinJSCache` object is essentially a wrapper object which
14 routes the request between these packages, to ensure that the minified
15 JavaScript text is either retrieved from RAM or minified from a source file as
20 Suppose one has a `MinJSCache` instance named `mjc`. It behaves somewhat like
21 an ES6 `Map` object, except that it only has the `mjc.get()` function, because
22 new objects are added to the cache by attempting to `get` them.
24 The interface for the `MinJSCache`-provided instance function `mjc.get()` is:
26 `await mjc.get(key)` — retrieves the object stored under `key`, where
27 `key` is the on-disk pathname to a JavaScript file. A `Buffer` object is
28 returned, containing the `utf-8`-encoded text resulting from running
29 `uglify-es` on the source file. The pathname and the returned result are cached
32 Before returning the cached copy, the existence and modification time of the
33 JavaScript file on disk is checked to make sure that the cache is up-to-date.
34 Otherwise, if the file doesn't exist an `ENOENT` exception is thrown, or if the
35 file exists it is loaded and minified and the cache updated for next time. The
36 minification is via disk, and skipped if an up-to-date disk result is present.
40 The `diag` argument to the constructor is a `bool`, which if `true` causes
41 messages to be printed via `console.log()` for all activities except for the
42 common case of retrieval when the object is already up-to-date. A `diag` value
43 of `undefined` is treated as `false`, thus it can be omitted in the usual case.
47 The `uglify-es` package is called with standard NDCODE options. This is part of
48 the reason to have `min_js_cache`, so as to provide a consistent interface to
49 minifiers for JavaScript, CSS, SVG and so on. However, if some control of the
50 underlying minifier is needed in future, we could add an `options` object to
51 pass through, in which we'd inject our NDCODE options where not overridden.
53 It is intended that we will shortly add a timer function (or possibly just a
54 function that the user should call periodically) to flush built templates from
55 the cache after a stale time. There is otherwise no way to delete an object
56 from the cache, except by first deleting it on disk, then trying to `get` it.
60 The development version can be cloned, downloaded, or browsed with `gitweb` at:
61 https://git.ndcode.org/public/min_js_cache.git
65 All of our NPM packages are MIT licensed, please see LICENSE in the repository.
69 The caching system is under active development (and is part of a larger project
70 that is also under development) and thus the API is tentative. Please go ahead
71 and incorporate the system into your project, or try out our example webserver
72 built on the system, subject to the caution that the API could change. Please
73 send us your experience and feedback, and let us know of improvements you make.
75 Contact: Nick Downing <nick@ndcode.org>