From 13be50a4a9e34d65fef834625f44545e849fed02 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Sun, 26 Feb 2017 05:58:26 +0800
Subject: [PATCH] faster tree transversal (#1462)

- convert `[].forEach()` to for-loops
---
 lib/ast.js      | 46 ++++++++++++++++++++++++++--------------------
 lib/compress.js |  2 +-
 2 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/lib/ast.js b/lib/ast.js
index 61643aed..f3df78fe 100644
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -145,12 +145,13 @@ var AST_SimpleStatement = DEFNODE("SimpleStatement", "body", {
 }, AST_Statement);
 
 function walk_body(node, visitor) {
-    if (node.body instanceof AST_Statement) {
-        node.body._walk(visitor);
+    var body = node.body;
+    if (body instanceof AST_Statement) {
+        body._walk(visitor);
+    }
+    else for (var i = 0, len = body.length; i < len; i++) {
+        body[i]._walk(visitor);
     }
-    else node.body.forEach(function(stat){
-        stat._walk(visitor);
-    });
 };
 
 var AST_Block = DEFNODE("Block", "body", {
@@ -371,9 +372,10 @@ var AST_Lambda = DEFNODE("Lambda", "name argnames uses_arguments", {
     _walk: function(visitor) {
         return visitor._visit(this, function(){
             if (this.name) this.name._walk(visitor);
-            this.argnames.forEach(function(arg){
-                arg._walk(visitor);
-            });
+            var argnames = this.argnames;
+            for (var i = 0, len = argnames.length; i < len; i++) {
+                argnames[i]._walk(visitor);
+            }
             walk_body(this, visitor);
         });
     }
@@ -533,9 +535,10 @@ var AST_Definitions = DEFNODE("Definitions", "definitions", {
     },
     _walk: function(visitor) {
         return visitor._visit(this, function(){
-            this.definitions.forEach(function(def){
-                def._walk(visitor);
-            });
+            var definitions = this.definitions;
+            for (var i = 0, len = definitions.length; i < len; i++) {
+                definitions[i]._walk(visitor);
+            }
         });
     }
 }, AST_Statement);
@@ -573,9 +576,10 @@ var AST_Call = DEFNODE("Call", "expression args", {
     _walk: function(visitor) {
         return visitor._visit(this, function(){
             this.expression._walk(visitor);
-            this.args.forEach(function(arg){
-                arg._walk(visitor);
-            });
+            var args = this.args;
+            for (var i = 0, len = args.length; i < len; i++) {
+                args[i]._walk(visitor);
+            }
         });
     }
 });
@@ -742,9 +746,10 @@ var AST_Array = DEFNODE("Array", "elements", {
     },
     _walk: function(visitor) {
         return visitor._visit(this, function(){
-            this.elements.forEach(function(el){
-                el._walk(visitor);
-            });
+            var elements = this.elements;
+            for (var i = 0, len = elements.length; i < len; i++) {
+                elements[i]._walk(visitor);
+            }
         });
     }
 });
@@ -756,9 +761,10 @@ var AST_Object = DEFNODE("Object", "properties", {
     },
     _walk: function(visitor) {
         return visitor._visit(this, function(){
-            this.properties.forEach(function(prop){
-                prop._walk(visitor);
-            });
+            var properties = this.properties;
+            for (var i = 0, len = properties.length; i < len; i++) {
+                properties[i]._walk(visitor);
+            }
         });
     }
 });
diff --git a/lib/compress.js b/lib/compress.js
index ccd6e23c..53833115 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1911,7 +1911,7 @@ merge(Compressor.prototype, {
         // returned if nothing changed.
         function trim(nodes, compressor, first_in_statement) {
             var ret = [], changed = false;
-            for (var i = 0, ii = nodes.length; i < ii; i++) {
+            for (var i = 0, len = nodes.length; i < len; i++) {
                 var node = nodes[i].drop_side_effect_free(compressor, first_in_statement);
                 changed |= node !== nodes[i];
                 if (node) {
-- 
2.34.1