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Avoid object creation and an unnecessary function call in Class#addMethods, when working around JScript DontEnum bug.

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This commit is contained in:
Juriy Zaytsev 2009-11-13 15:49:22 -05:00
parent 18f2ac65c3
commit b3fc07922c
2 changed files with 17 additions and 3 deletions
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2
CHANGELOG
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@ -1,3 +1,5 @@
* Avoid object creation and an unnecessary function call in `Class#addMethods`, when working around JScript DontEnum bug. Replace with feature test and a simple boolean check at runtime. (kangax)
* Optimize Element#immediateDescendants. (kangax, Tobie Langel)
* Remove unnecessary function object creation and `Number#times` in `Element._getContentFromAnonymousElement`. (kangax)

18
src/lang/class.js
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@ -9,6 +9,17 @@
* inheritance](http://prototypejs.org/learn/class-inheritance).
**/
var Class = (function() {
// Some versions of JScript fail to enumerate over properties, names of which
// correspond to non-enumerable properties in the prototype chain
var IS_DONTENUM_BUGGY = (function(){
for (var p in { toString: 1 }) {
// check actual property name, so that it works with augmented Object.prototype
if (p === 'toString') return false;
}
return true;
})();
/**
* Class.create([superclass][, methods...]) -> Class
* - superclass (Class): The optional superclass to inherit methods from.
@ -138,9 +149,10 @@ var Class = (function() {
var ancestor = this.superclass && this.superclass.prototype,
properties = Object.keys(source);
// IE6 doesn't enumerate toString and valueOf properties,
// Force copy if they're not coming from Object.prototype.
if (!Object.keys({ toString: true }).length) {
// IE6 doesn't enumerate `toString` and `valueOf` (among other built-in `Object.prototype`) properties,
// Force copy if they're not Object.prototype ones.
// Do not copy other Object.prototype.* for performance reasons
if (IS_DONTENUM_BUGGY) {
if (source.toString != Object.prototype.toString)
properties.push("toString");
if (source.valueOf != Object.prototype.valueOf)