本文介绍fix-ie5.js库如何解决IE5浏览器中JavaScript核心对象的方法缺失问题。针对IE5不支持Array的push/pop、Function的apply以及String.replace处理函数的情况，该脚本通过原型扩展实现了兼容。代码检测IE5.0用户代理，并重新定义相关方法以模拟现代浏览器行为，确保旧版环境下的脚本正常运行。
IE5 JavaScript兼容性问题分析
在IE5浏览器环境中运行JavaScript时，会遇到一些标准方法不可用的情况。
具体表现为：Array对象不支持push()和pop()方法；Function对象不支持apply()方法；此外，String对象的replace方法也无法接受替换处理函数作为参数。
通过引入特定的修复代码，可以解决上述方法在IE5环境下无效的问题。
/*
fix-ie5.js 修复代码实现
fix-ie5.js, version 1.0 (pre-release) (2005/05/15) x3
Copyright 2005, Dean Edwards
Web: http://dean.edwards.name/
This software is licensed under the CC-GNU LGPL
Web: http://creativecommons.org/licenses/LGPL/2.1/
*/
if (/MSIE 5.0/.test(navigator.userAgent)) new function() {
var $$apply = function($function, $object, $arguments) {
$function.apply($object, $arguments);
};
// fix String.replace
if (''.replace(/^/, String)) {
// preserve String.replace
var _stringReplace = String.prototype.replace;
// create String.replace for handling functions
var _functionReplace = function($expression, $replacement) {
var $match, $newString = "", $string = this;
while ($string && ($match = $expression.exec($string))) {
$newString += $string.slice(0, $match.index) + $$apply($replacement, this, $match);
$string = $string.slice($match.lastIndex);
}
return $newString + $string;
};
// replace String.replace
String.prototype.replace = function ($expression, $replacement) {
this.replace = (typeof $replacement == "function") ? _functionReplace : _stringReplace;
return this.replace($expression, $replacement);
};
}
// fix Function.apply
if (!Function.apply) {
var APPLY = "apply-" + Number(new Date);
$$apply = function(f, o, a) {
var r;
o[APPLY] = f;
switch (a.length) { // deconstruct for speed
case 0: r = o[APPLY](); break;
case 1: r = o[APPLY](a[0]); break;
case 2: r = o[APPLY](a[0], a[1]); break;
case 3: r = o[APPLY](a[0], a[1], a[2]); break;
case 4: r = o[APPLY](a[0], a[1], a[2], a[3]); break;
default:
var aa = [], i = a.length - 1;
do aa[i] = "a[" + i + "]"; while (i--);
eval("r=o[APPLY](" + aa + ")");
}
delete o[APPLY];
return r;
};
// fix ICommon
ICommon.valueOf.prototype.inherit = function() {
return $$apply(arguments.callee.caller.ancestor, this, arguments);
};
}
// array fixes
if (![].push) Array.prototype.push = function() {
for (var i = 0; i < arguments.length; i++) {
this[this.length] = arguments[i];
}
return this.length;
};
if (![].pop) Array.prototype.pop = function() {
var $item = this[this.length - 1];
this.length--;
return $item;
};
};