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测试页面代码如下：
<html>
<head>
<title>test Javascript</title>
</head>
<body>
<script type="text/javascript">
var StringBuffer = function(){
this._strings = new Array;
};
StringBuffer.prototype.append = function(str){
this._strings.push(str);
};
StringBuffer.prototype.toString = function(){
return this._strings.join(´´);
};
//--string buffer execute speed test--
var date1 = new Date();
var buffer = new StringBuffer();
for (var i=0; i<10000; i++) {
buffer.append(´test´+i);
}
//document.write(buffer.toString()+´<br/>´);
var date2 = new Date();
alert(date2.getTime()-date1.getTime());
/*
var buffer = new StringBuffer();
buffer.append(´test1´);
buffer.append(´test2´);
buffer.append(´test3´);
buffer.append(´test4´);
buffer.append(´test5´);
document.write(buffer.toString());
*/
/*
var date1 = new Date();
var buffer = ´´;
for (var i=0; i<10000; i++) {
buffer += ´test´+i;
}
var date2 = new Date();
alert(date2.getTime() - date1.getTime());
*/
</script>
</body>
</html>
测试结果：
1、在IE6和IE7下，10000次运行两者效率相差数量级，10万次循环IE无响应；
2、在Firefox2.0和Firefox3.0下，两者效率相差无几，无论是10000次循环还是10万次循环；
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