书中附带的测试代码如下
复制代码 代码如下:
<html>
<head>
<title>Example</title>
</head>
<body>
<p><strong>Note:</strong> The latest versions of Firefox seem to have fixed the string concatenation problem. If you are using Firefox 1.0 or later, the string buffer may actually take longer than normal string concatenation.</p>
<script type="text/javascript">
function StringBuffer() {
this.__strings__ = new Array;
}
StringBuffer.prototype.append = function (str) {
this.__strings__.push(str);
};
StringBuffer.prototype.toString = function () {
return this.__strings__.join("");
};
var d1 = new Date();
var str = "";
for (var i=0; i < 10000; i++) {
str += "text";
}
var d2 = new Date();
document.write("Concatenation with plus: " + (d2.getTime() - d1.getTime()) + " milliseconds");
var buffer = new StringBuffer();
d1 = new Date();
for (var i=0; i < 10000; i++) {
buffer.append("text");
}
var result = buffer.toString();
d2 = new Date();
document.write("<br />Concatenation with StringBuffer: " + (d2.getTime() - d1.getTime()) + " milliseconds");
</script>
</body>
</html>
在 Firefox/3.0.3中执行的结果如下：
Concatenation with plus: 5 milliseconds
Concatenation with StringBuffer: 10 milliseconds
在IE6中执行结果如下：
Concatenation with plus: 234 milliseconds
Concatenation with StringBuffer: 62 milliseconds
1.两种方式性能差别很大
2.看来IE6字符串连接处理能力比FF3很差呀
3.IE6和FF3两种方式结果相反，看来以后写连接优化还有注意浏览器呀