案例：JavaScript案例     状态：可编辑再运行    进入竖版
 运行结果　
​x
 
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<html>
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<body>
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​
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<script type="text/javascript">
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​
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function StringBuffer () {
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  this._strings_ = new Array();
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}
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​
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StringBuffer.prototype.append = function(str) {
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  this._strings_.push(str);
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};
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​
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StringBuffer.prototype.toString = function() {
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  return this._strings_.join("");
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};
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​
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var d1 = new Date();
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var str = "";
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for (var i=0; i < 10000; i++) {
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    str += "text";
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}
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var d2 = new Date();
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​
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document.write("Concatenation with plus: "
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 + (d2.getTime() - d1.getTime()) + " milliseconds");
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​
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var buffer = new StringBuffer();
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d1 = new Date();
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for (var i=0; i < 10000; i++) {
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    buffer.append("text");
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}
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var result = buffer.toString();
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d2 = new Date();
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​
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document.write("<br />Concatenation with StringBuffer: "
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 + (d2.getTime() - d1.getTime()) + " milliseconds");
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​
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</script>
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​
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</body>
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</html>
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​