案例：JavaScript案例     状态：可编辑再运行    进入竖版
 运行结果　
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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.prototype.originalToString = Function.prototype.toString;
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​
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Function.prototype.toString = function() {
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  if (this.originalToString().length > 100) {
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    return "Function too long to display.";
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  } else {
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    return this.originalToString();
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  }
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};
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​
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function sayHi() {
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  alert("hi");
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}
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​
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document.write(sayHi.toString());
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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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​