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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var arr = new Array(3)
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arr[0] = "John"
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arr[1] = "Andy"
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arr[2] = "Wendy"
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​
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document.write("Original length: " + arr.length)
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document.write("<br />")
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​
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arr.length=5
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document.write("New length: " + arr.length)
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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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​