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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<head>
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<script type="text/javascript">
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function insertBeforeSelected()
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  {
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  var x=document.getElementById("mySelect");
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  if (x.selectedIndex>=0)
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    {
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    var y=document.createElement('option');
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    y.text='Kiwi';
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    var sel=x.options[x.selectedIndex];
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    try
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      {
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      x.add(y,sel); // standards compliant
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      }
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    catch(ex)
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      {
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      x.add(y,x.selectedIndex); // IE only
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      }
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    }
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  }
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</script>
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</head>
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<body>
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​
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<form>
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<select id="mySelect">
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  <option>Apple</option>
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  <option>Pear</option>
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  <option>Banana</option>
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  <option>Orange</option>
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</select>
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<input type="button" onclick="insertBeforeSelected()" value="Insert option before selected" />
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</form>
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​
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</body>
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</html>
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​