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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<head>
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<script type="text/javascript">
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function alertIndex()
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  {
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  var x=document.getElementById("mySelect").selectedIndex;
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  var y=document.getElementsByTagName("option");
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  alert(y[x].text + " has the index of: " + y[x].index);
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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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请选择您喜欢的水果：
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<select id="mySelect">
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  <option>苹果</option>
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  <option>桃子</option>
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  <option>香蕉</option>
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  <option>桔子</option>
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</select>
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<br />
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<br />
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<input type="button" onclick="alertIndex()" value="显示被选水果的 index">
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</form>
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​
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</body>
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</html>
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​