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 alertValue()
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  {
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  var x=document.getElementById("mySelect").selectedIndex;
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  alert(document.getElementsByTagName("option")[x].value);
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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 your favorite fruit:
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<select id="mySelect">
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  <option value="apple">Apple</option>
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  <option value="orange">Orange</option>
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  <option value="pineapple">Pineapple</option>
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  <option value="banana">Banana</option>
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</select>
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<br /><br />
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<input type="button" onclick="alertValue()" value="Alert selected value">
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</form>
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​
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</body>
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</html>
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​