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 alertDefaultSelected()
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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("Is " + y[x].text + " selected by default? " + y[x].defaultSelected);
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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>Apple</option>
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  <option>Orange</option>
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  <option selected="selected">Pineapple</option>
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  <option>Banana</option>
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</select>
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<br />
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<br />
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<input type="button" onclick="alertDefaultSelected()" value="Is the chosen fruit selected by default?">
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</form>
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​
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</body>
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</html>
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​