案例：jQuery案例     状态：可编辑再运行    进入竖版
 运行结果　
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<!DOCTYPE html>
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<html>
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<head>
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  <style>div { color:red; }</style>
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  <script type="text/javascript" src="/js/jquery.js"></script>
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</head>
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​
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<body>
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  <form><p><input type="checkbox" /></p></form>
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  <div></div>
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​
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<script>
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  var isFormParent = $("input[type='checkbox']").parent().is("form");
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  $("div").text("isFormParent = " + isFormParent);
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</script>
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​
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</body>
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</html>
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​