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<title>菜鸟教程(runoob.com)</title>
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<h2>实例</h2>
<p> .show 类强制一个元素显示:</p>
<p class="show">该段落强制显示</p>
<p> .hidden 类强制一个元素隐藏 :</p>
<p class="hidden">该段落强制隐藏</p>
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