案例：javascript案例     状态：可编辑再运行    进入竖版
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<!DOCTYPE html>
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<html>
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<body>
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<h3>演示如何访问 Search 字段</h3>
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<input type="search" id="mySearch" placeholder="搜索..">
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<p>点击按钮来获得 search 字段的占位符文本。</p>
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<button onclick="myFunction()">试一下</button>
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<p id="demo"></p>
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<script>
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function myFunction() {
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    var x = document.getElementById("mySearch").placeholder;
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    document.getElementById("demo").innerHTML = x;
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}
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</script>
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​
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</body>
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</html>
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