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<html>3
<head>4
<meta charset="utf-8">5
<title>蜜蜂教程(mifengjc.com)</title>6
<style type="text/css">7
.democlass {8
color: red;9
}10
</style>11
</head>12
<body>13
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<h1>Hello World</h1>15
<p id="demo">单击按钮设置H1的class属性为“democlass”</p>16
<button onclick="myFunction()">点我</button>17
<script>18
function myFunction() {19
var h = document.getElementsByTagName("H1")[0];20
var typ = document.createAttribute("class");21
typ.nodeValue = "democlass";22
h.attributes.setNamedItem(typ);23
}24
</script>25
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</body>27
</html>