菜鸟教程在线编辑器

 
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<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
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#ex1 {
  color: red;
}
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<h1>setProperty() 方法</h1>

<p>点击按钮设置一个新的 CSS 属性，并使用 "important" 优先级。</p>

<button onclick="myFunction()">点我</button>

<div id="ex1">一些文本。</div>

<script>
function myFunction() {
  var declaration = document.styleSheets[0].cssRules[0].style;
  var setprop = declaration.setProperty("background-color", "yellow", "important");
}
</script>

</body>
</html>
              