在线运行代码 - 菜鸟教程

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(cainiaoplay.com)</title>
<style>#ex1 {
  color: red !important;
}
</style>
</head>
<body>
<h1>getPropertyPriority() 属性</h1>

<p>点击按钮返回 color 属性是否设置了 "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 priority = declaration.getPropertyPriority("color");
  alert(priority);
}
</script>

</body>
</html>
源代码

动行结果
