菜鸟教程在线编辑器

 
                <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<h1 style="color: red; font-size: 50px;">length 属性</h1>

<p>点击按钮返回 h1 元素设置的样式数目。</p>

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

<p id="demo"></p>

<script>
function myFunction() {
  var elmnt = document.getElementsByTagName("h1")[0];
  var x = elmnt.style.length;
  document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>
              