元素对象 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>蜜蜂教程(mifengjc.com)</title>
  <style type="text/css">
    .democlass {
      color: red;
    }
  </style>
</head>
<body>

  <h1>Hello World</h1>
  <p id="demo">单击按钮来设置标题上面的类属性节点。</p>
  <button onclick="myFunction()">点我</button>
  <script>
    function myFunction() {
      var atr = document.createAttribute("class");
      atr.nodeValue = "democlass";
      var h = document.getElementsByTagName("H1")[0];
      h.setAttributeNode(atr);
    };
  </script>

</body>
</html>
        