<!DOCTYPE html> <html> <style> .democlass { color: red; } </style> <body> <h1>Element 对象</h1> <h2>setAttributeNode() 方法</h2> <p>点击“更改”,设置第一个标题的 class 属性节点。</p> <button onclick="myFunction()">更改</button> <script> function myFunction() { const attr = document.createAttribute("class"); attr.value = "democlass"; const element = document.getElementsByTagName("H1")[0]; element.setAttributeNode(attr); } </script> </body> </html>