​x
 
<!DOCTYPE html>
<html>
<head>
<style>
.democlass {
  color: red;
}
</style>
</head>
<body>
​
<h1 class="democlass">Hello World</h1>
​
<p id="demo">单击按钮从 h1 元素中删除 class 属性。</p>
​
<button onclick="myFunction()">试一试</button>
​
<script>
function myFunction() {
  document.getElementsByTagName("H1")[0].removeAttribute("class"); 
}
</script>
​
</body>
</html>
​