abstract：<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Document</title></head><body><div><ul><li>列表一</li><li>列表
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<div>
<ul>
<li>列表一</li>
<li>列表二</li>
<li>列表三</li>
</ul>
</div>
<script type="text/javascript">
let red=document.getElementsByClassName{'header'};
red[0].style.backgroundColor='green';
</script>
</body>
</html>
Correcting teacher：韦小宝Correction time：2019-02-16 14:10:52
Teacher's summary：写的很基础 选择器就相当于是一条线 可以连接我们的操作和dom