1. 添加新元素
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8>
<title>动态添加新元素</title>
</head>
<body>
<ul class=example>
<li class=child>Coffee</li>
<li class=child>Tea</li>
<li class=child>Coffee</li>
<li class=child>Tea</li>
</ul>
[removed]
var child = document.getElementsByClassName(
