Bootstrap实现汉堡包菜单

代码如下

<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Navbar Demo</title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" rel="stylesheet">

  </head>
  <body>

  	<div class="navbar navbar-default">
  		<div class="navbar-header">
  			<button data-toggle="collapse" data-target="#navbar-menu" class="navbar-toggle collapsed">
  				<span class="icon-bar"></span>
  				<span class="icon-bar"></span>
  				<span class="icon-bar"></span>
  			</button>
  			<a href="#" class="navbar-brand">Brand</a>
  		</div>
  		<div id="navbar-menu" class="navbar-collapse collapse">
  			<ul class="nav navbar-nav">
  				<li><a href="#">Home</a></li>
  				<li><a href="#">Download</a></li>
  				<li><a href="#">Document</a></li>
  			</ul>
  		</div>
  	</div>
	<div class="container">
		
		123

	</div>

    <script src="https://cdn.jsdelivr.net/npm/jquery@1.12.4/dist/jquery.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/js/bootstrap.min.js"></script>
  </body>
</html>