<!DOCTYPE html>
<html>
<head>
<title>Bootstrap实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://apps.bdimg.com/libs/bootstrap/3.3.0/css/bootstrap.min.css">
<script src="https://libs.baidu.com/jquery/2.1.4/jquery.min.js"></script>
<script src="https://apps.bdimg.com/libs/bootstrap/3.3.0/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h2>Collapse-down Glyph</h2>
<p>Collapse-down icon: <span class="glyphicon glyphicon-collapse-down"></span></p>
<p>Collapse-down icon as a link:
<a href="#">
<span class="glyphicon glyphicon-collapse-down"></span>
</a>
</p>
<p>Collapse-down icon on a button:
<button type="button" class="btn btn-default btn-sm">
<span class="glyphicon glyphicon-collapse-down"></span> Collapse
</button>
</p>
<p>Collapse-down icon on a styled link button:
<a href="#" class="btn btn-info btn-lg">
<span class="glyphicon glyphicon-collapse-down"></span> Collapse
</a>
</p>
</div>
</body>
</html>