<!DOCTYPE html>
<html>
<head>
<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>Dropdowns</h2>
<p>Add the .dropdown-menu-right class to .dropdown-menu to right-align the dropdown menu:</p>
<div class="dropdown">
<button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">Dropdown实例
<span class="caret"></span></button>
<ul class="dropdown-menu dropdown-menu-right">
<li><a href="#">HTML</a></li>
<li><a href="#">CSS</a></li>
<li><a href="#">JavaScript</a></li>
<li class="divider"></li>
<li><a href="#">About Us</a></li>
</ul>
</div>
</div>
</body>
</html>