1.運行效果如圖所示
![wKioL1klNLLwqMEXAAAdWxpTKoE037.png-wh_50]( "QQ截圖20170524151705.png")
2.實現代碼如下
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>表單控件——下拉菜單（菜單項狀態）</title>
<!-- 最新版本的 Bootstrap 核心 CSS 文件 -->
<link rel="stylesheet"
href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css"
integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u"
crossorigin="anonymous">
<!-- 可選的 Bootstrap 主題文件（一般不用引入） -->
<link rel="stylesheet"
href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap-theme.min.css"
integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp"
crossorigin="anonymous">
</head>
<body>
<div class="dropdown">
<button class="btn btn-default dropdown-toggle" type="button"
id="dropdownMenu1" data-toggle="dropdown">
下拉菜單
<span class="caret"></span>
</button>
<ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
<li role="presentation" class="active">
<a role="menuitem" tabindex="-1" href="#">下拉菜單項</a></li>
<li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜單項</a></li>
<li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜單項</a></li>
<li role="presentation" class="divider"></li>
<li role="presentation" class="disabled">
<a role="menuitem" tabindex="-1" href="#">下拉菜單項</a></li>
</ul>
</div>
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
<!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
<script src="https://cdn.bootcss.com/bootstrap/3.3.7/js/bootstrap.min.js"
integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa"
crossorigin="anonymous"></script>
</body>
</html>
