代码示例：（标识：bs_dropdown-active）
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/js/bootstrap.bundle.js"></script>
</head>
<body>
<div class="p-4">
<h2>下拉菜单</h2>
<p>.active 类为活动链接添加蓝色背景色。</p>
<p>.disabled 类禁用下拉项（灰色文本颜色和悬停时的禁止停车标志）。</p>
<div class="dropdown">
<button type="button" class="btn btn-primary dropdown-toggle" data-bs-toggle="dropdown">
Dropdown button
</button>
<ul class="dropdown-menu">
<li><a class="dropdown-item" href="#">普通的</a></li>
<li><a class="dropdown-item active" href="#">活动的</a></li>
<li><a class="dropdown-item disabled" href="#">禁用的</a></li>
</ul>
</div>
</div>
</body>
</html>
