代码示例：（标识：bs_navbar_dropdown）
<!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>
<nav class="navbar navbar-expand-sm bg-dark navbar-dark">
<div class="container-fluid">
<a class="navbar-brand" href="#">Logo</a>
<button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#collapsibleNavbar">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="collapsibleNavbar">
<ul class="navbar-nav">
<li class="nav-item">
<a class="nav-link" href="#">链接</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">链接</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">链接</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" role="button" data-bs-toggle="dropdown">下拉菜单</a>
<ul class="dropdown-menu">
<li><a class="dropdown-item" href="#">链接</a></li>
<li><a class="dropdown-item" href="#">另一个链接</a></li>
<li><a class="dropdown-item" href="#">第三个链接</a></li>
</ul>
</li>
</ul>
</div>
</div>
</nav>
<div class="container-fluid mt-3">
<h3>下拉菜单导航栏</h3>
<p>本例在导航栏中添加了一个下拉菜单。</p>
</div>
</body>
</html>
