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<!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.jsdelivr.net/npm/bootstrap@5.1.2/dist/css/bootstrap.min.css" rel="stylesheet">
  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.2/dist/js/bootstrap.bundle.min.js"></script>
</head>
<body>

<div class="container-fluid mt-3">
  <h3>可折叠导航栏</h3>
  <p>在此例中，导航栏在小屏幕上隐藏，并由右上角的按钮替换（请尝试重新调整此窗口的大小）。</p>
  <p>只有当按钮被点击时，导航栏才会显示。</p>
  <p>提示：您还可以删除 .navbar-expand-md 类以始终隐藏导航栏链接并显示切换按钮。</p>
</div>

</body>
</html>

W3School TIY Editor