| 通常,小屏幕上我们都会折叠导航栏,通过点击来显示导航选项。 
 要创建折叠导航栏,可以在按钮上添加 class="navbar-toggle", data-toggle="collapse" 与 data-target="#thetarget" 类。然后在设置了 class="collapse navbar-collapse" 类的  div 上包裹导航内容(链接), div 元素上的 id 匹配按钮 data-target 的上指定的 id:
 
 实例:
 
 <!DOCTYPE html>
 <html>
 <head>
 <title>Bootstrap4 实例</title>
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.1.0/css/bootstrap.min.css" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >
 <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" ></script>
 <script src="https://cdn.bootcss.com/popper.js/1.12.5/umd/popper.min.js" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" ></script>
 <script src="https://cdn.bootcss.com/bootstrap/4.1.0/js/bootstrap.min.js" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" ></script>
 </head>
 <body>
 <nav class="navbar navbar-expand-md bg-dark navbar-dark">
 <a class="navbar-brand" href="#">Navbar</a>
 <button class="navbar-toggler" type="button" data-toggle="collapse" data-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="#">Link</a>
 </li>
 <li class="nav-item">
 <a class="nav-link" href="#">Link</a>
 </li>
 <li class="nav-item">
 <a class="nav-link" href="#">Link</a>
 </li>
 </ul>
 </div>
 </nav>
 <br>
 <div class="container">
 <h3>折叠导航栏</h3>
 <p>通常,小屏幕上我们都会折叠导航栏,通过点击来显示导航选项。</p>
 <p>提示: 如果你删除 .navbar-expand-md 类,导航链接会一直隐藏,且切换按钮会一直显示。</p>
 </div>
 </body>
 </html>
 |