源代码：
左右布局
点击运行
<!DOCTYPE html> <html> <head> <title>Bootstrap 实例</title> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script> <script src="https://cdn.staticfile.org/popper.js/1.15.0/umd/popper.min.js"></script> <script src="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></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>
运行结果