<meta name="viewport" content="width=device-width, initial-scale=1">

<link rel="stylesheet" href="/static/lib/bootstrap/4.0.0/css/bootstrap.min.css">

<script src="/static/lib/jquery/3.3.1/jquery.min.js"></script>

<script src="/static/lib/popper.js/1.12.9/umd/popper.min.js"></script>

<script src="/static/lib/bootstrap/4.0.0/js/bootstrap.min.js"></script>

<div class="container">

    <br/>

    <h1>折叠导航栏</h1>

    <nav class="navbar navbar-expand-md bg-dark navbar-dark">

  <!-- Brand -->

  <a class="navbar-brand" href="#">导航栏</a>

​

  <!-- Toggler/collapsibe Button -->

  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#collapsibleNavbar">

    <span class="navbar-toggler-icon"></span>

  </button>

​

  <!-- Navbar links -->