mobile menu bootstrap

1<div class="pos-f-t">
2  <div class="collapse" id="navbarToggleExternalContent">
3    <div class="bg-dark p-4">
4      <h4 class="text-white">Collapsed content</h4>
5      <span class="text-muted">Toggleable via the navbar brand.</span>
6    </div>
7  </div>
8  <nav class="navbar navbar-dark bg-dark">
9    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarToggleExternalContent" aria-controls="navbarToggleExternalContent" aria-expanded="false" aria-label="Toggle navigation">
10      <span class="navbar-toggler-icon"></span>
11    </button>
12  </nav>
13</div>