navbar in bootstrap4
<div class="pos-f-t">
<div class="collapse" id="navbarToggleExternalContent">
<div class="bg-dark p-4">
<h4 class="text-white">Collapsed content</h4>
<span class="text-muted">Toggleable via the navbar brand.</span>
</div>
</div>
<nav class="navbar navbar-dark bg-dark">
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarToggleExternalContent" aria-controls="navbarToggleExternalContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
</nav>
</div>