What is the purpose of the following code for vertical menus?
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".sidebar-navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<span class="visible-xs navbar-brand">Sidebar menu</span>
The span class “visible-xs navbar-brand” means the brand will only be displayed on extra small devices (<768 pixels).