Bootstrap toggable menu icon doesn't work on small device - html

Question

i added at my hoe page a navbar with toggable icon on small screen; It is the typical navbar of bootstrap.
I have the problem that when i go on developer tool and resize the screen in order to test the responsive part, happen that the icon doesn't toggle, it is like is not active.
Any help?
Here is the code:
<nav id="header" class="navbar navbar-default">
<div class="container">
<!-- Brand and toggle get grouped for better mobile display -->
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navmenu" aria-expanded="false" aria-controls="navmenu">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#"><img id="logo" src="images/art-of-hair.png"></a>
</div>
<!-- Collect the nav links, forms, and other content for toggling -->
<div id="navmenu" class="collapse navbar-collapse navbar-right">
<ul class="nav navbar-nav">
<li class="active">Home<span class="sr-only">Home</span></li>
<li>Hair Styles</li>
<li class="">About</li>
<li class="">Contact</li>
</ul>
</div><!-- /.navbar-collapse -->
</div><!-- /.container-fluid -->
</nav>
and css:
* {
margin: 0;
}
body {
font-family: 'Alice', serif;
}
#header {
height:200px;
}
#logo {
width: 300px;
height:150px;
}
#navmenu {
margin:30px 120px 0 0;
}

Answer 1

In case of toggle, I guess you also need some jQuery to make the toggle function.
Maybe try something like this:
<script>
$("button").click(function(){
$("#navmenu").slideToggle();
});
</script>