<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<h1>
hello world
</h1>
<div class="button_container" id="toggle">
<span class="top"></span>
<span class="middle"></span>
<span class="bottom"></span>
</div>
<div class="overlay" id="overlay">
<nav class="overlay-menu">
<ul>
<li><a href="#">Home</a></li>
<li><a href="#">About</a></li>
<li><a href="#">Work</a></li>
<li><a href="#">Contact</a></li>
</ul>
</nav>
</div>
<script>
var el = document.querySelector('#toggle');
var ovrlays = document.querySelector('#overlay');
el.onclick = function () {
el.classList.toggle('active');
ovrlays.classList.toggle('open');
}
</script>
