JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header">HEADER</div>
<div id="container">CONTAINER</div>

<a href="#" id="menu"><span>&#9776</span> MENU</a>

<script type="text/javascript">
     var a = document.getElementById('menu');

     a.onclick = function() {
        var header    = document.getElementById("header");
        var container = document.getElementById("container");

        header.style.display = "block";
        container.style.marginLeft = "auto";
     }
</script>

CSS

#header {display:none;}
#container {margin-left: 400px;}