Edit in JSFiddle

	<script>
		function openNav() {
			document.getElementById('mysidenav').style.width = '250px';
			document.getElementById('main').style.marginLeft = '250px';
			document.body.style.backgroundColor = 'rgba(0,0,0,0.4)';
		}
		function closeNav() {
			document.getElementById('mysidenav').style.width = '0';
			document.getElementById('main').style.marginLeft = '0';
			document.body.style.backgroundColor = 'white';
		}
	</script>