Mobile menu with pure JS

Mobile menu

document.addEventListener('DOMContentLoaded', mainReady);

var global = null;

function mainReady(){
	var global = new Global();
	global.init();
}

function Global(){
	
}

Global.prototype = {
	constructor: Global,
	init: function(){
		'use strict';
		this._navigationMobile();
	},

	_navigationMobile: function(){
		(function(window, document, html){
			var $button_open = document.querySelector('.js-button-open');
		  	var $button_close = document.querySelector('.js-button-close');
		  	var $navigation_mobile = document.querySelector('.js-navigation-mobile');

		  	$button_open.addEventListener('click', function() {
		    	$navigation_mobile.classList.add('js-is-open');
		    	document.body.classList.add('js-is-open');
		    	document.body.style.overflow = 'hidden';
		    	html.style.overflowY = 'hidden';
		  	});
			$button_close.addEventListener('click', function() {
			   	$navigation_mobile.classList.remove('js-is-open');
			    document.body.classList.remove('js-is-open');
			    document.body.style.overflow = 'visible';
			    html.style.overflowY = 'auto';
			});
		})(window, document, document.querySelector('html'));
	}
}