jQuery omzetten naar puur Javascript

jQuery(document).ready(function($) { 
	// Hide mobile menu by default	
	$('#mobile-nav').hide();

	// Display mobile menu when clicked	
	$( "#mobile-nav-toggle" ).click(function() { 
		$( "#mobile-nav" ).toggle(); 
	}); 

	// Hide mobile submenu by default	
	$(''#sub-menu').hide();

	// Add toggle that displays mobile submenu
	var subnavToggle = $( '<button />', { 'id': 'subnav-toggle' })
		.append( "+" );
	$( "#mobile-nav" ).find( '#menu-item-has-children > a, #page_item_has_children > a' ).after( subnavToggle );

	// Display mobile submenu when clicked	
	$( "#subnav-toggle" ).click(function() { 
		$(this).next('#sub-menu').toggle(); 
	}); 
});

function nav {
	// Hide mobile menu by default
	document.getElementById('mobile-nav').style.display = 'none';

	// Display mobile menu when clicked
	document.getElementById('mobile-nav-toggle').addEventListener("click", function() {
  		document.getElementById('mobile-nav').style.display = 'block';
	});

	// Hide mobile submenu by default
	document.getElementById('submenu').style.display = 'none';

	// Add toggle that displays mobile submenu

	// Display mobile submenu when clicked	
};