https://www.amtechmechanical.com/workhorse/nav/resp-nav.js

1// jQuery plugin from tutorial http://www.hongkiat.com/blog/responsive-web-nav/
2
3    $(function() {  
4        var pull        = $('#pull'); 
5			topNav      = $('#topNav');
6            menu        = $('nav ul.nav');  
7            menuHeight  = menu.height();  
8      
9        $(pull).on('click', function(e) {  
10            e.preventDefault();  
11            menu.slideToggle("slow");
12        });
13		$(topNav).on('click', function(e) {  
14            e.preventDefault();  
15            menu.slideToggle("slow");
16        });
17    });  
18	
19	$(window).resize(function(){  
20    var w = $(window).width();  
21    if(w > 620 && menu.is(':hidden')) {  
22        menu.removeAttr('style');  
23    }  
24});