https://callnowbutton.com/src/js/nav.js

1function toggle(className, property, state){
2  var elements = document.getElementsByClassName(className)
3
4  for (var i = 0; i < elements.length; i++){
5      elements[i].style[property] = state;
6  }
7}
8
9const mobileNavigationOpen = document.getElementById("mobile-nav-open");
10const mobileNavigationClose = document.getElementById("mobile-nav-close");
11
12mobileNavigationOpen.addEventListener('click', function() {
13  document.getElementById("nav-panel").classList.add("expanded");
14  toggle('mobile-nav-open','display','none');
15  toggle('mobile-nav-close','display','block');
16})
17mobileNavigationClose.addEventListener('click', function() {
18  document.getElementById("nav-panel").classList.remove("expanded");
19  toggle('mobile-nav-open','display','block');
20  toggle('mobile-nav-close','display','none');
21})
22
23window.onscroll = function() {runOnScroll()};
24
25function runOnScroll() {
26  if (document.documentElement.scrollTop > 1) {
27    document.getElementById("topbar").className = "scrolled";
28  } else {
29    document.getElementById("topbar").className = "";
30  }
31}