cus_Menu.js

var acc = document.getElementsByClassName("accordion");
            var i; 
            for (i = 0; i < acc.length; i++) {
              acc[i].addEventListener("click", function() {
                this.classList.toggle("active");
                var subMenu = this.nextElementSibling;
                if (subMenu.style.maxHeight) {
                    subMenu.style.maxHeight = null;
                } else {
                    subMenu.style.maxHeight = subMenu.scrollHeight + "px";
                } 
              });
            }