blowfish/assets/js/mobilemenu.js

var menuButton = document.getElementById("menu-button");
var menuCloseButton = document.getElementById("menu-close-button");
var menuWrapper = document.getElementById("menu-wrapper");

var menuOpen = false;

var openMenu = function (e) {
  if (!menuOpen) {
    menuOpen = true;
    document.body.style.overflowY = "hidden";
    menuButton.style.visibility = "hidden";
    menuWrapper.style.visibility = "visible";
    menuWrapper.style.opacity = "1";
    window.onbeforeunload = function (event) {
      closeMenu()
    }
  }
};

var closeMenu = function (e) {
  if (menuOpen) {
    menuOpen = false;
    document.body.style.overflowY = "auto";
    menuButton.style.visibility = "visible";
    menuWrapper.style.visibility = "hidden";
    menuWrapper.style.opacity = "0";
    window.onbeforeunload = function (event) { }
    e.stopPropagation();
  }
}

menuButton.addEventListener("click", openMenu);
menuCloseButton.addEventListener("click", closeMenu);