This for bootstrap Menu and dropdown menu without jquery

BootstrapMenu.js

var MenuUI = {
    el: {
      toggle: document.getElementsByClassName('navbar-toggler')[0],
      collapse: document.getElementsByClassName('navbar-collapse')[0],
      dropdowns: document.getElementsByClassName('dropdown'),
    },
    init: function () {
      let toggle = MenuUI.el.toggle
      // dropdown open
      MenuUI.openDropdown()
      // Event listeners
      window.addEventListener('resize', MenuUI.closeMenusOnResize, false)
      toggle.addEventListener('click', MenuUI.toggleMenu, false)
    },
    openDropdown: function () {
      // Add click handling to dropdowns
      dropdowns = MenuUI.el.dropdowns
      for (var i = 0; i < dropdowns.length; i++) {
        dropdowns[i].addEventListener('click', function () {
          var open = this.classList.contains('show')
          MenuUI.closeMenus()
          if (!open) {
            this.getElementsByClassName('dropdown-toggle')[0].setAttribute(
              'aria-expanded',
              true
            )
            this.getElementsByClassName('dropdown-menu')[0].classList.toggle(
              'show'
            )
            this.classList.toggle('show')
          }
        })
      }
    },
    closeMenus: function () {
      let dropdowns = MenuUI.el.dropdowns
      for (var j = 0; j < dropdowns.length; j++) {
        dropdowns[j]
          .getElementsByClassName('dropdown-toggle')[0]
          .setAttribute('aria-expanded', false)
        dropdowns[j]
          .getElementsByClassName('dropdown-menu')[0]
          .classList.remove('show')
        dropdowns[j].classList.remove('show')
      }
    },
    toggleMenu: function () {
      let collapse = MenuUI.el.collapse,
        toggle = MenuUI.el.toggle
      MenuUI.closeMenus()
      collapse.classList.toggle('show')
      toggle.classList.toggle('collapsed')
      var x = toggle.getAttribute('aria-expanded')
      if (x == 'true') {
        x = 'false'
      } else {
        x = 'true'
      }
      toggle.setAttribute('aria-expanded', x)
    },
    closeMenusOnResize: function () {
      let toggle = MenuUI.el.toggle,
        collapse = MenuUI.el.collapse
      MenuUI.closeMenus()
      toggle.classList.add('collapsed')
      collapse.classList.remove('show')
      toggle.setAttribute('aria-expanded', false)
    },
  }
  MenuUI.init()