How to use the material-components-web.menu.MDCSimpleMenu function in material-components-web

mounted () {
    this.menu = new menu.MDCSimpleMenu(this.$el.querySelector('.bottombar-menu'))
    // Add event listener to some button to toggle the menu on and off.
    this.$el.querySelector('.toggle-menu').addEventListener('click', (event) => {
      event.stopPropagation()
      event.preventDefault()
      this.scenesMenu.open = false
      this.menu.open = !this.menu.open
    })

    this.scenesMenu = new menu.MDCSimpleMenu(this.$el.querySelector('.scenes-menu'))
    // Add event listener to some button to toggle the menu on and off.
    this.$el.querySelector('.toggle-scenes-menu').addEventListener('click', (event) => {
      event.stopPropagation()
      event.preventDefault()
      this.menu.open = false
      this.scenesMenu.open = !this.scenesMenu.open
    })
  },
  methods: {

mounted () {
    this.menu = new menu.MDCSimpleMenu(this.$el.querySelector('.mdc-simple-menu'))
    // Add event listener to some button to toggle the menu on and off.
    this.$el.querySelector('.toggle-menu').addEventListener('click', (event) => {
      event.preventDefault()
      this.menu.open = !this.menu.open
    })
  },
  methods: {

mounted () {
    this.menu = new menu.MDCSimpleMenu(this.$el.querySelector('.bottombar-menu'))
    // Add event listener to some button to toggle the menu on and off.
    this.$el.querySelector('.toggle-menu').addEventListener('click', (event) => {
      event.stopPropagation()
      event.preventDefault()
      this.scenesMenu.open = false
      this.menu.open = !this.menu.open
    })

    this.scenesMenu = new menu.MDCSimpleMenu(this.$el.querySelector('.scenes-menu'))
    // Add event listener to some button to toggle the menu on and off.
    this.$el.querySelector('.toggle-scenes-menu').addEventListener('click', (event) => {
      event.stopPropagation()
      event.preventDefault()
      this.menu.open = false
      this.scenesMenu.open = !this.scenesMenu.open
    })

mounted () {
    this.menu = new menu.MDCSimpleMenu(this.$el.querySelector('.mdc-toolbar__section .mdc-simple-menu'))
    // Add event listener to some button to toggle the menu on and off.
    this.$el.querySelector('.mdc-toolbar__section  .toggle-menu').addEventListener('click', (event) => {
      event.preventDefault()
      this.menu.open = !this.menu.open
    })
  },
  watch: {

mounted () {
    this.menu = new menu.MDCSimpleMenu(this.$el.querySelector('.mdc-simple-menu'))
    // Add event listener to some button to toggle the menu on and off.
    this.$el.querySelector('.toggle-menu').addEventListener('click', (event) => {
      event.preventDefault()
      this.menu.open = !this.menu.open
    })
  },
  methods: {