index.js

const routes = [
    {
        path: '/',
        component: Main
    },
    {
       path: '/enterprise',
       component: Enterprise
    }
];
const router = new VueRouter({
    mode: "history",
    routes: routes
});

window.app = new Vue({
  router,
  render: function (createElement) {
      return createElement(Viewport)
  }
})

Viewport.js

import 'vue-material/dist/vue-material.css'
import 'vue-material/dist/theme/default-dark.css'
export default {
   data:()=>({
       message: "Now it is for real",
       title: "Jackie R. Gleason",
       menuVisible: false
   }),
   methods: {
       toggleMenu () {
           this.menuVisible = !this.menuVisible
       }
   },
   beforeRouteLeave(to, from, next){
       console.log("Event called");
       this.menuVisible = false;
   }
}

Viewport.vue

<template src="./Viewport.html">
</template>

<script src="./Viewport.js">
</script>

<style src="./Viewport.css">
</style>