import Vue from 'vue'
import Router from 'vue-router'

Vue.use(Router)

Router.prototype.goBack = function () {
 this.isBack = true
 window.history.go(-1)
}
const router = new Router({
 routes: [
  {
   path: '/',
   name: 'PageTransition', 
   component: PageTransition, // 引入頁面切換組件
   children: [{
    path: '',
    component: Index // 父路由訪問頁面，例如，訪問www.aaa.com/ 顯示的是Index組件
   }, {
    path: '/pageA',
    component: PageA // 子路由組件 例如，訪問www.aaa.com/pageA 顯示為PageA
   }, {
    path: '/pageB',
    component: PageB // 子路由組件 例如，訪問www.aaa.com/pageB 顯示為PageB
   }]
  }
 ]
})

//templete  
<transition name='transitionName' keep-alive>
    <router-view></router-view>
  </transition>

//script
  beforeRouteUpdate(to,from,next){
    let isBack = this.$router.isBack;
    if( isBack ){
      this.transitionName = 'slide-right'
    }else{
      this.transitionName = 'slide-left'
    }
    this.$router.isBack = false;
  }
//style
.slide-left-enter, .slide-right-leave-active {
 opacity: 0;
 -webkit-transform: translate(50px, 0);
 transform: translate(50px, 0);
}
.slide-left-leave-active, .slide-right-enter {
 opacity: 0;
 -webkit-transform: translate(-50px, 0);
 transform: translate(-50px, 0);
}

<div class="left" @click="goback"><</div>

methods: {
  goback () {
   this.$router.goBack()
  }
 }