<template>
  <div id="app">
    <keep-alive>
      <router-view v-if='$route.meta.keepAlive'/>
    </keep-alive>
    <router-view  v-if='!$route.meta.keepAlive'/>
  </div>
</template>

 {
      path: '/home',
      name: 'home',
      component: resolve => require(['@/views/home/index.vue'], resolve),
      meta: {
        title: '首頁',
        index: 1,
        keepAlive: true,
        scrollTop: 0
      }
    },
    {
      path: '/classify',
      name: 'classify',
      component: resolve => require(['@/views/classify/index.vue'], resolve),
      meta: {
        title: '分類',
        index: 1,
        keepAlive: true,
        scrollTop: 0
      }
    },
    {
      path: '/shopping',
      name: 'shopping',
      component: resolve => require(['@/views/shopping/index.vue'], resolve),
      meta: {
        title: '購物車',
        index: 1,
        keepAlive: true,
        scrollTop: 0
      }
    },
    {
      path: '/detail',
      name: 'detail',
      component: resolve => require(['@/views/detail/index.vue'], resolve),
      meta: {
        title: '詳情',
        index: 2,
        // keepAlive: true,
        // scrollTop: 0
      }
    },

router.beforeEach((to, from, next) => {  
  if (from.meta.keepAlive) {
    const $wrapper = document.querySelector('.app-wrapper'); // 列表的外層容器 注意找到滾動的盒子
    const scrollTop = $wrapper ? $wrapper.scrollTop : 0;
    console.log('scrollTop=', scrollTop)
    from.meta.scrollTop = scrollTop;
  }
  next();
});

activated () {
    const scrollTop = this.$route.meta.scrollTop;
    const $wrapper = document.querySelector('.app-wrapper');
    if (scrollTop && $wrapper) {
      $wrapper.scrollTop = scrollTop;
    }
  },

activated() {
    const $wrapper = document.querySelector(".app-wrapper");
    $wrapper.scrollTop = 0;
  },