vue2.0

    <keep-alive>
      <router-view />
    </keep-alive>

vue3.0

    <suspense>
      <router-view v-slot="{ Component }">
        <keep-alive>
          <component :is="Component" />
        </keep-alive>
      </router-view>
    </suspense>

注意点

如果 router-view 嵌套的子组件里面还有router-view, 那么子组件里面也要加上keep-alive