共7个文件：

 一、main.js

// 引入Vue
import Vue from 'vue'
// 引入app组件，它是所有组件的父组件
import App from './App.vue'
// 引入VueRouter插件
// eslint-disable-next-line no-unused-vars
import VueRouter from 'vue-router'

import router from './router' // index.js可以省略

Vue.use(VueRouter) //vue-router

// 引入Vuex
// eslint-disable-next-line no-unused-vars
import Vuex from 'vuex'

// 引入store
import store from './store/index.js'

// ElementUI

import ElementUI from 'element-ui' //element-ui的全部组件
import 'element-ui/lib/theme-chalk/index.css'//element-ui的css
Vue.use(ElementUI) //使用elementUI


// 关闭vue生产提示
Vue.config.productionTip = false
// 创建vue实例对象 -- vm
const vm = new Vue({
  el: "#app",
  // 完成了这个功能：将APP组件放入窗口中
  render: h => h(App),
  router:router,
  store:store,
  beforeCreate() {
    Vue.prototype.$bus = this;
  },

})

二、index.js

// 引入路由
// eslint-disable-next-line no-unused-vars
import VueRouter from 'vue-router'
import Box_1 from '../pages/Box_1.vue'
import Box_2 from '../pages/Box_2.vue'
import Menu_1 from '../pages/Menu_1.vue'
import Menu_2 from '../pages/Menu_2.vue'


// 创建一个路由器

export default new VueRouter({
    routes: [

        {
            path: '/Box_1',
            component: Box_1,
            children: [
                {
                    path: 'Menu_1',
                    component: Menu_1
                },
                {
                    path: 'Menu_2',
                    component: Menu_2
                },

            ]
        },
        {
            path: '/Box_2',
            component: Box_2,
            children: [
                {
                    path: 'Menu_1',
                    component: Menu_1
                },
                {
                    path: 'Menu_2',
                    component: Menu_2
                },

            ]
        },
    ]


})

三、App.vue

<template>
  <div id="myapp">
    <!-- 第1行 -->

    <div class="left">
      <!-- 路由跳转链接 -->
      <router-link class="box_1" to="/Box_1" active-class="active">
        Box1组件>
      </router-link>
      <!-- 路由跳转链接 -->
      <router-link class="box_2" to="/Box_2" active-class="active">
        Box2组件>
      </router-link>
    </div>
    <div class="right">
      <!-- 显示路由组件 -->
      <router-view> </router-view>
    </div>
  </div>
</template>

<script>
// 注册组件
export default {
  name: "App",
  data() {
    return {};
  },
  mounted() {
    console.log("=============");
    console.log(this);
  },
};
</script>

<style scoped>
body {
  margin: 0;
  padding: 0;
  background-color: rgb(147, 149, 149);
}
a:link {
  color: #ff0000;
  text-decoration: none;
}
#myapp {
  display: flex;
  flex-direction: row;
}
.left {
  width: 0px;
  height: 100px;
  flex-grow: 2.7;
  padding-top: 10px;
  /* background-color: rgb(255, 220, 220); */
}
.box_1 {
  display: block;
  margin-left: 10px;
  width: 110px;
  height: 50px;
  line-height: 50px;
  text-align: center;
  border: 1px rgb(224, 224, 224) solid;
  border-top-left-radius: 10px;
  border-top-right-radius: 10px;
}
.box_2 {
  display: block;
  width: 110px;
  height: 50px;
  margin-left: 10px;
  line-height: 50px;
  text-align: center;
  margin-top: -1px;
  border: 1px rgb(224, 224, 224) solid;
  border-bottom-left-radius: 10px;
  border-bottom-right-radius: 10px;
}

.box_select {
  background-color: red;
}

.right {
  margin-top: 12px;
  width: 0px;
  height: 100px;
  flex-grow: 6;
  /* background-color: rgb(207, 252, 209); */
  overflow: hidden;
}
.active {
  background-color: rgb(22, 122, 214);
  color: white;
}
</style>

四、Box_1.vue

<template>
  <div class="m_box">
    <div class="top">
      <!-- 路由跳转链接 -->
      <router-link class="box_1" to="/Box_1/menu_1" active-class="active">
        菜单1
      </router-link>
      <!-- 路由跳转链接 -->
      <router-link class="box_2" to="/Box_1/menu_2" active-class="active">
        菜单2
      </router-link>
    </div>
    <div class="bottom">
      <!-- 我是Box_1组件! -->
      <router-view></router-view>
    </div>
  </div>
</template>

<script>
export default {
  name: "Box_1",
};
</script>

<style scoped>
a:link {
  color: #ff0000;
  text-decoration: none;
}
.m_box {
  width: 95%;
  height: 98px;
  border: 1px rgb(253, 211, 211) solid;
  text-align: center;
  line-height: 100px;
  overflow: hidden;
  /* background-color: rgb(248, 248, 248); */
  font-size: 13px;
}

.box_1 {
  display: block;
  float: left;
  margin-left: 10px;
  width: 60px;
  height: 25px;
  line-height: 25px;
  text-align: center;
  border: 1px rgb(224, 224, 224) solid;
  border-radius: 5px;
  background-color: antiquewhite;
}
.box_2 {
  display: block;
  float: left;
  width: 60px;
  height: 25px;
  margin-left: 2px;
  line-height: 25px;
  text-align: center;
  margin-top: -1px;
  border: 1px rgb(224, 224, 224) solid;
  background-color: antiquewhite;
  border-radius: 5px;
}
.active {
  background-color: rgb(255, 0, 0);
  color: white;
}
</style>

五、Box_2.vue

<template>
  <div class="m_box">我是Box_2组件!</div>
</template>

<script>
export default {
  name: "Box_2",
};
</script>

<style scoped>
.m_box {
  width: 95%;
  height: 98px;
  border: 1px rgb(253, 211, 211) solid;
  text-align: center;
  line-height: 98px;
  overflow: hidden;
  background-color: rgb(248, 248, 248);
}
</style>

六、Menu_1.vue

<template>
  <div class="m_box">我是Menu_1组件!</div>
</template>

<script>
export default {
  name: "Menu_1",
};
</script>

<style scoped>
.m_box {
  width: 95%;
  height: 68px;
  border: 1px rgb(253, 211, 211) solid;
  text-align: center;
  line-height: 68px;
  overflow: hidden;
  background-color: rgb(248, 248, 248);
}
</style>

七、Menu_2.vue

<template>
  <div class="m_box">我是Menu_2组件!</div>
</template>

<script>
export default {
  name: "Menu_2",
};
</script>

<style scoped>
.m_box {
  width: 95%;
  height: 68px;
  border: 1px rgb(253, 211, 211) solid;
  text-align: center;
  line-height: 68px;
  overflow: hidden;
  background-color: rgb(248, 248, 248);
}
</style>