1、首先要知道为什么一刷新就复原了，是因为default-active属性设置的是默认值，是一个死值，一旦刷新就会复原，造成高亮不能保持，那么怎么解决呢？

2、很简单，无需像一些博主一样绑定path。思路：既然一刷新就复原了，那么我们在切换的时候就将值存储在本地存储或vuex中呗。

方法一：本地存储

<el-menu
  :default-active="activeIndex2" class="el-menu-demo" mode="horizontal"
  @select="handleSelect" background-color="#545c64" text-color="#fff"
  active-text-color="#ffd04b"
>
    <el-menu-item :index="String(index)" v-for="(item,index) in list" :key="item.id">{{ item.name }}</el-menu-item>
    <el-submenu index="4">
      <template slot="title">我的工作台</template>
      <el-menu-item index="4-1">设置</el-menu-item>
      <el-menu-item index="4-2" >退出</el-menu-item>
    </el-submenu>
</el-menu>

<script>
export default {
  name: "showTop",
  data() {
    return {
      list: [{name:"首页",id:0},{name:"商品",id:1},{name:"订单",id:2},{name:"会员",id:3},{name:"设置",id:4},{name:"管理员",id:5}],
      activeIndex2: null
    };
  },
  mounted(){
    if(localStorage.getItem('activeIndex2')){
      this.activeIndex2 =localStorage.getItem('activeIndex2')
    }else{
      this.activeIndex2 =String(this.list[0].id)
    }
  },
  methods: {
    // 顶部导航栏点击事件
    handleSelect(key, keyPath) {
        console.log(key,keyPath);
        // 解决element ui组件库中顶部导航栏刷新复原问题，也可存储在vuex中
        localStorage.setItem('activeIndex2',String(this.list[key].id))
        // 判断是否是退出按钮
        if(key=='4-2'){
          // 清空本地缓存的token
          localStorage.removeItem('token')
          // 跳转至登录页
            this.$router.push({name:'login'})
        }
      }
  },
};
</script>

方法二：vuex+本地存储

<el-menu
  :default-active="activeIndex2" class="el-menu-demo" mode="horizontal"
  @select="handleSelect" background-color="#545c64" text-color="#fff"
  active-text-color="#ffd04b"
>
    <el-menu-item :index="String(index)" v-for="(item,index) in list" :key="item.id">{{ item.name }}</el-menu-item>
    <el-submenu index="4">
      <template slot="title">我的工作台</template>
      <el-menu-item index="4-1">设置</el-menu-item>
      <el-menu-item index="4-2" >退出</el-menu-item>
    </el-submenu>
</el-menu>

<script>
import { mapMutations} from 'vuex';
export default {
  name: "showTop",
  data() {
    return {
      list: [{name:"首页",id:0},{name:"商品",id:1},{name:"订单",id:2},{name:"会员",id:3},{name:"设置",id:4},{name:"管理员",id:5}],
      activeIndex2: null
    };
  },
  mounted(){
    if(localStorage.getItem('activeIndex2')){
      this.activeIndex2 =localStorage.getItem('activeIndex2')
    }else{
      this.activeIndex2 =String(this.list[0].id)
    }
  },
  methods: {
    ...mapMutations(['setActiveIndex2']),
    // 顶部导航栏点击事件
    handleSelect(key, keyPath) {
        console.log(key,keyPath);
        // 存储到vuex中，但是要记住还需要在vuex中存储到本地存储中
        this.setActiveIndex2(String(this.list[key].id))
        // 判断是否是退出按钮
        if(key=='4-2'){
          // 清空本地缓存的token
          localStorage.removeItem('token')
          // 跳转至登录页
            this.$router.push({name:'login'})
        }
      }
  },
};
</script>

//store中的index.js
import Vue from "vue"
import Vuex from "vuex"
Vue.use(Vuex)

export default new Vuex.Store({
    state:{
        activeIndex:'',
    },
    mutations:{
        setActiveIndex2(state,e){
            state.activeIndex = e
            window.localStorage.setItem('activeIndex2',e)
        }
    },
})

import Vue from 'vue'
import App from './App.vue'
import ElementUI from 'element-ui';
import 'element-ui/lib/theme-chalk/index.css';
import router from '../router';
import store from '../store';
Vue.use(ElementUI);

Vue.config.productionTip = false

new Vue({
  router,
  store,
  render: h => h(App),
}).$mount('#app')

效果图：