vue页面刷新数据丢失问题

参考： https://blog.csdn.net/aliven1/article/details/80743470
          https://blog.csdn.net/liang377122210/article/details/78880438
          https://blog.csdn.net/goodaxuan/article/details/82113123

我的需求： 进入商城后调接口获取用户id，并把id存入session中。之后跳转页面或刷新页面时，直接从session中取出id，无需再调接口。

main.js文件中：

import Vue from 'vue';
import App from './App';
import router from './router';
import Vuex from 'vuex';
···
import store from './store'; //vuex部分

Vue.prototype.$http = axios;
axios.defaults.baseURL = '***';
axios.defaults.headers['Content-Type'] = 'application/x-www-form-urlencoded;charset=UTF-8';

Vue.prototype.userInfo = function(succallback, failcallback) {
  var _this = this;
  if (_this.userId) {
    succallback && succallback(_this.userInfo);
    return;
  }
  if (sessionStorage.getItem("userMsg")) {
    let t = sessionStorage.getItem("userMsg"),
      obj = JSON.parse(t),
      userMsg = obj.userMsg;
    _this.uMID = userMsg.uMID;
    _this.userInfo = {
      'uMID': userMsg.uMID
    };
    succallback && succallback(_this.userInfo);
  } else {
    _this.$http.get('***').then(function(res) {
        if (res.status === 200 && res.data.result === "0") {
          var data = res.data.message;
          _this.userInfo = {
            'uMID': data.uMID
          };
          _this.uMid = data.uMID;
          _this.$store.commit('set_userMsg', data);
          sessionStorage.setItem("userMsg", JSON.stringify(_this.$store.state));
          //在页面加载时读取sessionStorage里的状态信息
          if (sessionStorage.getItem("userMsg")) {
            _this.$store.replaceState(Object.assign({}, _this.$store.state, JSON.parse(sessionStorage.getItem(
              "userMsg"))));
          }
          //在页面刷新时将vuex里的信息保存到sessionStorage里
          window.addEventListener("beforeunload", () => {
            sessionStorage.setItem("userMsg", JSON.stringify(_this.$store.state))
          })
          succallback && succallback(_this.userInfo);
        }
      })
      .catch(function(error) {
        console.log(error);
        failcallback && failcallback(error);
      });
  }
};

new Vue({
  el: '#app',
  router,
  store,
  data() {
    return {
      uMID: ''
    }
  },
  components: {
    App
  },
  template: '<App/>'
})

store.js：

import Vue from "vue";
import Vuex from "vuex";

Vue.use(Vuex);

export default new Vuex.Store({
  state: {
    userMsg: '',
    userId: ''
  },
  getters: {
    userId: state => state.userId
  },
  mutations: {
    changeUserId(state, userId) {
      state.userId = userId;
    },
    set_userMsg(state, data) {
      state.userMsg = data
    }
  },
  actions: {},
  modules: {}
});

组件中：

···
data() {
      return {
        uMID: ''
      }
},
created() {
      let _this = this;
      _this.getUser();
},
 methods: {
      getUser: function() {
        let _this = this;
        _this.userInfo(function(userId) {
          _this.uMID = userId.uMID;
          ···  //需要uMID的操作最好在这里进行
        });
      }
}
···