vue tab栏缓存解决跳转页面后返回的状态保持

<!DOCTYPE html>
<html lang="zh-cn">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
    <script src="./vue.js"></script>
    <style>
      .div {
        background-color: #ccc;
        height: 100px;
        width: 100px;
        float: left;
        margin-left: 10px;
      }
      .active {
        color: #f91;
      }
    </style>
  </head>
  <body>
    <div id="app" style="overflow: hidden">
      <a
        v-bind:class="[showTab.num == 1 ? 'active div' : 'div']"
        href="http://www.baidu.com"
        v-on:click="changeTab(1)"
      >
        关注
      </a>
      <a
        v-bind:class="[showTab.num == 2 ? 'active div' : 'div']"
        href="http://www.baidu.com"
        v-on:click="changeTab(2)"
      >
        知识点
      </a>
      <a
        v-bind:class="[showTab.num == 0 ? 'active div' : 'div']"
        href="http://www.baidu.com"
        v-on:click="changeTab(0)"
      >
        动态
      </a>
    </div>
    <script>
      const vm = new Vue({
        // element
        // 作用：指定页面中的哪块内容作为Vue的视图
        el: '#app',
        // 数据
        data: {
          showTab: {
            num: 1
          }
        },
        mounted() {
          if (localStorage.getItem('tabNum')) {
            console.log(1)
            this.showTab.num = localStorage.getItem('tabNum')
          }
        },
        methods: {
          changeTab(data) {
            this.$set(this.showTab, 'num', data)
            localStorage.setItem('tabNum', data)
          }
        }
      })
    </script>
  </body>
</html>