<template>
  <div class="app">
      <headVue ></headVue>
      <div class="fu">
          <div class="nav">
              <ul>
                  <li v-for="(arr,$index) in arrs" :index="$index" @mouseover="f($index,$event)" @mouseout="ff">{{arr.name}}
                      <ul class="zi" >
                          <li v-for="(arr1, $index2) in arr1s" v-if="arr1.flag && $index == $index2"><a :href="arr1.url">{{arr1.text}}</a></li>
                      </ul>
                  </li>

              </ul>
          </div>
      </div>
      <footerVue></footerVue>
  </div>
</template>

<script>
    export default {
        name: 'app',
        data () {
            return {
                arrs: [
                    {name: '选项卡1'},
                    {name: '选项卡2'},
                    {name: '选项卡3'}
                ],
                arr1s: [
                    {text: 'text1', url: 'https://www.baidu.com', flag: false},
                    {text: 'text2', url: 'https://www.mi.com', flag: false},
                    {text: 'text3', url: 'https://www.ss.com', flag: false}
                ]
            }
        },
        components: {
        },
        methods: {
            f: function (a, b) {
                this.arr1s.forEach(function (ele) {
                    ele.flag = false
                })
                this.$set(this.arr1s[a], 'flag', true)
            },
            ff: function () {
                // this.flag = false
                this.arr1s.forEach(function (ele) {
                    ele.flag = false
                })
            }
        }
    }

</script>

怎么回事呀。。求解