v-for="(item,index) of hot"    //数组遍历

v-for="(item,key,index) of cities"   //对象遍历

//key 是对象的属性     item对应的属性值

 <div class="area" v-for="(item,key) of cities" :key="key">

        <div class="title border-topbottom">{{key}}</div>

        <div class="item-list">

          <div class="item border-bottom" v-for="city of item " :key="city.id">{{city.name}}</div>

        </div>

</div>