vue 实现v-for循环回来的数据动态绑定id

<ul>
<li v-for="(site,index) in sites" :key="index" :id="forId(index)">
 <span class="channel-li-li-border">
 <span class="firstLevel">{{site.name}}</span>
 </span>
</li>
</ul>

<script>
 new Vue({
 el: '#cat2s',
 data: function(){
 return {
 brandList: [],
 sites: [
   { name: '품질검수 서비스' },
   { name: '배송물류 서비스' },
   { name: '브랜드사 리스트'}
  ]
 }
 },
 methods: {
 forId:function(index){
 return "forid_" +index
 },
}
})
</script>