基于vue中解决v-for使用报红并出现警告的问题

(Emitted value instead of an instance of Error) <Option v-for="item in searchTypeList">: component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.

<ul 
class="clearfix course-list">
<li 
class="left" 
v-for="(item,index)
in gradeClassfy.primary.grade"
:key="index"><a
href="#" rel="external nofollow" >{{item.name}}</a></li>
</ul>