vue-v-for的key值為什么會一直重復(fù)？

AB是兩個tab頁，切換的時候已經(jīng)把addlist致為空數(shù)組了，js部分打印index值為啥是undefined？求解

<div class="tit">區(qū)域編號 A</div>
      <div class="item" v-for="item in addList" :key="item.index" v-if="addList.length>0">
        <el-input v-model="item.shelves_number" disabled></el-input>
        <el-input v-model="item.shelves_layer" disabled></el-input>
        <el-input v-model="item.shelves_layer_num" disabled></el-input>
        <span>{{item.shelves_num}}</span>
        <span><button @click="delBtn_2(item.index,addList)">刪除</button></span>
 </div>

<div class="tit">區(qū)域編號 B</div>
      <div class="item" v-for="item in addList" :key="item.index" v-if="addList.length>0">
        <el-input v-model="item.shelves_number" disabled></el-input>
        <el-input v-model="item.shelves_layer" disabled></el-input>
        <el-input v-model="item.shelves_layer_num" disabled></el-input>
        <span>{{item.shelves_num}}</span>
        <span><button @click="delBtn_2(item.index,addList)">刪除</button></span>
 </div>

js部分

delBtn_2(index,data){ 
      console.log(index);
      data.splice(index,1);
      this.setList.splice(index,1);