避免使用非原始值作為關鍵字，而使用字串/數字值代替。
解決方法：

<el-carousel class="swiper-container" :interval="5000" arrow="hover" @change="carouselItem">
  <el-carousel-item v-for="item in photoList" :key="item">
    <div class="swiper-slide">
      <div class="swiper" v-for="index in item">
       <a @click='goTo(2)' ><img  :src="index" /></a>
      </div>
    </div>
  </el-carousel-item>
</el-carousel>
 

for迴圈中，繫結的key值不能為物件，而是取一個字串或數值，如下圖：

<el-carousel class="swiper-container" :interval="5000" arrow="hover" @change="carouselItem">
  <el-carousel-item v-for="item in photoList" :key="item.id">
    <div class="swiper-slide">
      <div class="swiper" v-for="index in item">
       <a @click='goTo(2)' ><img  :src="index" /></a>
      </div>
    </div>
  </el-carousel-item>
</el-carousel>