<transition-group name="breadcrumb">
        <el-breadcrumb-item v-for="(item,index)  in levelList" :key="item.title" v-if='item.title'>
          <span v-if='item.redirect==="noredirect"||index==levelList.length-1' class="no-redirect">{{ item.title }}</span>
          <router-link v-else :to="item.redirect||item.path">{{ item.title }}</router-link>
        </el-breadcrumb-item>
      </transition-group>

注意：

這裏的 <transition-group> 的子元素不能使用 v-for 的index當作key

(Emitted value instead of an instance of Error) Do not use v-for index as key on                   

<transition-group> children, this is the same as not using keys.