vue 中使用 better-scroll ，怎么获取某个元素的offsetTop，急！！！！！！！！！！！！！！

Question

 better() { 
    this.$nextTick(() => {
        this.scroll = new BScroll(this.$refs.wrapper, {
          pullUpLoad: {   //上拉距离
            threshold: -5,
            resizePolling: 60
          },
        })
        this.scroll.on('scroll', (pos) => {
          console.log(pos.y)
          console.log("aaaa",this.$refs.tabs.offsetTop)
        })
      this.load()   //绑定上拉
    })
  },
  
  this.scroll.on('scroll', (pos) => {
      console.log(pos.y)
      console.log("aaaa",this.$refs.tabs.offsetTop)
  })
  
  <div ref="tabs">
        <van-tabs v-model="active" animated @click="onClick">
            <van-tab v-for="(item,index) in menuList" :title="item.name" :key="index"></van-tab>
        </van-tabs>
      </div>