判断后台读取的图片是否加载完成

let img = this.$refs.wrapper.getElementsByTagName("img");
      let count = 0;
      let length = img.length;
      if (length) {
        let timer = setInterval(() => {
          if (count == length) {
            this.scroll.refresh(); //bs提供的刷新的方法，详见官网
            clearInterval(timer);
          } else if (img[count].complete) {
            count++;
          }
        }, 100);
      }