code: function checkUplodingStatus() {
          checkTimer = setInterval(function () {
              if (uploading === 0 && checkTimer) {
                  clearInterval(checkTimer);
                  checkTimer = null;
                  // 检测通过，开始检测50ms内是否还有新请求
                  waitforNewUpload();
              }
          }, 10);
      }
docs: 每10ms检测一次uploading状态，当前没有上传任务时，uploading为0
  @return {[type]} [description]