code: function sliceList(opt) {
          var that = this;
          var defer = $.Deferred();
  
          var file = opt.file;
  
          that.getAppSign(function (sign) {
  
              opt.sign = sign;
              var url = that.getCgiUrl(opt.path, opt.sign);
  
              var formData = new FormData();
              formData.append('op', 'upload_slice_list');
  
              $.ajax({
                  type: 'POST',
                  dataType: "JSON",
                  url: url,
                  data: formData,
                  success: function (res) {
                      res = res || {};
                      if (res.code == 0) {
                          opt.session = res.data.session;
                          opt.slice_size = res.data.slice_size;
                          var listparts = res.data.listparts || [];
                          opt.listparts = listparts;
                          var len = listparts.length;
                          if (len) {
                              var lastPart = opt.listparts[len - 1];
                              var last_offset = lastPart.offset;
                              if (last_offset + lastPart.datalen > file.size) {
                                  defer.resolve();
                                  return defer.promise();
                              }
                              opt.offset = last_offset;
                          }
  
                          defer.resolve(res);
                      } else {
                          defer.reject(res);
                      }
  
                  },
                  error: function () {
                      defer.reject();
                  },
                  processData: false,
                  contentType: false
              });
  
  
          });
  
  
          return defer.promise();
      }
docs: 分片上传LIST接口