code: function(id, chunkIdx, response, xhr) {
              var chunkData = handler._getChunkData(id, chunkIdx);
  
              handler._getFileState(id).attemptingResume = false;
  
              delete handler._getFileState(id).temp.chunkProgress[chunkIdx];
              handler._getFileState(id).loaded += chunkData.size;
  
              options.onUploadChunkSuccess(id, handler._getChunkDataForCallback(chunkData), response, xhr);
          }
docs: Called when each chunk has uploaded successfully