code: function initRead (reader, file) {
      // Already loading something
      if (reader.readyState === FileReader.LOADING) {
          throw new FileError(FileError.INVALID_STATE_ERR);
      }
  
      reader._result = null;
      reader._error = null;
      reader._progress = 0;
      reader._readyState = FileReader.LOADING;
  
      if (typeof file.localURL === 'string') {
          reader._localURL = file.localURL;
      } else {
          reader._localURL = '';
          return true;
      }
  
      if (reader.onloadstart) {
          reader.onloadstart(new ProgressEvent('loadstart', {target: reader}));
      }
  }
docs: When the read has been aborted. For instance, by invoking the abort() method.