code: function MarcRecord(record) {
    if (!(this instanceof MarcRecord)) {
      return new MarcRecord(record);
    }
  
    if (record instanceof MarcRecord) {
      this.leader = record.leader;
      this.fields = [];
  
      for (var fieldNo = 0; fieldNo < record.fields.length; fieldNo++) {
        var field = record.fields[fieldNo];
        if (field instanceof MarcControlField) {
          this.addVariableField(new MarcControlField(field));
        } else {
          this.addVariableField(new MarcDataField(field));
        }
      }
    } else {
      this.leader = MarcRecord.DEFAULT_LEADER;
      this.fields = record instanceof Array ? record : [];
    }
  }
docs: /*
  Represents a MARC record.