info_tren/lib/utils/string.dart

extension TakeWhile on String {
  String takeWhile(Function charValidator) {
    StringBuffer output = StringBuffer();

    for (final char in codeUnits) {
      if (charValidator(char)) {
        output.writeCharCode(char);
      } else {
        break;
      }
    }

    return output.toString();
  }
}