toCardString function

String toCardString(
  1. String cardNumber
)

Implementation

String toCardString(String cardNumber) {
  final List<String> cardNum = [];
  int spacesAdded = 0;
  for (final char in cardNumber.characters) {
    cardNum.add(char);
    if ((cardNum.length - spacesAdded) % 4 == 0) {
      cardNum.add(' ');
      spacesAdded += 1;
    }
  }

  return cardNum.join();
}