checkLuhnValidity function

bool checkLuhnValidity(String ccNum)

Implementation of the Luhn algorithm in Dart. It is also known as the "modulus 10" algorithm

For more info on Luhn algorithm check these URLS https://en.wikipedia.org/wiki/Luhn_algorithm https://www.geeksforgeeks.org/luhn-algorithm Checks the validity of the card number using the Luhn algorithm (the modulus 10 algorithm)

This method assumes that the incoming string is trimmed of whitespace and does not contain non-numerical characters. i.e. 'A-Z', 'a-z', etc.

Implementation

/// Checks the validity of the card number using the Luhn algorithm (the modulus 10 algorithm)
///
/// This method assumes that the incoming string is trimmed of whitespace
/// and does not contain non-numerical characters. i.e. 'A-Z', 'a-z', etc.
bool checkLuhnValidity(String ccNum) {
  int sum = 0;
  bool alternate = false;

  for (int i = ccNum.length - 1; i >= 0; i--) {
    int digit = int.parse(ccNum[i]);

    if (alternate) {
      digit *= 2;
      if (digit > 9) {
        digit = (digit % 10) + 1;
      }
    }

    sum += digit;

    alternate = !alternate;
  }

  return sum % 10 == 0;
}