isCreditCard function

bool isCreditCard(String str)

Returns true if str is a valid credit card number (Luhn check).

Implementation

bool isCreditCard(String str) {
  final sanitized = str.replaceAll(RegExp('[^0-9]+'), '');
  if (!creditCardReg.hasMatch(sanitized)) return false;

  var sum = 0;
  var shouldDouble = false;

  for (var i = sanitized.length - 1; i >= 0; i--) {
    var tmpNum = int.parse(sanitized[i]);

    if (shouldDouble) {
      tmpNum *= 2;
      if (tmpNum >= 10) {
        sum += (tmpNum % 10) + 1;
      } else {
        sum += tmpNum;
      }
    } else {
      sum += tmpNum;
    }
    shouldDouble = !shouldDouble;
  }

  return sum % 10 == 0;
}