formatCardNumber static method

String? formatCardNumber(
  1. String cardNumber
)

"6037-9912-3456-7890", or null when invalid.

Implementation

static String? formatCardNumber(String cardNumber) {
  if (!validateCardNumber(cardNumber)) return null;
  return "${cardNumber.substring(0, 4)}-${cardNumber.substring(4, 8)}-${cardNumber.substring(8, 12)}-${cardNumber.substring(12)}";
}