maskCard method

String maskCard(
  1. String input
)

Special case for card-like sequences: mask all but last 4 digits and keep spacing where possible.

Implementation

String maskCard(String input) {
  final digits = input.replaceAll(RegExp(r'\D'), '');
  if (digits.length < 8) return mask(input);
  final last4 = digits.substring(digits.length - 4);
  return '${maskChar * (digits.length - 4)}$last4';
}