maskPhoneNumber static method

String maskPhoneNumber(String phone, { int visibleStartDigits = 0, int visibleEndDigits = 4, String maskChar = '•', })

Masks digit characters for safe display.

Non-digits (+, spaces, -, ()) are kept as-is. Example: [phone] with visibleEndDigits 4 → +1 ••• ••• 2671

Implementation

static String maskPhoneNumber(
  String phone, {
  int visibleStartDigits = 0,
  int visibleEndDigits = 4,
  String maskChar = '•',
}) {
  if (phone.isEmpty) return phone;

  final digitPositions = <int>[
    for (var i = 0; i < phone.length; i++)
      if (_isDigit(phone.codeUnitAt(i))) i,
  ];

  final count = digitPositions.length;

  if (count == 0) return phone;

  if (count <= visibleStartDigits + visibleEndDigits) return phone;

  final chars = phone.split('');

  for (var d = 0; d < count; d++) {
    final show =
        d < visibleStartDigits || d >= count - visibleEndDigits;
    if (!show) chars[digitPositions[d]] = maskChar;
  }

  return chars.join();
}