duplicate_count_on_list.dart

final duplicatedList = <String>[
  'Tayfer',
  'Ismail',
  'RoyalCoder',
  'Tayfer',
  'RoyalCoder',
  'Tayfer',
  'FatherRussia',
  'RoyalCoder',
  'Sdk',
  'FatherRussia',
  'Sdk',
  'Tomic'
      'Sdk',
];

extension DuplicateCountOnList<T> on List<T> {
  int get duplicateCount {
    final tempList = <T>[];
    for (final item in this) {
      if (!tempList.contains(item)) {
        tempList.add(item);
      }
    }
    return tempList.length;
  }
}

void main() {
  print(duplicatedList.duplicateCount);
}