Изучаем Dart 2019 / ДЗ по функциям

main.dart

void main() {
  List<String> data = ["dart", "abc", "good luck"];

  print(wordValue(data));
}

List<int> wordValue(List<String> array) {
  List<String> alphabet = 'abcdefghijklmnopqrstuvwxyz'.split('');
  List<int> arr = [];

  for (var word in array) {
    int i = 0;

    word
        .split('')
        .where((char) => char != ' ')
        .toList()
        .forEach((char) => i += (alphabet.indexOf(char) + 1));

    arr.add((array.indexOf(word) + 1) * i);
  }
  return arr;
}