groupBy<K> method

Map<K, List<E>> groupBy<K>(
  1. K keySelector(
    1. E element
    )
)

Groups elements by a key produced from each element.

Implementation

Map<K, List<E>> groupBy<K>(K Function(E element) keySelector) {
  final result = <K, List<E>>{};
  for (final element in this) {
    (result[keySelector(element)] ??= <E>[]).add(element);
  }
  return result;
}