groupBy<K> method

Map<K, List<T>> groupBy<K>(
  1. K keyFunction(
    1. T
    )
)

Implementation

Map<K, List<T>> groupBy<K>(K Function(T) keyFunction) {
  return fold(
    <K, List<T>>{},
    (Map<K, List<T>> map, T element) {
      return map..putIfAbsent(keyFunction(element), () => <T>[]).add(element);
    },
  );
}