Function groupByFactory

src/Operations.js:384–395

(collection, grouper, context)

}

export function groupByFactory(collection, grouper, context) {
  const isKeyedIter = isKeyed(collection);
  const groups = (isOrdered(collection) ? OrderedMap() : Map()).asMutable();
  collection.__iterate((v, k) => {
    groups.update(
      grouper.call(context, v, k, collection),
      (a) => ((a = a || []), a.push(isKeyedIter ? [k, v] : v), a)
    );
  });
  const coerce = collectionClass(collection);
  return groups.map((arr) => reify(collection, coerce(arr))).asImmutable();
}

export function partitionFactory(collection, predicate, context) {
  const isKeyedIter = isKeyed(collection);