getObject.ts

type GetValueFn<TIdentity, TValue> = (id: TIdentity) => Promise<TValue>;
type KeyValueObject<TValue> = { [key: string]: TValue };

const getObject = <TIdentity, TValue>(
  getValue: GetValueFn<TIdentity, TValue>
) => async (itemIds: Array<TIdentity>): Promise<KeyValueObject<TValue>> => {
  return Object.fromEntries(
    await Promise.all(
      itemIds.map(async itemId => [itemId, await getValue(itemId)])
    )
  );
};

type Movie = Readonly<{ id: number; title: string }>;

const getMovie = async (id: number): Promise<Movie> => {
  switch (id) {
    case 1:
      return { id, title: "Avengers: Endgame" };
    case 2:
      return { id, title: "Toy Story 4" };
    case 3:
      return { id, title: "The Lion King" };
    case 4:
      return { id, title: "Aladdin" };
    case 5:
      return { id, title: "Captain Marvel" };
  }

  throw new Error("No movie could be found with this id.");
};

(async (): Promise<void> => {
  const getMovies = getObject(getMovie);

  const movies = await getMovies([1, 2, 3]);

  // {
  //   1: { id: 1, title: "Avengers: Endgame" },
  //   2: { id: 2, title: "Toy Story 4" },
  //   3: { id: 3, title: "The Lion King" },
  // }
  console.log(movies);
})();