allEntries.ts

/**
 * Creates a promise that is resolved with a disctionary of results when all of the provided Promises
 * resolve, or rejected when any Promise is rejected.
 *
 * This function is derived from the standard `Promise.all` function, but it works with a dictionary
 * of promises instead of an array.
 *
 * @param values A dictionary of Promises.
 *
 * @example
 * ```ts
 * const { a, b, c } = await allEntries({
 *		a: Promise.resolve(1),
 *		b: Promise.resolve(2),
 *		c: Promise.resolve(3),
 * });
 * ```
 *
 * @returns A new Promise that is resolved with a dictionary of results.
 */
export async function allEntries<T extends Record<string, unknown>>(
  values: T
): Promise<{
  [K in keyof T]: T[K] extends () => Promise<infer U> ? U : Awaited<T[K]>;
}> {
  const entries = await Promise.all(
    Object.entries(values).map(([key, value]) =>
      Promise.resolve(value).then((res) => [key, res])
    )
  );

  return Object.fromEntries(entries) as {
    [K in keyof T]: T[K] extends () => Promise<infer U> ? U : Awaited<T[K]>;
  };
}