run Promise.all while being aware of the current progress

promiseAllWithProgress.ts

type OnPromiseProgressCallback = (resolvedPromises: number) => void;

/**
 * Run `Promise.all` for all given promises inside an array.
 * For each item complete it will call the given `onProgress` callback.
 *
 * NOTE: It will call the `onProgress` at the end as well, since asynchronous
 * code is a mess to deal with in Javascript.
 */
const promiseAllWithProgress = async <TResult>(
  values: Array<Promise<TResult>>,
  onProgress: OnPromiseProgressCallback,
) => {
  let resolvedPromises = 0;

  const response = await Promise.all(
    values.map((pending) =>
      pending.then((res) => {
        void setTimeout(onProgress, 1, (resolvedPromises += 1) / values.length);
        return res;
      }),
    ),
  );

  onProgress(1);

  return response;
};

export { promiseAllWithProgress };