batch-async.ts

export const batchAsync = async function <T>(
  iterable: Iterable<T> | AsyncIterable<T>,
  callback: (value: T) => Promise<void>,
  limit: number,
) {
  const batch = new Set<Promise<void>>();

  for await (const value of iterable) {
    const promise = callback(value).finally(() => {
      batch.delete(promise);
    });
    batch.add(promise);

    if (batch.size >= limit) {
      await Promise.race(batch);
    }
  }

  await Promise.all(batch);
}