Take n items as a batch from an asyncIterator until done

take.js

async function* take(n, obj) {
  let done;
  const iterator = obj[Symbol.asyncIterator]();
  while(!done) {
    yield Promise.all(
      Array.from(
        {length: n},
        async function() {
          const result = await this.next();
          done = result.done;
          return result.value;
        },
        iterator
      )
    );
  }
}

// example
// useful for controlling parallelism
// take 10 at a time from asyncIterableObject to work on in parallel, wait until all 10 items are complete
//   before getting next batch.
for await (const batch of take(10, asyncIterableObject)) {
  await Promise.all(
    batch.map(async item => await item.doStuff())
  );
}