Promise Iterator

PromiseIterator.ts

/**
 * Yields promises as they settle.
 * @param promises List of promise to yield through
 */
export default async function* PromiseIterator<P>(promises: Iterable<Promise<P>>): AsyncGenerator<[Promise<P>], void, void> {
	const pending = new Set<Promise<P>>(promises)
	const settled = new Set<Promise<P>>()

	// Move pending promises to `settled` when they settle
	pending.forEach((promise) =>
		promise
			.catch(() => void 0)
			.finally(() => {
				pending.delete(promise)
				settled.add(promise)
			})
	)

	// Yield promises as they settle, until all promises have been yielded
	while (pending.size || settled.size) {
		await Promise.race([Promise.race(settled), Promise.race(pending)]).catch(() => void 0)
		for (const result of settled) {
			settled.delete(result)
			yield [result]
		}
	}
}