43Implement asyncFilter() with asynchronous predicates

array.filter(async (x) => …) does not work: every async function returns a promise, and a promise is always truthy, so nothing is removed.

Implement asyncFilter(items, predicate). It calls the async predicate(item, index) for every item in parallel and resolves to the items whose predicate resolved to a truthy value, in their original order.

const reachable = await asyncFilter(urls, async (url) => {
  const res = await fetch(url, { method: "HEAD" });
  return res.ok;
});

Requirements

• Run all predicates in parallel.
• Keep the original order of the kept items.
• Any truthy resolved value keeps the item.
• Reject if any predicate rejects or throws.
• Accept any iterable; an empty input resolves to [].