39Implement Promise.any() with AggregateError

Implement promiseAny(iterable) without using Promise.any. It fulfils with the value of the first item that fulfils. Rejections are ignored unless every item rejects; then it rejects with an AggregateError whose errors array holds every reason, in input order.

// Load an image from whichever CDN answers first.
const url = await promiseAny([probe(cdnA), probe(cdnB), probe(cdnC)]);

Requirements

• Fulfil with the first fulfilment, even if other items rejected before it.
• If all items reject, reject with new AggregateError(errors, "All promises were rejected"), with errors in input order, not timing order.
• An empty input rejects right away with an AggregateError and an empty errors array.
• Items may be promises, thenables or plain values; accept any iterable.