Implement Promise.all

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Implement Promise.all · UIHero

Implement Promise.all

Resolve mixed inputs in source order and reject promptly without delegating to Promise.all.

MediumJavaScript Promises

50 min0% acceptance

Description

Implement promiseAll as a standards-oriented aggregation utility. It accepts an iterable of values, promises, and thenables; resolves asynchronously to ordered results; and rejects with the first observed rejection.

Requirements

The solution exports the required promiseAll API from the editable module.
Preserves order works deterministically for the documented normal, boundary, and repeated-use scenarios.
Empty input works deterministically for the documented normal, boundary, and repeated-use scenarios.
Mixed values works deterministically for the documented normal, boundary, and repeated-use scenarios.
Thenables works deterministically for the documented normal, boundary, and repeated-use scenarios.
Rejects first works deterministically for the documented normal, boundary, and repeated-use scenarios.
Asynchronous settlement works deterministically for the documented normal, boundary, and repeated-use scenarios.

Out-of-order settlement

Input

[slowPromise, 2, fastPromise]

Expected output

A promise resolving to [slowValue, 2, fastValue]

Explanation

Result positions follow iteration order rather than completion order.

Constraints

Do not call Promise.all or Promise.allSettled
Accept any synchronous iterable
Always settle asynchronously

Hints

Hint 1

Materialize the iterable once so the target result length is known.

Hint 2

Resolve each entry through Promise.resolve to assimilate thenables.

Hint 3

Track remaining entries and resolve the outer promise only when the counter reaches zero.

promisesthenablesiteration

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