What is the time and space complexity of Implement Promise.any?

Time complexity: O(n). Space complexity: O(n).

Implement Promise.any

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Solution Guide: Implement Promise.any

Approach

Resolve with the first fulfilled promise value, ignoring rejections until all have failed. Track rejected count and store errors by index. Only reject with an AggregateError when every promise has rejected.

Complexity Analysis

Time: O(n)
Space: O(n)

Pattern

Promise Combinator

Why It Works

The first fulfillment short-circuits to resolve the outer promise, while rejections are silently collected. Only when all promises reject does the aggregate error surface.

Updated Feb 2026