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JavaScript Promise Patterns: all vs allSettled vs race vs any, forEach Async Bug, Timeouts and a Concurrency Limit

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Self-Hosting & Infra intermediate 6 min read $0.01 Updated 2026-10-20

Verified in Node 22: Promise.all rejecting fast, allSettled statuses, race with fulfilled and rejected first settlers, any returning the first success or an AggregateError, sequential versus parallel timing, forEach not awaiting, a timeout wrapper and a pool never exceeding 3 concurrent tasks.

Choose the right Promise combinator, run work in parallel instead of in sequence, avoid async inside forEach, add timeouts that do not leak, and cap concurrency with a small worker pool. All behaviors executed in Node 22.

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