JS Promises: Promise.all vs Promise.allSettled

JS Promises: Promise.all vs Promise.allSettled

Promise.all(iterable)

• Resolves when all resolve; rejects as soon as one rejects (fail-fast).
• Result: array of values in same order.
• Use when: you need every call to succeed (e.g. load user + posts + settings for one screen).

Promise.allSettled(iterable)

• Always resolves after all finish. Never rejects.
• Result: array of { status: 'fulfilled', value } or { status: 'rejected', reason }.
• Use when: partial failure is OK (e.g. batch uploads, validation across many fields — you want to know which failed).

Quick pick:

• All must succeed, order matters → Promise.all.
• Want to see who succeeded/failed → Promise.allSettled, then filter by status.

Async/await:
const results = await Promise.all([...]) or await Promise.allSettled([...]). For all, wrap in try/catch for the first rejection.

Older runtimes: Promise.allSettled needs a polyfill or Node 12.9+ / modern browsers.