Promise.all and Promise.allSettled

Parallel Promises

Promise.all runs promises in parallel and resolves when all succeed (or rejects on first failure). Promise.allSettled waits for all regardless of outcome.

Example

const [user, posts, comments] = await Promise.all([
  fetch("/api/user").then(r => r.json()),
  fetch("/api/posts").then(r => r.json()),
  fetch("/api/comments").then(r => r.json()),
]);
// Never fails — inspect each result
const results = await Promise.allSettled([p1, p2, p3]);
results.forEach(({ status, value, reason }) => { /* ... */ });

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Pro Tip

Promise.all fails fast — use Promise.allSettled when you need all results even if some fail.

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