What is the difference between Promise.all, Promise.race, and Promise.allSettled?

Question

Accepted Answer

These static Promise methods coordinate multiple async operations differently:

Method	Resolves when	Rejects when	Result
`Promise.all`	All promises fulfill	Any promise rejects	Array of fulfilled values
`Promise.race`	First promise settles (fulfill or reject)	First rejection wins	First settled value/reason
`Promise.allSettled`	All promises settle (fulfill or reject)	Never rejects	Array of `{ status, value/reason }`
`Promise.any`	First fulfillment	All reject	First fulfilled value

const p1 = Promise.resolve(1)
const p2 = Promise.resolve(2)
const p3 = Promise.reject('fail')

await Promise.all([p1, p2])       // [1, 2]
await Promise.allSettled([p1, p3]) // [{status:'fulfilled',...}, {status:'rejected',...}]
await Promise.race([p1, p2])       // 1 (first to settle)

Interview tips

Use Promise.all for parallel fetches where one failure should fail everything.
Use Promise.allSettled when you need every outcome (e.g. batch API calls, partial success UI).
Use Promise.race for timeouts or first-responder patterns.
Promise.all short-circuits on first rejection — other promises still run but results are ignored.