Promise.race and Promise.allSettled in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does Promise.race do in JavaScript?

Promise.race returns a new promise that settles as soon as any of the input promises settles (either resolves or rejects). It "races" all promises and settles with the first one that finishes.

intermediate

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

Promise.allSettled waits for all promises to settle (resolve or reject) and returns their results regardless of success or failure. Promise.all waits for all to resolve but rejects immediately if any promise rejects.

beginner

What does the result of Promise.allSettled look like?

It returns an array of objects, each with a status property ("fulfilled" or "rejected") and either a value (for fulfilled) or reason (for rejected).

beginner

If you want to get the first promise that finishes regardless of success or failure, which method do you use?

You use Promise.race because it settles as soon as any promise settles, whether it resolves or rejects.

beginner

Can Promise.allSettled be used to handle multiple promises without stopping on errors?

Yes, Promise.allSettled lets you wait for all promises to finish and see which succeeded or failed without stopping early due to errors.

What does Promise.race return?

A The last promise to resolve

B An array of all resolved values

C An array of all rejected reasons

D The result of the first promise to settle (resolve or reject)

Promise.race settles as soon as the first promise settles, returning its result or error.

Which method waits for all promises to finish regardless of success or failure?

A Promise.race

B Promise.allSettled

C Promise.all

D Promise.any

Promise.allSettled waits for all promises to settle, no matter if they resolve or reject.

What happens if one promise rejects in Promise.all?

A It immediately rejects with that error

B It ignores the rejection

C It waits for all promises anyway

D It returns an array of results

Promise.all rejects immediately if any promise rejects.

What property indicates a promise was fulfilled in Promise.allSettled results?

A status: 'rejected'

B reason: 'fulfilled'

C status: 'fulfilled'

D value: 'fulfilled'

The status property is either 'fulfilled' or 'rejected'.

Which method would you use to get the fastest successful promise result, ignoring failures?

A Promise.any

B Promise.allSettled

C Promise.race

D Promise.all

Promise.any returns the first fulfilled promise, ignoring rejected ones.

Explain how Promise.race works and give a simple example.

Think about a race where the first to finish wins.

Describe the purpose of Promise.allSettled and how its results are structured.

It tells you how every promise ended, no matter what.