Hey! 👋

Check out today's ⚡️ Dev Tip 💡 👇

Follow me on Twitter @shahzaibkhalid for more Dev Tips! ✨

Let’s say we want to run many promises to execute in
parallel and wait till all of them are ready. 🧐

// some dummy promises to play with 🍭
const p1 = new Promise(resolve => resolve('Shahzaib'));
const p2 = new Promise((_ ,reject) => reject('User does not exists!'));
const p3 = new Promise(resolve => resolve('Lahore'));

Promise.all (short-circuits if any of the promises is rejected)

If any of the passed promises is rejected, the promise
returned by Promise.all immediately rejects with that error. ❌

Promise.all([p1, p2, p3])
  .then(response => console.log(response))
  .catch(error => console.log(error)); // 👉'User does not exists!'

Promise.allSettled (does not short-circuits)

Waits for all passed promises to settle (either resolved or rejected). 🥳

The resulting array has:

• {status: 'fulfilled', value: result} - for successful responses
• {status: 'rejected', reason: error} - for errors

Promise.allSettled([p1, p2, p3])
  .then(response => console.log(response));

/**
 * 👉 [ {status: 'fulfilled', value: 'Shahzaib'},
 *      {status: 'rejected', reason: 'User does not exists!'},
 *      {status: 'fulfilled, value: 'Lahore'} ] 🚀
 */

Hope you learned something new today. Do let me know what do you think about this Dev Tip in the comments below. 👀

Peace. ✌️