JavaScript Interview Question #86

What does Promise.all() do?

Promises, Async/Await, Fetch & Modern JavaScript Mid-Level Intermediate

Quick Interview Answer

Promise.all accepts an iterable of values or Promises and returns a Promise that fulfills when all inputs fulfill. The fulfilled result is an array preserving the input order.

Detailed Explanation

Promise.all accepts an iterable of values or Promises and returns a Promise that fulfills when all inputs fulfill. The fulfilled result is an array preserving the input order.

If any input Promise rejects, the Promise returned by Promise.all rejects with that reason. This is appropriate when all operations are required for the overall task to succeed.

Code Example

const [user, orders, notifications] =
    await Promise.all([
        getUser(),
        getOrders(),
        getNotifications()
    ]);

console.log(user, orders, notifications);