Node.js Async Patterns & Error Handling 2

Question 1

What does `Promise.allSettled()` return when some promises reject?

Accepted Answer

It resolves with an array of outcome objects for all promises

Answer

`Promise.allSettled()` always resolves with an array of objects each having `status` ('fulfilled' or 'rejected') and either `value` or `reason`.

Question 2

In Node.js, what is the correct way to handle errors in an async/await function?

Accepted Answer

Wrap await expressions in try/catch blocks

Answer

In async/await code, try/catch blocks are the idiomatic way to catch rejected promises.

Question 3

What happens if you `await` a non-Promise value in Node.js?

Accepted Answer

It wraps the value in a resolved Promise and returns it

Answer

`await` on a non-thenable value is equivalent to `await Promise.resolve(value)` and simply returns the value.

Question 4

Which Node.js utility converts callback-based functions into Promise-returning functions?

Accepted Answer

util.promisify()

Answer

`util.promisify()` wraps a Node.js-style (err, value) callback function and returns a version that returns a Promise.

Question 5

What is the output order of the following code?
```
console.log('A');
setTimeout(() => console.log('B'), 0);
Promise.resolve().then(() => console.log('C'));
console.log('D');
```

Accepted Answer

A, D, C, B

Answer

Synchronous code (A, D) runs first, then microtasks like Promise callbacks (C), then macrotasks like setTimeout (B).

Node.js Practice Test

Node.js Practice Test

Node.js Async Patterns & Error Handling 2