Questions

3 of 17

1Explain the concept of 'callback hell' and how to mitigate it.

2What is a Promise in JavaScript?

3Explain the three states of a Promise.

4How do you create a new Promise in JavaScript?

5What is the purpose of `Promise.resolve()` and `Promise.reject()`?

6How do you handle the result of a Promise?

7What is Promise chaining?

8How do you handle errors in a chain of Promises?

9What is the purpose of `Promise.all()`, `Promise.race()`, `Promise.any()`, `Promise.allSettled()`?

10How can you handle multiple Promises concurrently without using `Promise.all()`?

11What is the purpose of the `async` and `await` keyword in JavaScript??

12How do you handle errors when using `async/await`?

13Do all `async` functions return Promises? Why or why not?

14How does `Promise.finally()` work?

15How do you convert a callback-based function into a Promise-based function?

16What is the purpose of `Promise.promisify()`?

17How can you create a custom Promise with timeout functionality?

03 / 17

Explain the three states of a Promise.

pending, fulfilled and rejected are three states of a promise.

1
Pending: The initial state, when the Promise is neither fulfilled nor rejected.
2
Fulfilled: The state when the asynchronous operation completes successfully.
3
Rejected: The state when the asynchronous operation encounters an error.