React Hooks Javascript 4

Question 1

What is the correct way to update state based on the previous state?

Accepted Answer

setCount(prev => prev + 1)

Answer

Using a functional updater ensures you reference the latest previous state safely.

Question 2

What does useReducer's dispatch function do?

Accepted Answer

Sends an action to the reducer to compute the next state

Answer

dispatch sends an action object that the reducer uses to produce new state.

Question 3

Which hook helps customize the instance value exposed to parent components via a ref?

Accepted Answer

useImperativeHandle

Answer

useImperativeHandle customizes the ref value exposed when using forwardRef.

Question 4

What is the main benefit of memoizing a callback with useCallback?

Accepted Answer

It prevents unnecessary re-renders of child components receiving the callback as a prop

Answer

A stable callback reference avoids re-rendering memoized children unnecessarily.

Question 5

Which hook fires synchronously after all DOM mutations, before the browser paints?

Accepted Answer

useLayoutEffect

Answer

useLayoutEffect runs synchronously after DOM mutations and before paint.

React Practice Test