React Hooks

Question 1

What is the primary purpose of React Hooks?

Accepted Answer

To use state and other React features in functional components

Answer

To replace all class components with functional components

Answer

To improve the performance of React applications

Answer

To add styling capabilities to React components

Question 2

Which hook would you use to perform side effects in a functional component?

Accepted Answer

useEffect

Answer

useState

Answer

useContext

Answer

useCallback

Question 3

What does the useState hook return?

Accepted Answer

An array with the current state value and a setter function

Answer

Just the current state value

Answer

An object with state and setState properties

Answer

A function to update the state

Question 4

When does useEffect run by default?

Accepted Answer

After every render (both mount and update)

Answer

Only when the component mounts

Answer

Only when the component updates

Answer

Only when the component unmounts

Question 5

How do you prevent useEffect from running on every render?

Accepted Answer

By providing a dependency array as the second argument

Answer

By using useCallback instead

Answer

By wrapping it in useMemo

Answer

By calling it conditionally with an if statement

Question 6

What is the purpose of the cleanup function in useEffect?

Accepted Answer

To clean up resources like subscriptions or timers when the component unmounts or dependencies change

Answer

To reset the component's state to its initial value

Answer

To prevent the effect from running multiple times

Answer

To optimize the component's performance

Question 7

Which hook would you use to access a React context value?

Accepted Answer

useContext

Answer

useReducer

Answer

useRef

Answer

useImperativeHandle

Question 8

What is the main difference between useMemo and useCallback?

Accepted Answer

useMemo memoizes a computed value, useCallback memoizes a function

Answer

useMemo is for state, useCallback is for effects

Answer

useMemo runs on mount, useCallback runs on update

Answer

useMemo is synchronous, useCallback is asynchronous

Question 9

When would you choose useReducer over useState?

Accepted Answer

When you have complex state logic involving multiple sub-values or when the next state depends on the previous one

Answer

When you need to store arrays or objects

Answer

When you want better performance

Answer

When you need to share state between components

Question 10

What happens if you call a hook conditionally or inside a loop?

Accepted Answer

It violates the Rules of Hooks and can cause bugs or crashes

Answer

It works normally but with reduced performance

Answer

It only works in development mode

Answer

It automatically gets moved to the top level by React