React Hooks useState Hook 2

Question 1

Can you store objects in useState?

Accepted Answer

Yes, but you must spread the previous state manually

Answer

useState does not merge objects like setState in class components; you must spread the old state yourself.

Question 2

What is the correct way to update one property of an object stored in state?

Accepted Answer

setUser({...user, name: 'Alice'})

Answer

Spreading the previous state and overriding the changed property ensures immutability.

Question 3

How should you add an item to an array stored in useState?

Accepted Answer

setItems([...items, newItem])

Answer

Spreading the existing array into a new array maintains immutability required by React.

Question 4

When does React batch multiple useState setter calls?

Accepted Answer

In React 18+ batching occurs in all contexts by default

Answer

React 18 introduced automatic batching for all contexts including promises, timeouts, and native events.

Question 5

What value does useState return before the setter is ever called?

Accepted Answer

The initial value passed to useState

Answer

Before any setter call, the state holds whatever value (or result of function) was passed as the initializer.

React Practice Test