React Hooks Introducing React Hooks 4

Question 1

What does the useState Hook return?

Accepted Answer

An array with the current state and an updater function

Answer

A single state value

Answer

An object with getters and setters

Answer

A promise

Question 2

What argument do you pass to useState?

Accepted Answer

The initial state

Answer

The next state

Answer

A reducer function

Answer

A dependency array

Question 3

Which built-in Hook handles side effects in function components?

Accepted Answer

useEffect

Answer

useState

Answer

useMemo

Answer

useRef

Question 4

useEffect serves a similar purpose to which combination of class lifecycle methods?

Accepted Answer

componentDidMount, componentDidUpdate, and componentWillUnmount

Answer

render and constructor

Answer

shouldComponentUpdate only

Answer

getDerivedStateFromProps

Question 5

How can you run a useEffect only once after the initial render?

Accepted Answer

Pass an empty dependency array []

Answer

Omit the dependency array

Answer

Pass null as the second argument

Answer

Return false from the effect

Question 6

How does a useEffect clean up after itself?

Accepted Answer

By returning a cleanup function

Answer

By calling this.cleanup()

Answer

By throwing an error

Answer

Cleanup is automatic and cannot be customized

Question 7

Which Hook is best for accessing values from React Context?

Accepted Answer

useContext

Answer

useState

Answer

useReducer

Answer

useCallback