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

useState returns a pair: the current state value and a function to update it.

Question 2

What argument do you pass to useState?

Accepted Answer

The initial state

Answer

The argument to useState is the initial state used only on the first render.

Question 3

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

Accepted Answer

useEffect

Answer

useEffect lets you perform side effects like data fetching and subscriptions.

Question 4

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

Accepted Answer

componentDidMount, componentDidUpdate, and componentWillUnmount

Answer

useEffect unifies the behavior of mount, update, and unmount lifecycle methods.

Question 5

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

Accepted Answer

Pass an empty dependency array []

Answer

An empty dependency array makes the effect run only after the first render.

React Practice Test