React Hooks Building React App 3

Question 1

When building a form, which hook tracks the input field's current value?

Accepted Answer

useState

Answer

useState is the standard hook for controlled input values.

Question 2

How do you make an input a controlled component in React?

Accepted Answer

Set value and onChange props

Answer

Binding value to state and updating it via onChange creates a controlled input.

Question 3

Which hook is best for fetching data when the App component first mounts?

Accepted Answer

useEffect with an empty dependency array

Answer

useEffect with [] runs once after the initial mount, ideal for fetching data.

Question 4

What should a data-fetching useEffect return to avoid memory leaks?

Accepted Answer

A cleanup function

Answer

Returning a cleanup function lets you cancel requests or clear timers on unmount.

Question 5

To display a list of items from state, which approach is used in JSX?

Accepted Answer

Array.map returning elements with keys

Answer

Array.map returns an element per item, each needing a unique key prop.

React Practice Test