React Review and Assessment 2

Question 1

What does the useState hook return?

Accepted Answer

An array with the state value and a setter function

Answer

useState returns an array containing the current state value and a function to update it.

Question 2

Which method runs after a class component is first rendered to the DOM?

Accepted Answer

componentDidMount

Answer

componentDidMount fires once immediately after the component mounts to the DOM.

Question 3

What is the purpose of the key prop when rendering lists?

Accepted Answer

To help React identify which items changed, were added, or removed

Answer

Keys give list items stable identity so React can efficiently update the DOM.

Question 4

How do you prevent a form's default submit behavior in React?

Accepted Answer

Call event.preventDefault() in the handler

Answer

Calling event.preventDefault() stops the browser from reloading on submit.

Question 5

What does the useEffect dependency array control?

Accepted Answer

When the effect re-runs based on changed values

Answer

The effect re-runs only when a value in the dependency array changes.

React Practice Test