React Hooks

Question 1

What is useState in React?

Accepted Answer

A hook that adds state to functional components, returning the current value and a function to update it

Answer

useState returns a pair: the current state value and a setter function. When the setter is called, the component re-renders with the new value.

Question 2

What is useEffect used for?

Accepted Answer

Performing side effects like data fetching, subscriptions, or DOM manipulation after render

Answer

useEffect runs after render and handles side effects. The dependency array controls when it re-runs. Cleanup functions handle teardown.

Question 3

What is the dependency array in useEffect?

Accepted Answer

An array of values that determines when the effect should re-run — changes trigger re-execution

Answer

The dependency array tells React which values to watch. Empty array = run once. No array = run every render. With values = run when those values change.

Question 4

What is useContext?

Accepted Answer

A hook that accesses context values without wrapping components in Consumer, enabling shared state across the component tree

Answer

useContext provides a way to pass data through the component tree without prop drilling, accessing values from the nearest matching Context Provider.

Question 5

What is useRef used for?

Accepted Answer

Creating a mutable reference that persists across renders without causing re-renders when changed

Answer

useRef creates a container for a mutable value that persists across renders. Common uses include accessing DOM elements and storing previous values.

React Practice Test

React Practice Test

React Hooks