React State Quiz

Take the React State Quiz to test your understanding of the React State and the related hooks.

React Quiz #03 - React State Interview Questions

Take the React State Quiz to test your understanding of the React State and the related hooks.

5 mins read

1. What is the correct way to update an object in the state?

state.key = value

setState({ key: value })

state = { ...state, key: value }

2. What is the expected output when clicking the ‘Increment Twice’ button?

const SampleComponent = () => {
 const [count, setCount] = useState(0);
     
 const incrementTwice = () => {
       setCount(count + 1);
       setCount(count + 1);
 };
     
 return (
         <div>
            <p>Count: {count}</p>
            <button onClick={incrementTwice}>Increment Twice</button>
         </div>
      );
  };

The count increases by 2 each time the button is clicked.

The count increases by 1 each time the button is clicked.

The count remains unchanged.

3. What is the purpose of the useEffect hook in relation to state in React?

To initialize state variables

To perform side effects when state changes

To update state automatically on every render

4. What is the recommended approach to handle asynchronous operations that modify the state in React?

Using async/await within a useEffect hook

Modifying the state directly within the asynchronous function

Using the useState hook combined with a callback function

5. Which hook is used to share state between multiple components in React?

useState

useContext

useReducer

6. What is the initial value of state when using the useState hook?

null

undefined

It depends on the provided initial value

7. What is the expected behavior when clicking the ‘Increment by 2’ button?

const SampleComponent = () => {
 const [count, setCount] = useState(0);
 
 const incrementByTwo = () => {
    setCount((prevCount) => prevCount + 2);
  };
 
  return (
     <div>
       <p>Count: {count}</p>
       <button onClick={incrementByTwo}>Increment by 2</button>
     </div>
   );
 };

The count increases by 2 each time the button is clicked.

The count increases by 1 each time the button is clicked.

The count remains unchanged.

8. How can you optimize the rendering performance when using the useState hook in React?

Use memoization techniques like useMemo or useCallback

Use a class component instead of a functional component

Split the state into multiple smaller states

9. What is the expected behavior when clicking the ‘Increment Async’ button?

const QuizComponent = () => {
   const [count, setCount] = useState(0);
   const incrementAsync = () => {
     setTimeout(() => {
       setCount(count + 1);
     }, 1000);
   };
 
   return (
     <div>
       <p>Count: {count}</p>
       <button onClick={incrementAsync}>Increment Async</button>
     </div>
   );
 };

The count increases immediately after the button is clicked.

The count increases after a delay of 1 second.

The count does not change.

10. Which hook is used for managing complex state transitions and actions in React like redux?

useState

useReducer

useContext