React Js MCQ Questions with answers and solutions Page 10

Q. What happens if you update state directly in React?

(A) React throws an error
(B) It updates the component correctly
(C) The component won’t re-render
(D) It updates all components

💬 Discuss

✅ Correct Answer: (C) The component won’t re-render

Explanation: React won't detect changes if state is mutated directly instead of using setState.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. Which hook is used to manage state in functional components?

(A) useEffect
(B) useContext
(C) useReducer
(D) useState

💬 Discuss

✅ Correct Answer: (D) useState

Explanation: `useState` is the primary hook used for state management in functional components.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. What does the second value returned by useState represent?

(A) The previous state
(B) The default value
(C) A function to update the state
(D) A backup value

💬 Discuss

✅ Correct Answer: (C) A function to update the state

Explanation: `useState` returns an array with the current state and a function to update it.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. What is the primary purpose of React Router?

(A) To handle HTTP requests
(B) To manage component lifecycle
(C) To enable routing in single-page applications
(D) To connect components with Redux

💬 Discuss

✅ Correct Answer: (C) To enable routing in single-page applications

Explanation: React Router allows dynamic routing in SPAs based on the URL.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. Which component in React Router is used to define a route?

(A) Router
(B) Route
(C) Link
(D) Switch

💬 Discuss

✅ Correct Answer: (B) Route

Explanation: `Route` defines the path and component to render for a given URL.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. What is React's virtual DOM?

(A) A copy of the real DOM that updates instantly
(B) An abstraction for server rendering
(C) A browser extension
(D) A CSS rendering engine

💬 Discuss

✅ Correct Answer: (A) A copy of the real DOM that updates instantly

Explanation: Virtual DOM is an in-memory representation of the real DOM used for efficient diffing.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. What is the role of the `key` prop in lists?

(A) To sort elements
(B) To style elements
(C) To uniquely identify elements
(D) To define props

💬 Discuss

✅ Correct Answer: (C) To uniquely identify elements

Explanation: Keys help React identify which items have changed or been removed.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. What is `useReducer` typically used for?

(A) For animation
(B) For complex state logic
(C) For routing
(D) For lazy loading

💬 Discuss

✅ Correct Answer: (B) For complex state logic

Explanation: `useReducer` is helpful for managing complex state transitions.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. Which React method is used to clean up resources in a component?

(A) componentCleanup
(B) useEffect return function
(C) useMemo
(D) componentDispose

💬 Discuss

✅ Correct Answer: (B) useEffect return function

Explanation: Returning a function from `useEffect` handles clean-up logic like unsubscribing or clearing timers.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

Q. Which of the following hooks is used to persist values across renders without causing re-renders?

(A) useState
(B) useEffect
(C) useMemo
(D) useRef

💬 Discuss

✅ Correct Answer: (D) useRef

Explanation: `useRef` persists values without triggering re-renders.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:16 pm in React Js

React Js MCQs with answers Page - 10

Q. What happens if you update state directly in React?

Q. Which hook is used to manage state in functional components?

Q. What does the second value returned by useState represent?

Q. What is the primary purpose of React Router?

Q. Which component in React Router is used to define a route?

Q. What is React's virtual DOM?

Q. What is the role of the `key` prop in lists?

Q. What is `useReducer` typically used for?

Q. Which React method is used to clean up resources in a component?

Q. Which of the following hooks is used to persist values across renders without causing re-renders?

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