React Js MCQs with answers Page - 8

Dear candidates you will find MCQ questions of React Js here. Learn these questions and prepare yourself for coming examinations and interviews. You can check the right answer of any question by clicking on any option or by clicking view answer button.
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Q. What does lifting state up mean in React?

  • (A) Creating global state
  • (B) Passing state to Redux
  • (C) Moving state to a common ancestor component
  • (D) Using local storage
💬 Discuss
✅ Correct Answer: (C) Moving state to a common ancestor component
Explanation: Lifting state up means moving state to the nearest common ancestor to share it across components.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. What is a pure component?

  • (A) A component that uses only functional logic
  • (B) A component that does not re-render unnecessarily
  • (C) A component without any state
  • (D) A component with only props
💬 Discuss
✅ Correct Answer: (B) A component that does not re-render unnecessarily
Explanation: Pure components implement shouldComponentUpdate with shallow prop and state comparison.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. How many root elements can a React component return?

  • (A) Multiple
  • (B) Only one
  • (C) Zero
  • (D) As many as you want
💬 Discuss
✅ Correct Answer: (B) Only one
Explanation: React components must return a single root element, which can be a div or React.Fragment.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. Which hook replaces lifecycle methods in functional components?

  • (A) useEffect
  • (B) useCallback
  • (C) useMemo
  • (D) useReducer
💬 Discuss
✅ Correct Answer: (A) useEffect
Explanation: useEffect allows performing side effects and replaces componentDidMount, componentDidUpdate, and componentWillUnmount.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. What happens if you use the same key for elements in a list?

  • (A) React warns but works fine
  • (B) Only the first element renders
  • (C) Unexpected behavior may occur
  • (D) Nothing happens
💬 Discuss
✅ Correct Answer: (C) Unexpected behavior may occur
Explanation: Using non-unique keys can cause rendering issues in lists.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. Which hook helps you prevent unnecessary function recreation?

  • (A) useRef
  • (B) useCallback
  • (C) useReducer
  • (D) useMemo
💬 Discuss
✅ Correct Answer: (B) useCallback
Explanation: useCallback memoizes a function so it's not recreated on every render.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. What is the main benefit of using React?

  • (A) Server-side rendering
  • (B) Fast and efficient UI updates
  • (C) Security
  • (D) Database support
💬 Discuss
✅ Correct Answer: (B) Fast and efficient UI updates
Explanation: React’s virtual DOM makes UI updates efficient.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. What is the role of a key in a list of elements?

  • (A) To apply styles
  • (B) To identify which items changed
  • (C) To improve performance
  • (D) To bind events
💬 Discuss
✅ Correct Answer: (B) To identify which items changed
Explanation: Keys help React identify which items have changed, are added, or removed.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. What happens when setState is called?

  • (A) The component is replaced
  • (B) The component is re-rendered
  • (C) Nothing happens
  • (D) The whole DOM is rebuilt
💬 Discuss
✅ Correct Answer: (B) The component is re-rendered
Explanation: Calling setState triggers a re-render with the updated state.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. How do you handle forms in React?

  • (A) Using traditional HTML methods
  • (B) Using refs only
  • (C) Using controlled components
  • (D) Only with third-party libraries
💬 Discuss
✅ Correct Answer: (C) Using controlled components
Explanation: In React, form elements are often controlled using state.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

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