React JS MCQs with answers Page - 10

Here, you will find a collection of MCQ questions on React JS. Go through these questions to enhance your preparation for upcoming examinations and interviews.

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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

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

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

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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

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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

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

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

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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

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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

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Q. What is `useReducer` typically used for?

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

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

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

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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

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