React JS MCQs with answers Page - 22

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 is the main difference between props and state?

  • (A) Props are immutable, state is mutable
  • (B) Props are mutable, state is immutable
  • (C) Both are immutable
  • (D) Both are mutable

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Q. Which React hook lets you optimize expensive calculations by caching their results?

  • (A) useMemo
  • (B) useState
  • (C) useCallback
  • (D) useEffect

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Q. How do you update state in a class component?

  • (A) By calling this.setState()
  • (B) By assigning directly to this.state
  • (C) By calling setState() without this
  • (D) By using useState hook

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Q. What does the React.StrictMode component do?

  • (A) Helps find potential problems by running additional checks
  • (B) Styles components
  • (C) Makes components render faster
  • (D) Replaces Error Boundaries

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Q. How can you pass a function as a prop in React?

  • (A) Just pass the function reference in the props object
  • (B) Call the function and pass the return value
  • (C) Use eval() to bind the function
  • (D) Functions cannot be passed as props

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Q. What will happen if you update the state directly without using setState in a class component?

  • (A) The component will not re-render
  • (B) The component will re-render
  • (C) It will throw an error
  • (D) State will be reset

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Q. What is JSX in React?

  • (A) A syntax extension that looks like HTML and is used with React
  • (B) A JavaScript library for routing
  • (C) A CSS preprocessor
  • (D) A database query language

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Q. Which lifecycle method is invoked immediately after a component is mounted in React class components?

  • (A) componentDidMount
  • (B) componentWillMount
  • (C) render
  • (D) componentWillUnmount

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Q. What hook would you use to manage state in a functional component?

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

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Q. What is the purpose of the useReducer hook in React?

  • (A) To manage complex state logic with reducers
  • (B) To perform side effects
  • (C) To memoize functions
  • (D) To access context

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