React JS MCQs with answers Page - 12

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. Which attribute is used in React to give CSS classes?

  • (A) class
  • (B) className
  • (C) css
  • (D) styleName

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Q. What is the main advantage of using keys in React lists?

  • (A) Faster search
  • (B) Easy sorting
  • (C) Helps React identify which items have changed
  • (D) Avoids duplicate rendering

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Q. Which method is used to change the state in a React class component?

  • (A) this.setChange()
  • (B) this.changeState()
  • (C) this.setState()
  • (D) this.updateState()

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Q. How many elements can a React component return?

  • (A) Only one element
  • (B) Only two elements
  • (C) Multiple elements using an array or fragment
  • (D) None

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Q. Which of the following is used for performance optimization in React?

  • (A) React.delay()
  • (B) React.cache()
  • (C) React.memo()
  • (D) React.optimize()

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Q. How do you pass data from parent to child component in React?

  • (A) Using setState
  • (B) Using props
  • (C) Using refs
  • (D) Using context

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Q. What will `useEffect(() => {}, [])` do?

  • (A) Run after every render
  • (B) Run only once after the initial render
  • (C) Never run
  • (D) Run before every render

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Q. Which hook is best for accessing DOM elements directly?

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

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Q. What is a React fragment?

  • (A) A single root element
  • (B) A placeholder for props
  • (C) A tool for debugging
  • (D) A way to group elements without extra nodes

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Q. Which React component lifecycle method is called before rendering?

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

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