React JS MCQs with answers Page - 11

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 does `React.StrictMode` do?

  • (A) Disables unused components
  • (B) Highlights potential problems in an application
  • (C) Automatically fixes bugs
  • (D) Prevents side effects

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Q. What is a controlled component?

  • (A) A component that controls its own rendering
  • (B) A component that manages its own state
  • (C) A component whose form input values are controlled by React
  • (D) A component that is reused

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Q. What is the purpose of `useMemo`?

  • (A) To fetch data
  • (B) To optimize performance by memoizing values
  • (C) To watch props
  • (D) To render UI elements

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Q. Which is true about props in React?

  • (A) Props are immutable
  • (B) Props can only be strings
  • (C) Props change during component lifetime
  • (D) Props are optional

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Q. What is the return type of a functional component?

  • (A) String
  • (B) HTML
  • (C) JSX
  • (D) Object

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Q. How does React achieve better performance?

  • (A) By using AJAX
  • (B) By caching the DOM
  • (C) By using the virtual DOM and efficient diffing
  • (D) By using CSS-in-JS

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Q. What happens if you try to render an array in JSX?

  • (A) It throws an error
  • (B) Only the first element renders
  • (C) All elements render correctly
  • (D) It ignores the array

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Q. What does `defaultValue` do in input elements?

  • (A) It sets a static initial value
  • (B) It changes the state
  • (C) It disables the input
  • (D) It binds the input to state

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Q. What does JSX stand for in React?

  • (A) JavaScript and XML
  • (B) Java Syntax Extension
  • (C) JavaScript XML Structure
  • (D) JavaScript eXtension

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Q. Which of the following is not a valid React hook?

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

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