React Js MCQs with answers Page - 6

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.
Share your questions by clicking Add Question

Q. What is the main purpose of useEffect in React?

  • (A) To update props
  • (B) To perform side effects
  • (C) To create components
  • (D) To render JSX
💬 Discuss
✅ Correct Answer: (B) To perform side effects
Explanation: useEffect is used to perform side effects such as data fetching or subscriptions.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. Which of the following will NOT cause a component to re-render?

  • (A) State change
  • (B) Prop change
  • (C) Context change
  • (D) Local variable change
💬 Discuss
✅ Correct Answer: (D) Local variable change
Explanation: Changing a local variable won't trigger a re-render in React.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. Which hook allows you to access the DOM element directly?

  • (A) useEffect
  • (B) useMemo
  • (C) useRef
  • (D) useState
💬 Discuss
✅ Correct Answer: (C) useRef
Explanation: useRef provides a way to access and persist a reference to a DOM element.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. Which lifecycle method is equivalent to useEffect with an empty dependency array?

  • (A) componentDidMount
  • (B) componentDidUpdate
  • (C) componentWillUnmount
  • (D) shouldComponentUpdate
💬 Discuss
✅ Correct Answer: (A) componentDidMount
Explanation: useEffect with an empty array runs only once, just like componentDidMount in class components.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. In JSX, how do you write a JavaScript expression?

  • (A) With double quotes
  • (B) With parentheses
  • (C) With square brackets
  • (D) With curly braces
💬 Discuss
✅ Correct Answer: (D) With curly braces
Explanation: JSX expressions are enclosed within curly braces.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. Which of these is not a valid React event?

  • (A) onClick
  • (B) onSubmit
  • (C) onHover
  • (D) onChange
💬 Discuss
✅ Correct Answer: (C) onHover
Explanation: React uses onMouseOver instead of onHover.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. What will happen if you modify state directly in React?

  • (A) Component re-renders correctly
  • (B) State change is ignored
  • (C) React throws an error
  • (D) Component may behave unexpectedly
💬 Discuss
✅ Correct Answer: (D) Component may behave unexpectedly
Explanation: Direct state mutation can lead to bugs and unpredictable behavior.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. What is the output of React.createElement?

  • (A) HTML element
  • (B) JSX code
  • (C) React element
  • (D) DOM node
💬 Discuss
✅ Correct Answer: (C) React element
Explanation: React.createElement returns a React element, not an actual DOM node.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. What does a React component return?

  • (A) String
  • (B) Object
  • (C) JSX
  • (D) HTML
💬 Discuss
✅ Correct Answer: (C) JSX
Explanation: React components return JSX, which is transpiled to React.createElement calls.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Q. Which command is used to start a React app in development mode?

  • (A) npm start
  • (B) npm build
  • (C) npm install
  • (D) npm test
💬 Discuss
✅ Correct Answer: (A) npm start
Explanation: npm start runs the app in development mode.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:14 pm in React Js

Programming Categories

📱 Download Our App

Learn MCQs on the go with our easy-to-use Android app

Get it on Google Play