React Js MCQ Questions with answers and solutions Page 7

Q. How can we prevent a component from re-rendering?

(A) Using useMemo only
(B) Using memo for functional components
(C) Avoid using props
(D) Using useEffect only

💬 Discuss

✅ Correct Answer: (B) Using memo for functional components

Explanation: memo can wrap functional components to prevent unnecessary re-renders.

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

Q. What is the default port for React development server?

(A) 3000
(B) 8080
(C) 5000
(D) 8000

💬 Discuss

✅ Correct Answer: (A) 3000

Explanation: React apps started with create-react-app run on port 3000 by default.

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

Q. Which of these is used to style React components?

(A) CSS
(B) Inline styles
(C) Styled-components
(D) All of the above

💬 Discuss

✅ Correct Answer: (D) All of the above

Explanation: All listed methods can be used to style React components.

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

Q. What will happen if a hook is used inside a conditional statement?

(A) It will work fine
(B) React will ignore it
(C) React will throw an error
(D) It will be skipped on first render

💬 Discuss

✅ Correct Answer: (C) React will throw an error

Explanation: Hooks must be called unconditionally at the top level of a function component.

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

Q. What is the key difference between props and state in React?

(A) Props are mutable, state is immutable
(B) Props are used for internal data, state for external
(C) Props are passed, state is managed internally
(D) No difference

💬 Discuss

✅ Correct Answer: (C) Props are passed, state is managed internally

Explanation: Props are passed from parent to child, state is managed within a component.

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

Q. Which hook should you use to manage complex state logic?

(A) useState
(B) useRef
(C) useEffect
(D) useReducer

💬 Discuss

✅ Correct Answer: (D) useReducer

Explanation: useReducer is better for handling complex state logic compared to useState.

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

Q. What is returned by the useState hook?

(A) Only the current state value
(B) A function to update the state
(C) An array with current state and setter function
(D) A single object

💬 Discuss

✅ Correct Answer: (C) An array with current state and setter function

Explanation: useState returns a pair: current state and a function to update it.

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

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

(A) Using props
(B) Using state
(C) Using callback functions
(D) Using refs

💬 Discuss

✅ Correct Answer: (C) Using callback functions

Explanation: A child can invoke a callback passed via props to send data to the parent.

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

Q. What is JSX?

(A) A templating engine
(B) A syntax extension for JavaScript
(C) A CSS preprocessor
(D) A database language

💬 Discuss

✅ Correct Answer: (B) A syntax extension for JavaScript

Explanation: JSX is a syntax extension that allows writing HTML-like code in JavaScript.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

Q. Which method is used to pass props to a component?

(A) this.props()
(B) props.push()
(C) Passing them as attributes
(D) props.assign()

💬 Discuss

✅ Correct Answer: (C) Passing them as attributes

Explanation: Props are passed to components like HTML attributes in JSX.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:15 pm in React Js

React Js MCQs with answers Page - 7

Q. How can we prevent a component from re-rendering?

Q. What is the default port for React development server?

Q. Which of these is used to style React components?

Q. What will happen if a hook is used inside a conditional statement?

Q. What is the key difference between props and state in React?

Q. Which hook should you use to manage complex state logic?

Q. What is returned by the useState hook?

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

Q. What is JSX?

Q. Which method is used to pass props to a component?

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