React Js MCQ Questions with answers and solutions Page 24

Q. Which of these hooks can replace both useState and useReducer in certain scenarios?

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

💬 Discuss

✅ Correct Answer: (A) useReducer

Explanation: useReducer can manage state and complex state transitions.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:32 pm in React Js

Q. What will happen if a React component returns false in its render method?

(A) It will render nothing
(B) It will throw an error
(C) It will render 'false' text
(D) It will crash the app

💬 Discuss

✅ Correct Answer: (A) It will render nothing

Explanation: Returning false or null means nothing is rendered.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:32 pm in React Js

Q. What does 'lifting state up' help to solve in React?

(A) Sharing state between sibling components
(B) Passing props to child components
(C) Styling components
(D) Handling events

💬 Discuss

✅ Correct Answer: (A) Sharing state between sibling components

Explanation: State is moved to the closest common ancestor to share it.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:32 pm in React Js

Q. What is the React DevTools used for?

(A) Inspecting React component hierarchy and state/props
(B) Building React components
(C) Managing backend APIs
(D) Styling React components

💬 Discuss

✅ Correct Answer: (A) Inspecting React component hierarchy and state/props

Explanation: React DevTools helps debug React apps.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:32 pm in React Js

Q. Which of the following is NOT true about React hooks?

(A) Hooks can only be called at the top level of a component
(B) Hooks can be called inside loops and conditions
(C) Hooks let you use state and other React features without classes
(D) Hooks follow the Rules of Hooks

💬 Discuss

✅ Correct Answer: (B) Hooks can be called inside loops and conditions

Explanation: Hooks must be called unconditionally at the top level.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:33 pm in React Js

Q. What is the main benefit of using useMemo hook?

(A) To memoize expensive calculations and avoid re-computations
(B) To manage side effects
(C) To access the DOM directly
(D) To fetch data asynchronously

💬 Discuss

✅ Correct Answer: (A) To memoize expensive calculations and avoid re-computations

Explanation: useMemo caches computed values between renders.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:33 pm in React Js

Q. What is the purpose of the React.StrictMode component?

(A) To highlight potential problems in an application during development
(B) To enable production optimizations
(C) To enforce CSS styling
(D) To disable lifecycle methods

💬 Discuss

✅ Correct Answer: (A) To highlight potential problems in an application during development

Explanation: StrictMode helps detect unsafe lifecycle methods, legacy API usage, and more.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:33 pm in React Js

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

(A) By passing a callback function from the parent to the child and invoking it with data
(B) By using props directly from the child
(C) By using the Context API only
(D) By modifying the parent's state directly

💬 Discuss

✅ Correct Answer: (A) By passing a callback function from the parent to the child and invoking it with data

Explanation: Data flows down via props; child can send data up via callbacks.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:33 pm in React Js

Q. What is the purpose of the useRef hook?

(A) To access and persist mutable values without causing re-renders
(B) To manage component state
(C) To trigger side effects
(D) To memoize functions

💬 Discuss

✅ Correct Answer: (A) To access and persist mutable values without causing re-renders

Explanation: useRef returns a mutable ref object that persists across renders.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:33 pm in React Js

Q. Which method in React class components can be used to update the state?

(A) this.setState()
(B) this.updateState()
(C) this.modifyState()
(D) this.changeState()

💬 Discuss

✅ Correct Answer: (A) this.setState()

Explanation: setState() schedules an update to a component's state.

Published by Mr. Dubey ⭐ 111.54K Points at 08-Jun-2025 03:33 pm in React Js

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