React Js MCQs with answers Page - 4

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.
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📊 React Js
Q. Which of the following is NOT a React hook?
  • (A) useContext
  • (B) useFetch
  • (C) useReducer
  • (D) useEffect
💬 Discuss
✅ Correct Answer: (B) useFetch

Explanation: useFetch is not a built-in hook in React, though it's commonly implemented by developers.

📊 React Js
Q. What is the purpose of useContext in React?
  • (A) To manage routing
  • (B) To fetch data
  • (C) To access context values
  • (D) To handle forms
💬 Discuss
✅ Correct Answer: (C) To access context values

Explanation: useContext allows functional components to access values from a React Context.

📊 React Js
Q. What is the default behavior of React when state changes?
  • (A) It re-renders only the changed component
  • (B) It re-renders the whole application
  • (C) It manually updates the DOM
  • (D) It blocks rendering
💬 Discuss
✅ Correct Answer: (A) It re-renders only the changed component

Explanation: React efficiently re-renders only the component whose state changed.

📊 React Js
Q. What is a controlled component in React?
  • (A) A component that controls another
  • (B) A component with its own state
  • (C) A form element controlled by React state
  • (D) A static component
💬 Discuss
✅ Correct Answer: (C) A form element controlled by React state

Explanation: Controlled components have form elements where the value is tied to state.

📊 React Js
Q. Which of the following is true about React keys in a list?
  • (A) They can be duplicated
  • (B) They should be the index of the array always
  • (C) They must be unique among siblings
  • (D) They are optional
💬 Discuss
✅ Correct Answer: (C) They must be unique among siblings

Explanation: React keys must be unique among sibling elements for optimal rendering.

📊 React Js
Q. What does JSX stand for?
  • (A) JavaScript Xtreme
  • (B) JavaScript XML
  • (C) Java Simple Extension
  • (D) Java Syntax Extension
💬 Discuss
✅ Correct Answer: (B) JavaScript XML

Explanation: JSX stands for JavaScript XML, allowing HTML-like syntax in JavaScript.

📊 React Js
Q. How do you pass a function as a prop in React?
  • (A) <Comp func='handleClick' />
  • (B) <Comp func={handleClick} />
  • (C) <Comp>handleClick</Comp>
  • (D) <Comp.handleClick />
💬 Discuss
✅ Correct Answer: (B) <Comp func={handleClick} />

Explanation: Functions are passed as props using curly braces in JSX.

📊 React Js
Q. When using useEffect with an empty dependency array, how often does it run?
  • (A) On every render
  • (B) Only on unmount
  • (C) Once after the initial render
  • (D) Every 5 seconds
💬 Discuss
✅ Correct Answer: (C) Once after the initial render

Explanation: An empty dependency array causes useEffect to run only once on mount.

📊 React Js
Q. What is React Router used for?
  • (A) Fetching data
  • (B) State management
  • (C) Client-side routing
  • (D) Form validation
💬 Discuss
✅ Correct Answer: (C) Client-side routing

Explanation: React Router handles navigation and routing in React single-page applications.

📊 React Js
Q. Which package is commonly used for form handling in React?
  • (A) formik
  • (B) redux
  • (C) react-dom
  • (D) axios
💬 Discuss
✅ Correct Answer: (A) formik

Explanation: Formik is a popular library for handling forms in React.

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