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ReactJS continues to be a dominant library in the world of front-end development. Whether you’re a budding developer or an experienced professional, preparing for ReactJS interview questions is crucial to showcase your expertise and stay competitive in 2025.

This comprehensive guide delves into the most commonly asked ReactJS interview questions, providing insightful answers and tips to help you excel in your next interview.

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ReactJS Interview Questions and Answers

1. What is ReactJS?

ReactJS is a JavaScript library developed by Facebook for building user interfaces, especially for single-page applications. It allows developers to create reusable UI components and manage the state of complex applications efficiently.GitHub

2. What are the key features of ReactJS?

• JSX: A syntax extension that allows writing HTML within JavaScript.
• Components: Building blocks of a React application.
• Virtual DOM: Enhances performance by minimizing direct DOM manipulations.
• One-way Data Binding: Ensures a unidirectional data flow.
• Hooks: Allow using state and other React features in functional components.Medium+2Simplilearn.com+2GeeksforGeeks+2Medium+3GeeksforGeeks+3GitHub+3Medium

3. What is JSX?

JSX stands for JavaScript XML. It allows developers to write HTML-like syntax within JavaScript, making the code more readable and easier to write. Browsers cannot read JSX directly; it needs to be transpiled using tools like Babel.Simplilearn.com+2Medium+2GitHub+2Simplilearn.com+1Turing+1

4. Differentiate between state and props in React.

• State: Managed within the component and can change over time.
• Props: Passed to the component from its parent and are read-only.Turing+1Medium+1

5. What is the Virtual DOM?

The Virtual DOM is a lightweight copy of the real DOM. When changes occur, React updates the Virtual DOM first, compares it with the previous version, and then updates the real DOM efficiently.DEV Community+3Simplilearn.com+3GeeksforGeeks+3Medium+1GitHub+1

6. What are React Hooks?

Hooks are functions that let you use state and other React features in functional components. Common hooks include useState, useEffect, useContext, and useRef.Medium

7. Explain the use of useState hook.

The useState hook allows you to add state to functional components. It returns an array with the current state value and a function to update it.

const [count, setCount] = useState(0);

8. What is the purpose of keys in React?

Keys help React identify which items have changed, are added, or are removed. They should be unique and are primarily used in lists to optimize rendering performance.Simplilearn.com+6DEV Community+6GreatFrontEnd+6

9. Differentiate between controlled and uncontrolled components.

• Controlled Components: Form data is handled by React through state.
• Uncontrolled Components: Form data is handled by the DOM itself.DEV Community+1Turing+1

10. What are higher-order components (HOC)?

HOCs are functions that take a component and return a new component. They are used for reusing component logic.Reddit

11. What is the difference between useEffect and useLayoutEffect?

• useEffect: Runs after the render is committed to the screen.
• useLayoutEffect: Runs synchronously after all DOM mutations.GreatFrontEnd

12. What is the Context API?

The Context API allows for sharing state across the entire app (or part of it) without having to pass props down manually at every level.

13. What are React Fragments?

React Fragments let you group multiple elements without adding extra nodes to the DOM.GreatFrontEnd

<>
  <Child1 />
  <Child2 />
</>

14. What is the purpose of useMemo and useCallback?

• useMemo: Memoizes the result of a computation.
• useCallback: Memoizes the function itself.

15. What is the difference between React.createElement and JSX?

React.createElement is a method to create React elements without JSX. JSX is a syntactic sugar over React.createElement.

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Benefits of Preparing for ReactJS Interview Questions

1. Enhanced Confidence: Being well-prepared boosts your self-assurance during interviews.
2. Demonstrated Expertise: Showcases your in-depth knowledge of ReactJS.
3. Competitive Edge: Sets you apart from other candidates.
4. Better Communication: Enables you to articulate your thoughts clearly.
5. Increased Success Rate: Higher chances of landing your desired role.GeeksforGeeks+3GreatFrontEnd+3GitHub+3

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FAQ Section

Q1: What is the latest version of ReactJS as of 2025?
A: The latest stable version of ReactJS is v19.1.0, released on March 28, 2025.GeeksforGeeks

Q2: Can web browsers read JSX directly?
A: No, browsers cannot read JSX directly. It needs to be transpiled into regular JavaScript using tools like Babel.Turing+2Simplilearn.com+2Medium+2

Q3: What are custom hooks in React?
A: Custom hooks are functions that start with “use” and allow you to extract and reuse stateful logic across multiple components.GeeksforGeeks