Here you go — a polished list of 30 Most Asked React JS Interview Questions for Freshers (2026), perfect for resumes, interview prep, and technical rounds.
1. What is React?
A JavaScript library for building fast, interactive user interfaces using a component‑based architecture.
2. What are components in React?
Reusable UI building blocks that return JSX. Two types: Functional and Class components.
3. What is JSX?
A JavaScript syntax extension that lets you write HTML-like code inside JavaScript.
4. What is the Virtual DOM?
A lightweight copy of the real DOM that React uses to update UI efficiently.
5. What are props in React?
Read‑only inputs passed from parent to child components.
6. What is state in React?
A component’s data that can change over time and triggers a re-render when updated.
7. What is the difference between state and props?
Props are external & immutable; state is internal & mutable.
8. What is useState?
A React Hook that allows functional components to manage state.
9. What is useEffect?
A Hook used for side effects like API calls, timers, event listeners, etc.
10. What is conditional rendering?
Showing or hiding UI elements based on conditions.
11. What are keys in React?
Unique identifiers used to track changes in lists and improve rendering.
12. What is React Router?
A library used for navigation between pages in React apps.
13. What is a controlled component?
A form element whose value is controlled by React state.
14. What is the difference between class and functional components?
Functional components use Hooks; classes use lifecycle methods and this.
15. What are React Hooks?
Functions that give functional components features like state and lifecycle.
16. Can Hooks be used inside loops or conditions?
No. Hooks must be used at the top level of a component.
17. What is the useRef hook?
Used to access or store mutable values without triggering re-renders.
18. What is context in React?
A way to share data across components without passing props manually.
19. What is Redux?
A predictable state container for managing complex application state.
20. What is the purpose of reducers in Redux?
Reducers specify how the app’s state changes in response to actions.
21. What are fragments in React?
A wrapper for grouping elements without adding extra DOM nodes.
22. What is memoization in React?
Optimization technique using React.memo, useMemo, useCallback to avoid unnecessary re-renders.
23. What is reconciliation?
React’s process of updating the DOM by comparing the Virtual DOM and real DOM.
24. What are lifecycle methods?
Methods in class components like componentDidMount, componentDidUpdate, componentWillUnmount.
25. What is an event in React?
Actions triggered by user interaction like clicks, keypresses.
26. How do you handle forms in React?
Using controlled components with state, or libraries like Formik / React Hook Form.
27. What is lifting state up?
Moving state to a common parent to share data between components.
28. What is React Strict Mode?
A tool for highlighting potential problems during development.
29. What is a higher‑order component (HOC)?
A function that takes a component and returns a new enhanced component.
30. How do you make an API call in React?
Using fetch(), axios, or with useEffect to perform the call after component load.
