Hiring the right talent is crucial for building scalable, high-performance web applications. For enterprise companies, startups, and seed-funded businesses investing in software development services, React is often at the heart of modern front-end development.
Whether you’re a hiring manager preparing a React technical interview or a developer gearing up for your next big opportunity, these 25 React coding interview questions with solutions will help you evaluate skills or prepare effectively.
This guide covers React interview questions and answers ranging from fundamental concepts to advanced features—ideal for both interviewers and candidates.
1. What is React?
React is a JavaScript library developed by Facebook for building dynamic user interfaces, especially single-page applications. It uses a component-based architecture and a virtual DOM for efficient updates.
2. What are Components in React?
Components are reusable building blocks of UI.
- Function components – Preferred in modern React development.
- Class components – Older approach, still supported.
3. What is JSX?
JSX (JavaScript XML) allows you to write HTML-like syntax in JavaScript.
jsx
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const element = <h1>Hello, World!</h1>;
4. What is the Virtual DOM?
A lightweight representation of the real DOM that React uses to optimize rendering by updating only what changes.
5. What are Props in React?
Props (properties) are read-only inputs that pass data from parent to child components.
6. What is State in React?
A built-in object to store mutable data within a component. When state changes, the UI re-renders.
jsx
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const [count, setCount] = useState(0);
7. What are Hooks in React?
Hooks allow you to use state and lifecycle features in functional components. Examples:
- useState
- useEffect
- useContext
8. What is useEffect()?
Executes side effects like API calls, subscriptions, and timers.
jsx
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useEffect(() => {
fetchData();
}, []);
9. What is Conditional Rendering?
Displaying UI elements based on specific conditions using if, ternary (? :), or logical AND (&&) operators.
10. Controlled vs. Uncontrolled Components
- Controlled: Managed by React state.
- Uncontrolled: Managed by DOM refs.
11. What is Lifting State Up?
Moving state to a common ancestor to share data between sibling components.
12. What is Context in React?
A way to share global data without passing props manually through each level.
jsx
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const MyContext = React.createContext();
13. What is a Key in React?
A unique identifier for list items, helping React efficiently manage updates.
14. What is Prop Drilling and How to Avoid It?
Prop drilling happens when props are passed through many layers. Avoid it using:
- Context API
- State management libraries like Redux or Zustand
15. How Do You Handle Events in React?
React uses camelCase syntax for event handlers.
jsx
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<button onClick={handleClick}>Click Me</button>
16. What is React.memo()?
A higher-order component that prevents unnecessary re-renders if props don’t change.
17. useMemo vs. useCallback
- useMemo: Caches computed values.
- useCallback: Caches function references.
18. What is Lazy Loading in React?
Delays component loading until it’s needed using React.lazy() and Suspense.
jsx
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const LazyComp = React.lazy(() => import(‘./LazyComp’));
19. What is Reconciliation?
React’s process of comparing the new and old virtual DOM to apply only necessary changes.
20. React Server Components
Render components on the server and send HTML to the client, reducing JavaScript bundle size.
21. What is the React Compiler (React Forget)?
A build-time optimization tool that auto-memoizes components.
22. What are React Actions in React 19?
Server-side functions tied to UI events, declared with “use server”.
23. How Does useTransition() Improve Performance?
Marks updates as low-priority, keeping critical UI updates responsive.
24. What is Hydration in React?
Attaches event listeners to server-rendered HTML so it becomes interactive.
25. How to Optimize Performance in Large React Apps
- Use React Compiler
- Code splitting (React.lazy)
- Memoization (useMemo, React.memo)
- Virtualization (react-window)
- Throttle/debounce heavy computations
- Avoid unnecessary re-renders
Final Thoughts
Whether you’re preparing for a React developer interview or conducting one, these React coding interview questions with solutions ensure that both candidates and hiring managers are well-prepared.
If you need a skilled React development team to bring your product vision to life, EmbarkingOnVoyage Digital Solutions delivers high-performance, scalable applications tailored for enterprise companies, startups, and seed-funded businesses.
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