If you are preparing for a React interview, this blog post is the right place to start. Here, I’ve compiled 100+ React interview questions with answers, divided into three sections – Freshers, Intermediate, and Experienced.

Whether you are just beginning your career, preparing for React.js placements, or looking to switch jobs as an experienced React developer, these questions will help you strengthen your concepts and boost your confidence.

Each section covers the most commonly asked React interview questions and answers that companies expect you to know. From fundamental React basics to advanced concepts like hooks, context API, performance optimization, and state management, this guide is designed to help you crack interviews at all levels.

No matter if you are a fresher starting out or a professional with years of experience, you can use this React interview preparation guide to ace your next React.js interview and grow in your professional career.

Before preparing moderate-level React questions Read : React Important Concepts For Interview

Top 30+ Moderate-Level React Interview Questions and Answers (2025 Guide)

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1. What is conditional rendering in React?

Conditional rendering means selectively displaying components or UI elements based on specific conditions, such as authentication status or data loading. This is typically achieved using JavaScript operators like ternary (? :) or logical (&&).
Example:

jsx{isLoggedIn ? <UserDashboard /> : <LoginPrompt />}

Concept: Conditional Rendering.

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2. What is React Router and why use it?

React Router lets applications navigate between different views without page reloads, enabling Single Page Application (SPA) behavior. It synchronizes UI components with the current route, helping create dynamic web apps where URLs map to components.
Concept: Routing.

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3. Explain the main components of React Router.

• BrowserRouter: Wraps the app and stores route history.
• Route: Defines component-to-path mapping.
• Switch: Ensures only the first matched route renders.
• Link: Creates navigation links between routes.
  These pieces work together for seamless navigation.
  Concept: Routing Structure.

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4. What is “lifting state up” and when should you use it?

Lifting state up means moving shared state from child components to a common parent. This technique facilitates communication between sibling components, especially when actions in one component affect another, such as form steps or dynamic filter lists.
Concept: State Management.

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5. How do you avoid ‘this’ binding in React?

To handle event binding efficiently:

• Use arrow functions for methods (automatically bind).
• Declare arrow functions directly in render or as class properties.
• Favor functional components and Hooks, where ‘this’ is not needed.
  This approach improves performance and code readability.
  Concept: Event Binding.

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6. What are different types of React Hooks?

• Basic Hooks: useState, useEffect
• Additional Hooks: useContext, useReducer, useCallback, useMemo, useRef
• Custom Hooks: User-defined for extracting reusable logic
  Hooks enable powerful state and side-effect management inside functional components.
  Concept: React Hooks.

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7. Describe lifecycle methods of a React class component during the update phase.

• shouldComponentUpdate: Decides if re-rendering is necessary.
• render: Outputs JSX.
• getSnapshotBeforeUpdate: Captures DOM info before update.
• componentDidUpdate: Runs after component updates, suitable for side effects like API calls.
  Mastering these methods helps manage side effects and optimize performance.
  Concept: Lifecycle Methods.

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8. What are Higher-Order Components (HOCs) in React?

HOCs are functions that wrap a component to add new features (like authentication or data fetching). They support code reuse, prop manipulation, conditional rendering, and logic sharing across multiple components.
Concept: HOC.

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9. What is Context API and when is it useful?

The Context API solves “prop drilling” by letting components share data directly, bypassing intermediate layers. It is ideal for global themes, authentication state, or language settings, improving application scalability.
Concept: Context API.

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10. How do you optimize React app performance?

• Memoize components with React.memo and values with useMemo
• Split code using dynamic imports (React.lazy)
• Minimize unnecessary renders and use key props for lists
• Consider server-side rendering and caching for larger applications
  These steps keep React apps fast and responsive.
  Concept: Performance Optimization.

11. Explain the issue with using index as a key in React lists.
    Using the index as a key can cause incorrect rendering when list items’ order changes, leading to performance issues and unexpected UI behavior. Use unique, stable IDs instead.
    Concept: List Rendering
12. How is state batching handled in React?
    React batches multiple setState calls for performance, updating the state asynchronously. This prevents unnecessary re-renders and improves efficiency.
    Concept: State Management
13. Describe controlled vs uncontrolled components.
    Controlled components manage form inputs via React state for predictable behavior. Uncontrolled components rely on the DOM to maintain state, typically accessed via refs.
    Concept: Forms
14. What is reconciliation?
    Reconciliation is how React efficiently updates the DOM by comparing the virtual DOM to the actual DOM and updating only the changed elements.
    Concept: Virtual DOM
15. How do you implement error boundaries?
    An error boundary is a class component implementing componentDidCatch and getDerivedStateFromError to catch errors in child components and display fallback UI.
    Concept: Error Handling
16. What are pure components?
    Pure components automatically perform shallow comparison of props and state, preventing unnecessary re-renders when data hasn’t changed.
    Concept: Optimization
17. What is React Portals?
    Portals allow rendering components outside the main DOM hierarchy, useful for modals and overlays that need to break out of parent container limitations.
    Concept: Portals
18. Why use useCallback and useMemo?
    useCallback memoizes functions and useMemo memoizes computed values to prevent unnecessary recalculations and re-renders, optimizing performance.
    Concept: Performance Optimization
19. How does lazy loading work in React?
    Lazy loading uses React.lazy and Suspense to load components only when needed, improving initial load time and reducing bundle size.
    Concept: Code Splitting
20. How do you efficiently fetch data in React?
    Use useEffect for side effects, manage loading states, clean up subscriptions, and leverage caching or server-side rendering for large-scale data needs.
    Concept: Data Fetching
21. What are render props?
    Render props pass a function as a prop to a component, allowing dynamic rendering and reusable logic between multiple components.
    Concept: Component Patterns
22. Explain useReducer hook.
    useReducer manages complex component state using a reducer function and initial state, similar to Redux but scoped to a component.
    Concept: Hooks
23. What is the Context API, and when is it used?
    Context API allows sharing global values like theme or user info across components without prop drilling, ideal for app-wide state.
    Concept: State Management
24. What are refs in React?
    Refs give direct access to DOM nodes or React elements, commonly used in forms, animations, or third-party integrations.
    Concept: Ref Handling
25. How do you optimize list rendering in React?
    Use unique keys, memoize list items, and for large data sets, use libraries like react-window for virtualization to render only visible rows.
    Concept: List Optimization
26. What is a custom hook?
    A custom hook is a reusable function leveraging built-in hooks for common logic across multiple components, promoting code DRYness and modularity.
    Concept: Hooks
27. How do you debounce an input field in React?
    Implement debouncing using useEffect with setTimeout or external libraries to limit how frequently a handler function executes as the user types.
    Concept: Optimization
28. What is prop drilling and how can you avoid it?
    Prop drilling is passing data through many layers of components; avoid it using Context API or state management libraries like Redux.
    Concept: State Management
29. Why use StrictMode in React?
    React.StrictMode helps identify potential problems during development, such as deprecated code or unsafe lifecycle methods.
    Concept: Development Tools
30. What is the purpose of key prop in React lists?
    Keys help React identify which items in a list have changed, been added, or removed, optimizing list re-rendering and maintaining UI consistency.
    Concept: List Rendering
31. How do you handle authentication in React?
    Use protected routes, manage authentication state with Context or Redux, store tokens securely, and validate on mount or render.
    Concept: Authentication
32. What is Server-Side Rendering (SSR) in React?
    SSR renders React components on the server and sends HTML to the browser, improving initial load speed and SEO; frameworks like Next.js enable SSR.
    Concept: Rendering
33. What are the three phases of React component lifecycle?
    Mounting (initialization), Updating (prop/state changes), Unmounting (removal from DOM), each with specific lifecycle methods.
    Concept: Lifecycle
34. How does React handle forms?
    React tracks form inputs via state, validates on change or submit, and can use form libraries like Formik for advanced use cases.
    Concept: Forms
35. What is an event pool in React?
    React uses SyntheticEvent pooling to reuse event objects for efficiency; calling event.persist() allows asynchronous usage.
    Concept: Event Handling
36. How do you pass functions as props in React?
    Pass a function reference from parent to child, enabling the child to trigger logic in the parent, facilitating inter-component communication.
    Concept: Props
37. How do you manage global state in React?
    Global state is managed with Context API, Redux, or MobX, depending on the size and complexity of your application.
    Concept: State Management
38. How does React handle keys for lists and what happens if omitted?
    Keys allow React to manage list item changes efficiently; omitting them causes re-render issues and potential UI bugs.
    Concept: List Rendering
39. How do you style React components?
    Use CSS, CSS Modules, styled-components, inline styles, or preprocessors for various levels of component-specific or global styling.
    Concept: Styling
40. How do you test React components?
    Use Jest and React Testing Library for unit and integration tests, performing assertions on component behavior and UI changes.
    Concept: Testing

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• React Interview Questions and Answers – Complete Preparation Guide : Freshers Level