React Interview Questions

Comprehensive collection of React interview questions and answers covering hooks, components, state management, and best practices.

What is React and Why is it Popular?

History of React: How it Evolved Over Time

Key Features and Benefits of React

What is JSX in React?

Element vs Component in React: Key Differences

How to Create Components in React (Class and Function)

When to Use Class Components vs Function Components

What are Pure Components in React?

What is State in React and How to Use It?

What are Props in React and Why are They Important?

State vs Props in React: Clear Comparison

HTML Events vs React Events: What's the Difference?

What are Synthetic Events in React?

How to Use Inline Conditional Expressions in React

What is the 'Key' Prop in React and Why it Matters

What is Virtual DOM and How it Works in React?

How Virtual DOM Improves Performance in React

Shadow DOM vs Virtual DOM: Explained

What is React Fiber and Why Was It Introduced?

Main Goals and Benefits of React Fiber

What are Controlled Components in React?

What are Uncontrolled Components in React?

createElement vs cloneElement: What's the Difference?

What is Lifting State Up in React?

Higher-Order Components (HOC) in React: What and Why

What is the 'children' Prop in React?

How to Write Comments in JSX (React)

What is Reconciliation in React?

Can Lazy Function in React Support Named Exports?

Why React Uses 'className' Instead of 'class'

What are Fragments in React and Why Use Them?

Fragments vs Container Divs in React

What are Portals in React and When to Use Them?

What are Stateless Components in React?

What are Stateful Components in React?

How to Validate Props in React Using PropTypes

Major Advantages of Using React

Limitations and Disadvantages of React

How to Do Static Type Checking in React

Purpose and Usage of react-dom Package

What is ReactDOMServer in React?

How to Use innerHTML Safely in React

How to Apply Styles in React (Inline, CSS Modules, Styled-Components)

Event Handling Differences Between React and HTML

Why Using Index as Key in React Lists Can Be Risky

How to Conditionally Render Components in React

Why You Should Be Careful When Spreading Props on DOM Elements

How to Memoize a React Component for Better Performance

How to Implement Server-Side Rendering (SSR) in React

How to Enable Production Mode in React Applications

Do Hooks replace Render Props and Higher-Order Components?

What is a Switching Component in React?

What are React Mixins and why are they not recommended?

What Pointer Events are supported in React?

Why should React Component Names start with Capital Letters?

What are Error Boundaries in React?

What is Internationalization (i18n) in React apps?

How do you implement localization in React applications?

Which libraries can be used for i18n in React?

Best practices for building multi-language support in React apps

What is React Router and why is it important?

How does React Router differ from traditional routing?

What are different types of Router components in React Router?

How to implement dynamic routing in React?

What are the differences between BrowserRouter and HashRouter?

Can browsers read JSX directly?

What is Babel and how does it work with JSX?

Can JSX tags have children elements?

How does JSX get transformed under the hood?

Is JSX mandatory for React development?

Why is testing important in React projects?

What are the popular libraries for testing React applications?

What is Jest and how does it work with React?

What is React Testing Library (RTL)?

What is shallow rendering in React testing?

What is snapshot testing in React?

What is Redux and why is it used with React?

What are the core principles of Redux?

How is Redux different from React's internal state management?

What are the main building blocks of Redux (Actions, Reducers, Store)?

What is Redux Thunk and why is it needed?

How does Redux Middleware work?

What is the role of the Provider component in Redux?

What are the differences between Redux Toolkit and plain Redux?

What are Hooks in React and why were they introduced?

Rules of Hooks – What are they?

Difference between useState and useReducer hooks

How does the useEffect hook work?

Best practices for using useEffect efficiently

What are custom Hooks and how to create them?

What is useMemo and why is it useful?

What is useCallback and when should it be used?

What is useRef and how is it different from useState?

How to use Context API with Hooks?

Common mistakes to avoid when using React Hooks

What is Context API in React and why is it used?

How to create and use a Context in React?

What problems does Context solve compared to prop drilling?

What are the limitations of the Context API?

How to optimize Context value updates to prevent unnecessary re-renders?

Difference between Context API and Redux

Why is performance optimization important in React apps?

What is React.memo and how does it work?

What is the difference between React.memo and useMemo?

How to prevent unnecessary re-renders in React?

How to optimize large lists in React?

What is virtualization and which libraries help with it?

How to use shouldComponentUpdate for performance optimization?

What is Code Splitting in React?

How does React.lazy work?

What is Suspense and how does it help with lazy loading?

How to implement dynamic imports in React?

What are the benefits and limitations of Code Splitting?

What is Concurrent Mode in React?

What are the goals of Concurrent Mode?

What features are enabled by Concurrent Mode?

How does Concurrent Mode affect rendering behavior?

What is the difference between blocking and concurrent rendering?

What is Suspense in React?

How does Suspense work with lazy components?

Can Suspense be used for data fetching?

What is the role of fallback prop in Suspense?

Best practices for using Suspense in production

What are Server Components in React?

How are Server Components different from traditional components?

What are the benefits of Server Components?

How to integrate Server Components into existing React apps?

Limitations and challenges with Server Components