React's Context API simplifies global state management, eliminating prop drilling. It creates a shared data store accessible to all components. Context Provider wraps the app, while useContext hook allows components to access and update shared state.

Custom hooks in React revolutionize code reuse and logic sharing. They simplify component logic extraction, enhance modularity, and improve code cleanliness. Custom hooks are versatile, reusable, and can handle various functionalities like data fetching, state management, and API abstractions.

React portals enable rendering components outside the main React tree, ideal for modals and tooltips. They maintain component logic while allowing flexible DOM placement, improving accessibility and event handling.

React Suspense enhances app performance through code-splitting and lazy loading. It allows smooth rendering of components while waiting for data or code, improving user experience and initial load times.

React error boundaries gracefully handle UI crashes, displaying fallback content. They catch errors in child components, improving debugging and user experience. Implement with class components using lifecycle methods.

React.memo optimizes performance by memoizing functional components, preventing unnecessary re-renders. It's effective for frequently-rendered components with stable props, but should be used judiciously alongside other optimization techniques.

React's useCallback and useMemo optimize rendering by memoizing functions and values. They prevent unnecessary re-renders and recalculations, improving performance in complex applications. Use judiciously, measure impact, and balance optimization with code clarity.

Immutability: creating new data copies instead of modifying existing ones. Benefits include predictability, easier debugging, and undo functionality. Libraries like Immutable.js and Immer simplify implementation. Balancing performance with immutability's advantages is crucial.

Compound components: flexible UI building blocks. Break complex components into smaller, focused parts. Intuitive APIs, reusable code, and easier state management. Enhances accessibility and testing. Powerful pattern for maintainable UIs.

Prop drilling in React can lead to messy code. Use Context API, component composition, state management libraries, or custom hooks to avoid passing data through unnecessary components, improving maintainability and efficiency.

useReducer simplifies complex state management in React. It uses a reducer function to handle state transitions based on actions, organizing logic and making code more maintainable for intricate state scenarios.

React Server Components blend server-side rendering with client-side interactivity, offering improved performance, reduced bundle size, and direct server resource access. They coexist with client components, allowing developers to optimize their React applications effectively.

React Testing Library tests components like users interact, focusing on behavior over implementation. It encourages accessible, robust tests by simulating user actions and checking outputs, leading to more maintainable and user-centric code.

Snapshot testing captures UI state, comparing future versions to detect changes. It's efficient for maintaining consistency, catching unintended modifications, and aiding collaboration in development teams.

React with TypeScript enhances development by adding static typing, catching errors early, and improving code robustness. It enables better IDE support, safer prop handling, and smoother refactoring, making complex React applications more manageable and reliable.

Bundle size optimization in React: code-splitting, lazy loading, and tree shaking. Break into chunks, load on demand, eliminate dead code. Use CDNs, specific imports, compression. Analyze with tools. Ongoing process for better performance.

React Profiler API identifies performance bottlenecks in React apps. It measures render times, detects unnecessary re-renders, and helps optimize components. Use tools like memoization, lazy loading, and effective state management for smoother user experiences.

Next.js enables server-side rendering, boosting speed and SEO. It simplifies React development with built-in features like automatic code splitting, image optimization, and API routes, enhancing performance and user experience.

Next.js SSG pre-builds pages, serving them instantly. Perfect for static content, it boosts speed and SEO. Combine with ISR for fresher content and client-side fetching for dynamic data.

React authentication: JWT tokens, protected routes, login forms. Secure API requests with interceptors. Implement token refresh, state management, error handling. Consider password resets, role-based access, and multi-factor authentication for enhanced security.