Definition: HOCs are functions that take a component and return a new component, allowing for code reuse and logic abstraction.
Use Cases: Commonly used for cross-cutting concerns like authentication, logging, or data fetching.
Composition: HOCs can be composed together to enhance components with multiple functionalities.
Naming Convention: Typically named with a prefix with (e.g., withRouter, withAuth), indicating the enhancement provided.
Limitations: Can lead to “wrapper hell” if overused, complicating the component hierarchy and props passing.
2. Render Props
Definition: A technique where a component uses a function as a prop to dynamically render content, allowing for greater flexibility.
Data Sharing: Enables sharing code between components without HOCs, facilitating the separation of concerns.
Context Usage: Works well with the React Context API for passing down state and behavior to deeply nested components.
Performance Considerations: Requires careful management of component updates to avoid unnecessary re-renders.
Example Libraries: Libraries like React Router and Recharts utilize render props for component customization.
3. Error Boundary
Purpose: A component that catches JavaScript errors in its child component tree, preventing crashes and providing a fallback UI.
Lifecycle Methods: Implements componentDidCatch and getDerivedStateFromError to handle errors gracefully.
Granularity: Can be used at different levels in the component hierarchy for targeted error handling.
Fallback UI: Can display a user-friendly error message while logging the error for debugging purposes.
Limitations: Only catches errors in lifecycle methods, render methods, and constructors, not in event handlers.
4. React.lazy and Suspense
Dynamic Imports: React.lazy allows for dynamic loading of components using import(), reducing initial bundle size.
Suspense: Provides a fallback UI (e.g., a loading spinner) while waiting for the lazy-loaded component to load.
Code Splitting: Facilitates code splitting by breaking down the application into smaller chunks, improving performance.
Nested Suspense: Supports nested Suspense components for more granular loading states across different parts of the app.
SSR Compatibility: Requires additional handling for server-side rendering to ensure components are rendered correctly on the server.
5. Virtual DOM and Reconciliation
Virtual DOM: A lightweight representation of the real DOM that allows React to optimize updates and improve performance.
Diffing Algorithm: React uses a diffing algorithm to efficiently determine what has changed between renders and update the DOM accordingly.
Batch Updates: Grouping multiple state updates into a single render cycle minimizes reflows and repaints.
Key Prop: Properly using keys in lists helps React identify which items have changed, are added, or are removed.
Performance Impact: Efficient reconciliation leads to smoother UI transitions and faster render times, enhancing user experience.
6. React Portals
Definition: Portals provide a way to render children into a DOM node outside the parent component hierarchy.
Use Cases: Useful for modals, tooltips, and dropdowns where you want to break free from the overflow and positioning constraints of parent elements.
Event Bubbling: Events still bubble up to the parent component as if they were part of the normal React tree.
Maintain Context: Allows access to the context of the parent component, ensuring the correct data flow.
Implementation: Created using ReactDOM.createPortal(child, container) where container is a DOM node.
7. Memoization
Purpose: Optimizes performance by caching results of expensive function calls and returning the cached result when the same inputs occur again.
React.memo: A higher-order component that prevents unnecessary re-renders for functional components by performing a shallow comparison of props.
useMemo Hook: Used to memoize values in functional components, recalculating them only when dependencies change.
useCallback Hook: Similar to useMemo, but used for memoizing functions to prevent re-creation on every render.
Performance Considerations: While helpful, overuse of memoization can lead to increased complexity and may not always yield performance benefits.
8. SSR & SSG
SSR (Server-Side Rendering): Renders components on the server and sends the fully rendered page to the client, improving initial load times and SEO.
SSG (Static Site Generation): Pre-renders pages at build time, serving static HTML for fast load times and better caching.
Frameworks: Next.js is a popular framework that supports both SSR and SSG, simplifying the implementation process.
Data Fetching: Requires specific data-fetching strategies (e.g., getServerSideProps for SSR, getStaticProps for SSG) to ensure data availability.
User Experience: Enhances user experience by reducing the time to first paint and improving SEO by providing crawlers with fully rendered content.
9. Immutable Data Structures
Definition: Data structures that cannot be modified after their creation, promoting predictable state management.
Benefits: Simplifies debugging and reasoning about state changes, as previous states are preserved and can be easily compared.
Libraries: Libraries like Immutable.js and immer help manage immutable data efficiently.
Performance Optimization: Enhances performance in React as shallow comparisons of state can determine when a re-render is necessary.
Redux Compatibility: Works well with Redux, where state immutability is a key principle for managing application state.
10. Higher Order Reducers
Definition: Functions that take a reducer and return a new reducer, allowing for shared logic and abstraction in state management.
Use Cases: Commonly used for combining reducers, managing state slices, or adding common functionality like logging or error handling.
Composition: Enables a modular approach to building reducers, making code easier to maintain and test.
Middleware Integration: Can be used in conjunction with middleware for more complex state interactions.
Redux Toolkit: Supports the concept through createSlice, which simplifies reducer creation and combines logic.
11. Web Workers
Definition: Background scripts that run independently of the main thread, allowing for concurrent execution of JavaScript.
Use Cases: Ideal for performing heavy computations or data processing without blocking the UI thread, improving app responsiveness.
Communication: Uses the postMessage API for communication between the main thread and worker threads.
Integration: Can be integrated into React applications to offload expensive tasks like data parsing or image processing.
Limitations: Cannot access the DOM directly, requiring data to be passed back and forth between the main thread and workers.
12. Custom Renderers
Definition: Allows developers to create custom rendering logic for different platforms (e.g., React Native, VR).
Flexibility: Provides the ability to define how components render based on specific needs beyond the traditional DOM.
Implementation: Involves implementing the render method and defining how React reconciles updates.
Use Cases: Useful for building frameworks or libraries that need to extend React’s capabilities to new environments.
Performance Optimization: Can be tailored to optimize rendering performance for specific use cases, such as mobile or gaming.
13. Server Side Events (SSE)
Definition: A standard for pushing real-time updates from the server to the client over HTTP.
Implementation: Can be implemented using the EventSource API, allowing clients to listen for messages sent from the server.
Use Cases: Ideal for applications requiring live updates, such as chat applications, notifications, or live dashboards.
Compatibility: Supported by most modern browsers, but may require polyfills for older versions.
Comparison to WebSockets: While both provide real-time communication, SSE is unidirectional (server to client), making it simpler for certain use cases.
14. Optimization and Performance Tuning
Profiling Tools: Use React DevTools and browser profiling tools to identify performance bottlenecks and optimize rendering.
Memoization: Implement React.memo, useMemo, and useCallback to reduce unnecessary re-renders and optimize rendering performance.
Code Splitting: Leverage dynamic imports and React.lazy to split your code into smaller chunks, improving load times.
Avoid Inline Functions: Passing inline functions to components can trigger unnecessary re-renders; prefer using useCallback instead.
Batch Updates: Ensure state updates are batched to minimize renders and optimize UI responsiveness.