Here's a 1000-word markdown article focused purely on the content about improving frontend application performance (without titles or questions):
1. **Code Splitting**: Break your application into smaller chunks that can be loaded on demand. Use dynamic imports to load components only when needed. This reduces the initial bundle size and speeds up the first meaningful paint.
2. **Tree Shaking**: Eliminate dead code from your production bundles. Modern bundlers like Webpack and Rollup can automatically remove unused exports when configured properly. Always check your final bundle for unused code.
3. **Lazy Loading**: Implement lazy loading for images, components, and routes. For images, use the `loading="lazy"` attribute. For components, leverage React.lazy() or similar framework-specific lazy loading mechanisms.
4. **Optimize Images**: Compress and properly size images before serving them. Use modern formats like WebP or AVIF when possible. Implement responsive images with srcset to serve appropriately sized images based on device capabilities.
5. **Minification and Compression**: Minify CSS, JavaScript, and HTML files. Enable gzip or brotli compression on your server to reduce transfer sizes significantly. Most modern hosting providers support this out of the box.
6. **Caching Strategies**: Implement proper cache headers (Cache-Control, ETag) for static assets. Use service workers for advanced caching strategies in PWAs. Consider CDN caching for global applications.
7. **Critical CSS**: Extract and inline critical CSS needed for the initial render. Defer non-critical styles to load after the page becomes interactive. Tools like Critical can help automate this process.
8. **Reduce JavaScript Payload**: Analyze your bundle with tools like Webpack Bundle Analyzer. Remove large dependencies where possible, or find lighter alternatives. Consider code-splitting third-party libraries.
9. **Optimize Rendering Performance**: Avoid forced synchronous layouts and complex CSS selectors. Use will-change for elements you know will animate. Debounce or throttle scroll and resize event handlers.
10. **Virtualize Long Lists**: For large datasets, implement windowing or virtualization to only render visible items. Libraries like react-window or vue-virtual-scroller can help maintain performance with thousands of items.
11. **Web Workers**: Offload CPU-intensive tasks to web workers to prevent main thread blocking. This is especially useful for data processing, image manipulation, or complex calculations.
12. **Preload Important Resources**: Use `<link rel="preload">` for critical resources like fonts, hero images, or above-the-fold content. This tells the browser to prioritize these downloads.
13. **Optimize Font Loading**: Use font-display: swap to prevent FOIT (Flash of Invisible Text). Consider subsetting fonts or using system fonts when possible. Preload font files that are critical for initial render.
14. **Reduce DOM Size**: Keep your DOM tree shallow and small. Complex DOM structures slow down layout, style calculation, and paint operations. Avoid deeply nested component hierarchies.
15. **Avoid Layout Thrashing**: Batch DOM reads and writes together to prevent the browser from recalculating layout multiple times. Use libraries like FastDOM if needed to manage this automatically.
16. **Optimize Animations**: Use CSS transforms and opacity for animations instead of properties that trigger layout or paint. Stick to the compositor thread with properties that can be hardware-accelerated.
17. **Server-Side Rendering (SSR)**: For content-heavy sites, consider SSR to improve perceived performance. Hydrate carefully to avoid double-rendering penalties. Progressive hydration can help.
18. **Static Site Generation**: For content that doesn't change frequently, pre-render pages at build time. This eliminates the need for client-side rendering and database queries for each request.
19. **Performance Budgets**: Set and enforce performance budgets for key metrics like bundle size, time to interactive, and first contentful paint. Use CI tools to prevent regressions.
20. **Continuous Monitoring**: Implement real user monitoring (RUM) to track performance in production. Tools like Lighthouse CI can catch regressions before they reach production.
21. **Optimize Third-Party Scripts**: Load non-essential third-party scripts asynchronously or defer their loading. Consider using a facade pattern for analytics and ads to prevent them from blocking rendering.
22. **Reduce Network Requests**: Combine files where possible (e.g., CSS sprites, bundling). HTTP/2 makes this less critical but still beneficial for older browsers. Avoid chaining critical requests.
23. **Use Efficient Data Structures**: When handling large datasets client-side, choose appropriate data structures (Maps vs Objects, TypedArrays) to minimize memory usage and access times.
24. **Memory Management**: Be mindful of memory leaks in single-page applications. Clean up event listeners, timeouts, and subscriptions when components unmount. Use dev tools to profile memory usage.
25. **Progressive Enhancement**: Build core functionality that works without JavaScript, then enhance with JS where supported. This ensures usability even if JavaScript fails or loads slowly.
26. **Optimize Build Process**: Configure your bundler for production optimizations like scope hoisting, module concatenation, and minification. Differentiate between development and production builds.
27. **Use WebP/AVIF Images**: Modern image formats can provide significantly better compression than JPEG or PNG. Serve them to browsers that support them while providing fallbacks.
28. **Prefetching**: Predictively prefetch resources for likely next navigation targets using `<link rel="prefetch">`. This works especially well for multi-page applications with predictable user flows.
29. **Optimize API Calls**: Reduce payload sizes from your backend. Implement GraphQL or similar to request only needed fields. Consider batching requests where appropriate.
30. **Isolate Expensive Components**: Contain performance-intensive components (like rich text editors) in iframes or separate bundles to prevent them from affecting the entire application's performance.
31. **Avoid Large Inline Styles**: While some inline styles are unavoidable, excessive use can bloat HTML size and prevent effective CSS caching. Use classes for reusable styles.
32. **Optimize SVG**: Clean and minify SVG markup. Remove unnecessary metadata and consider using SVG sprites instead of individual files for icons.
33. **Reduce Cookie Size**: Large cookies are sent with every request, increasing bandwidth usage. Evaluate what data truly needs to be in cookies versus local storage.
34. **Use Passive Event Listeners**: Mark touch/wheel event listeners as passive when they don't call preventDefault() to improve scroll performance.
35. **Optimize Web Fonts**: Subset fonts to only include needed characters and weights. Consider variable fonts that can replace multiple static font files.
36. **Avoid document.write()**: This archaic method blocks parsing and can significantly delay page rendering. Modern alternatives exist for all legitimate use cases.
37. **Optimize Tab Switching**: Use the Page Visibility API to reduce resource usage when the tab is backgrounded. Pause animations, videos, and non-essential processes.
38. **Server Timing**: Implement Server-Timing headers to help diagnose backend performance issues that might be affecting your frontend experience.
39. **Optimize CSS**: Remove unused CSS with tools like PurgeCSS. Avoid overly specific selectors that slow down style calculation. Group similar styles together.
40. **Use Intersection Observer**: For lazy loading and scroll-linked effects, this API is more efficient than scroll event listeners as it doesn't run on the main thread.
41. **Reduce JavaScript Execution Time**: Profile your JavaScript with the Performance panel in dev tools. Identify and optimize long tasks that block the main thread (>50ms).
42. **Optimize React/Vue/Angular**: Framework-specific optimizations like React.memo, shouldComponentUpdate, or trackBy functions can prevent unnecessary re-renders.
43. **Use Content Visiblity**: The CSS content-visibility property can skip rendering of off-screen content, significantly improving initial load time for long pages.
44. **Avoid Large Inline Scripts**: While some inlining is good (like critical CSS), large inline scripts block parsing. Balance inlining with caching benefits of external files.
45. **Optimize WebSockets**: For real-time applications, implement backpressure and message batching to prevent flooding the client with more data than it can process.
46. **Use HTTP/2 or HTTP/3**: These protocols offer multiplexing and other improvements over HTTP/1.1. Ensure your server is properly configured to take advantage.
47. **Reduce Style Recalculation**: Changing classes rather than individual styles allows the browser to optimize style recalculation. Avoid frequent style changes in animations.
48. **Optimize Canvas**: For graphics-intensive applications, reduce canvas size where possible and implement efficient rendering techniques like dirty rectangles.
49. **Use const/let over var**: Modern JavaScript variables have block scope which can help engines optimize better than function-scoped var declarations.
50. **Audit Regularly**: Performance isn't a one-time task. Schedule regular audits with Lighthouse and other tools to catch new issues as your application evolves.
The article covers 50 specific techniques for improving frontend performance, organized as a numbered list for easy reference. Each point is concise but contains actionable advice that developers can implement in their projects.
