Optimizing Frontend

This is the most asked frontend interview question, Let’s see ?

https://prasadbylapudi.notion.site/Frontend-preparation-158de34ca92480ceb22be2293ec4e2eb

1. Code Splitting

• What it does: Breaks your code into smaller bundles to load only what’s necessary.
• How to implement: Use tools like Webpack, Rollup, or native features in frameworks like React’s React.lazy and Suspense.

const LazyComponent = React.lazy(() => import('./Component'));

2. Minification and Compression

• Minify CSS, JavaScript, and HTML: Tools like Terser or UglifyJS can reduce file sizes.
• Gzip/Brotli Compression: Configure your server (e.g., Nginx) to compress files before sending them to the client.

3. Optimize Images

• Use modern formats: Convert images to WebP or AVIF for smaller file sizes.
• Lazy Loading: Load images only when they appear in the viewport.

<img src="image.jpg" loading="lazy" alt="Optimized Image">

• CDN: Use a Content Delivery Network like Cloudinary to optimize and serve images.

4. Cache Assets

• Browser Caching: Set cache-control headers for static assets.
• Service Workers: Use Progressive Web App (PWA) techniques to cache resources for offline availability.

5. Optimize CSS

• Remove unused CSS: Use tools like PurgeCSS.
• Critical CSS: Inline the above-the-fold CSS for faster rendering.
• CSS-in-JS: Dynamically generate styles for React components when needed.

6. Use a Virtual DOM Efficiently

• React: Ensure components are properly memoized using React.memo and useMemo/useCallback hooks to avoid unnecessary re-renders.

const memoizedValue = useMemo(() => computeValue(input), [input]);

7. Optimize Network Requests

• Debouncing/Throttling: Control how often events like input changes trigger API calls.
• HTTP/2: Enable multiplexing to load multiple assets over a single connection.
• Prefetch/Preload: Load resources likely needed soon using <link rel="preload">.

8. Implement Lazy Loading and Infinite Scrolling

• Lazy-load components, routes, or data that aren’t initially visible.
• For infinite scrolling, ensure efficient state management and pagination.

9. Optimize Rendering

• Avoid Large DOM Trees: Keep your DOM hierarchy simple.
• Reduce Repaints and Reflows: Minimize layout thrashing by batching DOM updates.
• Virtualization: Use libraries like React Virtualized or React Window for large lists

10. Monitor and Debug

• Tools:
• Lighthouse (Google Chrome): Analyze page performance.
• Webpack Bundle Analyzer: Visualize size of bundles.
• React DevTools: Identify slow components.
• Sentry: Monitor performance in production.
• Example Lighthouse Score: Aim for scores above 90 in performance, accessibility, and best practices.

11. Use Framework Optimizations

• React:
• SSR (Next.js) for faster initial page loads.
• Use Static Site Generation (SSG) for predictable data.
• Vue: Leverage Vue’s tree-shaking capabilities and component-level caching.
• Angular: Optimize with Ahead-of-Time (AOT) compilation.

12. Improve Accessibility

• Ensure semantic HTML, ARIA roles, and proper tab navigation to reduce accessibility issues.

13. Reduce Third-Party Dependencies

• Audit and remove unnecessary libraries or dependencies.
• Use lighter alternatives where possible (e.g., Lodash subsets).

14. Use CDN for Static Assets

• Deliver JavaScript, CSS, and media files via a Content Delivery Network (e.g., Cloudflare, AWS CloudFront).

15. Optimize Fonts

• Subset fonts: Use only the glyphs needed.
• Preload critical fonts:

<link rel="preload" href="font.woff2" as="font" type="font/woff2" crossorigin="anonymous">