Modern Web Performance Optimization Techniques

Feb 6, 2024

Web performance isn't just about speed - it's about user experience, accessibility, and business metrics. Through various projects, I've compiled a set of effective optimization strategies that have consistently improved performance metrics.

Key focus areas:

1. Bundle optimization Modern bundlers like webpack and Rollup offer powerful optimization capabilities:

   • Code splitting: Break your bundle into smaller chunks loaded on demand

     // Instead of importing directly
     import HeavyComponent from './HeavyComponent'
     
     // Use dynamic import
     const HeavyComponent = lazy(() => import('./HeavyComponent'))
     

   • Tree shaking: Eliminate unused code from your bundle

     // Bad: imports entire library
     import _ from 'lodash'
     
     // Good: imports only what's needed
     import map from 'lodash/map'
     

   • Dynamic imports: Load modules when needed

     button.onclick = async () => {
       const module = await import('./heavy-module.js')
       module.doSomething()
     }
     

2. Asset optimization Proper asset handling can dramatically improve load times:

   • Image optimization: Use modern formats and lazy loading

     <img 
       src="image.webp"
       loading="lazy"
       srcset="image-400.webp 400w, image-800.webp 800w"
       sizes="(max-width: 400px) 400px, 800px"
     />
     

   • Font loading: Optimize font delivery

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

3. Runtime performance Keep your app responsive with these techniques:

   • Virtual lists: Render only visible items

     function VirtualList({ items }) {
       const [visibleRange, setVisibleRange] = useState({ start: 0, end: 10 })
       return (
         <div onScroll={updateVisibleRange}>
           {items.slice(visibleRange.start, visibleRange.end)}
         </div>
       )
     }
     

   • Debouncing: Limit function call frequency. This can be useful for search bars, autocomplete, etc.

     const debouncedSearch = debounce((query) => {
       performExpensiveSearch(query)
     }, 300)
     

   • Web Workers: Offload heavy computations to a separate thread (e.g. image processing, video encoding, etc.).

     const worker = new Worker('worker.js')
     worker.postMessage({ data: complexData })
     worker.onmessage = (e) => {
       updateUIWithResult(e.data)
     }
     

The most impactful changes often come from understanding your application's specific bottlenecks through proper profiling and measurement. Tools like Lighthouse and WebPageTest are great at identifying optimization opportunities.