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Frontend Performance Guide
Core Web Vitals optimization: code splitting, image optimization, caching strategies, and bundle analysis tools.
JSONMarkdownJavaScriptReactNginx
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performance-optimization-guide/
├── LICENSE
├── README.md
├── configs/
│ └── performance-budget.json
├── examples/
│ ├── caching/
│ │ ├── cache-headers-reference.md
│ │ └── service-worker.js
│ ├── code-splitting/
│ │ └── lazy-loading-patterns.jsx
│ ├── image-optimization/
│ │ └── image-optimization-guide.md
│ └── measurement/
│ └── rum-setup-guide.md
├── free-sample.zip
├── guide/
│ ├── cls-optimization.md
│ ├── inp-optimization.md
│ └── lcp-optimization.md
├── guides/
│ ├── cls-optimization.md
│ ├── inp-optimization.md
│ └── lcp-optimization.md
├── index.html
└── scripts/
└── bundle-analyzer.js
📖 Documentation Preview README excerpt
Performance Optimization Guide
A comprehensive, actionable guide to web performance optimization. Covers all three Core Web Vitals (LCP, CLS, INP), code splitting, image optimization, caching strategies, bundle analysis, and real user monitoring.
What's Included
Core Web Vitals Guides
| File | Description |
|---|---|
guides/lcp-optimization.md | Largest Contentful Paint — image optimization, preloading, render-blocking resources, TTFB, font loading |
guides/cls-optimization.md | Cumulative Layout Shift — image dimensions, font FOUT, dynamic content, skeleton screens, CSS containment |
guides/inp-optimization.md | Interaction to Next Paint — long tasks, main thread optimization, Web Workers, debouncing, React patterns |
Code Splitting
| File | Description |
|---|---|
examples/code-splitting/lazy-loading-patterns.jsx | Route-based, component-based, and library-based code splitting with React.lazy, Suspense, error boundaries, and webpack/Vite configuration |
Image Optimization
| File | Description |
|---|---|
examples/image-optimization/image-optimization-guide.md | Format selection decision tree, responsive images (srcset/sizes/<picture>), lazy loading, Sharp build script, image CDN configuration |
Caching Strategies
| File | Description |
|---|---|
examples/caching/service-worker.js | Complete service worker with 5 caching strategies (Cache First, Network First, Stale While Revalidate, Network Only, Cache Only) |
examples/caching/cache-headers-reference.md | Cache-Control headers for every resource type with Nginx, Vercel, and Netlify configuration examples |
Bundle Analysis
| File | Description |
|---|---|
scripts/bundle-analyzer.js | Analyze webpack/Vite bundle stats — identifies largest packages, potential duplicates, and optimization recommendations |
Performance Budgets
| File | Description |
|---|---|
configs/performance-budget.json | Resource size budgets, Core Web Vitals thresholds, request count limits, Lighthouse score targets, and CI enforcement configuration |
Real User Monitoring
| File | Description |
|---|---|
examples/measurement/rum-setup-guide.md | Collecting Core Web Vitals from real users, building dashboards, SQL query examples, alerting on regressions |
Quick Start
1. Measure Your Current Performance
Lab testing (immediate):
... continues with setup instructions, usage examples, and more.
📄 Code Sample .js preview
scripts/bundle-analyzer.js
/**
* bundle-analyzer.js — Analyze JavaScript bundle composition and identify optimization targets
*
* Parses webpack/Vite/esbuild bundle stats and produces a report showing:
* - Which modules are largest
* - Which dependencies are duplicated
* - Which chunks could be split
* - Estimated savings from tree-shaking
*
* WHY: Bundle size directly impacts load time. Knowing WHERE the bytes are
* lets you focus optimization effort where it matters most.
*
* USAGE:
* # Generate stats file first:
* # webpack: npx webpack --json > stats.json
* # Vite: npx vite build -- --stats (or use rollup-plugin-visualizer)
*
* node bundle-analyzer.js stats.json
* node bundle-analyzer.js stats.json --threshold 10 # Only show modules >10KB
* node bundle-analyzer.js stats.json --format json # Output as JSON
*/
const fs = require('fs');
const path = require('path');
// ---------------------------------------------------------------------------
// CLI Parsing
// ---------------------------------------------------------------------------
function parseArgs() {
const args = process.argv.slice(2);
const parsed = {
statsFile: null,
threshold: 5, // KB — only show modules larger than this
format: 'text', // 'text' or 'json'
};
for (let i = 0; i < args.length; i++) {
if (args[i] === '--threshold' && args[i + 1]) {
parsed.threshold = parseFloat(args[++i]);
} else if (args[i] === '--format' && args[i + 1]) {
parsed.format = args[++i];
} else if (args[i] === '--help') {
console.log(`
Usage: node bundle-analyzer.js <stats.json> [options]
Options:
--threshold <KB> Only show modules larger than this (default: 5)
--format <type> Output format: text or json (default: text)
--help Show this help message
# ... 322 more lines ...