Progressive Enhancement & Graceful Degradation

Progressive Enhancement – start with a fully functional HTML page, then layer CSS and JavaScript.

• Use feature detection (if ('fetch' in window) { … }).
• Provide <noscript> fallback content.
• Keep core functionality available without JS.

Graceful Degradation – build the rich experience first, then ensure it still works when features are missing.

Example: Feature‑detect fetch

if('fetch' in window){
  fetch('/data.json').then(r=>r.json()).then(d=>render(d));
} else {
  console.warn('Fetch not supported – loading static data');
}