Lesson 20 / 25
Service Workers and offline support
Implement Service Workers for offline support, instant loading, and improved resilience.
Service Worker lifecycle and registration
Register with navigator.serviceWorker.register(). Lifecycle: install (cache assets), activate (clean old cache), fetch (intercept requests). Supports offline with cached responses, instant repeat visits with cache-first strategy.
Caching strategies with Service Workers
Cache First: return cache if available, fallback to network. Network First: try network, fallback to cache. Stale-While-Revalidate: serve cache immediately, update in background. Choose strategy per resource type.
Service Worker best practices
Scope carefully to avoid unexpected behavior. Version caches to enable updates. Use self-closing versions for deployments. Monitor updates in analytics. Test offline mode regularly.
Quick check
Quick check: What is Cache First strategy?
- Return cache if available, fallback to network
- Always fetch from network first
- Disable caching