Introduction to Service Workers : https://www.youtube.com/watch?v=jVfXiv03y5c

Introduction to Service Worker : https://developers.google.com/web/ilt/pwa/introduction-to-service-worker

Service Workers: an Introduction : https://developers.google.com/web/fundamentals/primers/service-workers/

Adding a Service Worker and Offline into your Web App : https://developers.google.com/web/fundamentals/codelabs/offline/

Service Worker Registration : https://developers.google.com/web/fundamentals/primers/service-workers/registration