I stumbled upon this site the other day from Mozilla that’s a collection of recipes to get started with a Service Worker — from caching strategies and notifications to providing an offline fallback to your users, this little cookbook has it all.
Service Workers are extremely powerful. They are the one technology that can make websites work offline, for example, and have true control over cache. But there is a lot to learn. Fortunately, Frontend Masters has a great course all about them.