I just finished making this Valentine’s Day app using service workers. For those unfamiliar with service workers, they are basically a proxy between the client and server allowing you to do some cool things as a developer by intercepting requests to the server and responses to the client. This can allow you to take an “offline first” approach by giving the user your app even if they have no connection or worse… the dreaded lie-fi (You know when you see that little circle spinning and spinning and nothing is happening at all, not even a message saying can’t connect?)
I learned about this from the free Udacity course Offline Web Applications. This is part of the Grow with Google Challenge Scholarship to the Mobile Web Specialist track I was recently awarded. I must thank freeCodeCamp and Quincy Larson for in no small part helping me get to the point of even applying for the scholarship.
I recommend anyone interested in Progressive Web Apps to check out that course and I also have a couple good links in the above article for starting your first “Offline App” as well as an introduction to the “Service Worker”.