How to Make a Progressive Web App

If you have a web app and you've made it that works on mobile and worked on desktop, you really have no reason to not make it a progressive web app. The only issue is if there is some data, obviously, like you said in your example with the shopping cart,. You would not be able to do that offline. So then at that point, you detect that you're offline or not and you make some kind of a decision.