Workbox.js Service Worker library (there is a newer version but this was only in alpha when I started the work).
Then I switched focus and did some CSS which was really good to do (from one part of the brain - the maths and coding part - to the other art part).
I juggled on a couple of evenings this week, the max of 5-ball cascade is 20 throws. I have also started to learn 5-ball reverse-cascade and 4-ball shower. I need to also concentrate on 3-ball shower from my left side to improve speed and accuracy.