I think the best way to go about it is to have a switch/checkbox for the user to opt-in. Only then will the browser prompt the user to enable notifications. It'

I think the best way to go about it is to have a switch/checkbox for the user to opt-in. Only then will the browser prompt the user to enable notifications. It's trivial to make this change. I'm amazed so many sites have this feature, because it was an absolute nightmare for me to get it working alongside Google's sw-precache library.