Google is doing it with straight HTML and CSS and probably some JS, see the Gaming Solution tab on Google Cloud: cloud.google.com Personally Canvas sounds easier, but you'll be writing everything yourself.
Regarding the datastructure, not sure if you are familiar with PSpice, there's a command line version available which if you used their syntax as an API / storage mechanism, you can easily store / update circuits using the PSpice syntax, OrCad is the GUI version of PSpice.