The state is represented by the url and html, but that's not the same as managing state in client-side memory using Javascript.

Hypermedia Systems is a great read, by the htmx creator, available here:

https://hypermedia.systems

But it's not on the server any more than with a JS app.

Not sure I understand what you mean.

The equivalent of the JS state doesn't live in the server side session, or something like that.