Detect page change for one page apps JS

I'm wondering if anyone has a solution for tracking "page" changes for one-page apps?

I understand the concept of a one-page app in that all the html/css for a page is preloaded and the pages are constructed based on dictating which elements of a page to hide/show. Even though technically it's a one-page app, the perception of the user is that it is several pages/experiences.

What's the best way to differentiate/track these pages/experiences in a one-page app environment?