This is a great talk by Ryan Florence (one of the creators of React Router) where he basically reimplements the basics of the library from scratch: https://www.youtube.com/watch?v=wPJxmZx62gI

I'd also just look at the React Router codebase. The components are pretty well written and somewhat easy to understand: https://github.com/ReactTraining/react-router/blob/master/pa...