[jgautsch]

> I'm now wondering if the first direction (state->url) couldn't just be thought of as a component. It just extracts parts of state and renders it into a string. The other direction would then be an action.

The specific component/state rendered is a reaction to the URL, not the other way around (this can get cloudy with semantics though). Keeping the URL and the current page state in sync takes the form of updating the path, and having your application react to that.

You're right it is perfectly feasible to render a different page/view when a link is clicked without a client-side router library, but the "swapping out components" part can get tricky for non-trivial cases like a hierarchical UI, or components that need to consume URL params.

A client-side router like react-router abstracts away a lot of the hard stuff you'd quickly run into on your own if A.) your app has navigation, and B.) you want to have URLs associated to views/states.