Best way to detect param changes in the same route

[oskarrough]

Assuming the following route:

crossroads.addRoute('/chapters/{id}', id => {
  console.log(id);
});

What is the right way to detect a change from /chapters/1 to /chapters/2? The match method is called but I can't seem to access the previous param.

More specifically, I'm looking for a way to trigger a custom exit method with the id param as argument.