Merge pull request #3214 from taion/document-onChange

Document new onChange hook

CHANGES.md

@@ -1,7 +1,10 @@
-## [HEAD]
+## [HEAD] \(v2.1.0\)
 > Unreleased
 
+- **Feature:** Add support for `onChange` hook on routes ([#3108])
+
 [HEAD]: https://github.com/reactjs/react-router/compare/latest...HEAD
+[#3108]: https://github.com/reactjs/react-router/pull/3108
 
 ## [v2.0.1]
 > March 9, 2016

docs/API.md

@@ -336,6 +336,11 @@ Called when a route is about to be entered. It provides the next router state an
 
 If `callback` is listed as a 3rd argument, this hook will run asynchronously, and the transition will block until `callback` is called.
 
+##### `onChange(prevState, nextState, replace, callback?)`
+Called on routes when the location changes, but the route itself neither enters or leaves. For example, this will be called when a route's children change, or when the location query changes. It provides the previous router state, the next router state, and a function to redirect to another path. `this` will be the route instance that triggered the hook.
+
+If `callback` is listed as a 4th argument, this hook will run asynchronously, and the transition will block until `callback` is called.
+
 ##### `onLeave()`
 Called when a route is about to be exited.