Rails and JSON example?

Does anyone know of a demo or tutorial in which ...

(1) In a browser some data is packaged up using JSON.
(2) an async request is sent to a rails app sending the JSON data. I
would like this to be done via jQuery.

(3) A rails app deserializes the JSON data.
(4) The Rails app then packages up some other data using JSON, again
(5) The Rails app sends this data back to the browser.

(6) jQuery code then deserializes the returned data.