When you are doing AJAX applications, you pass data back to the calling page, some of the examples I have seen are in XML and you then do some parsing of that XML in JavaScript.

I found the JSON (JavaScript Object Notation) library a while ago, but finally managed to use it. Basically it gives you a way to pass complex objects in JavaScript back so you dont need to parse them as such.

There are is also UDF's for coldfusion that can convert CF objects to JavaScript objects. Something like WDDX (which I am also going to give a little whirl in my testing of ajax libraries and methods)