XPCOM object callback to javascript

[Karim Metwalli]

I'm writing an a XPCOM object that I would like to see callback its 
parent which is a piece of javascript code. Are callbacks from C++ to 
JavaScript possible? How do I get a pointer to a JavaScript function? 
Otherwize, can I send an event to the JavaScript?

If you know of a sample, please send it my way.
K