If function is attached using jQuery, you can see it using firebug.
jQuery events are stored using data method and with key as events.
So $("desiredSelector").data("events") will show up all events attached to that particular element.
For details check this link.

If function is attached using jQuery, you can see it using firebug.
jQuery events are stored using data method and with key as events.
So $("desiredSelector").data("events") will show up all events attached to that particular element.
For details check this link.
For event defined in Javascript you can check the onClick property or use the method suggested by jfriend00.

EDIT :
There is a jQuery plugin which make this more simple.