Conventional HTML lets you submit data via forms to a website and the destination (target) is usually visible in the sourcecode. Now, with JS it's a bit more difficult. You have to go through the JS files and find out what happens and where all the data is being sent to.
Is there an easier way to pin down where my data ends up (i.e. what file/address it is being sent to)??
Something like: I click on the button and it shows me what type of action was used and the destination URL?!
I'm on Ubuntu.
Are you trying to prevent phishing attacks or merely capture redirects/ajax calls on button clicks .. what's the purpose of this experiment?
Because Firebug (a firefox add-on) or Chrome Inspector (native to Chrome, not quite as robust as Firebug) will do the things that you're asking for, and give you lots more information to boot.
Additionally, you might consider setting up a local proxy on your machine and capturing all http traffic. It really depends on what you're trying to accomplish.