Tool to identify which external javascript references are actually being used on a page

I'm working on a website that currently has the same block of external JavaScript references on each page (added via a master page). I'd like to go through the site and identify which script files are actually necessary for each specific page to improve performance. Problem is there are a lot of pages and I'm not sure how to do it without resorting to manual trial and error process.

Is there a Firefox plug-in or some other tool that will identify which JavaScript references could actually be called by the page and which are 开发者_开发知识库not necessary?

you can use firebug plus his plugin for javascript code coverage: http://getfirebug.com/extensions/index.html#firebugcodecoverage