Comprehensive Wikipedia Entry on Javascript: http://en.wikipedia.org/wiki/JavaScript
John J. Lee has an (unmaintained) Python-Javascript bridge:
http://wwwsearch.sourceforge.net/python-spidermonkey/
OS X 10.4 now includes Javascript and Cocoa bridges which can be used in Widgets and /WebKit objects.
But PyObjC may be superior.
From The ADC article "Using PyObjC for Developing Cocoa Applications with Python" ( http://developer.apple.com/cocoa/pyobjc.html)
**Many Bridges to Your Destination** PyObjC is just one of many Cocoa bridges. Apple has offered its Java bridge since Mac OS X 10.0, and Mac OS X Tiger 10.4 rolled out a /JavaScript bridge which allows Dashboard Widgets to communicate with Objective-C objects. Third-party developers have also created bridges for C#, Lisp, Perl, Ruby and Smalltalk to name a few. And, of course, Python.