JavaScript Extended Big Number Library (JSEBN)
If you are interested in a big integer JavaScript library, you can visit this link. On that page you can download all of the source code files and try out a demo of some of the features of the JSEBN. This code was originally created by Tom Wu. You can find his original version here. I have extended his implementation to include various probable prime tests, some extra math functions, and some convenience functions. You can find the files, the demos, and the list of changes at this link.