jspaillier is a simple proof-of-concept Javascript implementation of the Paillier homomorphic encryption scheme. A demonstration of the code can be found at here.
Do keep in mind this is proof-of-concept code. Also, doing crypto in Javascript is typically considered to be a Bad Idea (tm), see also the discussion "Javascript Cryptography Considered Harmful".
jspaillier has a single dependency: jsbn. You will need at least jsbn.js, jsbn2.js, prng4.js, and rng.js
See the included demo page for information on how to use this library.
A large part of the work on this library was done at TNO in a project supported by the "COMMIT/" program.