For those who aren't familiar Andrej Karpathy has done a lot of cool stuff with ML in JS. Particularly he has a CNN library -- deep learning comes to JS!

http://cs.stanford.edu/people/karpathy/convnetjs/

http://cs.stanford.edu/people/karpathy/svmjs/demo/

Heather Arthur (npm libraries brain, classifier) has also done a bunch of cool stuff!

https://github.com/harthur