Math.js!

I used this the other day to do matrix math in Javascript.
It was pretty nice! The only thing I wish it had was operator overloading...but I guess that's just a javascript problem...

http://mathjs.org/

I made the following project with my brother, @mckeown12, using math.js ;)
http://www.math.miami.edu/~mckeown/animation/
I think he's planning on writing a steemit post about it soon.
Also you can check out his talk he'll give at FPSAC in London here:
http://www.math.miami.edu/~mckeown/fpsac/