I'm currently working on bringing BLAS [1] and LAPACK [2] to JavaScript. And here is a matrix/vector library with some of the BLAS functions implemented [3].

[1] https://github.com/mateogianolio/nblas

[2] https://github.com/mateogianolio/nlapack

[3] https://github.com/mateogianolio/vectorious/tree/opt-cblas