Getting offtopic here from FORTRAN, but there have been several attempts at numeric libraries in javascript (math.js, numjs), they are either lightweight, or unmaintained and in a sorry state, or require async execution that expect remote hardware (Googles tensor libs) which makes them a bit difficult to use in a general setting.

Hopefully WebASM will result in a native numpy-like library for JS because numpy is a very well-thought-out library and interface, it's really addictive.