For some reason it's somewhat hard to find C-style science code examples in some disciplines. Python feels a bit like a plague in this respect. Everytime I have to wrap my head around while converting code to C-like language (C, C++, PHP, JS).
You need something like numpy to make working in javasctipt easier before there will be a proliferation of of ML in JS.
I really love JS for its distribution and some of the visualizations are amazing. But the low level, numerically stable, matrix math primitives are sorely lacking.
I can see JS useful for a UI to a robot, but I can't see it replacing Python for math, or C++ for speed, or LISP for planning systems.
That said, I can imagine node.js being a better async message router than the current C++ one.
ROS is glued together with XML-RPC, which I think was a mistake (why not JSON???)