But everyone knows it is significantly faster than Python. Probably at least a few times for pure JS vs. pure Python programs. Not that it matters, Python is basically glue to run mostly C and C++ programs.
Because it's obviously not the idiomatic way to use Python. No one is going to bother writing a program that way in Python, they'd just write it in C or C++ then link it.
Did you? :-)
That Node pidigits program also uses GMP.
Besides those 2, did you notice other JS programs not 50x faster than the corresponding Python programs ?