Some anecdata: Node was roughly as fast as dmd, the D compiler for fast iteration. The LLVM and GCC based D compilers are hugely faster. By using JavaScript yo

Some anecdata: Node was roughly as fast as dmd, the D compiler for fast iteration. The LLVM and GCC based D compilers are hugely faster. By using JavaScript you are throwing away something like 2-3x. There will be cases where JS can keep up because it reduces to a local loop which gets optimized the same way as any other language, but all those little other bits add up. Same with Python. If you do everything in numpy you can be very fast, but what happens if you don't? You could use a fancy jit but now you have a deeper stack with no control over the emitted code - nice if you already have the code, but not ideal.