Node/V8 is insanely fast. I never quite realized exactly how fast until I worked on this: https://www.spakhm.com/ts-wolfram-bench. It's mindblowing how fast it is.
It's not that V8 has performance parity with Mathematica. The Mathematica interpreter is written in highly optimized C by experts over many years. My barely optimized js/V8 code has performance parity to _that C code_. That's what should blow your mind.