Trivial benchmarks where all of the significant data structures and networking are done in C++ and the tiny amount of Javascript is just passing some strings around. I guess it's "fast" if you can restrict yourself to little more than hello world where you do nothing more than pass a few strings to functions written in faster languages.

Notice that in the Java, C#, Go, Rust, Swift or Ocaml benchmarks almost all of the underlying data structures and much of the networking stack are built in the respective language. This is not possible with Javascript, Python, Ruby etc. because it would be ludicrously slow and extremely memory inefficient.