Kudos to the author for including their code. Too many benchmarks don't. And it is amazing that JS is even in the same ballpark as Java.
That said, like all benchmarks, there are systematic biases. I looked at the binary trees benchmark. The obvious problem is that it uses far too few iterations (100), so the runtime was 60 milliseconds (on my laptop). That's really not enough time for JIT to kick in, although probably JS does JIT more eagerly than Java. I upped it to 10000 iterations: (OpenJDK) Java took 3.3s, JS (with node) took 7.8s, C++ took 15s. (C++ is really hurt by garbage collection vs alloc/free.) Switching C++ to use Google's TCMalloc brought it down to 10s.
When you see a benchmark that says that X is faster than Java, and X does not include the letter C, take it with a pinch of salt!
That said, like all benchmarks, there are systematic biases. I looked at the binary trees benchmark. The obvious problem is that it uses far too few iterations (100), so the runtime was 60 milliseconds (on my laptop). That's really not enough time for JIT to kick in, although probably JS does JIT more eagerly than Java. I upped it to 10000 iterations: (OpenJDK) Java took 3.3s, JS (with node) took 7.8s, C++ took 15s. (C++ is really hurt by garbage collection vs alloc/free.) Switching C++ to use Google's TCMalloc brought it down to 10s.
When you see a benchmark that says that X is faster than Java, and X does not include the letter C, take it with a pinch of salt!