I think that by “between python and java” they meant “faster than python and slower than java”. I think Java still beats JS unless you get lucky.
You’re totally right that benchmarking and profiling is hard even for native code. I think this post fetishizes whether or not a piece of code got JITed a little too much. Maybe the author had a bad time with microbenchmarks. There’s this anti pattern in the JS world to extract a small code sample into a loop and see how fast it goes - something that C perf hackers usually know not to do. That tactic proves especially misleading in a JIT since JITs salivate at the sight of loops.
You’re totally right that benchmarking and profiling is hard even for native code. I think this post fetishizes whether or not a piece of code got JITed a little too much. Maybe the author had a bad time with microbenchmarks. There’s this anti pattern in the JS world to extract a small code sample into a loop and see how fast it goes - something that C perf hackers usually know not to do. That tactic proves especially misleading in a JIT since JITs salivate at the sight of loops.