That's fair, but that's also stuff that you just can't really do in Java in general¹, so it's not useful for a comparison. The fact is that the vast majority of

That's fair, but that's also stuff that you just can't really do in Java in general¹, so it's not useful for a comparison. The fact is that the vast majority of JavaScript code is pretty static and there's nothing preventing it from running as fast as Java other than man-decades of compiler engineering. ― ¹ Possibly excluding reflection. It's been a long time since I used the Java reflection APIs and I have no idea if you can do things like add class fields named after arbitrary strings at runtime. Even if you could, presumably this bails out of jitted code so the situation is basically the same as in JS.