[random32840]

JS is generally very fast because these monolithic VMs have had so much money poured into them that their optimisation process is unparalleled. V8 can sometimes get performance on par with C. "Overhead" is arguable, JS may be garbage in a lot of ways but modern JS is quite efficient.

[skohan]

sometimes is the key word there. It's amazing what kind of performance can be reached with JS given the monumental amount of effort which has gone into optimizing it, but there are structural reasons JS hsa a performance ceiling. JIT compilation can't change the fact that it's a highly dynamic, weakly typed language which is garbage collected. You might be able to find examples where a JIT compiled block of JS code performs comparably to a similar block of C code, but there are design patterns available in languages like C/C++ and Rust which aren't even expressible in JS which allow an extremely high level of optimization using careful memory management techniques.

Also web is basically a single-threaded runtime environment. For the foreseeable future, increased parallelism is the main way we can expect to get increased computing performance, and it's basically not available on the web.