Luckily, they didn't, and instead pulled in the the `benchmark` library as a development dependency. The author of said library works on V8, and already considered all those problems and much, much, more[1].
There's no portion of the code that does warmups. There's no portion of code that "blackholes" the results to keep the JIT from optimizing away the code under benchmark. There is a lot of code though... so that's... good?
You make the assumption that just because a lib is popular or widely used it is "correct" or "the best". When it comes to microbenchmarks, that's usually flawed. Very VERY few people actually get them right, benchmark.js is no exception.
That, of course, doesn't mean that benchmark.js can't be useful. For macrobenchmarks it will be roughly right. However, for something as small as leftpad, it's almost certainly not the right way to measure performance.
The article is completely consumed with getting the timing of benchmarking right. Which, to be fair, is a place where microbenchmarks often go wrong. It, however, isn't the ONLY place they go wrong.
This isn't true - Benchmark.js will repeatedly rerun benchmarks until it gathers statistically meaningful results.
> There's no portion of code that "blackholes" the results to keep the JIT from optimizing away the code under benchmark.
True, and there's actually nothing benchmark.js can do to ensure that doesn't happen in the general case but when this does happen the results are usually pretty obvious - we'd see billions of ops/sec. Incidentally the left-pad benchmarks do not suffer from this issue.
This is the "benchmark lib" that was mentioned in the very first sentece of the comment you replied to.