Semicolons could be considered idiomatic or stylistic, for example. Requiring strict equality operators feels more of an idiomatic way to avoid bugs, rather than simply whitespace. Eslint certainly has a number of rules that are more idiomatic than stylistic.

If you're touching on the lack of consistency in, say, open source javascript, I agree, code is all over the place. Also, I think you're looking at a language that has had dramatically more evolution (especially in recent time) than most other popularly used languages. Old code without promises and suffering from callback hell feels archaic.

However, I think if you look at, say, TypeScript repos (which is cheating, I know, it's not javascript), there is more homogeneity, at least from what I've seen.

Of course it evolved. It’s easy to evolve if it was literally nothing in the first place.