I think idioms and style have some level of overlap.

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.