i could see nested callbacks favoring two spaces, but overall it's not a style unique to javascript. for example, a lot of ruby i've seen (admittedly it's been

i could see nested callbacks favoring two spaces, but overall it's not a style unique to javascript. for example, a lot of ruby i've seen (admittedly it's been a while) used two spaces, and i don't recall it being any more prone to deeply nested code than other languages. that said js code tends to be rendered in a variety of other places like browser dev tools, which may influence this as well.