I was reading a discussion about CoffeeScript today and I saw someone make a claim to the effect of "avoid CoffeeScript, since you will eventually need to work with libraries/features/etc that only work in JS." Is this the case? I've started learning CoffeeScript recently and as far as I can tell there is a 1-1 match between the two languages, but I'm not very familiar with JS so I'm not sure.
I've seen this and I'm not asking for a general discussion of the merits of JS vs CoffeeScript. Also, I don't want to count embedded snippets of JS in CoffeeScript as "getting the job done in CoffeeScript," since that makes the question boring.