If you don't know JS really well, I wouldn't recommend Coffeescript. It's hard to tell what will work correctly and what won't unless you're quite familiar with the actual code the Coffeescript is compiling down to. I don't know how true this is for other transpiling languages, but it's definitely true for Coffeescript.

I'm a pretty experienced JS dev, so I know exactly what my CS is compiling to and what that's going to do. If I didn't, CS would make me tear my hair out within a week. As it is, it's just shorthand for JS with a bunch of quality of life improvements (?, no var, etc).