Compilation of some CoffeeScript files while saving

I work with CoffeeScript in Node and a browser, and I only want to compile browser-specific files.

I have vim to compile a file if it has an extension .js.coffeebut writes to the file with the extension .js.js. I can pass the arguments to the compilation command, but then I need vim to find out the file name, and then remove the extra one .js.

Here is the relevant part of my vimrc file.

au BufWritePost *.js.coffee CoffeeMake!