Full description
CoffeeScript is a little language that compiles into JavaScript. Underneath
that awkward Java-esque patina, JavaScript has always had a gorgeous heart.
CoffeeScript is an attempt to expose the good parts of JavaScript in a
simple way. The golden rule of CoffeeScript is: "It's just JavaScript." The
code compiles one-to-one into the equivalent JS, and there is no
interpretation at runtime. You can use any existing JavaScript library
seamlessly from CoffeeScript (and vice-versa). The compiled output is
readable, pretty-printed, and tends to run as fast or faster than the
equivalent handwritten JavaScript.