Not just a hack. Recognized developers such as Brendan Eich (creator of javascript) or Douglas Crockford (author of Javascript: The Good Parts) say that Coffeescript is good stuff. Coffeescript is a "transpiler", a source-to-source compiler wich translates a high level, very flexible and powerfull language such as coffeescript into plain old javascript. It doesn't change the underlying language at all, it keeps its object model and its data types. It just adds a more expressive and succinct syntax, inspired in python and ruby (and these languages have a very well deserved reputation for expressiveness and joy amongst programmers for a reason).