CoffeeScript was born out of frustration with JavaScript’s (then major) shortcomings compared to back-end languages like Ruby and Python. Try building an app i

CoffeeScript was born out of frustration with JavaScript’s (then major) shortcomings compared to back-end languages like Ruby and Python. Try building an app in ES3 JavaScript (i.e. it has to support IE7 with no transpiling) if you haven’t before. It can be rather frustrating if you’re used to modern features. Prototype.js was the kick that eventually led to the standard library updates in ES5, and (as another post has said) CoffeeScript was the kick that eventually led to language- and syntax-level updates in subsequent versions.