.coffee File — CoffeeScript Source

CoffeeScript is a programming language that transcompiles to JavaScript, offering a cleaner syntax inspired by Python, Ruby, and Haskell. Created by Jeremy Ashkenas in 2009, CoffeeScript introduced many features that were later adopted by JavaScript itself in ES6+ — including arrow functions, destructuring, template strings, classes, and default parameters. COFFEE files contain source code that uses significant whitespace (indentation-based blocks), implicit returns, comprehensions, string interpolation, existential operators, and chained comparisons. CoffeeScript was extremely influential in the JavaScript ecosystem's evolution and was widely adopted from 2010-2015, particularly in the Ruby on Rails community (it was the default JavaScript language in Rails). Dropbox's web frontend was famously written in CoffeeScript. The language compiles to clean, readable JavaScript and follows a one-to-one mapping philosophy. While CoffeeScript's usage has declined significantly as modern JavaScript (ES6+) and TypeScript adopted many of its innovations, it remains maintained and used in legacy codebases. The language demonstrated that JavaScript's syntax could be dramatically improved, paving the way for the ES6+ revolution.