CoffeeScript

CoffeeScript is a programming language that compiles to JavaScript. It adds syntactic sugar inspired by Ruby, Python, and Haskell in an effort to enhance JavaScript's brevity and readability. Some added features include list comprehension and destructuring assignment.

CoffeeScript support is included in Ruby on Rails version 3.1 and Play Framework. In 2011, Brendan Eich referenced CoffeeScript as an influence on his thoughts about the future of JavaScript.

On December 13, 2009, Jeremy Ashkenas made the first Git commit of CoffeeScript with the comment "initial commit of the mystery language". The compiler was written in Ruby. On December 24, he made the first tagged and documented release, 0.1.0. On February 21, 2010, he committed version 0.5, which replaced the Ruby compiler with a self-hosting version in pure CoffeeScript. By that time the project had attracted several other contributors on GitHub, and was receiving over 300 page hits per day.

On December 24, 2010, Ashkenas announced the release of stable 1.0.0 to Hacker News, the site where the project was announced for the first time.

On September 18, 2017, version 2.0.0 was introduced, which "aims to bring CoffeeScript into the modern JavaScript era, closing gaps in compatibility with JavaScript while preserving the clean syntax that is CoffeeScript's hallmark".

Almost everything is an expression in CoffeeScript, for example, if, switch and for expressions (which have no return value in JavaScript) return a value. As in Perl and Ruby, these control statements also have postfix versions; for example, if can also be written in consequent if condition form.

Many unnecessary parentheses and braces can be omitted; for example, blocks of code can be denoted by indentation instead of braces, function calls are implicit, and object literals are often detected automatically.

To compute the body mass index in JavaScript, one could write: