Elm!

CoffeeScript is a little language that compiles into JavaScript. Underneath all those awkward braces and semicolons, JavaScript has always had a gorgeous object model at its heart. CoffeeScript is an attempt to expose the good parts of JavaScript in a simple way. You can use any existing JavaScript library seamlessly from CoffeeScript (and vice-versa).

LiveScript is a language which compiles down to JavaScript. It is a fork of Coco which is in turn derived from CoffeeScript. Like those two it has a relatively straightforward mapping to JavaScript. LiveScript is Coco but much more compatible with CoffeeScript, more functional, and more feature rich. LiveScript aims for increased expressiveness and code beauty.

Kaffeine is a set of extensions to the Javascript syntax that attempt to make it nicer to use. It compiles directly into javascript that is very similar, readable and line for line equivalent to the input (you can beautify if you like).

Bublé is an ES2015 compiler. It takes your ES2015 JavaScript code and turns it into code that can run in today's environments, including old versions of Node.js and Internet Explorer.