Traceur is a JavaScript.next-to-JavaScript-of-today compiler that allows you to use features from the future today.

Traceur is a JavaScript.next-to-JavaScript-of-today compiler that allows you to use features from the future today. It allows to use features like classes, modules, etc. proposed by ECMAScript Harmony.

JavaScript 

http://code.google.com/p/traceur-compiler/
http://code.google.com/p/traceur-compiler/