Traceur Compiler at gos.i
Embed this image by adding following code in your web-page.
  <a href="http://getopensource.info/traceur" title="Traceur Compiler at getOpenSource.info">
    <img src="http://getopensource.info/traceur/svg/traceur.svg" alt="Traceur Compiler at gos.i" />
  </a>

Traceur Compiler

Google's vehicle for Javascript Language Design Experimentation

Traceur is a JavaScript.next-to-JavaScript-of-today compiler that allows you to use features from the future today. Traceur's goal is to inform the design of new JavaScript features which are only valuable if they allow you to write better code. Traceur allows you to try out new and proposed language features today, helping you say what you mean in your code while informing the standards process.