This is an excellent idea, and is the goal of a project that Google announced at JSConf 2011 with much fanfare (some of it from Brendan Eich himself), Traceur:

This is an excellent idea, and is the goal of a project that Google announced at JSConf 2011 with much fanfare (some of it from Brendan Eich himself), Traceur: http://code.google.com/p/traceur-compiler/ http://code.google.com/p/traceur-compiler/ However, Traceur has gained little traction. With the announcement of Dart, it's clear that Google's heart isn't really into the project. See also: http://stackoverflow.com/questions/6506519/ecmascriptharmony-es6-to-javascript-compiler http://stackoverflow.com/questions/6506519/ecmascriptharmony...