This is the wrong approach. Javascript is rapidly becoming the "bytecode" of browsers. Look at established projects like Haxe and GWT which take higher level languages and compile them down to low-level javascript. Pyjamas is even a python port of Gwt, not sure how well tested.
This approach solves many problems. Browser developers only have to support one language (javascript), and already projects like the V8 engine are making that fast and standardized. Developers can use the language of their choice.
It's what Java should have been in the first place. It's a pity that this is all built on an oddball language like javascript, but perhaps that's the only way this could have happened because there's no legacy javascript outside the browser.
