It does work, but you need a browser which supports all of the used ES6 features (even in sloppy mode). As far as I can tell, it should work in Microsoft Edge.

It does work, but you need a browser which supports all of the used ES6 features (even in sloppy mode). As far as I can tell, it should work in Microsoft Edge. It will work in Firefox once they enable `let` without specifying the script version. It will work in Chrome once they fix for-of and once they make `let` work outside of strict mode.