v8 does not optimize blocks inside try catch (not too fresh http://www.html5rocks.com/en/tutorials/speed/v8/ http://www.html5rocks.com/en/tutorials/speed/v8/) a

v8 does not optimize blocks inside try catch (not too fresh http://www.html5rocks.com/en/tutorials/speed/v8/ http://www.html5rocks.com/en/tutorials/speed/v8/) and about generators and optimizations (http://wingolog.org/archives/2013/06/11/ecmascript-generators-from-a-performance-perspective http://wingolog.org/archives/2013/06/11/ecmascript-generator...)