For loop optimization

[Optimizes](http://stackoverflow.com/questions/2742396/javascript-for-loop-efficiency) the for loop.

Any part of the loop that is in the second part `for(first;second;third)` will be checked once per loop.  It gets costly to access an object property every run through unless necessary.  It is more efficient to access a number, especially in [chrome](http://jsperf.com/native-map-versus-array-looping).