1.Where it was safe == operators have been replaced with === to avoid unnecessary type casting. 2.length attribute of arrays assign to variable to speed up the for-loop execution 3. hasOwnProperty verification for all for-in loops added - to avoid unnecessary walk-through prototype elements 4. missing semicolons added 5. double variable declarations removed from some functions

Those hasOwnProperty checks seem to be unnecessary: all those objects are simple JS data structures with proto === Object.prototype, e.g. no non-own properties are being enumerated... ?

Some of JS developers would say that hasOwnProperty check should be an integral part of for..in loop. Even if there is nothing added to object's prototype. However it is just theoretical discussion. In practice - I never had a need to navigate through prototype properties of an object, this is why I always add the check. In such case I never have to bother when I add something enumerable to the prototype...

I can guarantee that I never modify Object.prototype, which is why adding hasOwnProperty check to "for (var p in {})" is redundant...

Also, consistently, I never enumerate non-Objects with "for (var p in what)" - which is why I can freely extend their prototypes :)

Revision 918 applies those parts of this patch which optimize array length getters in loops.

Thanks, the array lengths were the most important.