Where the question breaks down is when you have different ways for a loop to be handled. So while Spidermonkey, the engine powering the JavaScript Mozilla Firefox, may process a forEach
differently then V8, Google Chrome's JavaScript engine. Not only that but the implementation between versions of each JavaScript engine may and in some cases do handle the forEach
differently. So now you have to compare the performance of each loop type in each of the many different JavaScript engines out there, and on top of that, you have to account for performance in different operating systems and the different CPU architecture of devices.