That's stupid, the reason you should not use `for... in` isn't because it's slow, it's because it's reflective. It's using reflection over object keys to itera

That's stupid, the reason you should not use `for... in` isn't because it's slow, it's because it's reflective. It's using reflection over object keys to iterate an array. This just happens to work because JavaScript arrays are also objects. `myArr.forEach(function(el){ // do things here });` Is perfectly fine.