Rule Definition
Even though function-based iteration represents a more convenient method of iteration, it is also quite a bit slower than loop-based iteration. The slowdown can be accounted for by the overhead associated with an extra method being called on each array item. In all cases, function-based iteration takes up to eight times as long as loop-based iteration and therefore isn't a suitable approach when execution time is a significant concern.

Remediation
Use the regular for loop to enumerate the array

Violation Code Sample

arr.forEach(function(v){v;}); // BAD

Fixed Code Sample

for(var i = 0, l = arr.length; i < l; i++){arr[i];} // GOOD

CISQ OMG, http://jsperf.com/foreach-vs-loop