See this Ext.Array code fragment.
According to jsPerf the most efficient way to iterate over an array or array-like collection is to avoid the native implementations entirely, opting for simple loops instead.
http://jsperf.com/for-vs-array-foreach
http://jsperf.com/for-vs-array-foreach/4
Code:
...
forEach: supportsForEach ? function(array, fn, scope) {
return array.forEach(fn, scope);
} : function(array, fn, scope) {
var i = 0,
ln = array.length;
for (; i < ln; i++) {
fn.call(scope, array[i], i, array);
}
},