Which for loop will run fastest?
for (var i = 0; i < arr.length; i++) { // some code here }
for (var i = 0, len = arr.length; i < len; i++) { // some code here }
for (var i = arr.length; i--; ) { // some code here }
for ( i = 0; i < arr.length; i++) { // some code here }