Obvious this is , but still has to be done ;o)

Ce we please optimise the "most common form" of for() loops?

Namely the ones iterating over an array or "array like" objects.

for (var i = fromIndex; i < arr.length; i++) {

This for loop looks up the .length property of the array (arr) each time through the loop.

Simply by setting a variable to store this number at the start of the loop, you can make the loop run much faster:

for (var i = fromIndex, ii = arr.length; i < ii; i++) {

This loop is better in that it avoids a property lookup each time through the loop, but this particular for loop is so simple that

it could be further simplified into a while loop, which will run much faster again:

var i = arr.length;

while (i--) {

// arr[i]

}

Thanks: DBJ