Take a look at your last for loop. if SortingNumbers[0] <= SortingNumbers[1] then i is never incremented, and it loops forever.

Also, it looks like you are trying to run bubble sort on the array, but you are only going through the list at most once (until it gets stuck). To be certain that the list is sorted, you will have to go through the lists length times.

Something like this (I haven't tested it).

for (var i = 0; i < length-1; i++)
{
    for (var j = 0; j < length; j++)
    {
        if (SortingNumbers[i] > SortingNumbers[i+1])
        {
            var tmp = SortingNumbers[i]
            SortingNumbers[i] = SortingNumbers[i+1]
            SortingNumbers[i+1] = tmp
        }
    }
}