Be careful with [].sort method. Maybe, the better way is to implement your own sorting method. Try in your bed the following simple example:

[3, 1, 2].sort(function(a, b)
{
alert([a, b]);
return a – b;
};

You can say that there is nothing to be suspected. But! Each time when the sorter function is called it performs some calculation over passed arguments “a” and “b”. It means that each time when “cmpStringsWithNumbers” is called it performs heavy calculations over the same values again and again.