Weird Behavoir While Using Function Aliases

I have the following script:

function Test(){}
Test.F = function(){}
Test.F.FF = function(){}
Test.F.FF.FFF = function(){}
Test.F.FF.FFF.FFFF = function(){}

//var alias = function(){};
var alias = Test.F.FF.FFF.FFFF;

var date1 = new Date();
for (var index = 0; index < 100000; index++)
Test.F.FF.FFF.FFFF();
//alias();
var date2 = new Date();
print(date2.getTime() - date1.getTime());


Why is it when I use Test.F.FF.FFF.FFFF() I get around 100ms and when I
get alias() I get around 280ms?

What is going on here? This is something I would have never anticipated
and I think that neither of you as well. Aliases whould work faster
then doing lockups at each iteration, right?
Also if I uncomment this line: var alias = function(){}, from 280ms I
get a drop to 265 ms?