JQuery / javascript if operator speed

Question

Considering:

var
isIE = $.browser.msie && !$.support.opacity, 
isIE6 = isIE && $.browser.version < 7;

Which will be faster:

if(isIE6){ doSomething(); }
else { doSomethingElse(); }

OR

if(!isIE6){ doSomethingElse(); }
else { doSomething(); }

Are they exactly the same as speed?

Answer 1

Given this test for 1,000,000 iteration cycles, no difference.

var test = true;

var count = 1000000;
var stop, start = new Date();

while(count--) {
    if(test) ; // Change to !test
    else ;
}

stop = new Date();

alert(stop - start);

Tested in Firefox, Safari and IE8.

Other processes running on the system that run the test several times in each browser return the same total change in milliseconds, regardless !.

Answer 2

, , ( ), ( , ), , , .

Answer 3

The first will be faster, because it requires one more step (the! Operator launches the action separately from the if statement).

However, there will be no real difference.

Answer 4

I would say that you are just checking this. Firebug has a profiler as well as one in IE8.

Grz, Kris.