Michael,
I thought I had thanked you for your post yesterday but don't see that
here today. Maybe I did a 'reply to author'?
In any event, thanks again. I implemented your code and see where I
went wrong. Also thanks for a good demonstration of how to use the call
( ) function -- very nice. I've always found the online descriptions
of call( ) rather confusing; yours is a nice clear demonstration of
its usefulness.
You are correct that my 'this' turned out to be the window object.
Bad!
Howard
On Nov 11, 10:23 am, "Michael Geary" <[EMAIL PROTECTED]> wrote:
> JSLitmus isn't testing what it appears to be testing.
>
> In the 'use instance var' case, take a look at what "this" is inside the
> test function. I'll bet it's the window object. That is the reason it's so
> much slower in Firefox. I didn't try it in IE, but the difference is
> probably even more dramatic there.
>
> It's not surprising that there is little difference in Chrome, with its
> completely different architecture.
>
> If 'this' a native JavaScript object, it's still slower to reference
> "this.foo" than it would be to reference "foo", but not by such a great
> difference.
>
> Compare with this test that provides known values of "this":
>
> var total = 1000000;
> function Test() {}
> Test.prototype.one = function() {
> var t1 = +new Date;
> var n = total;
> var x = 0;
> while( n-- ) x++;
> var t2 = +new Date;
> console.log( ( t2 - t1 ) / 1000 );};
>
> Test.prototype.two = function() {
> var t1 = +new Date;
> var n = total;
> this.x = 0;
> while( n-- ) this.x++;
> var t2 = +new Date;
> console.log( ( t2 - t1 ) / 1000 );
>
> };
>
> test = new Test;
> test.one();
> test.two();
>
> test.one.call(window);
> test.two.call(window);
>
> In an example run, that logged these values to the Firebug console:
>
> 0.051 - test.one()
> 0.199 - test.two()
> 0.052 - test.one.call(window)
> 2.408 - test.two.call(window)
>
> As you can see, test.two() is several times slower than test.one() when it's
> called as a method of the test object, but dramatically slower when it's
> called as a method of the window object.
>
> -Mike
>
> > From: howardk
>
> > I've been experimenting with several different coding styles
> > for plug- ins. Lately I've been curious about the difference
> > in performance between using local variables vs. instance
> > variables for storing state. JSLitmus, while not itself
> > jQuery-based, has just given me the answers I've been looking
> > for. I found them a bit surprising:
>
> > http://www.fatdog.com/litmus_tests/InstanceVsLocalTest.html
>
> > (Apologies for the color scheme! :-)
> >Howard
