[jQuery] Re: JSLitmus invaluable tool
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 = 100;
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
[jQuery] Re: JSLitmus invaluable tool
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 = 100;
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
[jQuery] Re: JSLitmus invaluable tool
With Normalize checked, I get infinity for both of them. With it unchecked, I get 12.6M and 10.9M. I'm using google chrome (which the test reports as Safari). --Erik On Tue, Nov 11, 2008 at 9:16 AM, howardk [EMAIL PROTECTED] wrote: 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
