> I have a big problem in my application, when I create a global class
> object is impossible for me to release the memory and I'm having
> memory leaks.

It looks to me like you're doing nearly everything you need to do (and
a little bit more). Remember that all you can do is make sure that
memory is no longer referenced (which it looks to me like you've done
almost completely) and that you've broken any _circular_ references
between DOM elements and JavaScript objects (you don't have any
circular references, but you've broken all refs from JavaScript->DOM,
which is a good thing to do). At that point, it's up to the JavaScript
implementation when (and whether) to actually reclaim the memory. Some
are more aggressive than others, and some are more effective than

Your actual quoted code ends up being very nearly a no-op, which I'm
guessing is for testing purposes. It creates 2,000 divs and pushes
them on an array (and another div it puts in a property) but never
adds them to the document. It then removes the references to them from
the array and releases the array (and clears the property). Assuming
this code:

    var t = new TestClass();

...by the time the line above is complete, the only remaining memory
references I see are the instance itself (`t` above) and the fact that
`t` has a property called `options` (which has the value null). If you
uncomment the `delete this.options;` line, then even the `options`
property that will be gone.

I took your code and put it (sans alerts) in a page that created 20
TestClass objects every 250ms and then threw them away. Using Chrome's
excellent about:memory page, I was able to see that the memory does
(eventually) get reclaimed by Chrome, Firefox, and Opera on Linux, IE6
on Windows 2000, and IE8 on Windows 7. They were wildly different
about when they did it. Chrome started at using 12k for the page,
which shot up to 60k almost immediately (certainly on the first 40-60
TestClass instances), and then allowed memory use to go up to 85-95k
before reclaiming back down to 62-64k and letting it climb again.
Firefox 3.6 started at about 50k and allowed use to creep up to 250k
before reclaiming back down to ~70k again (rinse, repeat). Opera was
the most aggressive about reclaiming the memory, starting at 38k,
jumping almost immediately to 57k and then staying there, almost
completely steady. On Windows, IE8 started at about 33k and allowed
that to grow to about 57-59k before reclaiming back down to 33k again
and allowing it to grow. (Wow is IE slow.) Even IE6 on Windows 2000
(measured via Task Manager rather than Chrome) reclaimed the memory
(occillating between 7k and 25k).

Then I modified the code to retain the TestClass instances, to test
whether the instances were somehow keeping the elements in memory. In
all five cases (Chrome, Firefox, and Opera under Linux, IE8 under
Windows, and IE6 under Windows), they weren't. The memory use was
virtually identical to the first test, which shows that by the time
you've done your "destroy", the instances *don't* retain any memory
references that prevent cleanup. (The instances themselves will be
very small.)

BTW, you don't need to explicitly null-out the array elements before
releasing the array. I've heard people say you do, but it doesn't make
any sense from a JavaScript specification perspective (not that that
matters, particularly not when you're talking about IE) but this
seemed like a good opportunity to test it for myself. Commenting out
the loop in `destroy` that nulls out the elements made no difference,
not even on IE6. I think it's a myth.

So that means your `destroy` can consist entirely of this:

    destroy: function() {
        delete this.options;

...since you're keeping everything on the `options` object.

Here are the test files:
http://pastie.org/1240577 - the basic counter test
http://pastie.org/1240579 - keep the instances test
http://pastie.org/1240582 - don't null out array entries test
http://pastie.org/1240613 - using the one-liner `destroy` above

T.J. Crowder
Independent Software Engineer
tj / crowder software / com
www / crowder software / com

On Oct 22, 10:52 am, jose maria Cano <josemaria.c...@gmail.com> wrote:
> Hi guys,
> I have a big problem in my application, when I create a global class
> object is impossible for me to release the memory and I'm having
> memory leaks.
> I've made a small class as example.
> var TestClass = Class.create({
>     initialize: function() {
>         this.options = {
>             vari: '',
>             array: '',
>             testDiv: ''
>         };
>         this.addElement();
>     },
>     addElement: function(element) {
>         var a = 0;
>         var arrayDivs = [];
>         alert('before create element');
>         for (var i = 0; i < 2000; i++) {
>             var div = new Element('div');
>             div.innerHTML = 'test' + i;
>             arrayDivs.push(div);
>         }
>         alert('after create element');
>         this.options.vari = 'pepe';
>         this.options.array = arrayDivs;
>         this.options.testDiv = new Element('div', { 'id':
> 'testdivPepe' });
>         this.destroy();
>     },
>     destroy: function() {
>         alert('before destroy');
>         for (var i = 0; i < this.options.array.length; i++) {
>             this.options.array[i] = null;
>             //this.options.array.pop();
>         }
>         //this.options.array.splice(0, this.options.array.length);
>         this.options.testDiv = null;
>         this.options.vari = null;
>         this.options.array = null;
>         this.options = null;
>         //delete this.options.array;
>         //delete this.options.testDiv;
>         //delete this.options.vari;
>         //delete this.options;
>         alert('after destroy');
>     }
> });
> I've tryed the delete, put the variable to null, to undefined, also
> remove() for the html and no way to release the memory.
> I really need some help here. can you give a hand here?
> Kr, Jose

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