Re: Loading Dom nodes into Memory - best practise

We found that IE leaks profusely when attaching dom objects to javascript
objects. And the the dynamic attachment of event handlers also caused
leaking.

What we did to minimize this was to create a global cache where javascript
objects where stored which had had dom objects and their associated events
rigged. On window.unload we would loop through this cache and unhook
DOMjects from Jobjects also setting the DOMjects events to null.

Bring up you task manager's process list and watch you browser's memory as
you refresh over and over. If it climbs but then levels out you should be
fine. If it never stops climbing you'll have to find your leak. The best way
to do this is to start simple and keep adding chunks of your code until the
leak is evident.

Regards,
Dave Cline

On 5/14/06, Lon Boonen <[email protected]> wrote:
>
> To Ian
>
> instead of refreshing a few hundred times you should attach a 10MB string
> to each DOM node you are storing. Then refreshing a single time will be
> conclusive if you take a look at Task Manager.
>
> How to build a 10MB string? Join a couple of arrays. It's fast and very
> obvious.
>
> To Richard.
>
> Have you measured the time needed for DOM traversal before you started
> this dom-nodes-storage-quest?
> It's very, very probably negligable.
> I myself never attach an event handler to anything but the
> documentElement. On each click I traverse the DOM looking for the level that
> is interested in handling the event. Time required is completely negligable.
>
> Just my thoughts.
>
> groetjes Lon
>
>
> ________________________________
>
> From: [email protected] on behalf of Ian Petersen
> Sent: Sun 14/05/2006 19:06
> To: [email protected]
> Subject: Re: [wdf-dom] Loading Dom nodes into Memory - best practise
>
>
>
> Hi Richard,
>
> Instead of just leaving the page open in your browser for a long time,
> try refreshing the page several hundred times.
>
> Holding DOM nodes in memory can cause a memory leak if you have any
> circular references in your data structures.  The simplest circular
> reference is a Javascript object that points to a DOM node that points
> back to that same Javascript object.  Any circle is a problem, though,
> so introducing extra Javascript objects or extra DOM nodes into the
> circle doesn't solve the problem.
>
> One particularly nasty trick in this problem is that event handlers
> can be part of the circle.  Functions are Javascript objects and, when
> they are closures, too, they can have references to other objects
> (including DOM nodes).  (In case you've never heard of a closure, it's
> basically a nested function.)
>
> If you can refresh your test page a few hundred (or a few thousand)
> times without crashing the browser, you're probably OK.  If the
> browser eventually crashes, then you'll need to break the circular
> references somehow.  You can either redesign your page to not create
> the circles in the first place or you can add unload handlers that go
> around breaking links as the browser dismantles the page.
>
> Ian
>
> On 5/14/06, Richard Garbutt <[email protected]> wrote:
> > Hi,
> >
> > I'm working on a project where I'm manipulating elements on the page
> > in response to user input. I've created objects which load the
> > elements to be manipulated as member variables on page load. The
> > objects provide an interface to manipulate the elements they are
> > responsible for. The event handlers use this interface.
> >
> > This approach makes event handling very responsive, as no dom
> > traversal is needed when the event fires. (Or very little - sometimes
> > I use firstChild or previousSibling.)
> >
> > I'm wondering if there are any problems caused by loading dom nodes
> > into browser memory and leaving them there for as long as the page is
> > open in the user's browser. I'm loading about 20-50 nodes like this.
> > Leaving the page open in Firefox and IE for several hours doesn't seem
> > to cause any problems - but I have plenty of memory.
> >
> > regards,
> > Richard
> >
> >
> >
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-- 
Dave Cline
www.davecline.com/
[email protected]


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