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IE javascript memory usage

Posted on 2008-10-08
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Last Modified: 2013-12-08
Load a page with the below code in IE7, the memory usage of the browser shoots up to about 100megs on my system and doesn't reduce down until the page is unloaded.  How do I clean up the memory the unused object is taking up?

In firefox if you try this the memory usage spikes and then a few seconds later reduces down, looks like their garbage collector takes care of it.
<script type="text/javascript">
    var obj = [];
    for (var x = 0; x < 999999; x++) obj[obj.length] = "a";
    obj = null;
    delete obj;
</script>

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Question by:eChalk
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9 Comments
 
LVL 44

Expert Comment

by:scrathcyboy
ID: 22674617
is there a purpose to this 1 million iteration loop?  Or are you just testing to see if javascript can tie up the entire system resources via the browser -- the answer is YES IT CAN !!
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Author Comment

by:eChalk
ID: 22674978
I have an extremely large page with lots of javascript objects and 3rd party components, and every time i refresh it is not releasing all of it's memory and growing very large in memory usage until the browser is closed.  This is a first step for me to be able to clean up... I'm wondering if in this case there is any way to clear the object from the browser memory without unloading the page.
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Accepted Solution

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Hube02 earned 500 total points
ID: 22675017
IE is known to have memory leaks, however, other browsers will also leak memory to some extent. There are many things that can cause this memory leakage and perhaps the code on your page incorporates some of the know issues.

You could start here: http://www.codeproject.com/KB/scripting/leakpatterns.aspx

Although, if you are using 3rd party components the problems may be difficult to locate. Many developers do not keep the problems in mind and in some cases do not know they are creating a problem. And then again, in some cases, it is not possible to avoid the problem completely.
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LVL 44

Expert Comment

by:scrathcyboy
ID: 22675051
"I have an extremely large page with lots of javascript objects and 3rd party components"

OK, the way to debug this is to run firefox, and use tools, error console, and look for any errors.  There are also more elaborate tools like firebug -- www.getfirebug.com/ -- which will tell you where the problems are.  

It would be a first guess to check the 3rd party components, that is what most would say.  But in your case if you are using javascript objects, I think that is the most likely place to look -- these objects will not be being closed correctly, and accumulate in the hundreds or thousands.  Try the debugging tools in firefox.
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Author Comment

by:eChalk
ID: 22678453
Firefox does not have as bad a leak as IE.  What tools are available in firefox to spot leaks?  I know of this one for IE (best of the ones i looked at): http://blogs.msdn.com/gpde/pages/javascript-memory-leak-detector.aspx
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LVL 44

Expert Comment

by:scrathcyboy
ID: 22680912
In FF, there is the built-in error console -- for more elaborate checking of objects not being closed, try their Firebug Plug in --  https://addons.mozilla.org/firefox/addon/1843
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LVL 44

Expert Comment

by:scrathcyboy
ID: 22852162
how come the comment 22680912 was not accepted then?
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Author Comment

by:eChalk
ID: 22852217
Because Firebug doesn't have an in depth memory tracing module.  Once the page unloads, theres no window to go to to see all the stuff still hanging, like the JavaScript Memory Leak Detector for IE.
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