How can I avoid causing memory leaks in Firefox?

Question

It seems that there is a lot of information on memory leaks in IE and how web developers can avoid them, but I can't find much on avoiding leaks in FF. I've found lots of random tips on how end users can tweak their preferences, or tips for extension developers, but little on what I can do as a web developer to make sure my pages don't leak. Am I missing something? It seems lazy to just blame it on the user and say "you've got too many extensions". Or are the major patterns the same as in IE -- circular references and all that?

Also, if anyone knows of any tools to troubleshoot leaks in FF, that would be great. I found this: https://addons.mozilla.org/en-US/firefox/addon/2490/ But it's apparently just for chrome and extension development.

Answer 1

Outside of the design patterns to favour the only truely safe way is to test your pages thoroughly. To monitor the memory usage of the browser Task Manager is alright but Process Explorer provides more accurate results.

JavaScript is one cause of memory leaks but be careful with flash movies on pages too. Our content team added a movie from our design department that used a thrid party transition affect and this swallowed 10Mb every 20s or so. Just watching the movie loop through it was obvious in TaskManager to see the memory jump when the affect occured and the it never quite release it all back.

Answer 2

I don't know if there is specific information for Firefox, but the generic tips still apply.

I suggest that you closely examine all loops and recursive functions. Re-use existing objects over creating new ones, and ensure that temporary objects and primitives exit scope so that they can be freed.

Answer 3

You can force to run a Garbage Collector in FireFox. The Garbadge Collector will destroy & release objects that are not used anymore. The only possibility of "Leaking memory" with a Garbage Collector is not a "leak" but a reference which makes no sense: remove all references to objects that you don't want to use.

Read more on this page:
http://adblockplus.org/blog/different-ways-to-force-garbage-collection

Answer 4

Take a look at this link: http://www.mozilla.org/performance/tools.html

Link found on http://stackoverflow.com/questions/171565/javascript-memory-profiler-for-firefox

Answer 5

A bunch of what you read about how to avoid memory leaks in browsers is about how to avoid things that cause the browser to fail to reclaim memory that it should reclaim.

However, a more substantial problem in many cases is about Web pages holding on to objects that they don't need anymore. It's only the browser's job to reclaim things that are no longer "reachable" -- that is, things that the script / page can't get to anymore. If you're accumulating objects in an array and not removing them when you're done with them, memory usage will go up as the array gets bigger, and there's nothing the browser can do about that.

To phrase that another way: that's an issue of a memory leak in the Web page rather than in the browser. And the tool you want for that is a memory profiling tool to examine the objects that are reachable in your page, so you can tell whether there's stuff in there that you should no longer be holding on to. Writing such a tool for Firefox has been on my list of things to do for a while, but I haven't gotten around to it yet. I think there might be some ongoing work on writing one that integrates into Firebug.