Question

I’m making a lightbox, do I need to use the

$(window.top).unload(function() { .. });

to do clean up of variables, or will all browsers automatically clean up everything and reset memory and what not?

Do I need to bother or will the browser do it for me? What with all the memory leaks and all..

Edit: I attached a lot of data to div elements. So do I need to do removeData at unload?

Answer 1

There are a couple different ways to create memory leaks in javascript. Most have to do with creating circular references between javascript objects and the DOM. see:

http://www.ibm.com/developerworks/web/library/wa-memleak/

but otherwise, no, you do not have to explicitly delete references to things – the javascript garbage collector will do this for you.

The code snippet that you posted has a side effect that you should be aware of, however. If you attach anything to the onunload handler for the document, then browsers that support caching the state of the DOM/javascript engine for fast retrieval when navigating backwards/forwards are no longer able to keep the page in the bfcache (see http://www.webkit.org/blog/516/webkit-page-cache-ii-the-unload-event/). This can have performance implications.