Does JavaScript have an equivalent to Perl's DESTROY method?

Question

Is there any method that is called or event that is dispatched right before an Element is cleaned up by the JavaScript garbage collector?

In Perl I would write:

package MyObj;

sub new {bless {}}

sub DESTROY {print "cleaning up @_\n"}

and then later:

{
    my $obj = MyObj->new;

    # do something with obj

}  # scope ends, and assuming there are no external references to $obj,
   #   the DESTROY method will be called before the object's memory is freed

My target platform is Firefox (and I have no need to support other browsers), so if there is only a Firefox specific way of doing this, that is fine.

And a little background: I am writing the Perl module XUL::Gui which serves as a bridge between Perl and Firefox, and I am currently working on plugging a few memory leaks related to DOM Elements sticking around forever, even after they are gone and no more references remain on the Perl side. So I am looking for ways to either figure out when JavaScript Elements will be destroyed, or a way to force JavaScript to cleanup an object.

If there is no way to do this in pure JavaScript, a solution using XPConnect/XPCOM or any other Mozilla specific technology is acceptable.

Answer 1

There's no mechanism for that in pure JavaScript.

Answer 2

Does XUL::Gui allow you to interact with the browser at the SpiderMonkey API layer? If so, https://developer.mozilla.org/en/SpiderMonkey/JSAPI_Reference/JSClass.finalize might be useful to you. Otherwise, you may be stuck since as Matthew Flaschen says above, there's no way to do it inside Javascript.