Are event listeners weak references?

[Tom]

There's not too much info about event listeners and the garbage collector in the node.js documentation, which is why I want to ask if event listeners are by default weak references. This is considered bad practice by some people, I believe.

Basically, when do I need to remove event listeners and when do I not have to remove them?

Regards,

Tom

[Rick Olson]

I don't think so. It just adds the function to an _events hash on the
EventEmitter:

http://github.com/ry/node/blob/master/lib/events.js#L66-69

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Rick Olson
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[Theturtle32]

There's no such thing as a weak reference in JavaScript.

If the event emitter is a very long-lived object, and you keep adding
new listeners to it, they would accumulate over time.

But when an event emitter is garbage collected, the listener functions
would also be garbage collected as long as there wasn't anything else
referencing them, as far as I'm aware. I believe that would normally
be the case with an anonymous function. Just don't hold another
reference to those functions and you should be fine.

Brian

[Tom]

"But when an event emitter is garbage collected, the listener functions
would also be garbage collected as long as there wasn't anything else
referencing them, as far as I'm aware."

Could anyone confirm this? It is surprising howmuch doubt there is about this subject, since (almost) any project with Node has to use these event listeners. Not having them garbage collected would result in a memory leak.

- Tom

2010/7/7 Theturtle32 <thetu...@gmail.com>

[r...@tinyclouds.org]

On Wed, Jul 7, 2010 at 1:39 PM, Tom <tomm...@gmail.com> wrote:
> "But when an event emitter is garbage collected, the listener functions
> would also be garbage collected as long as there wasn't anything else
> referencing them, as far as I'm aware."
> Could anyone confirm this? It is surprising howmuch doubt there is about
> this subject, since (almost) any project with Node has to use these event
> listeners. Not having them garbage collected would result in a memory leak.

Event emitters get collected like all other objects.

[Tom]

Yes. The issue is the collection of the event listeners though. Is this done whenever an event emitter is qualified for collection? TheTurtle did say so, but he was not 100% sure either.

- Tom

2010/7/7 <r...@tinyclouds.org>

--

[Marco Rogers]

Tom the event listeners are just functions that are held in the
_events hash in the emitter. When the emitter gets collected the hash
gets collected and there's nothing else referencing the listener
functions. So eventually they get collected too. It's just
javascript. Nothing fancy happening.

I think there is some confusion because v8 has the concept of weak
references on the C++ side. But there is nothing there in the event
emitter code that would keep listeners from being collected. Does
that help?

:Marco

> > nodejs+un...@googlegroups.com<nodejs%2Bunsu...@googlegroups.com>
> > .

[r...@tinyclouds.org]

On Wed, Jul 7, 2010 at 3:22 PM, Tom <tomm...@gmail.com> wrote:
> Yes. The issue is the collection of the event listeners though. Is this done
> whenever an event emitter is qualified for collection? TheTurtle did say so,
> but he was not 100% sure either.

Yes, Event Listeners get garbage collected like all other objects.

[Tom]

Yes, thank you.

2010/7/7 <r...@tinyclouds.org>