A naive question: don't you get working weakref by using a WeakMap and
getting and setting using the same key? A naive point of view suggests
that. What am I not seeing here?
Herby
Isiah Meadows wrote:
I'm resurrecting this [1] because I have found a use case where I needed
a weak reference. Is there any chance this could get into the language?
Here's my particular use case: making a stream with a rotating
destination that itself acts as a stream (snippet of that code, or what
I'd like it to be).
```js
function rotateStream(interval, format) {
// Without the weak reference here, there's a memory leak
const ref = new WeakReference({})
setStream(ref.get(), format)
setInterval(function () {
if (ref.exists()) setStream(ref.get(), format)
else clearInterval(this)
}, interval)
return ref.get()
}
```
This basically rotates an active stream, with the weak reference
pointing to the said stream. The alternative requires explicit marking
(in this case, with a `close` method):
```js
function leakyRotateStream(interval, format) {
let stream = {close() {
clearInterval(timer)
timer = stream = null
}}
const timer = setInterval(function () {
setStream(stream, format)
}, interval)
setStream(stream, format)
return stream
}
```
In this use case, weak references would simplify the implementation and
reduce memory costs. And I would rather take advantage of the GC
machinery than explicit memory management (as explicit as C), as it
would be easier to collect when that's the only thing referenced.
(The setInterval callback is gc'd with all its references when it's
cleared from within.)
Thankfully, I'm using Node.js, so `weak` [2] is an option (the only
option, really). But I would definitely appreciate if it was available
in JS proper, across engines. V8, SpiderMonkey, and JSC all have weak
references to JS objects as part of their public API, and I would be
surprised if the implementation work would be anything significant.
[1]: https://esdiscuss.org/topic/what-is-the-status-of-weak-references
[2]: https://github.com/TooTallNate/node-weak
--
Isiah Meadows
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