Why would you destroy a node and `.then()` pause it? It doesn't make
sense even in plain English. If the contract of the method (expected
behavior) is to destroy the internal node, using it after is a error.
You can easily reimplement your use case reversing the logic:
```` js
setTimeout(() => {
demo.node.pause();
demo.destroy();
}, 3000);
````
Another solution is to implement a `beforeDestroy` event emitter and
listen to it, this way is certain that the code will be executed
always before the node is gone and after any async destroy logic:
```` js
class Demo {
constructor(el) {
this.beforeDestroy = new EventEmitter();
// Using the @angular/core EventEmitter because is more "close to English"
this.node = el;
}
destroy() {
return new Promise(resolve => resolve())
.then(() => this.beforeDestroy.emit())
.finally(() => {
this.node = null;
});
}
}
const demo = new Demo(document.querySelector('video'));
demo.beforeDestroy.subscribe(() => {
demo.node.pause();
});
setTimeout(() => {
demo.destroy();
}, 3000);
````
Anyway, the `then`, `catch` and `finally` methods mimic the serial
try/catch/finally, simply doesn't make sense finally statements
protecting code beyond it's try block definition, and chaining new
`.then`s _are_ beyond the promise definition. Also, async functions
already has finally blocks implementations in the same way as the
current `.finally` method spec, implementing a different behaviour
would be unnecessarily confusing.
Em sex, 7 de set de 2018 às 16:16, Jon Ronnenberg
<[email protected]> escreveu:
>
> I know I am late to the game and that Promise.prototype.finally is already in
> stage 4 but(!).
>
> It's just not very useful to have a final function when it's not the final
> function to run. If it's suppose to be for cleanup, then the current
> implementation is seriously lacking usefulness.
>
> Consider the following example:
>
> <audio
> class="i-am-the-element"
> autoplay="autoplay"
> controls="controls">
> <source type="audio/mp3"
> src="http:\/\/play.dogmazic.net\/play\/index.php?type=song&oid=22951&uid=-1&name=Black%20poetry%20-%20Aime-.mp3">
> </audio>
> <script>
> class Demo {
> constructor (element) {
> this.node = element
> }
> destroy () {
> return new Promise(resolve => {
> // do something or nothing
> resolve()
> }).finally(() => {
> // schedule for DOM removal
> this.node = null
> })
> }
> }
>
> const demo = new Demo(document.querySelector('.i-am-the-element'))
>
> setTimeout(() => {
> demo.destroy().then(() => {
> // will throw an error because finally was run before
> demo.node.pause()
> }).catch(console.error)
> }, 3000)
> </script>
>
> One grand idea about promises is to delegate and compose asynchronous
> functions, but the current implementation can not be used to for code
> delegation.
>
> From the top of my head the only way to have consumer code, tap into an
> execution process is to use callbacks which is what Promises were suppose to
> help alleviate.
>
> <audio
> class="i-am-the-element"
> autoplay="autoplay"
> controls="controls">
> <source type="audio/mp3"
> src="http:\/\/play.dogmazic.net\/play\/index.php?type=song&oid=22951&uid=-1&name=Black%20poetry%20-%20Aime-.mp3">
> </audio>
> <script>
> class Demo {
> constructor (element) {
> this.node = element
> }
> destroy (callback) {
> // do something or nothing
> try {
> callback()
> } finally {
> // schedule for DOM removal
> this.node = null
> }
> }
> }
>
> const demo = new Demo(document.querySelector('.i-am-the-element'))
>
> setTimeout(() => {
> demo.destroy(() => {
> demo.node.pause()
> })
> }, 3000)
> </script>
>
> If at all possible, please amend to the spec before it's too late! ... or
> just drop it.
>
> My current use-case is that I work with PSPDFKit and can not get DOM access
> but rather schedule removal of DOM nodes via their API, but I can pause
> audio/video - just not using Promise.prototype.finally as it is currently
> envisioned.
>
> Regards, Jon
>
> PS. Tested in Firefox 63.0b3 and Safari 11.1.2
> Here is a polyfill if you need:
> https://cdn.polyfill.io/v2/polyfill.minify.js?features=Promise.prototype.finally&flags=gated
>
> _______________________________________________
> es-discuss mailing list
> [email protected]
> https://mail.mozilla.org/listinfo/es-discuss
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