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
,
t
a
p
into a
n
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
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