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@simevidas
Forked from AdaRoseCannon/Finished polyfill.js
Last active August 3, 2020 10:58
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Animation.prototype.finished polyfill
// only polyfill .finished in browsers that already support animate()
if (document.body.animate) {
// Chrome does not seem to expose the Animation constructor globally
if (typeof Animation === 'undefined') {
window.Animation = document.body.animate({}).constructor;
}
if (Animation.prototype.finished === undefined) {
Object.defineProperty(Animation.prototype, 'finished', {
get() {
if (!this._finished) {
this._finished = this.playState === 'finished' ?
Promise.resolve() :
new Promise((resolve, reject) => {
this.addEventListener('finish', resolve, {once: true});
this.addEventListener('cancel', reject, {once: true});
});
}
return this._finished;
}
});
}
}
@AdaRoseCannon
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Nice!!

@simevidas
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Author

Also works with await (inside an async function):

try { 
    await animation.finished;    
    // animation finished
} catch (e) {
    // animation aborted
}

Demo: https://jsbin.com/yejanag/edit?js,output

@AdaRoseCannon
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:D that's how I've been using it in my own code.

Promises and async functions are nice.

@simevidas
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After adding both the official Web Animations polyfill, and the above finished polyfill, I got the demos working in Edge, too, but there seems to be an issue in iOS Safari, which I’m unable to debug.

@davej
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davej commented Jul 12, 2019

I was getting an error in Safari 13 (tech preview):

Unhandled Promise Rejection: TypeError: The Animation.finished getter can only be used on instances of Animation

So I forked this to fix the error: https://gist.github.com/davej/23b0481016bcdb969df46423c6284771

image

@simevidas
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👍 Good to see more (full?) animation API support in the next version of Safari.

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