mastodon/app/javascript/mastodon/load_polyfills.js

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// Convenience function to load polyfills and return a promise when it's done.
// If there are no polyfills, then this is just Promise.resolve() which means
// it will execute in the same tick of the event loop (i.e. near-instant).
function importBasePolyfills() {
return import(/* webpackChunkName: "base_polyfills" */ './base_polyfills');
}
function importExtraPolyfills() {
return import(/* webpackChunkName: "extra_polyfills" */ './extra_polyfills');
}
function loadPolyfills() {
const needsBasePolyfills = !(
Array.prototype.includes &&
HTMLCanvasElement.prototype.toBlob &&
window.Intl &&
Number.isNaN &&
Object.assign &&
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Object.values &&
window.Symbol
);
// Latest version of Firefox and Safari do not have IntersectionObserver.
// Edge does not have requestIdleCallback and object-fit CSS property.
// This avoids shipping them all the polyfills.
const needsExtraPolyfills = !(
window.IntersectionObserver &&
window.IntersectionObserverEntry &&
'isIntersecting' in IntersectionObserverEntry.prototype &&
window.requestIdleCallback &&
'object-fit' in (new Image()).style
);
return Promise.all([
needsBasePolyfills && importBasePolyfills(),
needsExtraPolyfills && importExtraPolyfills(),
]);
}
export default loadPolyfills;