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// Wrapper for IntersectionObserver in order to make working with it
// a bit easier. We also follow this performance advice:
// "If you need to observe multiple elements, it is both possible and
// advised to observe multiple elements using the same IntersectionObserver
// instance by calling observe() multiple times."
// https://developers.google.com/web/updates/2016/04/intersectionobserver
class IntersectionObserverWrapper {
callbacks = {};
observerBacklog = [];
observer = null;
connect (options) {
const onIntersection = (entries) => {
entries.forEach(entry => {
const id = entry.target.getAttribute('data-id');
if (this.callbacks[id]) {
this.callbacks[id](entry);
}
});
};
this.observer = new IntersectionObserver(onIntersection, options);
this.observerBacklog.forEach(([ id, node, callback ]) => {
this.observe(id, node, callback);
});
this.observerBacklog = null;
}
observe (id, node, callback) {
if (!this.observer) {
this.observerBacklog.push([ id, node, callback ]);
} else {
this.callbacks[id] = callback;
this.observer.observe(node);
}
}
unobserve (id, node) {
if (this.observer) {
delete this.callbacks[id];
this.observer.unobserve(node);
}
}
disconnect () {
if (this.observer) {
this.callbacks = {};
this.observer.disconnect();
this.observer = null;
}
}
}
export default IntersectionObserverWrapper;
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