export default class BaseObservableCollection {
constructor() {
this._handlers = new Set();
}
onSubscribeFirst() {
onUnsubscribeLast() {
subscribe(handler) {
this._handlers.add(handler);
if (this._handlers.length === 1) {
this.onSubscribeFirst();
return () => {
if (handler) {
this._handlers.delete(this._handler);
if (this._handlers.length === 0) {
this.onUnsubscribeLast();
handler = null;
return null;
};
// Add iterator over handlers here