function Observable(forEach) {
this._forEach = forEach;
}
Observable.prototype = {
forEach: function (onNext, onError, onCompleted) {
if (typeof onNext === "function") {
return this._forEach({
onNext,
onError: onError || function () {},
onCompleted: onCompleted || function () {},
});
} else {
return this._forEach(onNext);
}
},
map: function (transformer) {
const self = this;
return new Observable(function forEach(observer) {
return self.forEach(
(data) => {
observer.onNext(transformer(data));
},
(e) => {
observer.onError(e);
},
() => {
observer.onCompleted();
}
);
});
},
filter: function (preditionFn) {
const self = this;
return new Observable(function forEach(observer) {
return self.forEach(
(data) => {
if (preditionFn(data)) {
observer.onNext(data);
}
},
(e) => {
observer.onError(e);
},
() => {
observer.onCompleted();
}
);
});
},
take: function (maxCount) {
const self = this;
let count = 0;
return new Observable(function forEach(observer) {
return self.forEach(
(data) => {
const sub = observer.onNext(data);
count++;
if (count === maxCount) {
observer.onCompleted();
sub.dispose();
}
return sub;
},
(e) => {
observer.onError(e);
},
() => {
observer.onCompleted();
}
);
});
},
};
Observable.fromEvent = function (dom, eventName) {
return new Observable(function forEach(observer) {
const handler = (e) => observer.onNext(e);
dom.addEventListener(eventName, handler);
return {
dispose: () => {
dom.removeEventListener(eventName, handler);
},
};
});
};
Observable.fromObservations = function (obj) {
return new Observable(function forEach(observer) {
const handler = (e) => observer.onNext(e);
Object?.observe?.(obj, handler);
return {
dispose: () => {
Object?.unobserve?.(obj, handler);
},
};
});
};