Observer Pattern Interfaces

Observer.d.ts

interface Observer {
    // Receive update from subject.
    update(subject: Subject | CustomEvent): void;
}

interface Subject {
    // Attach an observer to the subject.
    attach(observer: Observer): void;

    // Detach an observer from the subject.
    detach(observer: Observer): void;

    // Notify all observers about an event.
    notify(event: CustomEvent | undefined): void;
}