observer pattern implementation in typescript

observerPattern.ts

interface Observer<ObservableClass, ObservableEventEnum>{
    update: (ObjectRef: ObservableClass, observableEventEnum: ObservableEventEnum) => void;
}   

class Observable<ObservableClass, ObservableEventEnum>{
    observers: Observer<ObservableClass, ObservableEventEnum>[];

    constructor(){
        this.observers = [];
    }

    attach(observer: Observer<ObservableClass, ObservableEventEnum>){
        this.observers.push(observer);
    }

    detach(observer: Observer<ObservableClass, ObservableEventEnum>){
        const indexOfObserver = this.observers.indexOf(observer);
        if(indexOfObserver > -1)
            this.observers.splice(indexOfObserver, 1);
    }

    notify(eventType: ObservableEventEnum){
        let objRef = ((this as unknown) as ObservableClass);
        this.observers.forEach(observer => {
            observer.update(objRef, eventType);
        });
    }
}