Practice the observer pattern in typescript

app.ts

import { Subject } from "./subject";
import { Observer } from "./observer";

const subject = new Subject();
const observer1 = new Observer('John');
const observer2 = new Observer('Tae');
const observer3 = new Observer('Jin');

subject.subscribe(observer1);
subject.subscribe(observer2);
subject.subscribe(observer3);

subject.notify('hello');

interface.ts

export interface ISubject {
    subscribe: Function;
    unsubscribe: Function;
    notify: Function;
}

export interface IObserver {
    onSubscribe: Function
}

observer.ts

import { IObserver } from "./interface";

export class Observer implements IObserver {
    private name: string;
    constructor(name: string) {
        this.name = name;
    }
    onSubscribe(data): void {
        console.log(`-> ${this.name}: data received ${data}`);
    }
}

subject.ts

import { ISubject, IObserver } from "./interface";

export class Subject implements ISubject {
    private subscribers: Array<IObserver> = [];
    subscribe(observer: IObserver): void {
        this.subscribers.push(observer);
    }
    unsubscribe(observer: IObserver): void {
        this.subscribers.filter(s => s != observer);
    }
    notify(data): void {
        this.subscribers.map(s => s.onSubscribe(data));
    }
}

tsconfig.json

{
    "forceConsistentCasingInFileNames": true,
    "noImplicitReturns": true,
    "strict": true,
    "noUnusedLocals": true,
}