observable.ts

type Subscriber<T> = (val: T) => void;
type Unsubscribe = () => void;

export class Observable<T> {
  private _val: T;
  private _listners: Array<Subscriber<T>>;

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

  set(val: T) {
    this._val = val;
    this._listners.forEach(e => e(val));
  }

  get(): T {
    return this._val;
  }

  subscribe(e: Subscriber<T>): Unsubscribe {
    this._listners.push(e);

    return () => this._listners = this._listners.filter(el => e!==el);
  }

}