Desktop notifications simple implementation

DesktopNotification.ts

/**
 * Interfaz para acceder a notificaciones desktop
 * 
 * DesktopNotification.$show("Hey", {
 *               body: `you have ${totalDisplayed} tasks to do`,
 *               icon: '/yourlogo.png'
 *  });
 * @author Daniel Vera Morales
 */
export class DesktopNotification {
    private notify: Notification;

    public static $show(title: string, attributes: NotificationOptions, callback?: (this: Notification, ev: Event) => any): Promise<Notification> {
        return (new DesktopNotification(title, attributes)).show(callback);
    }

    constructor(readonly title: string, readonly attributes: NotificationOptions) { }

    /**
     * Verifica que exista esta caracteristica en el navegador 
     */
    isAvailable(): boolean {
        return ("Notification" in window);
    }

    /**
     * Despliega una notificación utilizando el titulo y los atributos del constructor.
     * 
     * Opcionalmente recibe un callback para ser ejecutado cuando se disparé el evento 
     * onShow.
     */
    show(callback?: (this: Notification, ev: Event) => any): Promise<Notification> {
        return new Promise<Notification>((accept, reject) => {

            if (!this.isAvailable()) {
                reject();
            }

            this.hasPermission().then(() => {
                const notification = new Notification(this.title, this.attributes);
                if (callback) {
                    notification.onshow = callback;
                }
                accept(notification);
            }).catch(reject);
        });


    }
    private hasPermission(): Promise<never> {
        return new Promise<never>((accept, reject) => {
            Notification.requestPermission(function (result) {
                if (result === 'denied')
                    reject();
                else {
                    accept();
                }
            });
        });
    }
}