How to convert promise method to rxjs Observables in angular 10

Question

I am new to typescript and angular and observables. My question is I have this method that takes a URL and returns the favicon of that URL. How can I use observables instead of promise

 getFavIcon(url: string): Promise<any> {
      return new Promise((resolve, reject) => {
        const hostname = this.getDomain(url);
        const src = 'http://' + hostname + '/favicon.ico';

        const image = new Image();
        image.onerror = () => {
            reject({ hasFavourite: false });

        };
        image.onload = () => {
            resolve({ hasFavourite: true, imageURL: src});
        };
        image.src = src;
      });
  }

Answer 1

Its creation is quite similar to promise apart from observable can be a continuous stream and you have complete() it to behave like Promise

 getFavIcon(url: string): Promise<any> {
      return new Observable((obs) => {
        const hostname = this.getDomain(url);
        const src = 'http://' + hostname + '/favicon.ico';

        const image = new Image();
        image.onerror = () => {
            obs.error({ hasFavourite: false });

        };
        image.onload = () => {
            obs.next({ hasFavourite: true, imageURL: src});
            obs.complete()
        };
        image.src = src;
      });
  }