observable.js

      // create observable
      const exampleObservable$ = new Observable((observer) => {
          
        // observable execution
        observer.next('example value 1');
        observer.next('example value 2');
        observer.next('example value 3’);
        
        observer.complete();
      })
      // subscribe
      const observer = exampleObservable$.subscribe((item) => {
          console.log(item);
        })
      // unsubscribe the observer
      observer.unsubscribe();