Example of a recursive call to an API using Observables

observable-recursive.js

// Example for article : https://medium.com/@simonb90/appels-api-itératifs-avec-rxjs-a1c2593c558b

/*
 *  Definition of API method:
 *    getEntitiesByPage(page: number): Observable<Entity[]>
 */

let iterator = new BehaviorSubject<number>(1);

iterator.mergeMap((i) => {
  return getEntitiesByPage(i).do((entities) => {
    if (entities.length > 0) {
      iterator.next(i + 1);
    }
  });
})
.takeWhile(entities => entities.length > 0)
.startWith([])
.scan((allEntities, currentPageEntities) =>
  allEntities.concat(currentPageEntities)
);