rickandmorty_api_fetch_1.js

const URL = 'https://rickandmortyapi.com/api/episode';

async function recursion(url) {
  const response = await fetch(url);
  const data = await response.json();
  if (data && data.info && data.info.next) {
    let d2 = await recursion(data.info.next);
   return await [...data.results, ...d2];
  }
  return [...data.results];
}

(async () => console.log(await recursion(URL)))();

rickandmorty_api_fetch_2.js

const URL = 'https://rickandmortyapi.com/api/episode';
const findProperty = (obj, arr) => arr.reduce((a, key) => (a ? a[key] : undefined), obj);
const getProp = (arr) => (obj) => findProperty(obj, arr);

async function hateoas(url, fnNextUrl, fnGetData) {
  const res = await fetch(url);
  const json = await res.json();
  if (fnNextUrl(json)) {
    let nextData = await hateoas(fnNextUrl(json), fnNextUrl, fnGetData);
    return [...fnGetData(json), ...nextData];
  }
  return [...fnGetData(json)];
}

(async () => console.log(await hateoas(URL, getProp(['info', 'next']), getProp(['results']))))();

rickandmorty_api_fetch_3.js

import { expand, reduce, EMPTY, Observable } from 'rxjs';

function getObservableFromFetch(url) {
  //Create and return an Observable.
  return new Observable(observer => {
    //Make use of Fetch API to get data from URL                              
    fetch(url)
      .then(res => {
        /*The response.json() doesn't return json, it returns a "readable stream" which is a promise which needs to be resolved to get the actual data.*/
        return res.json();
      })
      .then(body => {
        observer.next(body);
        /*Complete the Observable as it won't produce any more event */
        observer.complete();
      })
      //Handle error
      .catch(err => observer.error(err));
  })
};

const URL = 'https://rickandmortyapi.com/api/episode';
getObservableFromFetch(URL).pipe(
  expand(response => response.info.next ? getObservableFromFetch(response.info.next) : EMPTY),
  reduce((acc, current) => acc.concat(current.results), [])
).subscribe({
  next: result => console.log(result)
});