Answer

new-job.js

const request = require('request');
const Rx = require('rxjs');
const { expand } = require('rxjs/operators');
const { empty } = require('rxjs/observable/empty');
const URL = 'https://letsrevolutionizetesting.com/challenge';

let makeHttpCall = (url = URL) => {
	return new Promise((resolve, reject) => {
		request.get(url, {json: true}, (e, res, body) => {
			if(e) {
				reject(e)
			}
			resolve(res)
		})
	})
}

const calls = Rx.Observable.fromPromise(makeHttpCall(URL));
let ids = calls.pipe(
	expand(x => {
			if(typeof x === 'object' && x.body.hasOwnProperty('follow')) {
				return makeHttpCall(x.body.follow)
			}
			console.log('Followed Until End:' + x.body.message)
			return empty()
		})
).takeWhile(x => x.hasOwnProperty('body'))

ids.subscribe(
	(x) => {
		if(typeof x === 'string') {
			console.log('done', x)
		}
		console.log('Following...')
	},
	(e) => {
		console.log('Error', e)
	},
	() => {
		console.log('Yay all done!')
	}
)