What is RxJS?

RxJS (Reactive Extensions for JavaScript) is a library for reactive programming using observables that makes it easier to compose asynchronous or callback-based code. RxJS provides an implementation of the Observable type.

RxJS offers a number of functions that can be used to create new observables. These functions can simplify the process of creating observables from things such as events, timers, promises, and so on.

Create an Observable out of a promise

import { from } from 'rxjs';

const data = from(fetch('/api/endpoint'));

// Subscribe to begin listening for async result
data.subscribe({
  next(response) { console.log(response); },
  error(err) { console.error('Error: ' + err); },
  complete() { console.log('Completed'); }
});

Create an Observable that will create an AJAX request

import { ajax } from 'rxjs/ajax';

const apiData = ajax('/api/data');

// Subscribe to create the request
apiData.subscribe(res => console.log(res.status, res.response));