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Build Reactive Websites with RxJS: Master Observables and Wrangle

Multicasting with the Subject Class

Let's see how we can use "Subject" and ‘AsyncSubject’ in RxJS.

We'll cover the following...

Subjects

At its core, a Subject acts much like a regular observable, but each subscription is hooked into the same source, like the publish/share example.

Subjects also are observers and have next, error, and done methods to send data to all subscribers at once:

TypeScript 3.3.4
const { Subject} = require('rxjs');
let mySubject = new Subject();
mySubject.subscribe(val => console.log('Subscription 1:', val));
mySubject.subscribe(val => console.log('Subscription 2:', val));
mySubject.next(42);
/*
  Console output:
  Subscription 1: 42
  Subscription 2: 42
*/

Because subjects are observers, they can be passed directly into a subscribe call, and all the events from the original observable will be sent through ...