Creates a "subject" by basically gluing an observer to an observable.
Creates a new Observable with this Subject as the source. You can do this to create custom Observer-side logic of the Subject and conceal it from code that uses the Observable.
Observable that the Subject casts to
Used as a NON-CANCELLABLE means of subscribing to an observable, for use with
APIs that expect promises, like async/await. You cannot unsubscribe from this.
WARNING: Only use this with observables you know will complete. If the source observable does not complete, you will end up with a promise that is hung up, and potentially all of the state of an async function hanging out in memory. To avoid this situation, look into adding something like timeout, {@link take}, {@link takeWhile}, or {@link takeUntil} amongst others.
import { interval, take } from 'rxjs';
const source$ = interval(1000).pipe(take(4));
async function getTotal() {
let total = 0;
await source$.forEach(value => {
total += value;
console.log('observable -> ' + value);
});
return total;
}
getTotal().then(
total => console.log('Total: ' + total)
);
// Expected:
// 'observable -> 0'
// 'observable -> 1'
// 'observable -> 2'
// 'observable -> 3'
// 'Total: 6'
a handler for each value emitted by the observable
a promise that either resolves on observable completion or rejects with the handled error
a handler for each value emitted by the observable
a constructor function used to instantiate the Promise
a promise that either resolves on observable completion or rejects with the handled error
A Subject is a special type of Observable that allows values to be multicasted to many Observers. Subjects are like EventEmitters.
Every Subject is an Observable and an Observer. You can subscribe to a Subject, and you can call next to feed values as well as error and complete.