Observable
A representation of any set of values over any amount of time. This is the most basic building block of RxJS.
§Implements
§Constructors
the function that is called when the Observable is
initially subscribed to. This function is given a Subscriber, to which new values
can be nexted, or an error method can be called to raise an error, or
complete can be called to notify of a successful completion.
§Properties
§Methods
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, take, takeWhile, or takeUntil amongst others.
Example
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
Passing a Promise constructor will no longer be available in upcoming versions of RxJS. This is because it adds weight to the library, for very little benefit. If you need this functionality, it is recommended that you either polyfill Promise, or you create an adapter to convert the returned native promise to whatever promise implementation you wanted. Will be removed in v8.
Creates a new Observable, with this Observable instance as the source, and the passed operator defined as the new observable's operator.
the operator defining the operation to take on the observable
a new observable with the Operator applied
Internal implementation detail, do not use directly. Will be made internal in v8.
If you have implemented an operator using lift, it is recommended that you create an
operator by simply returning new Observable() directly. See "Creating new operators from
scratch" section here: https://rxjs.dev/guide/operators
Instead of passing separate callback arguments, use an observer argument. Signatures taking separate callback arguments will be removed in v8. Details: https://rxjs.dev/deprecations/subscribe-arguments
Replaced with firstValueFrom and lastValueFrom. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise
Replaced with firstValueFrom and lastValueFrom. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise
Replaced with firstValueFrom and lastValueFrom. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise