Optional_bufferSize: numberThe size of the buffer to replay on subscription
Optional_windowTime: numberThe amount of time the buffered items will stay buffered
Optional_timestampProvider: TimestampProviderAn object with a now() method that provides the current timestamp. This is used to
calculate the amount of time something has been buffered.
StaticcreateCreates 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 this 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, take, takeWhile, or 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
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.
Optionalnext: null | ((value: T) => void)Optionalerror: null | ((error: any) => void)Optionalcomplete: null | (() => void)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
A variant of Subject that "replays" old values to new subscribers by emitting them when they first subscribe.
ReplaySubjecthas an internal buffer that will store a specified number of values that it has observed. LikeSubject,ReplaySubject"observes" values by having them passed to itsnextmethod. When it observes a value, it will store that value for a time determined by the configuration of theReplaySubject, as passed to its constructor.When a new subscriber subscribes to the
ReplaySubjectinstance, it will synchronously emit all values in its buffer in a First-In-First-Out (FIFO) manner. TheReplaySubjectwill also complete, if it has observed completion; and it will error if it has observed an error.There are two main configuration items to be concerned with:
bufferSize- This will determine how many items are stored in the buffer, defaults to infinite.windowTime- The amount of time to hold a value in the buffer before removing it from the buffer.Both configurations may exist simultaneously. So if you would like to buffer a maximum of 3 values, as long as the values are less than 2 seconds old, you could do so with a
new ReplaySubject(3, 2000).Differences with BehaviorSubject
BehaviorSubjectis similar tonew ReplaySubject(1), with a couple of exceptions:BehaviorSubjectcomes "primed" with a single value upon construction.ReplaySubjectwill replay values, even after observing an error, whereBehaviorSubjectwill not.See