W3cubDocs

/RxJS

throttle

function stable

Emits a value from the source Observable, then ignores subsequent source values for a duration determined by another Observable, then repeats this process.

`throttle<T>(durationSelector: (value: T) => SubscribableOrPromise<any>, config: ThrottleConfig = defaultThrottleConfig): MonoTypeOperatorFunction<T>`

Parameters

durationSelector

A function that receives a value from the source Observable, for computing the silencing duration for each source value, returned as an Observable or a Promise.

config

Optional. Default is defaultThrottleConfig.

a configuration object to define leading and trailing behavior. Defaults to { leading: true, trailing: false }.

Returns

MonoTypeOperatorFunction<T>: An Observable that performs the throttle operation to limit the rate of emissions from the source.

Description

It's like throttleTime, but the silencing duration is determined by a second Observable.

throttle marble diagram

throttle emits the source Observable values on the output Observable when its internal timer is disabled, and ignores source values when the timer is enabled. Initially, the timer is disabled. As soon as the first source value arrives, it is forwarded to the output Observable, and then the timer is enabled by calling the durationSelector function with the source value, which returns the "duration" Observable. When the duration Observable emits a value or completes, the timer is disabled, and this process repeats for the next source value.

Example

Emit clicks at a rate of at most one click per second

import { fromEvent } from 'rxjs';
import { throttle } from 'rxjs/operators';

const clicks = fromEvent(document, 'click');
const result = clicks.pipe(throttle(ev => interval(1000)));
result.subscribe(x => console.log(x));