throttleTime

function stable

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

`throttleTime<T>(duration: number, scheduler: SchedulerLike = asyncScheduler, config: ThrottleConfig = defaultThrottleConfig): MonoTypeOperatorFunction<T>`

Parameters

duration

Time to wait before emitting another value after emitting the last value, measured in milliseconds or the time unit determined internally by the optional scheduler.

scheduler

Optional. Default is asyncScheduler.

The SchedulerLike to use for managing the timers that handle the throttling. Defaults to asyncScheduler.

config

Optional. Default is defaultThrottleConfig.

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

Returns

MonoTypeOperatorFunction<T>: A function that returns an Observable that performs the throttle operation to limit the rate of emissions from the source.

Description

Lets a value pass, then ignores source values for the next duration milliseconds.

throttleTime marble diagram

throttleTime 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. After duration milliseconds (or the time unit determined internally by the optional scheduler) has passed, the timer is disabled, and this process repeats for the next source value. Optionally takes a SchedulerLike for managing timers.

Examples

Limit click rate

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

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

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

Double Click

The following example only emits clicks which happen within a subsequent delay of 400ms of the previous click. This for example can emulate a double click. It makes use of the trailing parameter of the throttle configuration.

import { fromEvent, asyncScheduler } from 'rxjs';
import { throttleTime, withLatestFrom } from 'rxjs/operators';

// defaultThottleConfig = { leading: true, trailing: false }
const throttleConfig = {
  leading: false,
  trailing: true
}

const click = fromEvent(document, 'click');
const doubleClick = click.pipe(
  throttleTime(400, asyncScheduler, throttleConfig)
);

doubleClick.subscribe((throttleValue: Event) => {
  console.log(`Double-clicked! Timestamp: ${throttleValue.timeStamp}`);
});

If you enable the leading parameter in this example, the output would be the primary click and the double click, but restricts additional clicks within 400ms.