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✏️ Editing: throttleTime.ts

import { asyncScheduler } from '../scheduler/async';
import { defaultThrottleConfig, throttle } from './throttle';
import { MonoTypeOperatorFunction, SchedulerLike } from '../types';
import { timer } from '../observable/timer';

/**
 * Emits a value from the source Observable, then ignores subsequent source
 * values for `duration` milliseconds, then repeats this process.
 *
 * <span class="informal">Lets a value pass, then ignores source values for the
 * next `duration` milliseconds.</span>
 *
 * ![](throttleTime.png)
 *
 * `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
 * {@link SchedulerLike} for managing timers.
 *
 * ## Examples
 *
 * #### Limit click rate
 *
 * Emit clicks at a rate of at most one click per second
 * ```ts
 * 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.
 *
 * ```ts
 * 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: ${throttleValue.timeStamp}`);
 * });
 * ```
 *
 * If you enable the `leading` parameter in this example, the output would be the primary click and
 * the double click, but restricts additional clicks within 400ms.
 *
 * @see {@link auditTime}
 * @see {@link debounceTime}
 * @see {@link delay}
 * @see {@link sampleTime}
 * @see {@link throttle}
 *
 * @param duration Time to wait before emitting another value after
 * emitting the last value, measured in milliseconds or the time unit determined
 * internally by the optional `scheduler`.
 * @param scheduler The {@link SchedulerLike} to use for
 * managing the timers that handle the throttling. Defaults to {@link asyncScheduler}.
 * @param config a configuration object to define `leading` and
 * `trailing` behavior. Defaults to `{ leading: true, trailing: false }`.
 * @return A function that returns an Observable that performs the throttle
 * operation to limit the rate of emissions from the source.
 */
export function throttleTime<T>(
  duration: number,
  scheduler: SchedulerLike = asyncScheduler,
  config = defaultThrottleConfig
): MonoTypeOperatorFunction<T> {
  const duration$ = timer(duration, scheduler);
  return throttle(() => duration$, config);
}

MR SKB