[RxJS] SampleTime & Sample

SampleTime

If there is no value emiited between sample time and previous emited value, ouput won't have anything.

import { fromEvent, interval } from 'rxjs';
import { sample, sampleTime, map } from 'rxjs/operators';

const click$ = fromEvent(document, 'click');
const timer$ = interval(1000);

click$
  .pipe(
    /*
     * At the duration you specify, sample time will emit the last
     * emitted value within that window. For instance, in this 
     * example we are sampling at an interval of 4s. When the 4s
     * interval timer begins, you can click twice. Once 4s passes,
     * the second click will be emitted. This behavior is then repeated.
     * If no values are emitted from the source in the sample
     * window no values are emitted by sampleTime.
     */
    sampleTime(4000),
    // @ts-ignore
    map(({ clientX, clientY }) => ({
      clientX,
      clientY
    }))
  )
  .subscribe(console.log);

 

Sample

import { fromEvent, interval } from 'rxjs';
import { sample, sampleTime, map } from 'rxjs/operators';

const click$ = fromEvent(document, 'click');
const timer$ = interval(1000);

timer$.pipe(
  /*
   * The sample window can also be based off another stream. 
   * For instance, in this example every time you click the
   * last value emitted by the timer$ observable will be emitted
   * by sample.
   */
  sample(click$)
).subscribe(console.log);