Using bufferCount in Rxjs: Retrieving the latest values

Question

Using bufferCount in Rxjs: Retrieving the latest values

Is there a method to access the most recent values emitted while using bufferCount(x), even if the buffer size does not reach x?

For example, in the code snippet below, only [0, 1] is printed. I would like the output to also include [2] under certain circumstances.

const subject = new Subject();

subject.asObservable()
  .pipe(bufferCount(2))
  .subscribe(console.log);

for(let i = 0; i < 3; i++) subject.next(i);

javascript rxjs

Answer 1

Answer №1

In order to receive the expected output, make sure to finish the inner observable:

subject.complete();

After completing the inner observable, the value [2] will be emitted as anticipated.

Answer 2

In order to receive the expected output, make sure to finish the inner observable:

subject.complete();

After completing the inner observable, the value [2] will be emitted as anticipated.

Answer 3

Answer №2

Utilize the takeLast operator to capture the final n values sent by the original Observable before it finishes. For instance:

import { fromEvent } from 'rxjs';
import { bufferCount, takeLast } from 'rxjs/operators';

const button = document.querySelector('button');
const click$ = fromEvent(button, 'click');

click$
  .pipe(
    bufferCount(5), // Buffer 5 clicks
    takeLast(1) // Capture the last buffer
  )
  .subscribe(buffer => {
    console.log('Last buffer:', buffer);
  });

The click$ Observable triggers with each user click on the button. By using bufferCount(5), we store 5 click events and send them as an array. Subsequently, takeLast(1) selects the final recorded buffer just before completion of the source Observable. Upon subscribing to this resultant Observable, the last emitted buffer is logged.

This will display the last set of 5 consecutive click events prior to the user ceasing to click the button. It's essential to note that if the user only clicked once, a single-click event array will be logged.

Answer 4

Utilize the takeLast operator to capture the final n values sent by the original Observable before it finishes. For instance:

import { fromEvent } from 'rxjs';
import { bufferCount, takeLast } from 'rxjs/operators';

const button = document.querySelector('button');
const click$ = fromEvent(button, 'click');

click$
  .pipe(
    bufferCount(5), // Buffer 5 clicks
    takeLast(1) // Capture the last buffer
  )
  .subscribe(buffer => {
    console.log('Last buffer:', buffer);
  });

The click$ Observable triggers with each user click on the button. By using bufferCount(5), we store 5 click events and send them as an array. Subsequently, takeLast(1) selects the final recorded buffer just before completion of the source Observable. Upon subscribing to this resultant Observable, the last emitted buffer is logged.

This will display the last set of 5 consecutive click events prior to the user ceasing to click the button. It's essential to note that if the user only clicked once, a single-click event array will be logged.

Using bufferCount in Rxjs: Retrieving the latest values

Answer №1

Answer №2

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