buffer

signature: buffer(closingNotifier: Observable): Observable

Collect output values until provided observable emits, emit as array.

Ultimate RxJS

Examples

Example 1: Using buffer to recognize double clicks

( StackBlitz)

// RxJS v6+
import { fromEvent } from 'rxjs';
import { buffer, filter, throttleTime } from 'rxjs/operators';
// streams
const clicks$ = fromEvent(document, 'click');
/*
Collect clicks that occur, after 250ms emit array of clicks
*/
clicks$
.pipe(
buffer(clicks$.pipe(throttleTime(250))),
// if array is greater than 1, double click occured
filter(clickArray => clickArray.length > 1)
)
.subscribe(() => console.log('Double Click!'));

Example 2: Buffer until document click

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { interval, fromEvent } from 'rxjs';
import { buffer } from 'rxjs/operators';
//Create an observable that emits a value every second
const myInterval = interval(1000);
//Create an observable that emits every time document is clicked
const bufferBy = fromEvent(document, 'click');
/*
Collect all values emitted by our interval observable until we click document. This will cause the bufferBy Observable to emit a value, satisfying the buffer. Pass us all collected values since last buffer as an array.
*/
const myBufferedInterval = myInterval.pipe(buffer(bufferBy));
//Print values to console
//ex. output: [1,2,3] ... [4,5,6,7,8]
const subscribe = myBufferedInterval.subscribe(val =>
console.log(' Buffered Values:', val)
);

Additional Resources

📁 Source Code: https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/buffer.ts