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/RxJS

window

function stable

Branch out the source Observable values as a nested Observable whenever windowBoundaries emits.

`window<T>(windowBoundaries: Observable<any>): OperatorFunction<T, Observable<T>>`

Parameters

windowBoundaries

An Observable that completes the previous window and starts a new window.

Returns

OperatorFunction<T, Observable<T>>: An Observable of windows, which are Observables emitting values of the source Observable.

Description

It's like buffer, but emits a nested Observable instead of an array.

window marble diagram

Returns an Observable that emits windows of items it collects from the source Observable. The output Observable emits connected, non-overlapping windows. It emits the current window and opens a new one whenever the Observable windowBoundaries emits an item. Because each window is an Observable, the output is a higher-order Observable.

Example

In every window of 1 second each, emit at most 2 click events

import { fromEvent, interval } from 'rxjs';
import { window, mergeAll, map, take } from 'rxjs/operators';

 const clicks = fromEvent(document, 'click');
 const sec = interval(1000);
 const result = clicks.pipe(
     window(sec),
     map(win => win.pipe(take(2))), // each window has at most 2 emissions
     mergeAll(),              // flatten the Observable-of-Observables
 );
 result.subscribe(x => console.log(x));