# windowWhen

#### signature: `windowWhen(closingSelector: function(): Observable): Observable`

## Close window at provided time frame emitting observable of collected values from source.

### Examples

**Example 1: Open and close window at interval**

( [StackBlitz](https://stackblitz.com/edit/typescript-52tu8k?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/tuhaposemo/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/gnx9fb3h/) )

```js
// RxJS v6+
import { interval, timer } from 'rxjs';
import { windowWhen, tap, mergeAll } from 'rxjs/operators';

//emit immediately then every 1s
const source = timer(0, 1000);
const example = source.pipe(
  //close window every 5s and emit observable of collected values from source
  windowWhen(() => interval(5000)),
  tap(_ => console.log('NEW WINDOW!'))
);

const subscribeTwo = example
  .pipe(
    //window emits nested observable
    mergeAll()
    /*
      output:
      "NEW WINDOW!"
      0
      1
      2
      3
      4
      "NEW WINDOW!"
      5
      6
      7
      8
      9
    */
  )
  .subscribe(val => console.log(val));
```

### Additional Resources

* [windowWhen](https://rxjs.dev/api/operators/windowWhen) 📰 - Official docs

***

> 📁 Source Code: <https://github.com/ReactiveX/rxjs/blob/master/packages/rxjs/src/internal/operators/windowWhen.ts>


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