doc/api/core/operators/forkjoinproto.md
# This is RxJS v 4. [Find the latest version here](https://github.com/reactivex/rxjs)### `Rx.Observable.prototype.forkJoin(...args, [resultSelector])`[Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/forkjoinproto.js "View in source") Runs all observable sequences in parallel and collect their last elements. #### Arguments1. `args`: `Arguments` | `Array` - An array or arguments of Observable sequences or Promises to collect the last elements for.2. `resultSelector`: `Function` - The result selector from all the values produced. If not specified, `forkJoin` will return the results as an array. #### Returns*(`Observable`)*: An observable sequence with an array collecting the last elements of all the input sequences or the result of the result selector if specified. #### Example```js// With a selectorvar source = Rx.Observable.just(42).forkJoin( Rx.Observable.range(0, 3), function (s1, s2) { return s1 + s2; }); var subscription = source.subscribe( function (x) { console.log('Next: %s', x); }, function (err) { console.log('Error: %s', err); }, function () { console.log('Completed'); }); // => Next: 44// => Completed // Without a selectorvar source = Rx.Observable.just(42).forkJoin( Rx.Observable.range(0, 3)); var subscription = source.subscribe( function (x) { console.log('Next: %s', x); }, function (err) { console.log('Error: %s', err); }, function () { console.log('Completed'); }); // => Next: [42, 2]// => Completed``` ### Location File:- [`/src/core/linq/observable/forkjoinproto.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/forkjoinproto.js) Dist:- [`rx.all.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.all.js)- [`rx.all.compat.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.all.compat.js)- [`rx.experimental.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.experimental.js) Prerequisites:- [`rx.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.js) | [`rx.compat.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.compat.js) | [`rx.lite.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.lite.js) | [`rx.lite.compat.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.lite.compat.js) NPM Packages:- [`rx`](https://www.npmjs.org/package/rx) NuGet Packages:- [`RxJS-All`](http://www.nuget.org/packages/RxJS-All)- [`RxJS-Experimental`](http://www.nuget.org/packages/RxJS-Experimental) Unit Tests:- [`/tests/observable/forkjoin.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/forkjoin.js)