doc/api/core/operators/flatmapobserver.md
# This is RxJS v 4. [Find the latest version here](https://github.com/reactivex/rxjs)### `Rx.Observable.prototype.flatMapObserver(onNext, onError, onCompleted, [thisArg])`### `Rx.Observable.prototype.selectManyObserver(onNext, onError, onCompleted, [thisArg])`[Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/selectmanyobserver.js "View in source") Projects each notification of an observable sequence to an observable sequence and merges the resulting observable sequences into one observable sequence. #### Arguments1. `onNext` *(`Function`)*: A transform function to apply to each element. The selector is called with the following information: 1. the value of the element 2. the index of the element2. `onError` *(`Function`)*: A transform function to apply when an error occurs in the source sequence.3. `onCompleted` *(`Function`)*: A transform function to apply when the end of the source sequence is reached.4. `[thisArg]` *(`Any`)*: Object to use as `this` when executing the transform functions. #### Returns*(`Observable`)*: An observable sequence whose elements are the result of invoking the one-to-many transform function corresponding to each notification in the input sequence. #### Example```jsvar source = Rx.Observable.range(1, 3) .flatMapObserver( function (x, i) { return Rx.Observable.repeat(x, i); }, function (err) { return Rx.Observable.return(42); }, function () { return Rx.Observable.empty(); }); var subscription = source.subscribe( function (x) { console.log('Next: ' + x); }, function (err) { console.log('Error: ' + err); }, function () { console.log('Completed'); }); // => Next: 2// => Next: 3// => Next: 3// => Completed``` ### Location File:- [`/src/core/linq/observable/selectmanyobserver.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/selectmanyobserver.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.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) NPM Packages:- [`rx`](https://www.npmjs.org/package/rx) NuGet Packages:- [`RxJS-All`](http://www.nuget.org/packages/RxJS-All/)- [`RxJS-Main`](http://www.nuget.org/packages/RxJS-Main/) Unit Tests:- [`/tests/observable/selectmanyobserver.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/selectmanyobserver.js)