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### `Rx.Observable.for(sources, resultSelector, [thisArg])`
[Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/for.js "View in source")
Concatenates the observable sequences or Promises obtained by running the specified result selector for each element in source.
There is an alias for this method called `forIn` for browsers <IE9
#### Arguments
1. `sources` *(Array)*: An array of values to turn into an observable sequence.
2. `resultSelector` *(`Function`)*: A function to apply to each item in the sources array to turn it into an observable sequence. The resultSelector is called with the following information:
1. the value of the element
2. the index of the element
3. the Observable object being subscribed
3. `[thisArg]` *(`Any`)*: Object to use as `this` when executing `resultSelector`.
#### Returns
*(`Observable`)*: An observable sequence from the concatenated observable sequences or Promises.
#### Example
```js
/* Using Observables */
var array = [1, 2, 3];
var source = Rx.Observable.for(
array,
function (x) {
return Rx.Observable.return(x);
});
var subscription = source.subscribe(
function (x) {
console.log('Next: ' + x);
},
function (err) {
console.log('Error: ' + err);
},
function () {
console.log('Completed');
});
// => Next: 1
// => Next: 2
// => Next: 3
// => Completed
/* Using Promises */
var array = [1, 2, 3];
var source = Rx.Observable.for(
array,
function (x) {
return RSVP.Promise.resolve(x);
});
var subscription = source.subscribe(
function (x) {
console.log('Next: ' + x);
},
function (err) {
console.log('Error: ' + err);
},
function () {
console.log('Completed');
});
// => Next: 1
// => Next: 2
// => Next: 3
// => Completed
```
### Location
File:
- [/src/core/linq/observable/for.js](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/for.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:
- If using `rx.expermental.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) | [`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-Complete`](http://www.nuget.org/packages/RxJS-Complete)
- [`RxJS-Experimental`](http://www.nuget.org/packages/RxJS-Experimental)
Unit Tests:
- [`/tests/observable/for.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/for.js)
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