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### `Rx.Observable.while(condition, source)`
### `Rx.Observable.whileDo(condition, source)` *DEPRECATED*
[Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/while.js "View in source")
Repeats source as long as condition holds emulating a while loop. There is an alias for this method called 'whileDo' for browsers <IE9.
### Arguments
1. `condition` *(`Function`)*: The condition which determines if the source will be repeated.
2. `source` *(`Observable`)*: The observable sequence that will be run if the condition function returns true.
#### Returns
*(`Observable`)*: An observable sequence which is repeated as long as the condition holds.
#### Example
```js
var i = 0;
// Repeat until condition no longer holds
var source = Rx.Observable.while(
function () { return i++ < 3 },
Rx.Observable.return(42)
);
var subscription = source.subscribe(
function (x) {
console.log('Next: ' + x);
},
function (err) {
console.log('Error: ' + err);
},
function () {
console.log('Completed');
});
// => Next: 42
// => Next: 42
// => Next: 42
// => Completed
```
### Location
File:
- [`/src/core/linq/observable/while.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/while.js)
Dist:
- [`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-Experimental`](http://www.nuget.org/packages/RxJS-Experimental)
Unit Tests:
- [`/tests/observable/while.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/while.js)
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