1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
|
### `Rx.Observable.prototype.defaultIfEmpty([defaultValue])`
[Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/defaultifempty.js "View in source")
Returns the elements of the specified sequence or the specified value in a singleton sequence if the sequence is empty.
#### Arguments
1. `[defaultValue=null]` *(`Any`)*: The value to return if the sequence is empty. If not provided, this defaults to null.
#### Returns
*(`Observable`)*: An observable sequence that contains the specified default value if the source is empty; otherwise, the elements of the source itself.
#### Example
```js
/* Without a default value */
var source = Rx.Observable.empty().defaultIfEmpty();
var subscription = source.subscribe(
function (x) {
console.log('Next: ' + x.toString());
},
function (err) {
console.log('Error: ' + err);
},
function () {
console.log('Completed');
});
// => Next: null
// => Completed
/* With a defaultValue */
var source = Rx.Observable.empty().defaultIfEmpty(false);
var subscription = source.subscribe(
function (x) {
console.log('Next: ' + x.toString());
},
function (err) {
console.log('Error: ' + err);
},
function () {
console.log('Completed');
});
// => Next: false
// => Completed
```
### Location
File:
- [`/src/core/linq/observable/defaultifempty.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/defaultifempty.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)
- [`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-Main`](http://www.nuget.org/packages/RxJS-Main/)
- [`RxJS-Lite`](http://www.nuget.org/packages/RxJS-Lite/)
Unit Tests:
- [`/tests/observable/defaultifempty.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/defaultifempty.js)
|
