> For the complete documentation index, see [llms.txt](https://soufatn.gitbook.io/rxjs-book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://soufatn.gitbook.io/rxjs-book/summary/observer/observer_methods/fromnotifier.md).

# fromNotifier

Creates an observer from a notification callback.

### Arguments

1. `handler` *(Function)*: Function that handles a notification.

### Returns

*(Observer)*: The observer object that invokes the specified handler using a notification corresponding to each message it receives.

### [Example](http://jsbin.com/difobe/3/edit?js,console)

```javascript
function handler(n) {
    // Handle next calls
    if (n.kind === 'N') {
        console.log('Next: ' + n.value);
    }

    // Handle error calls
    if (n.kind === 'E') {
        console.log('Error: ' + n.exception);
    }

    // Handle completed
    if (n.kind === 'C') {
        console.log('Completed');
    }
}

Rx.Observer.fromNotifier(handler).onNext(42);
// => Next: 42

Rx.Observer.fromNotifier(handler).onError(new Error('error!!!'));
// => Error: Error: error!!!

Rx.Observer.fromNotifier(handler).onCompleted();
// => false
```

### Example