# Function: type()

> **type**(`type`): \<`T`\>(`source$`) => `T` & `object`

`type` is a custom RxJS [operator](https://rxjs.dev/guide/operators) that mutates an RxJS [Observable](https://rxjs.dev/guide/observable)
by setting a `type` property. It takes one argument, which will appear as the action type in Redux DevTools:

![Action Type in Redux Devtools](https://state-adapt.github.io/assets/devtools-timer$.png)

#### Example: Converting an observable into a source

```typescript
import { timer } from 'rxjs';
import { type } from '@state-adapt/rxjs';

const timer$ = timer(1000).pipe(type('timer$'));

timer$.subscribe(console.log);
// 0
```