# Emitter [](https://travis-ci.org/component/emitter)
Event emitter component.
## Installation
```
$ component install component/emitter
```
## API
### Emitter(obj)
The `Emitter` may also be used as a mixin. For example
a "plain" object may become an emitter, or you may
extend an existing prototype.
As an `Emitter` instance:
```js
var Emitter = require('emitter');
var emitter = new Emitter;
emitter.emit('something');
```
As a mixin:
```js
var Emitter = require('emitter');
var user = { name: 'tobi' };
Emitter(user);
user.emit('im a user');
```
As a prototype mixin:
```js
var Emitter = require('emitter');
Emitter(User.prototype);
```
### Emitter#on(event, fn)
Register an `event` handler `fn`.
### Emitter#once(event, fn)
Register a single-shot `event` handler `fn`,
removed immediately after it is invoked the
first time.
### Emitter#off(event, fn)
* Pass `event` and `fn` to remove a listener.
* Pass `event` to remove all listeners on that event.
* Pass nothing to remove all listeners on all events.
### Emitter#emit(event, ...)
Emit an `event` with variable option args.
### Emitter#listeners(event)
Return an array of callbacks, or an empty array.
### Emitter#hasListeners(event)
Check if this emitter has `event` handlers.
## License
MIT