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# Nitt
> Small, functional event emitter / pubsub.
- **Small:** less than 300 bytes gzipped
- **Familiar:** similar names (on, off, once, emit) & ideas as [Node's EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
- **Functional:** methods don't rely on `this`, unless you want to...
- **No dependency:** Nitt has no external dependencies
## Table of Contents
- [Nitt](#nitt)
- [Table of Contents](#table-of-contents)
- [Install](#install)
- [Usage](#usage)
- [API](#api)
- [nitt](#nitt)
- [on](#on)
- [once](#once)
- [when](#when)
- [off](#off)
- [emit](#emit)
- [Caveats](#caveats)
- [Contribute](#contribute)
- [Acknowledments](#acknowledments)
- [License](#license)
## Install
This project uses [node](http://nodejs.org) and [npm](https://npmjs.com). Go check them out if you don't have them locally installed.
```sh
$ npm install --save nitt
```
## Usage
```js
import nitt from 'nitt';
const emitter = nitt();
// listen to an event
emitter.on('foo', e => console.log('foo', e));
// listen to all events
emitter.on('*', (type, e) => console.log(type, e));
// listen to a single event
emitter.once('foo', e => console.log('foo', e));
// fire an event
emitter.emit('foo', { a: 'b' });
// working with handler references:
function onFoo() {}
emitter.on('foo', onFoo); // listen
emitter.off('foo', onFoo); // unlisten
emitter.once('foo', onFoo); // listen to a single event
// using a promise
const promise = emitter.when('bar');
promise.then(evt => console.log(evt));
emitter.emit('bar', 'done'); // prints 'done' in the console
```
## API
### nitt
Nitt: Small (<300B) functional event emitter / pubsub.
**Parameters**
- `all` **EventHandlerMap**
Returns **Nitt**
### on
Register an event handler for the given type.
**Parameters**
- `type` **[String](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String)** Type of event to listen for, or `"*"` for all events
- `handler` **[Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function)** Function to call in response to given event
### once
Register an event handler that is executed just once.
**Parameters**
- `type` **[String](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String)** Type of event to listen for, or `"*"` for all events
- `handler` **[Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function)** Function to call in response to given event
### when
Returns a promise for a single event
**Parameters**
- `type` **[String](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String)** Type of event to listen for, or `"*"` for all events
Returns **[Promise](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise)**
### off
Remove an event handler for the given type.
**Parameters**
- `type` **[String](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String)** Type of event to unregister `handler` from, or `"*"`
- `handler` **[Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function)** Handler function to remove
### emit
Invoke all handlers for the given type.
If present, `"*"` handlers are invoked after type-matched handlers.
**Parameters**
- `type` **[String](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String)** The event type to invoke
- `evt` **Any?** Any value (object is recommended and powerful), passed to each handler
## Caveats
Keep in mind, due to the nature, of the once handlers that self deregister, you are currently not able to remove (off) a once / when handlers.
## Contribute
If you want to contribute, I would be happy to look in to your PRs.
## Acknowledments
I would like to thank [Jason Miller](https://jasonformat.com/) (@developit) for developing `mitt`. `nitt` is no more than just `mitt` with a few extras.
## License
[MIT License](https://opensource.org/licenses/MIT)
|
