@posva/event-emitter
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Type safe and light event emitter / pubsub class
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# EventEmitter [](https://github.com/posva/event-emitter/actions/workflows/ci.yml) [](https://www.npmjs.com/package/@posva/event-emitter) [](https://codecov.io/github/posva/event-emitter) [](https://esm.dev/open-source)
> Typed event and lightweight event emitter with a class based API
- ⛓️ **Typed**: Powerful autocompletion and type checking
- 📦 **Class based**: Add event emitting to your classes
- 💨 **Lightweight**: 188 bytes min+brotli
- 🌐 **Runtime Agnostic**: Works everywhere: Browser, node, Bun...
## Installation
```sh
npm i /event-emitter
```
## Usage
```ts
import { EventEmitter } from '@posva/event-emitter'
const emitter = new EventEmitter<{
// Define the events you want to emit and their arguments
start: []
// non tuples are also supported
end: { reason: string }
// You can also define multiple arguments
sum: [number, number]
}>()
// no arguments
emitter.emit('start')
// object payload
emitter.emit('end', { reason: 'finished' })
// multiple arguments
emitter.emit('sum', 1, 2)
emitter.on('end', ({ reason }) => console.log('ended:', reason))
// You can also listen to all events
emitter.on('*', (event, payload) => {
if (event === 'end') {
// payload is always an array
const [{ reason }] = payload
} else if (event === 'sum') {
const [a, b] = payload
}
})
```
Since `EventEmitter` is a class, you can extend it in your own classes:
```ts
class CardGame extends EventEmitter<{
start: []
end: { winner: string }
draw: [player: string, card: string]
play: [player: string, card: string]
}> {
start() {
this.emit('start')
}
end(winner: string) {
this.emit('end', { winner })
}
}
```
## API
Most of the code can be discovered through the autocompletion but the API documentation is available at [https://event-emitter.esm.is](https://event-emitter.esm.is).
## Related
- [mitt](https://github.com/developit/mitt): this library is a fork of mitt with a class based API and better types
## License
[MIT](http://opensource.org/licenses/MIT)