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...
npm i @posva/event-emitterimport { 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:
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 })
}
}Most of the code can be discovered through the autocompletion but the API documentation is available at https://event-emitter.esm.is.
- mitt: this library is a fork of mitt with a class based API and better types