@byungi/event-emitter

Small (< 600Byte), type-safe event emitter that support old browsers

Install

npm i @byungi/event-emitter

UMD

<script src="https://unpkg.com/@byungi/event-emitter"></script>
<script>
    const emitter = new EventEmitter.default();
</script>

Browser ESM

<script type="module">
    import EventEmitter from 'https://unpkg.com/@byungi/event-emitter/dist/index.esm.js'
    const emitter = new EventEmitter();
</script>

Example

interface Events {
    a(): void
    b(a: number, b: string): void
}
const emitter = new EventEmitter<Events>()

// ✔️ Compiled.
emitter.on('a', () => { /.../ })
emitter.on('b', (a, b) => { /.../ })
emitter.emit('a')
emitter.emit('b', 100, 'test')

// ❌ Compile error.
emitter.on('a', (a, b) => { /.../ })
emitter.on('b', (other:boolean) => { /.../ })
emitter.on('c', () => { /.../ })
emitter.emit('a', 100, 'test')
emitter.emit('b')
emitter.emit('c')

Browser compatibility

IE6+

API

new EventEmitter()

Create an event emitter instance.

emitter.on(name, listener)

Add an event listener. Returns function to off.

const off = emitter.on('a', listener)
off() // == emitter.off('a', listener)

ee.off(name[, listener])

Remove an event listener(s).

ee.has(name[, listener])

Returns whether there is an event listener.

ee.emit(name, ...params)

Emit event to listeners.

ee.once(name, listener)

Add an event listener that runs once.

License

MIT