@suckless/emitter

Type-safe event emitter. Zero dependencies, runtime-agnostic.

Install

npm install @suckless/emitter

Usage

import { createEmitter } from "@suckless/emitter"

type Events = {
	message: [string]
	error: [Error]
	connect: []
}

const emitter = createEmitter<Events>()

// Subscribe — returns an unsubscribe function
const off = emitter.on("message", (msg) => console.log(msg))

// Emit
emitter.emit("message", "hello")

// Unsubscribe
off()

// Fire once
emitter.once("connect", () => console.log("connected"))

How it works

Event names and argument types are enforced at compile time through a generic event map. Each event maps to a tuple of arguments, giving you full autocomplete and type checking on both emit and listener parameters.

Listeners are stored in insertion-order Sets. Emit iterates a snapshot, so adding or removing listeners during emission is safe.

API

createEmitter<E>(): Emitter<E>

Creates a new emitter. E is a record mapping event names to argument tuples.

emitter.on(event, listener): () => void

Subscribes to an event. Returns an unsubscribe function.

emitter.once(event, listener): () => void

Like on, but the listener fires at most once. Returns an unsubscribe function that can cancel before firing.

emitter.emit(event, ...args): void

Fires all listeners for the event with the given arguments.

Cleanup

The emitter implements Disposable for cleanup:

using emitter = createEmitter<Events>()

License

MIT