snuffydev / lil-emit

a fully typed event emitter, in 253 bytes

lil-emit

a typed 253 byte event emitter

Yes, another tiny event emitter library.

Install

npm  install --save  lil-emit    // npm
pnpm install --save  lil-emit    // pnpm
yarn add             lil-emit    // yarn

And then use!

import { emitter } from "lil-emit";

interface MyEvents {
	click: [number, number];
	update: Record<string, unknown>;
}

// Create our event handler
const ee = emitter<MyEvents>();

const handler = (data) => console.log(data);

// Listen for our events to be fired
// (It's best to avoid using lambda functions for the callback)
ee.on("click", handler);

ee.on("update", handler);

// Dispatch our 'click' event
ee.dispatch("click", [32, 425]);

// Stop listening to the 'click' event
ee.off("click", handler);
// ...or all events
ee.off("*");

That's all that's needed!

Guide

The following guide will reference this event handler function at different points:

function handler(a, b, c) {
	console.log(a, b, c);
}

.on(name, callback)

Registers an event handler for a given name.

Callback

The callback has the type (...data) => void, where (...data) is the data being emitted. For example:

ee.on("test", handler);
// or the leaky way
ee.on("test", (a, b, c) => console.log(a, b, c));

.dispatch(name, ...data)

Invokes all listeners for the given event name.

To demonstrate, here's how you would dispatch to the example above:

ee.dispatch("test", "One", "Two", "Three!");

.off(name, callback)

Unregisters an event handler from an event.

// This won't work.
ee.off("test", (a, b, c) => console.log(a, b, c));

// But this will!
ee.off("test", handler);

You can also do .off("*") to remove all event listeners, from all events.