emttr

A tiny pub/sub utility in vanilla JavaScript.

Features

• Simple pub/sub pattern
• Lightweight and dependency-free
• Duplicate subscription protection
• Easy unsubscribe handling
• Debug helpers for inspecting subscribers

Installation

npm install emttr

Usage

import Emttr from "emttr";

const emttr = new Emttr();

const subscription = emttr.subscribe("user:login", data => {
  console.log("User logged in:", data);
});

emttr.publish("user:login", { name: "Geet" });

subscription.unsubscribe();

API

new Emttr()

Creates a new emitter instance.

subscribe(event, callback)

Subscribes a callback to an event.

Parameters

• event - the event name
• callback - the function to run when the event is published

Returns

An object with an unsubscribe() method.

const subscription = emttr.subscribe("message", data => {
  console.log(data);
});

subscription.unsubscribe();

publish(event, data)

Publishes data to all subscribers of an event.

Parameters

• event - the event name
• data - optional data passed to each subscriber

emttr.publish("message", { text: "Hello world" });

clear(event)

Clears subscribers for a specific event.

emttr.clear("message");

clear()

Clears all subscribers.

emttr.clear();

debug()

Returns helper methods for inspecting subscriber state.

Example

const debug = emttr.debug();

console.log(debug.count("message"));
console.log(debug.subscribers());

Available methods

• count(event) - returns the number of subscribers for an event
• subscribers() - returns a copied object of all subscribers

Full Example

import Emttr from "emttr";

const emttr = new Emttr();

const sub1 = emttr.subscribe("order:created", order => {
  console.log("Order received:", order);
});

const sub2 = emttr.subscribe("order:created", order => {
  console.log("Processing order:", order.id);
});

emttr.publish("order:created", { id: 101, item: "Pizza" });

console.log(emttr.debug().count("order:created")); // 2
console.log(emttr.debug().subscribers());

sub1.unsubscribe();
sub2.unsubscribe();

License

MIT