@supercat1337/event-emitter

event-emitter

Environment agnostic event emitter

This package allows you to create an event emitter that can be used in any environment. You can define types for the events that you want to emit and listen to.

Installation

$ npm install @supercat1337/event-emitter

Usage

Basic example

import { EventEmitter } from "@supercat1337/event-emitter";

// Create an event emitter with a custom event type
/** @type {EventEmitter<"foo">} */
var ev = new EventEmitter();

ev.on("foo", () => {
    console.log("Hello!");
});

// IDE will complain if we emit an event that doesn't exist
ev.emit("bar"); // $ExpectError
ev.emit("foo");

Example of unsubscribing from an event

import { EventEmitter } from "@supercat1337/event-emitter";

/** @type {EventEmitter<"foo">} */
var ev = new EventEmitter;
var foo = 0
var action = () => {
    foo++;
};

var unsubscriber = ev.on("foo", action);

ev.emit("foo");
unsubscriber();

ev.emit("foo");

if (foo == 1) {
    console.log("Success!");
} else {
    console.log("Fail!");
}

Example of using the Once method

import { EventEmitter } from "@supercat1337/event-emitter";

/** @type {EventEmitter<"foo">} */
var ev = new EventEmitter;

var foo = 0

ev.once("foo", () => {
    foo++;
});

ev.emit("foo");
ev.emit("foo");
ev.emit("foo");

if (foo == 1) {
    console.log("Success!");
} else {
    console.log("Fail!");
}