event-emitter-typesafe

This package is meant to give you an easy to use way of defining the events an object can emit in two different ways, both are typesafe with TypeScript.

usage

extending

The easiest way is to just extend the provided EventEmitter.

import {EventEmitter} from "event-emitter-typesafe";

// define all available events by their name and their structure
interface ExampleEvents {
    'example-a': { data: number },
    'example-b': { data: number },
    'example-c': { data: number },
    'example-d': { data: number }
}

// your class you want to extend to a event emitter
class Example extends EventEmitter<ExampleEvents> {}

const e = new Example();

// both calls have their correct typings attached
e.addEventListener('example-c', (ev) => console.log(ev.data));
e.dispatch('example-c', {data: 12});

You can find this in examples\example-extending.ts

mixin

You can also use the second option which leverages TypeScript mixins which allows you to not add EventEmitter to the prototype chain. This can be useful if you have a class already which needs to extend another class. Mixins results in pretty much the same types as extending does.

import {EventEmitterDef, makeEventEmitter} from "event-emitter-typesafe";

class SomeOtherClass {}

// your class you want to extend to a event emitter but which also extends another class
class Example extends SomeOtherClass {}

// define all available events by their name and their structure
interface ExampleEvents {
    'example-a': { data: number },
    'example-b': { data: number },
    'example-c': { data: number },
    'example-d': { data: number }
}

// use a mixin to extend the type definition of the Example class
// typescript will add the event definitions to this class type definition
interface Example extends EventEmitterDef<ExampleEvents> {}

// actually add the implementation to the Example prototype
makeEventEmitter(Example);

// usage is transparent
const e = new Example();

// both calls have their correct typings attached
e.addEventListener('example-c', (ev) => console.log(ev.data));
e.dispatch('example-c', {data: 12});

You can find this in examples\example-mixin.ts

standalone

You could always just create an instance of the EventEmitter instead of extending it.

similar

The package @servie/events is quite similar but does not provide a mixing option.