Very simple typed event emitter with a simplified api interface, inspired by strict-event-emitter-types
- Very simple api,
on,once,off,fireandclearmethods - The
on,once,offandfiremethods are typed, so you can be sure that the event you are listening to is of the type you expect and receive the correct payload - The
on,oncemethods returns a function that you can use to remove the listener without having to pass the event name and the listener function
npm install create-typed-emitterimport { createEmitter } from 'create-typed-emitter';
// create an interface for your emitter events
interface EmitterInterface {
event: { foo: string; bar: number };
// other events signatures come here
}
const emitter = createEmitter<EmitterInterface>();
// typescript will complain if you try to fire an event that doesn't exist
// typescript will complain if the payload is not of the correct type
emitter.on('event', ({ foo, bar }) => {
console.log(foo, bar);
});
// this will fail as the event listened does not exist in the typed interface
emitter.on('foo', ({ foo, bar }) => {
console.log(foo, bar);
});
// this will work, the event fired is of the correct type and have the correct payload
emitter.fire('event', { foo: 'bar', bar: 1 });
// this will fail because bar is missing
emitter.fire('event', { foo: 'bar' });
// this will fail because foo is not a string
emitter.fire('event', { foo: 1, bar: 1 });
// this will fail because the emitted event does not exist
emitter.fire('foo', { foo: 'bar', bar: 1 });
// this will execute the listener only once
emitter.once('event', ({ foo, bar }) => {
console.log(foo, bar);
});
// this will remove the listener added without referencing the listener function
const off = emitter.once('event', ({ foo, bar }) => {
console.log(foo, bar);
});
// later remove the listener (useful in useEffect cleanup in React for example)
off();
MIT