event-emitter-typesafe v0.1.3
event-emitter-typesafe
This package is meant to give you an easy to use way of defining an event emitter which is typesafe. Those definitions
can be either applied by mixin or by extension of the EventEmitter
class.
In either way those classes offer the three main methods add
, remove
and dispatch
and several alias. The API
documentation is available at: https://feirell.github.io/event-emitter-typesafe/.
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();
// add, remove and emit have their correct typings attached
e.once('example-c', () => console.log('example c was emitted'));
e.addEventListener('example-c', (ev) => console.log(ev.data));
// the first and the second listener will be called
e.emit('example-c', {data: 12});
// only the second listener will be called since the other one detached itself
// dispatch is just an alias for emit
e.dispatch('example-c', {data: 42});
e.on('example-a', () => { });
You can find this in examples\example-extending.ts
mixin
You can also use the second option which leverages TypeScript mixins which allow you to provide the functionality off
the EventEmitter
without extending it. This can be useful if you already are extending another class.
Mixins results in pretty much the same type situation as you would have with extension.
import {EventEmitterInt, 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 EventEmitterInt<ExampleEvents> {}
// actually add the implementation to the Example prototype
makeEventEmitter(Example);
// usage is transparent
const e = new Example();
// add, remove and emit 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 mixin option and some of the alias.