@dominicstop/ts-event-emitter
v1.1.0
Published
Yet another event emitter written in typescript.
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ts-event-emitter
(yet another) event emitter written in typescript 😔
Installation
# install via npm...
npm install @dominicstop/ts-event-emitter
# or install via yarn.
yarn add @dominicstop/ts-event-emitter
Usage
Basic Usage
type EventKeys = 'Foo' | 'Baz';
export const emitter: TSEventEmitter<EventKeys, {
Foo: string;
Baz: { age: number } | null;
}> = new TSEventEmitter();
emitter.once('Foo', (event) => { console.log(event) });
emitter.emit('Foo', 'hello world');
emitter.once('Baz', (event) => { console.log(event?.age) });
emitter.emit('Baz', { age: 23 });
In-Depth Usage
// 1. Create a string enum...
enum Events { Foo = 'Foo', Bar = 'Bar', Baz = 'Baz' };
// 1.1. ...or alt., a union of strings (whichever you prefer).
type EventKeys = 'Foo' | 'Bar' | 'Baz';
// 2. Create the emitter + event map...
// * For each key in the event enum, define the type of the
// `event` argument that the listener will receive.
// * As mentioned in 1.1. you can also use the `EventKeys` union
// in place of the `Events` enum.
export const emitter: TSEventEmitter<EventKeys, {
// 2.1. For the event `TestEnum.Foo`, this will be its event object.
Foo: { name: string },
// 2.2. If you don't want to pass an event argument,
// then set it to `null` or `undefined`.
// * This means the event listener won't receive any arguments
// and you can't pass a data argument to `emit` (see step 4.2.)
Bar: null,
// 2.3. or alt., you can make the event param "optional".
Baz: null | { age: number }
}> = new TSEventEmitter();
// 3.1. `event` arg. will be inferred as `(event: { name: string }) => void`
emitter.once('Foo', (event) => { console.log(event.name) });
// 3.2.`event` arg. will be inferred as `() => void`
// * Note: If you try to add an event param, TS produces an error.
emitter.once('Bar', () => { /** no-op */ });
// 3.3. `event` will be inferred as
// `(event: { age: number } | null) => void`.
// * As such, we need to use the optional chaining operator to access `event`.
emitter.once(Events.Baz, (event) => { console.log(event?.age) });
// 4. Next, lets broadcast some events.
emitter.emit(Events.Foo, { name: 'd'});
emitter.emit('Baz', { age: 1 });
// 4.1. Note: You can't pass a data argument with the 'Bar' event
// because in step 2.2., the event object is defined as `null`.
emitter.emit('Bar');
// 4.2. We must explicitly pass a null/undefined value for the data
// argument since it can be optional (e.g. step 2.3.)
emitter.emit('Baz', null);
Documentation
TSEvenEmitter
| Property/Method | Description |
| ------------------------------------------------------------ | ----------- |
| 🔤 addListener
⚛️ (eventKey, listener) => { unsubscribe: () => void }
| |
| 🔤 removeListener
⚛️ (eventKey, listenerToRemove) => void
| |
| 🔤 once
⚛️ (eventKey, listener) => void
| |
| 🔤 removeAllListeners
⚛️ () => void
| |
| 🔤 emit
⚛️ (eventKey, data) => void
| |