Class: EventEmitterService

Defined in: packages/event-emitter/src/event-emitter.service.ts:52

Injectable event emitter service.

Supports synchronous and asynchronous handlers, wildcard patterns, and typed events. Use @InjectEventEmitter() or @Inject(EVENT_EMITTER_TOKEN) to inject this service.

Dispatch performance: exact (non-wildcard) patterns are indexed in a Map for O(1) lookup, and each wildcard pattern's RegExp is compiled once at registration time, so emit/emitAsync/listenerCount never scan the full registration list nor recompile regexes on the request path.

Example

@Injectable()
export class OrderService {
  constructor(private readonly events: EventEmitterService) {}

  async placeOrder(order: Order) {
    await this.events.emitAsync('order.created', order);
  }
}

Constructors

Constructor

new EventEmitterService(options?): EventEmitterService;

Defined in: packages/event-emitter/src/event-emitter.service.ts:68

Parameters

Parameter	Type
options	EventEmitterModuleOptions

Returns

EventEmitterService

Methods

emit()

emit(event, payload?): boolean;

Defined in: packages/event-emitter/src/event-emitter.service.ts:79

Emit an event synchronously. Returns true if at least one handler was invoked (async handlers are fired but not awaited — use emitAsync if you need to wait for them).

Parameters

Parameter	Type
event	string | symbol
payload?	unknown

Returns

boolean

---

emitAsync()

emitAsync(event, payload?): Promise<unknown[]>;

Defined in: packages/event-emitter/src/event-emitter.service.ts:102

Emit an event and await all async handlers. Returns an array of values resolved by each handler.

Parameters

Parameter	Type
event	string | symbol
payload?	unknown

Returns

Promise<unknown[]>

---

listenerCount()

listenerCount(event): number;

Defined in: packages/event-emitter/src/event-emitter.service.ts:204

Returns the number of handlers registered for event.

Parameters

Parameter	Type
event	string | symbol

Returns

number

---

off()

off<T>(event, handler?): this;

Defined in: packages/event-emitter/src/event-emitter.service.ts:153

Remove a specific handler (or all handlers for an event when omitted).

Type Parameters

Type Parameter	Default type
T	unknown

Parameters

Parameter	Type
event	string | symbol
handler?	EventHandler<T>

Returns

this

---

on()

on<T>(event, handler): this;

Defined in: packages/event-emitter/src/event-emitter.service.ts:131

Register a persistent event handler.

Type Parameters

Type Parameter	Default type
T	unknown

Parameters

Parameter	Type
event	string | symbol
handler	EventHandler<T>

Returns

this

---

once()

once<T>(event, handler): this;

Defined in: packages/event-emitter/src/event-emitter.service.ts:142

Register a one-time event handler.

Type Parameters

Type Parameter	Default type
T	unknown

Parameters

Parameter	Type
event	string | symbol
handler	EventHandler<T>

Returns

this

---

removeAllListeners()

removeAllListeners(event?): this;

Defined in: packages/event-emitter/src/event-emitter.service.ts:189

Remove all listeners, optionally scoped to a specific event.

Parameters

Parameter	Type
event?	string | symbol

Returns

this