Events ​

EventEmitter package provides a simple observer implementation, allowing you to subscribe and listen for various events that occur in your application. Events serve as a great way to decouple various aspects of your application, since a single event can have multiple listeners that do not depend on each other.

EventEmitterModule internally uses the EventTarget API.

Getting started ​

No need to install an extra module, you can import it from danet/mod.ts

import { EventEmitterModule, EventEmitter } from `danet/mod.ts`

Import the EventEmitterModule into the root AppModule:

import { Module, EventEmitterModule } from 'danet/mod.ts';

@Module({
  import: [EventEmitterModule],
})
export class AppModule {}

Dispatching Events ​

To dispatch (i.e., fire) an event, first inject EventEmitter using standard constructor injection:

constructor(private eventEmitter: EventEmitter) {}

::: Hint 💡 Import the EventEmitter from the danet/mod.ts package. :::

Then use it in a class as follows:

this.eventEmitter.emit(
  'order.created',
  new OrderCreatedEvent({
    orderId: 1,
    payload: {},
  }),
);

Listening to Events ​

To declare an event listener, decorate a method with the @OnEvent() decorator preceding the method definition containing the code to be executed, as follows:

class OrderListeners {
    @OnEvent('order.created')
    handleOrderCreatedEvent(payload: OrderCreatedEvent) {
      // handle and process "OrderCreatedEvent" event
    }
}