Callbacks

Execute logic when a listener library loads.

Define a listenerLoaded callback function within a listener library:

loadedExample.ts

import { ListenerEvent } from "@listener-js/listener"

export class LoadedExample {
  private listenerLoaded(
    lid: string[],
    event: ListenerEvent
  ) {
    // setup logic goes here
  }
}

export default new LoadedExample()

Callbacks functions can be asynchronous. When a library has asynchronous callbacks, the end user can await the promise returned by listener.load.

The import in this example has no effect on compiled output. It is purely for accessing types.

Callback arguments

Callbacks receive two arguments, a listener id (lid) and a listener event object:

interface ListenerEvent {
  instance: any
  listener: Listener
  existing?: string[]
  instances?: Record<string, any>
  options?: Record<string, any>
}

Property	Description
instance	Listener library instance
listener	Listener instance
existing?	Existing (already loaded) listener libraries
instances?	Library instances passed into the listener.load invocation
options?	Options passed into the listener.load invocation

Available callbacks

Callback	Timing
listenerLoaded	Once this listener library is ready
listenerLoadedAny	Once any listener library is ready
listenerBeforeLoaded	Before listenerLoaded
listenerBeforeLoadedAny	Before listenerLoadedAny
listenerAfterLoaded	After listenerLoaded
listenerAfterLoadedAny	After listenerLoadedAny
listenerReset	Before listener.reset