TinyEmitter

TinyEmitter<T> (from scenerystack/axon) is the same discrete-event abstraction as Emitter — addListener, removeListener, emit, dispose — but without the PhET-iO instrumentation, tandem, or parameters metadata layered on top. Emitter actually is a thin TinyEmitter wrapper internally; reach for TinyEmitter directly when you're writing axon-internal or high-frequency code (per-frame or per-listener-call overhead matters) and don't need PhET-iO data-stream support.

import { TinyEmitter } from 'scenerystack/axon';

const resizeEmitter = new TinyEmitter<[ width: number, height: number ]>();

resizeEmitter.addListener( ( width, height ) => {
  console.log( `resized to ${width}x${height}` );
} );

resizeEmitter.emit( 800, 600 );

Constructor

Unlike Emitter's single config-object constructor, TinyEmitter takes up to four positional arguments (any of which may be omitted or passed as null) instead of an options object — this avoids allocating an options object on hot construction paths:

new TinyEmitter<T>(
  onBeforeNotify?: TEmitterListener<T> | null,
  hasListenerOrderDependencies?: boolean | null,
  reentrantNotificationStrategy?: 'stack' | 'queue' | null,
  disableListenerLimit?: boolean | null
)

Parameter	Default	Effect
onBeforeNotify	undefined	Called with the same arguments as emit(), just before listeners are notified
hasListenerOrderDependencies	undefined	Set true to assert that listener order must stay fixed (relevant only under the ?listenerOrder debug query parameter)
reentrantNotificationStrategy	'stack'	'stack': a nested emit() call (triggered from within a listener) fully resolves before the outer emit() continues notifying. 'queue': nested emit() calls are queued and notified breadth-first, after the current round finishes
disableListenerLimit	undefined	Skips the dev-mode assertion that flags runaway listener counts

Methods

Method	Effect
emit( ...args )	Calls every listener synchronously with args
addListener( listener )	Registers a listener; asserts if the same listener is already registered
removeListener( listener )	Removes a specific listener
removeAllListeners()	Removes every listener
hasListener( listener )	Checks whether a listener is registered
hasListeners()	Whether any listener is registered
getListenerCount()	Number of registered listeners
forEachListener( callback )	Invokes callback once per listener — used internally by TinyProperty
dispose()	Removes all listeners

TinyEmitter is what Emitter is built from

Emitter is a TinyEmitter plus PhET-iO tandem/parameters options and phetioReadOnly bookkeeping — the actual emit()/addListener() mechanics (including the 'stack' vs. 'queue' reentrancy handling) live entirely in TinyEmitter. Use Emitter for anything that needs a tandem for the data stream or PhET-iO API docs; use TinyEmitter for internal plumbing (as TinyProperty, TinyForwardingProperty, and TinyStaticProperty all do) where allocating that metadata on every instance would be wasted memory.