TinyProperty

TinyProperty<T> (from scenerystack/axon) is a lightweight observable value wrapper that implements enough of the Property interface (.value, .get()/.set(), link()/lazyLink()/unlink()) to be used interchangeably in many places, but without Property's validation, PhET-iO instrumentation, or reset()/initialValue bookkeeping. It directly extends TinyEmitter rather than composing one, specifically to save memory — scenery uses a TinyProperty for every Node's dozens of internal state values (opacityProperty, visibleProperty's underlying storage, pickableProperty, etc.), so the per-instance overhead matters at that scale.

import { TinyProperty } from 'scenerystack/axon';

const opacityProperty = new TinyProperty( 1 );

opacityProperty.link( opacity => console.log( 'opacity:', opacity ) ); // logs "opacity: 1"
opacityProperty.value = 0.5;                                          // logs "opacity: 0.5"

Constructor

new TinyProperty<T>(
  value: T,
  onBeforeNotify?: TinyEmitterOptions<...>['onBeforeNotify'] | null,
  hasListenerOrderDependencies?: boolean | null,
  reentrantNotificationStrategy?: 'stack' | 'queue' | null,
  disableListenerLimit?: boolean | null
)

The trailing four parameters are forwarded straight to the underlying TinyEmitter — TinyProperty itself only adds the first value argument. Unlike plain TinyEmitter (which defaults to 'stack'), TinyProperty defaults reentrantNotificationStrategy to 'queue', so that if a listener changes the value again while still notifying (a → b, and a listener sets b → c), all listeners see the a→b change in order before any b→c notification begins.

Methods and members

Member	Effect
value (getter/setter)	Reads or writes the current value; setting is a no-op if the new value areValuesEqual the old one
get() / set( value )	Same as .value, provided as explicit methods for hot inner loops
link( listener )	Adds a listener and immediately calls it with ( value, null, this )
lazyLink( listener )	Adds a listener without an immediate callback
unlink( listener ) / unlinkAll()	Removes one or all listeners
linkAttribute( object, attributeName )	Sets object[attributeName] = value whenever the value changes
valueComparisonStrategy	Get/set the equality strategy (defaults to 'reference') used by areValuesEqual to decide whether to notify
isSettable()	Always returns true for TinyProperty
dispose()	Unlinks all listeners, then disposes the underlying TinyEmitter

Not validated, not instrumented, no reset

TinyProperty has no validValues/valueType/isValidValue checking, no tandem, and no initialValue/reset() — assigning any value of the declared type always succeeds silently. It exists purely as a memory-lean building block for framework internals (scenery Node state, DynamicProperty's internal wrapping, MappedProperty). For simulation model state that simulation-author code creates directly, use Property (or a typed subclass) instead — the safety and PhET-iO support are almost always worth the extra bytes.