Function: observeSignal()

observeSignal<T>(signal, callback, opt?): EffectDisposer | undefined

Subscribes to a signal and invokes callback immediately and on every subsequent change.

On subscription a SignalObserveArgs object is created and callback is invoked synchronously with isInitial: true. Future notifications update newValue/prevValue/hasChanged and invoke callback again. The returned disposer (when non-null) can be used to unsubscribe; it is also automatically registered as a disposing listener on lifecycleNode / lifecycleRoot so it is cleaned up when the owning DOM node is disposed.

Type Parameters

T

T

Type of the signal's value.

Parameters

signal

SignalLike<T>

Signal-like object to observe (must have subscribe/peek/value).

callback

ObserveSignalCallback<T>

Function called initially and on each change.

opt?

Optional lifecycle wiring.

lifecycleNode?

EventTarget

Optional DOM node whose disposing event will automatically dispose the subscription via addDisposingListener.

useLifecycleRoot?

boolean

When true, the current lifecycle root (see currentLifecycleRoot) at subscription time is recorded as SignalObserveArgs.lifecycleRoot.

Returns

EffectDisposer | undefined

A disposer function for the subscription, or null/undefined if the signal does not expose one.