Signals Effects

Use effect(...) when you want reactive side effects that rerun after dependencies change.

import { State, effect } from '@ecopages/signals';
 
const count = new State(0);
 
const dispose = effect(() => {
	console.log('count =', count.get());
});
 
count.set(1);
dispose();

watch(...)

Use watch(...) when you want the next and previous derived values.

import { State, watch } from '@ecopages/signals';
 
const count = new State(0);
 
const stopWatching = watch(
	() => count.get(),
	(nextValue, previousValue) => {
		console.log(previousValue, '->', nextValue);
	},
);
 
count.set(1);
stopWatching();

watch(...) is built on top of a computed signal plus an effect, so it inherits computed equality behavior and effect scheduling.

Scheduling

Effects and watchers accept a scheduler option. The default uses a microtask queue.

subtle.Watcher

Use subtle.Watcher when you need lower-level invalidation workflows.

• it reports staleness rather than recalculated values
• calling watch(...) re-arms the watcher by resetting the pending set and notification latch
• watched and unwatched hooks let signals react when a low-level watcher starts or stops observing them