effect()

Runs a side effect when all dependencies have resolved after a change; returns dispose(). Eagerly subscribes to deps on creation. Not a store — no get() or source().

Signature

function effect(
	deps: Store<unknown>[],
	fn: () => undefined | (() => void),
	opts?: { name?: string },
): () => void

Parameters

Parameter	Type	Description
deps	Store<unknown>[]	Stores to watch; effect runs when dirty tracking shows all deps settled.
fn	`() => undefined	(() => void)`
opts	{ name?: string }	Optional { name } for Inspector.

Returns

() => void — call to unsubscribe and run final cleanup.

Basic Usage

import { state, effect } from 'callbag-recharge';

const count = state(0);
let runs = 0;
const stop = effect([count], () => {
    runs++;
  });
// runs === 1
count.set(1);
// runs === 2
stop();

Options / Behavior Details

• Immediate first run: fn() runs once right after wiring deps.
• RESOLVED skip: If deps send RESOLVED without value changes, the effect may not re-run.
• Cleanup: Return a function from fn to tear down listeners before the next run.

See Also

• derived
• state
• subscribe