subscribe()

Subscribes to a store's DATA emissions with previous-value tracking. Returns a Subscription with unsubscribe() and signal() for upstream lifecycle control.

Signature

function subscribe<T>(
	store: Store<T>,
	cb: (value: T, prev: T | undefined) => void,
	opts?: { onEnd?: (error?: unknown) => void },
): Subscription

Parameters

Parameter	Type	Description
store	Store<T>	The Store<T> to listen to.
cb	`(value: T, prev: T	undefined) => void`
opts	{ onEnd?: (error?: unknown) => void }	Optional onEnd when the stream completes or errors.

Returns

Subscription — unsubscribe() to disconnect, signal(s) to send lifecycle signals upstream.

Basic Usage

import { state, subscribe, RESET } from 'callbag-recharge';

const n = state(0);
const sub = subscribe(n, (v, prev) => console.log(v));
n.set(1);
sub.signal(RESET);    // send RESET upstream
sub.unsubscribe();    // disconnect

See Also

• effect
• forEach — simpler value-only subscription