Pub/Sub

pubSub.ts

const pubSub = <UpdateType>() => {
	type Subscriber = ({ update, unsubscribe }: { update: UpdateType; unsubscribe: () => void }) => void

	const subscribers = new Set<Subscriber>()

	const subscribe = (sub: Subscriber) => subscribers.add(sub)
	const publish = (update: UpdateType) => {
		subscribers.forEach((sub) => {
			const unsubscribe = () => subscribers.delete(sub)
			sub({ update, unsubscribe })
		})
	}

	return {
		subscribe,
		publish,
	}
}

const updateHandler = ({ update, unsubscribe }: { update: string; unsubscribe: () => void }) => {
	console.log('update:', update)

	if (update === 'update 2') {
		unsubscribe()
	}
}

const { subscribe, publish } = pubSub<string>()

publish('update 0') // no subscribers yet
subscribe(updateHandler)
publish('update 1') // update: update 1
publish('update 2') // update: update 2
publish('update 3') // no subscribers left