SharedWorkerTransport

Cross-tab delivery through one SharedWorker per origin.

BroadcastChannel is the better default for pure fan-out and stays the default. This transport buys something else: a single place that is not a tab. The relay outlives any individual tab, so the thing every “the leader owns the socket” design actually wants — one connection, held somewhere no user can close mid-flight — becomes possible without electing a leader at all.

What it does not buy: durability. The worker is torn down when the last port closes, exactly like a BroadcastChannel with no listeners. State still lives in the tabs; this moves the wire, not the source of truth.

The relay script is three lines and ships with the library:

// sw-relay.js — your app hosts this file
import 'use-everywhere/shared-worker';

createSharedStore('cart', {
  transport: new SharedWorkerTransport({
    url: new URL('./sw-relay.js', import.meta.url),
  }),
});

Implements

• Transport

Constructors

Constructor

new SharedWorkerTransport(options): SharedWorkerTransport;

Parameters

Parameter	Type
options	SharedWorkerTransportOptions

Returns

SharedWorkerTransport

Properties

kind

readonly kind: TransportKind = 'shared-worker';

What this transport is. Optional so a custom transport need not declare one.

Implementation of

Transport.kind

Methods

close()

close(): void;

Returns

void

Implementation of

Transport.close

---

post()

post(data): void;

Parameters

Parameter	Type
data	unknown

Returns

void

Implementation of

Transport.post

---

subscribe()

subscribe(listener): () => void;

Parameters

Parameter	Type
listener	(data) => void

Returns

() => void

Implementation of

Transport.subscribe