createBus#

import { createBus } from 'janux';

const bus = createBus();
const off = bus.on('cart.cleared', (payload) => console.log(payload));

bus.emit('cart.cleared', { at: Date.now() });
off();

createBus(): EventBus — the event channel that connects components, stores and the server. One bus per client (or per test); the runtime creates and wires it for you.

Method	Signature	Notes
`emit`	`(event: string, payload: unknown) => void`	Synchronous: handlers run in registration order before `emit` returns.
`on`	`(event: string, handler: BusHandler) => () => void`	Returns an unsubscribe function.

What travels on it#

Component emits — declared in a definition, emitted from an intent's run via emit('cart.cleared', {...}).
Store events — a store's on: { 'cart.cleared': ... } handlers subscribe here, which is how one island reacts to another without importing it.
Source refreshes — an every(...).orOn('inventory.changed') policy listens on this bus.

Events are plain strings by convention noun.verb, and payloads are schema-validated at the component boundary — the bus itself is deliberately dumb.

When to create one yourself#

Only in tests and custom embeddings, where you need two instances to share a channel:

import { createBus, createInstance } from 'janux';

const bus = createBus();
const cart = createInstance(Cart, { bus });
const analytics = createInstance(Analytics, { bus });

await cart.intents.clear({});
analytics.snapshot().clears;   // 1 — the store saw the event

An unsubscribed handler is removed immediately; a handler that throws propagates to the emit caller (nothing is swallowed).