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Module-level bus ​

Problem ​

Implement module-level bus in a production-friendly way with @vielzeug/eventit while keeping setup and cleanup explicit.

Runnable Example ​

The snippet below is copy-paste runnable in a TypeScript project with @vielzeug/eventit installed.

Define a shared bus as a module singleton. Any module can import it to publish or subscribe.

ts
// src/events/app-bus.ts
import { createBus } from '@vielzeug/eventit';

type AppEvents = {
  'user:login': { userId: string; email: string };
  'user:logout': void;
  'cart:updated': { items: CartItem[]; total: number };
  'theme:change': 'light' | 'dark';
};

export const appBus = createBus<AppEvents>({
  onError: (err, event, payload) => console.error(`[bus] error in "${event}"`, err, payload),
});

// src/cart/cart-module.ts
import { appBus } from '../events/app-bus';

appBus.on('user:login', ({ userId }) => loadCart(userId));
appBus.on('user:logout', clearCart);

Expected Output ​

  • The example runs without type errors in a standard TypeScript setup.
  • The main flow produces the behavior described in the recipe title.

Common Pitfalls ​

  • Forgetting cleanup/dispose calls can leak listeners or stale state.
  • Skipping explicit typing can hide integration issues until runtime.
  • Not handling error branches makes examples harder to adapt safely.