postal

Pub/Sub message bus for JavaScript and TypeScript.

Features

• TypeScript-first — full type inference on channels, topics, and message data
• AMQP-style wildcards — * matches a single topic segment, # matches zero or more
• Channel-scoped messaging — isolate message domains with named channels
• Request/handle RPC — built-in request/response pattern
• Wire taps — global observers that see every message on the bus
• Transport system — bridge pub/sub across iframes, workers, and browser tabs
• Zero dependencies — no lodash, no nothing

Install

npm install postal

Quick Example

import { getChannel } from "postal";

const orders = getChannel("orders");

orders.subscribe("order.created", envelope => {
    console.log("New order:", envelope.payload.orderId);
});

orders.publish("order.created", { orderId: "abc-123" });

For the full API — wildcards, RPC, wire taps, transports — see the docs.

Upgrading from v2? postal v3 is a ground-up rewrite with breaking changes to the module system, subscriber callbacks, envelope shape, and more. See the v2 → v3 migration guide before upgrading.

Packages

Package	npm	Description
postal	postal	Core message bus
postal-transport-messageport	postal-transport-messageport	MessagePort transport for iframes and workers
postal-transport-broadcastchannel	postal-transport-broadcastchannel	BroadcastChannel transport for cross-tab messaging

Development

pnpm install       # Install dependencies
pnpm build         # Build all packages
pnpm test          # Run all tests
pnpm lint          # Lint all packages
pnpm run checks    # lint + test + build (CI gate)

License

MIT