Transports

For the conceptual explanation of when each transport is used, see the Transports guide. This page documents its exact shape.

Note

BroadcastTransport and MemoryTransport are internal details: Tabus picks them automatically and they aren’t exported from the package’s public entry point. Only ITransport (the contract type) is part of the public exports.

ITransport

interface ITransport {
  send(msg: TabusMessage): void;
  onMessage(listener: (msg: TabusMessage) => void): void;
  destroy(): void;
}

Member	Description
send(msg)	Sends a TabusMessage through the transport.
onMessage(listener)	Registers a listener that’s invoked with every TabusMessage received.
destroy()	Releases the transport’s resources (closes the underlying channel).

Caution

Deduplication by tabId is Tabus’s responsibility, not the transport’s. Any new ITransport implementation must respect this contract: it can safely hand the emitter its own message back.

BroadcastTransport

A thin wrapper around the native BroadcastChannel API.

Method	Implementation
send(msg)	bc.postMessage(msg)
onMessage(listener)	bc.addEventListener("message", ...)
destroy()	bc.close()

It’s the default transport used in any browser that supports BroadcastChannel, and it communicates real tabs, windows, and workers of the same origin.

MemoryTransport

In-memory fallback, active when BroadcastChannel doesn’t exist (Node, SSR, very old browsers).

• Keeps a module-level registry: Map<string, Set<listener>>, shared by every MemoryTransport instance within the same process.
• Only works within the same process/tab — it doesn’t cross real tabs, because without BroadcastChannel that concept doesn’t exist.
• Unlike BroadcastTransport, the emitter’s own listener is invoked by send(); it’s Tabus, not the transport, that filters by tabId.
• Emits a console.warn once per channel name, warning that the fallback kicked in.

__resetMemoryBus()

function __resetMemoryBus(): void

Clears MemoryTransport’s internal module-level registry (the listeners and the record of channels already warned about).

Caution

This is a function internal to the transport module, not part of the package’s public entry point (you can’t do import { __resetMemoryBus } from "tabus-js"). It exists solely so the library’s own test suite can clear global state between tests — don’t use it in application code.

Next step

Exports summarizes what all of this exports publicly from tabus-js.