@oh-just-another/events

L0 typed event emitter. Pure TS — no DOM, no React, no Node API. Underpins the pub/sub in Editor / History / Collab.

No runtime dependencies.

Install

pnpm add @oh-just-another/events

Usage

import { createEmitter, type Emitter } from "@oh-just-another/events";

interface EditorEvents {
  mode: (mode: "select" | "draw") => void;
  change: () => void;
}

const emitter: Emitter<EditorEvents> = createEmitter<EditorEvents>();

const off = emitter.on("mode", (m) => console.log(m)); // m inferred as "select" | "draw"
emitter.emit("mode", "select"); // payload is typechecked, returns listener count
off(); // unsubscribe

Behaviour

• on(event, fn) returns an idempotent unsubscribe function.
• emit(event, ...args) calls every listener synchronously and returns how many ran. Listeners are snapshotted first, so on / off from inside a listener take effect on the next emit.
• A listener exception does not abort the loop: remaining listeners still run, and the first error is re-thrown afterwards (mirrors DOM EventTarget).
• off, clear(event?), listenerCount(event) round out the surface.

Exports

| Name | Kind | Notes | | --------------- | -------- | ---------------------------------------------------------------------------- | | createEmitter | function | <E>() => Emitter<E>. Creates a fresh typed emitter. | | Emitter | type | The pub/sub interface: on / off / emit / clear / listenerCount. | | EventMap | type | Conventional event-map shape (Record<string, listener>). Not a constraint. |