remitter

remitter

A tiny TypeScript friendly event emitter that supports lazy re-emitting events form other sources.

Install

npm add remitter

Usage

import { Remitter } from "remitter";

interface EventData {
  event1: string;
  event2: void;
}

const remitter = new Remitter<EventData>();

const disposer = remitter.on("event1", value => {
  console.log("event1", value);
});

remitter.once("event1", value => {
  console.log("event1-once", value);
});

remitter.count("event1"); // 2

remitter.emit("event1", "hello"); // logs "event1 hello" and "event1-once hello"

remitter.emit("event1", "hello"); // logs "event1 hello"

remitter.emit("event2"); // nothing logs

disposer();
remitter.emit("event1", "world"); // nothing logs

remitter.clear("event2"); // remove all listeners for event2
remitter.count(); // 0

remitter.dispose(); // removes all listeners and dispose tapped events

Listen to any event

import { Remitter } from "remitter";

interface EventData {
  event1: string;
  event2: string;
}

const remitter = new Remitter<EventData>();

remitter.on(remitter.ANY_EVENT, ({ event, data }) => {
  console.log(event, data);
});

remitter.emit("event1", "hello"); // logs "event1 hello"
remitter.emit("event2", "world"); // logs "event2 world"

Remit

You may tap into other events easily with remit. It is lazy-executed when listener count of the event name grows from 0 to 1. It is disposed when listener count of the event name drops from 1 to 0.

remitter.remit("cursor", () => {
  const handler = ev => {
    remitter.emit("cursor", { x: ev.clientX, y: ev.clientY });
  };

  window.addEventListener("mousemove", handler);

  return () => {
    window.removeListener("mousemove", handler);
  };
});

// Remit callback does not execute until the first "cursor" listener is added
remitter.on("cursor", value => {
  console.log("cursor", value);
});

// Remit callback is disposed when no listener on the
// "cursor" event. (`window.removeListener` triggered)
remitter.clear("cursor");

The callback function can also be a pure function.

const myCursorEvent = remitter => {
  const handler = ev => {
    remitter.emit("cursor", { x: ev.clientX, y: ev.clientY });
  };

  window.addEventListener("mousemove", handler);

  return () => {
    window.removeListener("mousemove", handler);
  };
};

remitter.remit("cursor", myCursorEvent);

Acknowledgment

Huge thanks to @recursivefunk for giving away the NPM package name remitter.

Changelog

0.3.0 (2023-08-17)

0.2.17 (2023-08-17)

0.2.16 (2023-08-16)

0.2.15 (2023-08-16)

0.2.14 (2023-08-16)

0.2.13 (2023-08-16)

0.2.12 (2023-08-07)

Features

• remitter: add ANY_EVENT (7fdc13e)

0.2.11 (2023-05-22)

Bug Fixes

• allow adding same listener to both on and once (f44cb44)

0.2.10 (2023-05-17)

0.2.9 (2022-08-30)

Features

• add once (d6b401b)

0.2.8 (2022-08-24)

Bug Fixes

• start remit immediately if eventName exists listeners (af2081e)

0.2.7 (2022-08-12)

0.2.6 (2022-07-12)

Bug Fixes

• listener typings (1ecc833)
• tpying (cb5cfb2)

0.2.3 (2022-06-17)

0.2.2 (2022-06-17)

0.2.1 (2022-06-16)