Package Exports

remitter
remitter/dist/index.js
remitter/dist/index.mjs

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (remitter) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

remitter

A tiny TypeScript friendly event emitter that supports lazy re-emitting events from 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.has("event1"); // true

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.has(); // false

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.onAny(({ event, data }) => {
  console.log(event, data);
});

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

Listen to unhandled subscriber errors

import { Remitter } from "remitter";

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

const remitter = new Remitter<EventData>();

remitter.onError(error => {
  console.log(error);
});

remitter.emit("event1", () => {
  throw new Error("error");
});

remitter.emit("event2", async () => {
  await new Promise(resolve => setTimeout(resolve, 100));
  throw new Error("async-error");
});

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.