Nitt

Small functional event emitter / pubsub.

Microscopic: weighs less than 200 bytes gzipped
Useful: a wildcard "*" event type listens to all events
Familiar: same names & ideas as Node's EventEmitter

nitt was made for the browser, but works in any JavaScript runtime. It has no dependencies and supports IE9+.

Install

This project uses node and npm. Go check them out if you don't have them locally installed.

$ npm install --save nitt

Then with a module bundler like rollup or webpack, use as you would anything else:

// using ES6 modules
import nitt from 'nitt'

// using CommonJS modules
var nitt = require('nitt')

The UMD build is also available on unpkg:

<script src="https://unpkg.com/nitt/dist/nitt.umd.js"></script>

You can find the library on window.nitt.

Usage

import nitt from 'nitt'

const emitter = nitt()

// listen to an event
emitter.on('foo', e => console.log('foo', e) )

// listen to all events
emitter.on('*', (type, e) => console.log(type, e) )

// fire an event
emitter.emit('foo', { a: 'b' })

// clearing all events
emitter.all.clear()

// working with handler references:
function onFoo() {}
emitter.on('foo', onFoo)   // listen
emitter.off('foo', onFoo)  // unlisten

Typescript

Set "strict": true in your tsconfig.json to get improved type inference for nitt instance methods.

import nitt from 'nitt';

type Events = {
  foo: string;
  bar?: number;
};

const emitter = nitt<Events>(); // inferred as emitter<Events>

emitter.on('foo', (e) => {}); // 'e' has inferred type 'string'

emitter.emit('foo', 42); // Error: Argument of type 'number' is not assignable to parameter of type 'string'. (2345)

Alternatively, you can use the provided emitter type:

import nitt, { emitter } from 'nitt';

type Events = {
  foo: string;
  bar?: number;
};

const emitter: emitter<Events> = nitt<Events>();

API

nitt

Nitt: Tiny (~200b) functional event emitter / pubsub.

Returns Nitt

all

A Map of event names to registered handler functions.

on

Register an event handler for the given type.

Parameters

type (string | symbol) Type of event to listen for, or '*' for all events
handler Function Function to call in response to given event

off

Remove an event handler for the given type. If handler is omitted, all handlers of the given type are removed.

Parameters

type (string | symbol) Type of event to unregister handler from ('*' to remove a wildcard handler)
handler Function? Handler function to remove