mitt

by developit

developit / mitt

🥊 Tiny 200 byte functional event emitter / pubsub.

4.9K Stars 214 Forks Last release: 3 months ago (2.1.0) 116 Commits 10 Releases

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mitt
npm build status gzip size

Mitt

Tiny 200b 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
  • Functional: methods don't rely on
    this
  • Great Name: somehow mitt wasn't taken

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

Table of Contents

Install

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

$ npm install --save mitt

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

// using ES6 modules
import mitt from 'mitt'

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

The UMD build is also available on unpkg:


You can find the library on

window.mitt
.

Usage

import mitt from 'mitt'

const emitter = mitt()

// 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

import mitt from 'mitt';
const emitter: mitt.Emitter = mitt();

Examples & Demos

Preact + Mitt Codepen Demo
preact + mitt preview


API

Table of Contents

mitt

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

Returns Mitt

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.

Parameters

  • type
    (string | symbol) Type of event to unregister
    handler
    from, or
    "*"
  • handler
    Function Handler function to remove

emit

Invoke all handlers for the given type. If present,

"*"
handlers are invoked after type-matched handlers.

Note: Manually firing "*" handlers is not supported.

Parameters

  • type
    (string | symbol) The event type to invoke
  • evt
    Any? Any value (object is recommended and powerful), passed to each handler

Contribute

First off, thanks for taking the time to contribute! Now, take a moment to be sure your contributions make sense to everyone else.

Reporting Issues

Found a problem? Want a new feature? First of all see if your issue or idea has already been reported. If don't, just open a new clear and descriptive issue.

Submitting pull requests

Pull requests are the greatest contributions, so be sure they are focused in scope, and do avoid unrelated commits.

  • Fork it!
  • Clone your fork:
    git clone https://github.com//mitt
  • Navigate to the newly cloned directory:
    cd mitt
  • Create a new branch for the new feature:
    git checkout -b my-new-feature
  • Install the tools necessary for development:
    npm install
  • Make your changes.
  • Commit your changes:
    git commit -am 'Add some feature'
  • Push to the branch:
    git push origin my-new-feature
  • Submit a pull request with full remarks documenting your changes.

License

MIT License © Jason Miller

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