Need help with mitt?
Click the “chat” button below for chat support from the developer who created it, or find similar developers for support.

About the developer

6.7K Stars 302 Forks MIT License 131 Commits 14 Opened issues


🥊 Tiny 200 byte functional event emitter / pubsub.

Services available


Need anything else?

Contributors list

npm build status gzip size


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
  • 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


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



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'foo', onFoo) // unlisten



"strict": true
in your tsconfig.json to get improved type inference for
instance methods.
import mitt from 'mitt';

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

const emitter = mitt(); // inferred as Emitter

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

import mitt, { Emitter } from 'mitt';

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

const emitter: Emitter = mitt();

Examples & Demos

Preact + Mitt Codepen Demo
preact + mitt preview


Table of Contents


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

Returns Mitt


A Map of event names to registered handler functions.


Register an event handler for the given type.


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


Remove an event handler for the given type. If

is omitted, all handlers of the given type are removed.


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


Invoke all handlers for the given type. If present,

handlers are invoked after type-matched handlers.

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


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


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
  • 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.


MIT License © Jason Miller

We use cookies. If you continue to browse the site, you agree to the use of cookies. For more information on our use of cookies please see our Privacy Policy.