mitt

# 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](https://nodejs.org/api/events.html#events_class_eventemitter) - **Functional:** methods don't rely on `this` - **Great Name:** somehow [mitt](https://npm.im/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](#install) - [Usage](#usage) - [Examples & Demos](#examples--demos) - [API](#api) - [Contribute](#contribute) - [License](#license) ## Install This project uses [node](http://nodejs.org) and [npm](https://npmjs.com). Go check them out if you don't have them locally installed. ```sh $ npm install --save mitt ``` Then with a module bundler like [rollup](http://rollupjs.org/) or [webpack](https://webpack.js.org/), use as you would anything else: ```javascript // using ES6 modules import mitt from 'mitt' // using CommonJS modules var mitt = require('mitt') ``` The [UMD](https://github.com/umdjs/umd) build is also available on [unpkg](https://unpkg.com): ```html ``` You can find the library on `window.mitt`. ## Usage ```js 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 Set `"strict": true` in your tsconfig.json to get improved type inference for `mitt` instance methods. ```ts 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 `Emitter` type: ```ts import mitt, { Emitter } from 'mitt'; type Events = { foo: string; bar?: number; }; const emitter: Emitter = mitt(); ``` ## Examples & Demos Preact + Mitt Codepen Demo

* * * ## API #### Table of Contents - [mitt](#mitt) - [all](#all) - [on](#on) - [Parameters](#parameters) - [off](#off) - [Parameters](#parameters-1) - [emit](#emit) - [Parameters](#parameters-2) ### 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](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) \| [symbol](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Symbol))** Type of event to listen for, or `'*'` for all events - `handler` **[Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/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](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) \| [symbol](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Symbol))** Type of event to unregister `handler` from, or `'*'` - `handler` **[Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/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](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) \| [symbol](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/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](../../issues). If don't, just open a [new clear and descriptive issue](../../issues/new). ### 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](https://opensource.org/licenses/MIT) © [Jason Miller](https://jasonformat.com/)

	Stars	Issues	Version	Updated	Created
EventEmitter	32	3	1.0.0	8 years ago	8 years ago
eventemitter3	3,223	13	5.0.1	a year ago	11 years ago
mitt	10,277	15	3.0.1	10 months ago	7 years ago
pubsub.js	147	3	1.5.2	7 years ago	11 years ago
pubsubjs	30	0	0.3.9	9 years ago	11 years ago

EventEmitter vs eventemitter3 vs mitt vs pubsub.js vs pubsubjs

Downloads in past1 Month3 Months6 Months1 Year2 Years5 YearsAll time

Stats

Popular Searches

Sick of boring JavaScript newsletters?

Downloads in past