| <p align="center"> |
| <img src="https://i.imgur.com/BqsX9NT.png" width="300" height="300" alt="mitt"> |
| <br> |
| <a href="https://www.npmjs.org/package/mitt"><img src="https://img.shields.io/npm/v/mitt.svg" alt="npm"></a> |
| <img src="https://github.com/developit/mitt/workflows/CI/badge.svg" alt="build status"> |
| <a href="https://unpkg.com/mitt/dist/mitt.js"><img src="https://img.badgesize.io/https://unpkg.com/mitt/dist/mitt.js?compression=gzip" alt="gzip size"></a> |
| </p> |
| |
| # 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 |
| <script src="https://unpkg.com/mitt/dist/mitt.umd.js"></script> |
| ``` |
| |
| 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<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: |
| |
| ```ts |
| import mitt, { Emitter } from 'mitt'; |
| |
| type Events = { |
| foo: string; |
| bar?: number; |
| }; |
| |
| const emitter: Emitter<Events> = mitt<Events>(); |
| ``` |
| |
| ## Examples & Demos |
| |
| <a href="http://codepen.io/developit/pen/rjMEwW?editors=0110"> |
| <b>Preact + Mitt Codepen Demo</b> |
| <br> |
| <img src="https://i.imgur.com/CjBgOfJ.png" width="278" alt="preact + mitt preview"> |
| </a> |
| |
| * * * |
| |
| ## API |
| |
| <!-- Generated by documentation.js. Update this documentation by updating the source code. --> |
| |
| #### 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/<your-username>/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/) |