161 lines
4.9 KiB
Markdown
161 lines
4.9 KiB
Markdown
<p align="center">
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<img src="https://i.imgur.com/BqsX9NT.png" width="300" height="300" alt="mitt">
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<br>
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<a href="https://www.npmjs.org/package/mitt"><img src="https://img.shields.io/npm/v/mitt.svg?style=flat" alt="npm"></a> <a href="https://travis-ci.org/developit/mitt"><img src="https://travis-ci.org/developit/mitt.svg?branch=master" alt="travis"></a> <a href="https://david-dm.org/developit/mitt"><img src="https://david-dm.org/developit/mitt/status.svg" alt="dependencies Status"></a>
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</p>
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# Mitt
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> Tiny 200b functional event emitter / pubsub.
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- **Microscopic:** weighs less than 200 bytes gzipped
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- **Useful:** a wildcard `"*"` event type listens to all events
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- **Familiar:** same names & ideas as [Node's EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
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- **Functional:** methods don't rely on `this`
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- **Great Name:** somehow [mitt](https://npm.im/mitt) wasn't taken
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Mitt was made for the browser, but works in any JavaScript runtime. It has no dependencies and supports IE9+.
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## Table of Contents
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- [Install](#install)
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- [Usage](#usage)
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- [Examples & Demos](#examples--demos)
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- [API](#api)
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- [Contribute](#contribute)
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- [License](#license)
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## Install
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This project uses [node](http://nodejs.org) and [npm](https://npmjs.com). Go check them out if you don't have them locally installed.
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```sh
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$ npm install --save mitt
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```
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Then with a module bundler like [rollup](http://rollupjs.org/) or [webpack](https://webpack.js.org/), use as you would anything else:
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```javascript
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// using ES6 modules
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import mitt from 'mitt'
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// using CommonJS modules
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var mitt = require('mitt')
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```
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The [UMD](https://github.com/umdjs/umd) build is also available on [unpkg](https://unpkg.com):
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```html
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<script src="https://unpkg.com/mitt/dist/mitt.umd.js"></script>
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```
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You can find the library on `window.mitt`.
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## Usage
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```js
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import mitt from 'mitt'
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let emitter = mitt()
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// listen to an event
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emitter.on('foo', e => console.log('foo', e) )
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// listen to all events
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emitter.on('*', (type, e) => console.log(type, e) )
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// fire an event
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emitter.emit('foo', { a: 'b' })
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// working with handler references:
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function onFoo() {}
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emitter.on('foo', onFoo) // listen
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emitter.off('foo', onFoo) // unlisten
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```
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### Typescript
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```ts
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import * as mitt from 'mitt';
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let emitter: mitt.Emitter = new mitt();
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```
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## Examples & Demos
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<a href="http://codepen.io/developit/pen/rjMEwW?editors=0110">
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<b>Preact + Mitt Codepen Demo</b>
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<br>
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<img src="https://i.imgur.com/CjBgOfJ.png" width="278" alt="preact + mitt preview">
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</a>
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* * *
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## API
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### mitt
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Mitt: Tiny (~200b) functional event emitter / pubsub.
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Returns **Mitt**
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#### emit
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Invoke all handlers for the given type.
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If present, `"*"` handlers are invoked after type-matched handlers.
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**Parameters**
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- `type` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** The event type to invoke
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- `evt` **\[Any]** Any value (object is recommended and powerful), passed to each handler
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### on
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Register an event handler for the given type.
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**Parameters**
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- `type` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** Type of event to listen for, or `"*"` for all events
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- `handler` **[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)** Function to call in response to given event
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### off
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Remove an event handler for the given type.
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**Parameters**
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- `type` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** Type of event to unregister `handler` from, or `"*"`
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- `handler` **[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)** Handler function to remove
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## Contribute
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First off, thanks for taking the time to contribute!
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Now, take a moment to be sure your contributions make sense to everyone else.
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Development Start:
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This project is typed with Flow Type annotations. To ensure you have the proper typings for this project run
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`flow-typed install`
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### Reporting Issues
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Found a problem? Want a new feature? First of all see if your issue or idea has [already been reported](../../issues).
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If don't, just open a [new clear and descriptive issue](../../issues/new).
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### Submitting pull requests
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Pull requests are the greatest contributions, so be sure they are focused in scope, and do avoid unrelated commits.
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- Fork it!
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- Clone your fork: `git clone https://github.com/<your-username>/mitt`
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- Navigate to the newly cloned directory: `cd mitt`
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- Create a new branch for the new feature: `git checkout -b my-new-feature`
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- Install the tools necessary for development: `npm install`
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- Make your changes.
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- Commit your changes: `git commit -am 'Add some feature'`
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- Push to the branch: `git push origin my-new-feature`
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- Submit a pull request with full remarks documenting your changes.
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## License
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[MIT License](LICENSE.md) © [Jason Miller](https://jasonformat.com/)
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