puppeteer/vendor/mitt/README.md
Jack Franklin f1a6b8d66d
chore: vendor Mitt & update project structure (#6209)
* chore: vendor Mitt into src/common/third-party

As discussed in #6203 we need to vendor our common dependencies in so
that when we ship an ESM build all imports point to file paths and do
not rely on Node resolution (e.g. a browser does not understand `import
mitt from 'mitt'`).
2020-07-14 16:57:29 +01:00

5.4 KiB

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:

<script src="https://unpkg.com/mitt/dist/mitt.umd.js"></script>

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' })

// 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

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/<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 © Jason Miller