Mittss

forked from mitt

What is Mittss?

Mittss is an lightweight and simple event emitter / pubsub, rewrite the mitt using a class.

• Lightweight: weighs less than 300 bytes gzipped
• Useful: a wildcard "*" event type listens to all events
• Familiar: same names & ideas as Node's EventEmitter
• Extendable: easily extendable with inheritance.
• Zero Dependencies: Works out of the box without additional libraries.

Installation

npm install mittss

or

pnpm add mittss

Usage

Visit the documentation website to explore more guides and API references.

Basic usage

import { Emitter } from 'mittss'

// Create a Emitter instance
const emitter = new Emitter()

// 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
emitter.once('foo', onFoo) // listen once

Typescript

Set "strict": true in your tsconfig.json to get improved type inference for mitt instance methods.

import { Emitter } from 'mittss'

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

const emitter = new Emitter<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)

Extending Emitter

Since Emitter is a class, you can easily extend it to add custom functionality:

class MyEmitter extends Emitter {
  constructor() {
    super()
  }

  greet(name) {
    this.emit('greet', name)
  }
}

const myEmitter = new MyEmitter()
myEmitter.on('greet', name => {
  console.log(`Hello, ${name}!`)
})

myEmitter.greet('Bob') // Output: Hello, Bob!

Functional Emitter

const mitt = <Events extends Record<EventType, unknown>>(
  all?: EventHandlerMap<Events>,
) => {
  return new Emitter<Events>(all)
}

const emitter = mitt()

Differences from mitt

Emitter is forked from mitt, with the following key differences:

• Implemented using class, supporting inheritance and extension.
• Provides a once method for one-time event listeners.

Acknowledgments

Thanks to mitt again for the inspiration.

License

MIT © nnecec