events

An extra minimal event emitter

featuring

• 0 production dependencies
• CJS and ESM versions
• 637 bytes minified and gzipped

install

npm i -S @nichoth/events

example

You can pass in an array of valid event names. If you subscribe to or emit an event not in the list, this will throw a runtime error. Also, you can create a typed event bus because Bus takes a type argument.

create an event bus, with types

import { Bus } from '@nichoth/events'

const eventTree = Bus.createEvents({
    a: ['b', 'c', 'd'],
    b: {
        _: ['e', 'f'],
        c: ['1', '2', '3']
    }
})
const events = Bus.flatten(eventTree)

const bus = new Bus<Array<typeof events[number]>>(events)

bus.on(eventTree.a)

create an event bus

import { Bus } from '@nichoth/events'
const bus = new Bus()

// you can pass in a list of event names that are allowed.
// If you subscribe or emit something not in the list, it will throw an error.
const bus2 = new Bus(['valid', 'events'])

create namespaced events

Take an object of arrays of strings, and return a new object where the leaf nodes are strings containing the full object path.

import { Bus } from '@nichoth/events'

Bus.createEvents({
    a: {
        _: [1, 2, 3]
        b: {
            c: [1,2,3]
        }
    }
})

// => {
//   a: {
//     1: 'a.1',
//     2: 'a.2',
//     3: 'a.3
//     b: {
//       c: {
//         1: 'a.b.c.1',
//         2: 'a.b.c.2',
//         3: 'a.b.c.3'
//       }
//     }
//   },
// }
//

Bus.flatten

Get an array of the leaf node values of an object of any shape, for example the return value of Bus.createEvents.

It's recommended to use the .flatten static function to get the event name values after calling .createEvents. Or, if you pass in anything that is not an array, the constructor will call .flatten on it.

import { Bus } from '@nichoth/events'

const events = Bus.createEvents({
    a: {
        _: [1, 2, 3]
        b: {
            c: [1,2,3]
        }
    }
})

// pass in a list of valid event names
const bus = new Bus(Bus.flatten(events))
// is the same as
const bust2 = new Bus(events)

subscribe

import { Bus } from '@nichoth/events'
const bus = new Bus()

const off = bus.on(events.a['1'], (data) => {
    t.equal(data, 'test data', 'first listener gets the event')
    off()  // unsubscribe
})

emit events

import { Bus } from '@nichoth/events'
const bus = new Bus()

bus.emit(events.a['1'], 'test data')

You can partially apply the the .emit function

const emitFoo = bus.emit('foo')

bus.on('foo', data => {
    console.log(data)
    // => { example: 'data' }
})

emitFoo({ example: 'data' })

develop

Install dev deps with --legacy-peer-deps.

npm i --legacy--peer-deps

test

npm test