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nanoevents
Advanced tools
Nanoevents is a tiny (less than 1KB) event emitter library for JavaScript. It provides a simple and efficient way to handle events in your application, making it ideal for both client-side and server-side development.
Event Emission
This feature allows you to emit events with associated data. The `emit` method triggers all listeners attached to the specified event.
const { createNanoEvents } = require('nanoevents');
const emitter = createNanoEvents();
emitter.emit('event', 'data');
Event Listening
This feature allows you to listen for specific events. The `on` method registers a callback function that will be called whenever the specified event is emitted.
const { createNanoEvents } = require('nanoevents');
const emitter = createNanoEvents();
emitter.on('event', data => {
console.log(data);
});
emitter.emit('event', 'data');
Event Unsubscription
This feature allows you to unsubscribe from events. The `on` method returns an unsubscribe function that can be called to remove the listener.
const { createNanoEvents } = require('nanoevents');
const emitter = createNanoEvents();
const unsubscribe = emitter.on('event', data => {
console.log(data);
});
emitter.emit('event', 'data');
unsubscribe();
emitter.emit('event', 'data');
EventEmitter3 is a high-performance event emitter for Node.js and the browser. It is more feature-rich compared to Nanoevents, offering wildcard event listeners and more advanced event handling capabilities.
Mitt is another tiny event emitter library. It is similar in size and simplicity to Nanoevents but offers a slightly different API. Mitt is also less than 1KB and is designed for minimal overhead.
The 'events' package is the Node.js core EventEmitter module extracted for use in browser environments. It is more heavyweight compared to Nanoevents but offers a robust set of features and is widely used in the Node.js ecosystem.
Simple and tiny event emitter library for JavaScript.
on
method returns unbind
function. You don’t need to save
callback to variable for removeListener
.emit
and on
methods.
No Node.js EventEmitter compatibility.import { createNanoEvents } from 'nanoevents'
const emitter = createNanoEvents()
const unbind = emitter.on('tick', volume => {
summary += volume
})
emitter.emit('tick', 2)
summary //=> 2
unbind()
emitter.emit('tick', 2)
summary //=> 2
npm install nanoevents
Nano Events accepts interface with event name to listener argument types mapping.
interface Events {
set: (name: string, count: number) => void,
tick: () => void
}
const emitter = createNanoEvents<Events>()
// Correct calls:
emitter.emit('set', 'prop', 1)
emitter.emit('tick')
// Compilation errors:
emitter.emit('set', 'prop', '1')
emitter.emit('tick', 2)
Because Nano Events API has only just 2 methods, you could just create proxy methods in your class or encapsulate them entirely.
class Ticker {
constructor () {
this.emitter = createNanoEvents()
this.internal = setInterval(() => {
this.emitter.emit('tick')
}, 100)
}
stop () {
clearInterval(this.internal)
this.emitter.emit('stop')
}
on (event, callback) {
return this.emitter.on(event, callback)
}
}
With Typescript:
import { createNanoEvents, Emitter } from "nanoevents"
interface Events {
start: (startedAt: number) => void
}
class Ticker {
emitter: Emitter
constructor () {
this.emitter = createNanoEvents<Events>()
}
on<E extends keyof Events>(event: E, callback: Events[E]) {
return this.emitter.on(event, callback)
}
}
Use on
method to add listener for specific event:
emitter.on('tick', number => {
console.log(number)
})
emitter.emit('tick', 1)
// Prints 1
emitter.emit('tick', 5)
// Prints 5
In case of your listener relies on some particular context
(if it uses this
within itself) you have to bind required
context explicitly before passing function in as a callback.
var app = {
userId: 1,
getListener () {
return () => {
console.log(this.userId)
}
}
}
emitter.on('print', app.getListener())
Note: binding with use of the .bind()
method won’t work as you might expect
and therefore is not recommended.
Methods on
returns unbind
function. Call it and this listener
will be removed from event.
const unbind = emitter.on('tick', number => {
console.log('on ' + number)
})
emitter.emit('tick', 1)
// Prints "on 1"
unbind()
emitter.emit('tick', 2)
// Prints nothing
Method emit
will execute all listeners. First argument is event name, others
will be passed to listeners.
emitter.on('tick', (a, b) => {
console.log(a, b)
})
emitter.emit('tick', 1, 'one')
// Prints 1, 'one'
You can get used events list by events
property.
const unbind = emitter.on('tick', () => { })
emitter.events //=> { tick: [ [Function] ] }
If you need add event listener only for first event dispatch, you can use this snippet:
class Ticker {
constructor () {
this.emitter = createNanoEvents()
}
…
once (event, callback) {
const unbind = this.emitter.on(event, (...args) => {
unbind()
callback(...args)
})
return unbind
}
}
emitter.on('event1', () => { })
emitter.on('event2', () => { })
emitter.events = { }
5.1.12
FAQs
Simple and tiny (107 bytes) event emitter library
The npm package nanoevents receives a total of 100,688 weekly downloads. As such, nanoevents popularity was classified as popular.
We found that nanoevents demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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