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Simple and tiny (107 bytes) event emitter library for JavaScript
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ai/nanoevents
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Simple and tiny event emitter library for JavaScript.
- Only108 bytes (minified and brotlied).It usesSize Limit to control size.
- The
onmethod returnsunbindfunction. You don’t need to savecallback to variable forremoveListener. - TypeScript and ES modules support.
- No aliases, just
emitandonmethods.No Node.jsEventEmitter compatibility.
import{createNanoEvents}from'nanoevents'constemitter=createNanoEvents()constunbind=emitter.on('tick',volume=>{summary+=volume})emitter.emit('tick',2)summary//=> 2unbind()emitter.emit('tick',2)summary//=> 2
- Table of Contents
- Install
- TypeScript
- Mixing to Object
- Add Listener
- Remove Listener
- Execute Listeners
- Events List
- Once
- Remove All Listeners
npm install nanoevents
Nano Events accepts interface with event nameto listener argument types mapping.
interfaceEvents{set:(name:string,count:number)=>void,tick:()=>void}constemitter=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 classor encapsulate them entirely.
classTicker{constructor(){this.emitter=createNanoEvents()this.internal=setInterval(()=>{this.emitter.emit('tick')},100)}stop(){clearInterval(this.internal)this.emitter.emit('stop')}on(event,callback){returnthis.emitter.on(event,callback)}}
With Typescript:
import{createNanoEvents,Emitter}from"nanoevents"interfaceEvents{start:(startedAt:number)=>void}classTicker{emitter:Emitterconstructor(){this.emitter=createNanoEvents<Events>()}on<EextendskeyofEvents>(event:E,callback:Events[E]){returnthis.emitter.on(event,callback)}}
Useon method to add listener for specific event:
emitter.on('tick',number=>{console.log(number)})emitter.emit('tick',1)// Prints 1emitter.emit('tick',5)// Prints 5
In case of your listener relies on some particular context(if it usesthis within itself) you have to bind requiredcontext explicitly before passing function in as a callback.
varapp={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 expectand therefore is not recommended.
Methodson returnsunbind function. Call it and this listenerwill be removed from event.
constunbind=emitter.on('tick',number=>{console.log('on '+number)})emitter.emit('tick',1)// Prints "on 1"unbind()emitter.emit('tick',2)// Prints nothing
Methodemit will execute all listeners. First argument is event name, otherswill 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 byevents property.
constunbind=emitter.on('tick',()=>{})emitter.events//=> { tick: [ [Function] ] }
If you need add event listener only for first event dispatch,you can use this snippet:
classTicker{constructor(){this.emitter=createNanoEvents()}…once(event,callback){constunbind=this.emitter.on(event,(...args)=>{unbind()callback(...args)})returnunbind}}
emitter.on('event1',()=>{})emitter.on('event2',()=>{})emitter.events={}
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Simple and tiny (107 bytes) event emitter library for JavaScript