als-event-emitter/index.js

A powerful, asynchronous, promise-based event emitter with support for chaining and advanced event handling.

const SmartPromise = require('als-smart-promise')
class EventEmitter {
   static once(listener) { SmartPromise.use(listener, { once: true, last:false }) }
   static onLast(listener) { SmartPromise.use(listener, { once: false, last:true }) }
   static onceLast(listener) { SmartPromise.use(listener, { once: true, last:true }) }
   static on(listener, options = {}) { SmartPromise.use(listener,options) }
   static removeAllListeners() {SmartPromise.chain.clear()}

   constructor(chain = true,timeout = null) {
      this.chain = chain
      this.timeout = timeout
      this.removeAllListeners()
   }

   removeAllListeners() {
      this.listeners = {}
      this.anyChain = new SmartPromise()
      return this
   }

   getChain(eventName, group) {
      if (!this.listeners[eventName]) {
         this.listeners[eventName] = new SmartPromise(this.timeout,eventName)
         this.listeners[eventName].link(this.anyChain)
         if(this.listeners[group]) this.listeners[eventName].link(this.listeners[group])
      }
      return this.listeners[eventName]
   }
   has(eventName) { return !!this.listeners[eventName] && this.listeners[eventName].chain.size > 0 }
   off(eventName) { delete this.listeners[eventName]; return this }
   on(eventName, listener, options = {}) {
      const { once = false, last = false, group } = options
      const chain = this.getChain(eventName, group)
      chain.use(listener, { once, last })
      return this
   }

   removeListener(listener) {
      this.anyChain.delete(listener)
      for (let eventName in this.listeners) {
         this.listeners[eventName].chain.delete(listener)
      }
      return this;
   }

   onAny(listener, options = {}) {
      const { once = false, last = false } = options
      this.anyChain.use(listener, { once, last })
      return this;
   }

   emit(eventName, ...args) {
      const chain = this.listeners[eventName] || this.anyChain;
      if (this.chain) return chain.execute(...args)
      const fns = chain.getFns()
      fns.forEach(fn => fn(...args));
   }

   once(eventName, listener, group) { return this.on(eventName, listener, { once: true, group }) }
   onLast(eventName, listener, group) { return this.on(eventName, listener, { once: false, last: true, group }) }
   onceLast(eventName, listener, group) { return this.on(eventName, listener, { once: true, last: true, group }) }

   onceAnyLast(listener) { return this.onAny(listener, { once: true, last: true }) }
   onAnyLast(listener) { return this.onAny(listener, { once: false, last: true }) }
   onceAny(listener) { return this.onAny(listener, { once: true }) }
}

module.exports = EventEmitter