Simple es6 eventEmitter

README.md

0tis-eventemitter

Simple es6 eventEmitter

Install

npm i -S gist:a965f9de8dcbb9894a914105e0ab2a58

How to use

import EventEmitter from '0tis-eventemitter';
class MyClass extends EventEmitter{
  constructor(){
    setInterval(this.init, 1);
  }
  init(){
    this.emit('init', 'My class initiated');
  }
}
const myClass = new MyClass();
myClass.on('init', msg=>console.log(msg));

EventEmitter.mjs

class EventsEmitter {
  constructor(){
    this.events = {};
  }
  on(name, callback, context, once = false){
    if(name == null) throw new Error('No first argument passed');
    if(callback == null) throw new Error('No second argument passed');
    if(typeof callback !== 'function') throw new Error('Second argument must be a function');
    
    if(typeof context === 'boolean' && context === true && once === false){
      [once, context] = [context, null];
    }
    
    this.events[name] = [...(this.events[name] || []), {callback, context, once}];
  }
  off(name, callback){
    if(name == null) throw new Error('No first argument passed');
    if(!this.events[name]) return;
    
    if(callback){
      if(callback == null) throw new Error('No second argument passed');
      if(typeof callback !== 'function') throw new Error('Second argument must be a function');
      this.events[name] = this.events[name].filter(event=>event.callback != callback);
    }
    else{
      delete this.events[name];
    }
  }
  emit(name, ...args){
    if(name == null) throw new Error('No first argument passed');
    
    (this.events[name] || []).forEach(event=>{
      try{
        event.callback.call(event.context, ...args);

        if(event.once){
          this.off(name, event.callback);
        }
      }
      catch(e){
        throw e;
      }
    });
  }
  
  //aliases
  once(name, callback, context){
    this.on(name, callback, context, true);
  }
  subscribe(name, callback, context){
    this.on(name, callback, context);
  }
  unsubscribe(name, callback){
    this.off(name, callback);
  }
  addListener(name, listener, context){
    this.on(name, listener, context);
  }
  removeListener(name, listener){
    this.off(name, listener);
  }
  removeListeners(name){
    this.off(name);
  }
  dispatchEvent(name, ...args){
    this.emit(name, ...args);
  }
}
export default EventEmitter;

package.json

{
  "version": "0.1.0",
  "name": "0tis-eventemitter",
  "main": "EventEmitter.mjs"
}