event emitter without 'on' and 'emit'

coolEmitter.js

'use strict';

function emitize(obj, eventName) {
  var _subscriptions = new Set();
  Object.defineProperty(obj, eventName, {
    set(func) { _subscriptions.add(func); }, 
    get() { 
      var emit = (...args)=>{
        _subscriptions.forEach(f=>f(...args)); 
      };
      
      Object.defineProperty(emit, 'off', { 
        set(func) { _subscriptions.delete(func);},
        get() { _subscriptions = new Set(); } 
      }); 
      return emit;
    }
  });
}

coolEmitterES5.js

'use strict';

function emitize(obj, eventName) {
  var _subscriptions = [];
  Object.defineProperty(obj, eventName, {
    set: function set(func) {
      _subscriptions.push(func);
    },
    get: function get() {
      var emit = function emit() {
        for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
          args[_key] = arguments[_key];
        }

        if (!_subscriptions) {
          return function () {};
        }
        _subscriptions.forEach(function (f) {
          return f.apply(undefined, args);
        });
      };

      Object.defineProperty(emit, 'off', {
        set: function set(func) {
          _subscriptions = _subscriptions.filter(function (f) {
            return f !== func;
          });
        },
        get: function get() {
          _subscriptions = [];
        }
      });

      return emit;
    }
  });
}

coolEmitterProxy.js

function createEmitter() {
  var target = {}
  return new Proxy(target, {
    get(target, property, receiver){
      var emit = (...args)=>{
        target._subscriptions.forEach(f=>f(...args)); 
      };
      return emit
  },
  set(target, prop, value, receiver) {
    if(prop === '_subscriptions'){throw new Error('dont subscribe to  _subscriptions!'); }
    if(typeof value !== 'function'){throw new Error('subscribe only functions!'); }

    if(!target._subscriptions){ target._subscriptions = [] }
    target._subscriptions.push(value);
    return true;
  }
  });
}


// ** usage ** //


function log(v) {
  console.log(v);
}
function logPlus1(v) {
  console.log(v + 1);
}


const emitter = createEmitter();
emitter.x = log; //subscribe to events ('x') with cb (log)

// emitter._subscriptions = log;
// emitter.x = '2'
emitter.x = logPlus1; 

emitter.x('x');

coolEmitterUsage.js

function log(v) {
  console.log(v);
}
function logPlus1(v) {
  console.log(v + 1);
}

var obj = {};
emitize(obj, 'x');
emitize(obj, 'y');
emitize(obj, 'z');

obj.x = log; //subscribe to events ('x') with cb (log)
obj.x = logPlus1; //another subscription, it won't override the previous one

obj.y = log;
obj.y = logPlus1;

obj.y.off = logPlus1; //unsbscribe logPlus1

obj.z = log;
obj.z = logPlus1;
obj.z.off; //unscbscribe all

obj.x('x'); //emits 'x' to all listeners;
//logs=>
//x
//x1
obj.y('y');
//logs=>
//y
obj.z('z');
// no logs

simpleEmitter.js

const emitter = {
  on(name, func){
    this._subscriptions[name] = this._subscriptions[name] || [];
    this._subscriptions[name].push(func)
  },
  off(name, func){
     this._subscriptions[name] = this._subscriptions[name].filter(f=>f!==func)
  },
  _subscriptions:{},
  emit(name, ...args){
    if(!this._subscriptions[name]){return; }
    this._subscriptions[name].forEach(f=>f(...args))
  }
}

simpleEmitterUsage.js

setTimeout(function(){
 emitter.emit('yyy', 5);  
}, 100)

setTimeout(function(){
 emitter.emit('yyy', 9);  
}, 50)


//emitter.on('yyy', function(v){console.log(v - 1)})

function log(v){
  console.log(v)
}

emitter.on('yyy', function(v){console.log(v + 1)})
emitter.on('yyy', log);

setTimeout(function(){
 emitter.off('yyy', log);  
}, 70)