var eventModel = {
 list: {},
 bind: function () {
 var args = [].slice.call(arguments),
 type = args[0],
 handlers = args.slice(1);
 if (typeof type === 'string' && handlers.length > 0) {
  for (var i = 0; i < handlers.length; i++) {
  if (typeof handlers[i] === 'function') {
   if (!this.list[type]) {
   this.list[type] = [];
   }
   this.list[type].push(handlers[i]);
  }
  }
 }
 },
 unbind: function () {
 var type = arguments[0],
 handlers = Array.prototype.slice.call(arguments, 1);
 if (typeof type === 'string') {
  if (handlers.length === 0) {
  this.list[type] = [];
  } else {
  for (var i = 0; i < handlers.length; i++) {
   if (typeof handlers[i] === 'function' && handlers[i] === this.list[type][i]) {
   this.list[type].splice(i, 1);
   }
  }
  }
 }
 },
 trigger: function () {
 var arguments = [].slice.call(arguments),
 type = arguments[0],
 args = arguments[1] instanceof Array && !arguments[2] ? arguments[1] : arguments.slice(1),
 handlers = this.list[type];
 for (var i = 0; i < handlers.length; i++) {
  handlers[i].apply(this, args.splice(0, handlers[i].length));
 }
 }
};

eventModel.bind('myevent1', function (a) {
 console.log(a); // 1
}, function(b) {
 console.log(b); // 2
}, function(c, d) {
 console.log(c + ' + ' + d); // a + b
});
eventModel.bind('myevent1', function (e) {
 console.log(e); // 50
});
eventModel.trigger('myevent1', 1,2,'a','b', 50);

<button id="bind">bind</button>
<button id="unbind">unbind</button>

var fnX = function () {
 console.log('fnX');
}
var fnY = function () {
 console.log('fnY');
}
eventModel.bind('myevent2', fnX, fnY);
document.getElementById('unbind').onclick = function () {
 eventModel.unbind('myevent2', fnX); //刪除 fnX 后，只剩下 fnY
};
document.getElementById('bind').onclick = function () {
 eventModel.trigger('myevent2'); //輸出 fnX fnY
 //在點擊unbind后，只輸出 fnY
};