function Signal() {
  this.handlers = [];
}

Signal.prototype.connect = function (handler) {
  if (this.handlers.indexOf(handler) == -1) {
    this.handlers.push(handler);
  }
};

Signal.prototype.disconnect = function (handler) {
  var index = this.handlers.indexOf(handler);

  if (index == -1) { 
    throw new Error("handler hasn't been connected");
  } else {
    var temp = [];

    for (var i = 0; i < this.handlers.length; ++i) {
      if (i == index) continue;
      temp.push(this.handlers[i]);
    }
    
    this.handlers = temp;
  }
};

Signal.prototype.emit = function () {
  var args = Array.prototype.slice.call(arguments);
  
  for (var i = 0; i < this.handlers.length; ++i) {
    this.handlers[i].apply(null, args);
  }
};

Signal.prototype.clearHandlers = function () {
  this.handlers = [];
};

function notify(user, message) {
  console.log('%s recieved message: %s', user, message);
};

var signal = new Signal();

signal.connect(notify);
signal.emit("John", "PHP is sucks");