function object(o) {
    function F() {}
    F.prototype = o;
    return new F();
}

function Responder(name) {
  this.name = name;
  this.response = function (input) {
    return "";
  };
}

function WhatResponder(name) {
    var that = object(new Responder(name));
    that.response = function (input) {
    return input + 'ってなに？';
    };
    return that;
}

function RandomResponder(name) {
    var that = object(new Responder(name));
    that.responses = ['今日は寒いね','チョコ食べたい','昨日10円拾った'];
    that.response = function (input) {  
        return this.responses[Math.floor(Math.random() * 3)];
    };
    return that;
}
function Unmo(name) {
  this.name = name;
  this.responder = RandomResponder('Random');
  this.dialogue = function (input) {
    return this.responder.response(input);
  };
  this.responder_name = function () {
    return this.responder.name;
  };
}

var u = new Unmo('proto');
var input = "あれ";

console.log(u.dialogue(input));