<script>
var Beverage = function(){};
Beverage.prototype.boilWater = function(){
  console.log("把水煮沸");
};
Beverage.prototype.brew = function(){
  throw new Error("子类必须重写该方法");
};
Beverage.prototype.pourInCup = function(){
  throw new Error("子类必须重写该方法");
};
Beverage.prototype.addCondiments = function(){
  throw new Error("子类必须重写该方法");
};
Beverage.prototype.customerWantsCondiments = function(){
  return true;
};
Beverage.prototype.init = function(){
  this.boilWater();
  this.brew();
  this.pourInCup();
  if(this.customerWantsCondiments){
    this.addCondiments();
  }
};
var Coffee = function(){};
Coffee.prototype = new Beverage();//继承父类Beverage
Coffee.prototype.boilWater = function(){
  console.log("把水煮沸");
};
Coffee.prototype.brew = function(){
  console.log("用沸水冲泡咖啡");
};
Coffee.prototype.pourInCup = function(){
  console.log("把咖啡倒进杯子");
};
Coffee.prototype.addCondiments = function(){
  console.log("加糖和牛奶");
};
var Tea = function(){};
Tea.prototype = new Beverage();//继承父类Beverage
Tea.prototype.boilWater = function(){
  console.log("把水煮沸");
};
Tea.prototype.brew = function(){
  console.log("用沸水浸泡茶叶");
};
Tea.prototype.pourInCup = function(){
  console.log("把茶水倒进杯子");
};
Tea.prototype.addCondiments = function(){
  console.log("加入柠檬");
};
Tea.prototype.customerWantsCondiments = function(){
  return window.confirm("请问需要加调料吗?");
};
var coffee = new Coffee();//实例化Coffee
coffee.init();
var tea = new Tea();//实例化Tea
tea.init();
</script>