Coffee.prototype = new Beverage(); 子类继承了父类，还是报错，怎么办？

var Beverage = function(){}
Beverage.prototype.boilWater = function(){
	console.log("煮沸水");
};

Beverage.prototype.brew = function(){
	// console.log("冲泡饮料");
	throw new Error("子类必须重写该方法");
};

Beverage.prototype.putInCup = function(){
	// console.log("倒进杯中");
	throw new Error("子类必须重写该方法");
};

Beverage.prototype.addCondiments = function(){
	// console.log("添加辅料");
	throw new Error("子类必须重写该方法");
};
Beverage.prototype.customIsWant = function(){
	// 演示钩子方法
	return true;
}
Beverage.prototype.init = function(){
	this.boilWater();
	this.brew();
	this.putInCup();
	if(this.customIsWant()){
		this.addCondiments();
	}
}

var Coffee = function(){}

Coffee.prototype.brew = function () {
  console.log("用开水冲泡咖啡");
}
Coffee.prototype.putInCup= function () {
  console.log("把咖啡倒进杯子里");
}
Coffee.prototype.addCondiments= function () {
  console.log("加糖和牛奶");
}
Coffee.prototype.customIsWant = function(){
	return false;
}

var Tea = function(){}

Tea.prototype.brew = function () {
  console.log("用开水冲泡茶");
}
Tea.prototype.putInCup= function () {
  console.log("把茶倒进杯子里");
}
Tea.prototype.addCondiments= function () {
  console.log("加柠檬");
}
Tea.prototype.customIsWant = function(){
	return window.confirm("请问需要加柠檬吗？");
}

// js的继承
Coffee.prototype = new Beverage(); 

Tea.prototype = new Beverage();

var coffee = new Coffee();
console.log(coffee.brew());
coffee.init();

var tea = new Tea();
tea.init();