javascript 写策略模式，商场收银打折优惠策略
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购物清单
方便面 : 100 x 50 = 5000 | 4000
菊花茶 : 10 x 50 = 500 | 500
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优惠使用 : 国庆1折优惠
购物合计 4500 -> 450
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首先封装收银机类，怎么把商品设进，怎么把收银金额输出。
然后封装商品，和金额独立
然后进行收银策略编写。打折，满返针对的是最后的结果。
收银机添加设置策略接口，调用原生金额接口，调用策略接口，获得策略后金额接口
下个需求到商品的具体折扣，譬如买几送几
封装策略到商品处，商品创建的时候根据自己的名字到工厂去领取自己的“福利”
后续还想实施，组合折扣，譬如买牙膏同时买牙刷，减5块钱
架构要大改了(・-・*) ，暂时搁置
/**
* by JackChen 2016-3-15 19.20.01
* 看完马士兵老师策略模式后作业
*
* 原文是讲解comparable接口 和 compareTo
*
* 所有实现了comparable接口的类都可以用于比较。
*
* 而更高级的是，我不同场景需要不同的比较时，通过定制本类的比较器，
* 借用比较器的compareTo，得到不同的比较结果
*
* 已实现
* 1. 单个物品多个数量
* 2. 多个物品多个数量
* 3. 多个物品结算打印
* 4. 多个物品总金额折扣策略（几折、满返）
* 5. 单个物品优惠策略（多少个送多少个）
*
* 待实现
* 6. 单个物品 买多个送多个 跟购物物品无关
* 7. 组合购买
*/
////////////////////////////////////////////////////////////////////////
/// 收银策略类
//普通收钱
var NormalStrategy = function() {
var self = this;
self.type = "total";
self.description = "没有使用优惠";
};
NormalStrategy.prototype = {};
NormalStrategy.prototype.constructor = NormalStrategy;
NormalStrategy.prototype.desc = function() {
return this.description;
};
NormalStrategy.prototype.discount = function(money) {
return money;
};
//折扣策略
var PrecentOffStrategy = function(description, precent) {
var self = this;
self.type = "total";
self.precent = precent;
self.description = description + (precent*10) + "折优惠";
};
PrecentOffStrategy.prototype = new NormalStrategy();
PrecentOffStrategy.prototype.constructor = PrecentOffStrategy;
PrecentOffStrategy.prototype.desc = function() {
return this.description;
};
PrecentOffStrategy.prototype.discount = function(money) {
return money * this.precent;
};
//满返策略
var GivebackStrategy = function(description, enough, giveback) {
var self = this;
self.type = "total";
self.enough = enough;
self.giveback = giveback;
self.description = description + "满"+ enough + "返" + giveback + "优惠";
};
GivebackStrategy.prototype = new NormalStrategy();
GivebackStrategy.prototype.constructor = GivebackStrategy;
GivebackStrategy.prototype.desc = function() {
return this.description;
};
GivebackStrategy.prototype.discount = function(money) {
if (money >= this.enough) {
money -= this.giveback;
};
return money;
};
////////////////////////////////////////////////////////////////////////
/// 销售品种折扣工厂
var SaleItemStrategyFactory = function() {
};
SaleItemStrategyFactory.prototype = {};
SaleItemStrategyFactory.prototype.constructor = SaleItemStrategyFactory;
SaleItemStrategyFactory.prototype.getInstance = function(name) {
var self = this;
var strategy = null;
switch (name) {
case "方便面":
strategy = new BuyMoreStrategy("特惠",4,1);
break;
default:
// statements_def
break;
}
return strategy;
};
//普通
var ItemNormalStrategy = function() {
var self = this;
self.type = "total";
self.description = "没有优惠";
};
ItemNormalStrategy.prototype = {};
ItemNormalStrategy.prototype.constructor = ItemNormalStrategy;
ItemNormalStrategy.prototype.desc = function() {
return this.description;
};
ItemNormalStrategy.prototype.discount = function(money) {
return money;
};
//买几送几
var BuyMoreStrategy = function(description, buy, free) {
var self = this;
self.type = "total";
self.buy = buy;
self.free = free;
self.description = description + "买"+ buy + "送" + free;
};
BuyMoreStrategy.prototype = new ItemNormalStrategy();
BuyMoreStrategy.prototype.constructor = BuyMoreStrategy;
BuyMoreStrategy.prototype.desc = function() {
return this.description;
};
BuyMoreStrategy.prototype.discount = function(item) {
var give = item.num / (this.buy + this.free);
var left = item.num % (this.buy + this.free);
money = (give* this.buy + left)*item.price;
return money;
};
////////////////////////////////////////////////////////////////////////
/// 销售品种
var SaleItem = function(name , price) {
var self = this;
self.name = name;
self.price = price;
self.num = 1;
self.strategy = factory.getInstance(self.name);
};
SaleItem.prototype = {};
SaleItem.prototype.constructor = SaleItem;
SaleItem.prototype.clone = function() {
var self = this;
var cloneItem = new SaleItem();
cloneItem.name = self.name;
cloneItem.price = self.price;
cloneItem.num = self.num;
cloneItem.strategy = self.strategy;
return cloneItem;
};
SaleItem.prototype.count = function() {
return this.price * this.num;
};
SaleItem.prototype.discountProcess = function(money) {
if (this.strategy) {
money = this.strategy.discount(this);
};
return money;
};
SaleItem.prototype.discount = function() {
return this.discountProcess(this.count());
};
////////////////////////////////////////////////////////////////////////
/// 收银策略类
var CashRegister = function() {
var self = this;
self.totalDiscountStrategy = new NormalStrategy();
self.arr = [];
};
CashRegister.prototype = {};
CashRegister.prototype.constructor = CashRegister;
//添加商品
CashRegister.prototype.add = function(item, num) {
var self = this;
if (num) {
item.num = num;
};
self.arr.push(item);
};
//添加折扣策略
CashRegister.prototype.setTotalDiscountStrategy = function(strategy) {
this.totalDiscountStrategy = strategy;
};
//总计金额
CashRegister.prototype.count = function() {
var self = this;
var totalMoney = 0;
self.arr.forEach( function(item, index) {
totalMoney += item.discount();
});
return totalMoney;
};
//折扣加入
CashRegister.prototype.discountProcess = function(money) {
var self = this;
if (self.totalDiscountStrategy) {
money = self.totalDiscountStrategy.discount(money);
};
return money;
};
//折后金额
CashRegister.prototype.discount = function() {
var self = this;
var totalMoney = self.count();
return self.discountProcess( totalMoney );
};
//结算清单
CashRegister.prototype.print = function() {
var self = this;
console.log('-----------------------------');
console.log(' 购物清单 ');
console.log('');
var totalMoney = 0;
self.arr.forEach(function(item, index) {
console.log(" %s : %s x %s = %s | ",item.name, item.price, item.num, item.count(),item.discount());
});
console.log('-----------------------------');
console.log(' 优惠使用 : ' + self.totalDiscountStrategy.desc())
console.log(' 购物合计 ' + self.count() +" -> "+ self.discount() );
console.log('');
};
////////////////////////////////////////////////////////////////////////
/// 测试类
var factory = new SaleItemStrategyFactory();
var cashRegister = new CashRegister();
cashRegister.setTotalDiscountStrategy(new PrecentOffStrategy("国庆",0.1));
// cashRegister.setTotalDiscountStrategy(new GivebackStrategy("劳动节",500,300));
// cashRegister.setTotalDiscountStrategy(new GivebackStrategy("劳动节",1000,500));
cashRegister.add(new SaleItem("方便面",100),50);
cashRegister.add(new SaleItem("菊花茶",10),50);
cashRegister.print();
