/* * pre：策略模式 * 示例：公司計算獎金，分A、B、C 三種績效，計算方式如下 * 績效為A，獎金乘以系數5 * 績效為B，獎金乘以系數4 * 績效為C，獎金乘以系數3 *///-------- 示例1 ----------var calculateBonus = function(performanceLevel, salary) { if(performanceLevel === 'A') {  return salary * 5; } if(performanceLevel === 'B') {  return salary * 4; } if(performanceLevel === 'C') {  return salary * 3; }};console.log(calculateBonus('A', 2000));/* 缺點:1、函數體系龐大，擁有太多的if-else語句；  2、如果增加績效D，需修改內部函數，違背封閉-開放原則；  3、復用性差，其他地方如果用到計算獎金，只能賦值黏貼； *///--------- 示例2 ------------var performanceA = function(salary) { return salary * 5;};var performanceB = function(salary) { return salary * 4;};var performanceC = function(salary) { return salary * 3;};var calculateBonus = function(performanceLevel, salary) { if(performanceLevel === 'A') {  return performanceA(salary); } if(performanceLevel === 'B') {  return performanceB(salary); } if(performanceLevel === 'C') {  return performanceC(salary); }};console.log(calculateBonus('A', 2000)); /* 缺點：1、函數體系龐大，系統變化時缺乏彈性 *///--------- 示例3 ------------// 策略模式重構：定義一系列算法，將它們一個個封裝起來。var performanceA = function(){};performanceA.prototype.caculate = function(salary){ return salary * 5;};var performanceB = function(){};performanceB.prototype.caculate = function(salary){ return salary * 4;};var performanceC = function(){};performanceC.prototype.caculate = function(salary){ return salary * 3;};var Bonus = function(){ this.salary = null; this.strategy = null;};Bonus.prototype.setSalary = function(salary){ this.salary = salary;};Bonus.prototype.setStrategy = function(strategy){ this.strategy = strategy;}Bonus.prototype.getBonus = function(){ return this.strategy.caculate(this.salary);}var bonus = new Bonus();bonus.setSalary(2000);bonus.setStrategy(new performanceA());console.log(bonus.getBonus());// ----------- 示例4 ---------------// javaScript版本var Strategies = { "A":function(salary){  return salary * 5; }, "B":function(salary){  return salary * 4; }, "C":function(salary){  return salary * 3; } };var caculateBonus = function(level,salary){ return Strategies[level](salary);};console.log(caculateBonus("A",2000));