JavaScript 设计模式之策略模式

策略模式

定义一系列的算法，把他们一个个封装起来，并且使他们可以相互替换。

使用策略模式计算奖金

1. 最初的代码实现

   let calculateBonus = function (performancelevel, salary) {
     if (performancelevel === "S") {
       return salary * 4;
     } else if (performancelevel === "A") {
       return salary * 3;
     } else {
       return salary * 2;
     }
   };
   console.log(calculateBonus("S", 30000)); // 120000
   console.log(calculateBonus("A", 20000)); // 60000
   

2. 组合函数重构代码

   let performanceS = function (salary) {
     return salary * 4;
   };
   let performanceA = function (salary) {
     return salary * 3;
   };
   let performanceB = function (salary) {
     return salary * 2;
   };
   let calculateBonus1 = function (performancelevel, salary) {
     if (performancelevel === "S") {
       return performanceS(salary);
     } else if (performancelevel === "A") {
       return performanceA(salary);
     } else if (performanceB === "B") {
       return performanceB(salary);
     }
   };
   console.log(calculateBonus1("S", 20000)); // 80000
   

3. 使用策略模式重构代码

   let performanceS1 = function () {};
   performanceS1.prototype.calculate = function (salary) {
     return salary * 4;
   };
   let performanceA1 = function () {};
   performanceA1.prototype.calculate = function (salary) {
     return salary * 3;
   };
   let performanceB1 = function () {};
   performanceB1.prototype.calculate = function (salary) {
     return salary * 2;
   };
   let 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 () {
     if (!this.strategy) {
       throw new Error("没有strategy属性");
     }
     return this.strategy.calculate(this.salary);
   };
   let bonus = new Bonus();
   bonus.setSalary(20000);
   bonus.setStrategy(new performanceS1());
   console.log(bonus.getBonus()); // 80000
   

JavaScript 版本的策略模式

let strategies = {
  S: function (salary) {
    return salary * 4;
  },
  A: function (salary) {
    return salary * 3;
  },
  B: function (salary) {
    return salary * 2;
  },
};
let calculateBonus2 = function (level, salary) {
  return strategies[level](salary);
};
console.log(calculateBonus2("S", 20000)); // 80000

表单验证

策略对象

let strategies = {
  isNonEmpty: function (value, errorMsg) {
    if (value === "") {
      return errorMsg;
    }
  },
  minLength: function (value, length, errorMsg) {
    if (value.length < length) {
      return errorMsg;
    }
  },
  isMobile: function (value, errorMsg) {
    if (!/(^1[3|5|8][0-9]{9}$)/.test(value)) {
      return errorMsg;
    }
  },
};

Validator 类

let Validator = function () {
  this.cache = [];
};
Validator.prototype.add = function (dom, rules) {
  let self = this;
  for (let i = 0, rule; (rule = rules[i++]); ) {
    (function (rule) {
      let strategyAry = rule.strategy.split(":");
      let errorMsg = rule.errorMsg;
      self.cache.push(function () {
        let strategy = strategyAry.shift();
        strategyAry.unshift(dom.value);
        strategyAry.push(errorMsg);
        return strategies[strategy].apply(dom, strategyAry);
      });
    })(rule);
  }
};
Validator.prototype.start = function () {
  for (let i = 0, validatorFunc; (validatorFunc = this.cache[i++]); ) {
    let errorMsg = validatorFunc();
    if (errorMsg) {
      return errorMsg;
    }
  }
};

本文地址：https://blog.csdn.net/qq_43262022/article/details/109234207