JavaScript策略模式详解：从年终奖计算到表单校验

function calculateBonus(level,salary){
    if(level === 'S'){
        return salary*4;
    }
    
    if(level === 'A'){
        return salary*3
    }

    if(level === 'B'){
        return salary*2
    }
}

console.log(calculateBonus("S",14000));  //56000
console.log(calculateBonus("A",10000)); //30000
console.log(calculateBonus("B",5000));  //10000

var strategies  = {
    "S":function(salary){
        return salary*4
    },
    "A":function(salary){
        return salary*3;
    },
    "B":function(salary){
        return salary*2
    }
}

var calculateBonus =function(level,salary){
    return strategies[level](salary);
} 
console.log(calculateBonus("S",14000));  //56000
console.log(calculateBonus("A",10000));  //30000
console.log(calculateBonus("B",5000));   //10000

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
        <form action="http:// xxx.com/register" id="registerForm" method="post">
            请输入用户名：<input type="text" name="userName"/ >
            请输入密码：<input type="text" name="password"/ >
            请输入手机号码：<input type="text" name="phoneNumber"/ >
            <button>提交</button>
        </form>
</body>
<script>
        // 定义策略类算法校验规则
        var 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  
    var Validator = function(){
        // 保存校验规则
        this.cache = [];
    };
    //添加校验规则的方法
    Validator.prototype.add = function( dom, rules ){
        var self = this;
        for ( var i = 0, rule; rule = rules[ i++ ]; ){
            (function( rule ){
                //将校验规则对象中的strategy属性的值进行分割
                var strategyAry = rule.strategy.split( ':' );
                var errorMsg = rule.errorMsg;
                self.cache.push(function(){
                    //将校验规则对象中的strategy属性的第一个值返回回来装进strategy中
                    var strategy = strategyAry.shift();
                    //组成参数
                    strategyAry.unshift( dom.value );
                    //组装参数
                    strategyAry.push( errorMsg );
                    //找到策略对象执行方法装进cache变量中
                    return strategies[ strategy ].apply( dom, strategyAry );
                });
                console.log(strategyAry);
            })( rule )
        }
    };
    //开始校验方法
    Validator.prototype.start = function(){
        for ( var i = 0, validatorFunc; validatorFunc = this.cache[ i++ ]; ){
             //循环cache执行方法校验
            var errorMsg = validatorFunc();
            //如果执行策略对象方法中返回了errorMsg，就说明方法已经报错（没有通过校验规则）
            if ( errorMsg ){
                return errorMsg;
            }
        }
    };

    //调用校验
    var registerForm = document.getElementById( 'registerForm' );
    //定义方法可以自定义添加校验规则
    var validataFunc = function(){
        //实例化对象
        var validator = new Validator();
        //自定义添加校验规则
        validator.add( registerForm.userName, [{
            strategy: 'isNonEmpty',
            errorMsg: '用户名不能为空'
        }, {
            strategy: 'minLength:6',
            errorMsg: '用户名长度不能小于10 位'
        }]);
        validator.add( registerForm.password, [{
            strategy: 'minLength:6',
            errorMsg: '密码长度不能小于6 位'
        }]);
        //调用方法循环执行校验
        var errorMsg = validator.start();
        return errorMsg;
    }
    //点击提交按钮（提交事件）
    registerForm.onsubmit = function(){
        //执行上面自定义的校验方法
        var errorMsg = validataFunc();
        //如果errorMsg存在，即代表校验没有通过
        if ( errorMsg ){
            alert ( errorMsg );
            return false;
        }

    };
</script>
</html>