JS实现会员等级积分效果

什么是职责链模式？

职责链模式（Chain of Responsibility）是一种行为设计模式，它允许多个对象有机会处理请求，这些对象形成一个链，并沿着该链传递请求，直到其中一个对象处理它为止，这种模式解耦了发送者和接收者之间的关系。

职责链模式的应用场景：

1、多级审批流程：例如请假申请需要经过不同级别的领导审批。

2、事件监听机制：类似于DOM事件的冒泡和捕获机制。

3、权限管理：不同的用户角色具有不同的权限，通过职责链模式可以灵活地控制访问。

会员等级积分系统的需求

假设一个电商平台有如下需求：

会员等级分为普通会员、银牌会员、金牌会员和钻石会员。

不同等级的会员消费积分规则不同。

当会员消费时，根据其等级计算相应的积分。

使用JavaScript实现职责链模式

下面是一个简单的示例，展示了如何使用职责链模式来实现会员等级积分效果。

定义会员等级类

 // Base Membership class to define common structure and behaviors class Membership {   constructor(name, nextMembership = null) {     this.name = name;     this.nextMembership = nextMembership;   }   // Method to handle request (calculate points)   calculatePoints(amount) {     console.log(No rules defined for ${this.name});     if (this.nextMembership) {       this.nextMembership.calculatePoints(amount);     }   } } // Concrete membership classes for different levels class BasicMembership extends Membership {   constructor(nextMembership = null) {     super('Basic', nextMembership);   }   calculatePoints(amount) {     if (amount >= 0 && amount <= 500) {       console.log(You earned 1 point for consuming $${amount} as a Basic member.);     } else {       super.calculatePoints(amount);     }   } } class SilverMembership extends Membership {   constructor(nextMembership = null) {     super('Silver', nextMembership);   }   calculatePoints(amount) {     if (amount > 500 && amount <= 1000) {       console.log(You earned 2 points for consuming $${amount} as a Silver member.);     } else {       super.calculatePoints(amount);     }   } } class GoldMembership extends Membership {   constructor(nextMembership = null) {     super('Gold', nextMembership);   }   calculatePoints(amount) {     if (amount > 1000 && amount <= 2000) {       console.log(You earned 3 points for consuming $${amount} as a Gold member.);     } else {       super.calculatePoints(amount);     }   } } class DiamondMembership extends Membership {   constructor() {     super('Diamond');   }   calculatePoints(amount) {     if (amount > 2000) {       console.log(You earned 4 points for consuming $${amount} as a Diamond member.);     } else {       super.calculatePoints(amount);     }   } }

创建责任链并测试

 // Create the chain of responsibility let basic = new BasicMembership(); let silver = new SilverMembership(basic); let gold = new GoldMembership(silver); let diamond = new DiamondMembership(gold); // Test the chain with different amounts diamond.calculatePoints(350); // Basic member rule applies diamond.calculatePoints(800); // Silver member rule applies diamond.calculatePoints(1500); // Gold member rule applies diamond.calculatePoints(2500); // Diamond member rule applies

输出结果：

 You earned 1 point for consuming $350 as a Basic member. You earned 2 points for consuming $800 as a Silver member. You earned 3 points for consuming $1500 as a Gold member. You earned 4 points for consuming $2500 as a Diamond member.

相关问题与解答

Q1: 如何扩展新的会员等级？

A1: 要扩展新的会员等级，可以继承Membership 基类，并重写calculatePoints 方法，然后将其添加到责任链中，增加一个白金会员等级：

 class PlatinumMembership extends Membership {   constructor(nextMembership = null) {     super('Platinum', nextMembership);   }   calculatePoints(amount) {     if (amount > 3000) {       console.log(You earned 5 points for consuming $${amount} as a Platinum member.);     } else {       super.calculatePoints(amount);     }   } } // Update the chain to include the new Platinum level let platinum = new PlatinumMembership(diamond); basic = new BasicMembership(platinum); // Reassign basic to the new chain head silver = new SilverMembership(basic); // Reassign silver to the new chain head gold = new GoldMembership(silver); // Reassign gold to the new chain head diamond = new DiamondMembership(gold); // Reassign diamond to the new chain head // Test the extended chain with higher amounts diamond.calculatePoints(4000); // Platinum member rule applies

Q2: 如果需要修改某个会员等级的积分规则，应该如何操作？

A2: 要修改某个会员等级的积分规则，只需要在对应的具体会员等级类中修改calculatePoints 方法即可，将金牌会员的积分规则从消费超过1000美元奖励3点改为消费超过1200美元奖励3点：

 class GoldMembership extends Membership {   calculatePoints(amount) {     if (amount > 1200 && amount <= 2000) { // Updated condition from 1000 to 1200       console.log(You earned 3 points for consuming $${amount} as a Gold member.);     } else {       super.calculatePoints(amount);     }   } }

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