重构顾问 AI 智能体

function processOrder(order) {
  // 验证订单
  if (!order.items || order.items.length === 0) {
    throw new Error('订单为空')
  }
  if (!order.customer) {
    throw new Error('没有客户')
  }

  // 计算总额
  let subtotal = 0
  for (const item of order.items) {
    subtotal += item.price * item.quantity
  }
  const tax = subtotal * 0.1
  const total = subtotal + tax

  // 应用折扣
  let discount = 0
  if (order.customer.isPremium) {
    discount = total * 0.15
  } else if (subtotal > 100) {
    discount = total * 0.05
  }

  return total - discount
}

方法做了4件事：验证、计算、税费、折扣

function processOrder(order) {
  validateOrder(order)
  const subtotal = calculateSubtotal(order.items)
  const total = applyTax(subtotal)
  return applyDiscount(total, order.customer)
}

function validateOrder(order) {
  if (!order.items?.length) throw new Error('订单为空')
  if (!order.customer) throw new Error('没有客户')
}

function calculateSubtotal(items) {
  return items.reduce((sum, item) =>
    sum + item.price * item.quantity, 0)
}

提取方法：每个函数只做好一件事

function calculateShipping(order) {
  switch (order.shippingType) {
    case 'express':
      return order.weight * 5.0 + 15
    case 'standard':
      return order.weight * 2.5 + 5
    case 'economy':
      return order.weight * 1.0
    case 'freight':
      return order.weight * 0.5 + 50
    default:
      throw new Error('未知类型')
  }
}

Switch 语句随着每种新配送类型而增长

interface ShippingStrategy {
  calculate(weight: number): number
}

const shippingStrategies: Record<string, ShippingStrategy> = {
  express: { calculate: w => w * 5.0 + 15 },
  standard: { calculate: w => w * 2.5 + 5 },
  economy: { calculate: w => w * 1.0 },
  freight: { calculate: w => w * 0.5 + 50 },
}

function calculateShipping(order) {
  const strategy = shippingStrategies[order.shippingType]
  if (!strategy) throw new Error('未知类型')
  return strategy.calculate(order.weight)
}

策略模式：无需修改现有代码即可添加新类型

class OrderProcessor {
  calculateTax(order) {
    const subtotal = order.items.reduce((sum, item) =>
      sum + item.price * item.quantity, 0)
    const taxRate = order.customer.region === 'EU'
      ? order.customer.country.vatRate
      : 0.0
    return subtotal * taxRate
  }
}

OrderProcessor 对 Order 和 Customer 的内部了解过多

class Order {
  calculateSubtotal() {
    return this.items.reduce((sum, item) =>
      sum + item.price * item.quantity, 0)
  }

  calculateTax() {
    return this.calculateSubtotal() * this.customer.getTaxRate()
  }
}

class Customer {
  getTaxRate() {
    return this.region === 'EU' ? this.country.vatRate : 0.0
  }
}

将行为移至拥有数据的类