质量守护者

function processOrder(order) {
  if (order) {
    if (order.items) {
      if (order.items.length > 0) {
        if (order.customer) {
          if (order.customer.active) {
            // Finally, the actual logic...
            return calculateTotal(order)
          }
        }
      }
    }
  }
  return null
}

5 层嵌套 — 难以阅读和维护

function processOrder(order) {
  if (!isValidOrder(order)) return null
  return calculateTotal(order)
}

function isValidOrder(order) {
  return order?.items?.length > 0
    && order?.customer?.active
}

提取守卫子句，扁平化结构

function calculateDiscount(total) {
  if (total > 100) return total * 0.1
  if (total > 50) return total * 0.05
  return 0
}

魔法数字：100、50、0.1 是什么意思？

const DISCOUNT_TIERS = {
  PREMIUM: { threshold: 100, rate: 0.10 },
  STANDARD: { threshold: 50, rate: 0.05 },
}

function calculateDiscount(total) {
  const tier = Object.values(DISCOUNT_TIERS)
    .find(t => total > t.threshold)
  return tier ? total * tier.rate : 0
}

提取有意义的常量名称

function calc(d, t) {
  const r = d / t
  const x = r * 3.6
  return x
}

晦涩的名称：d、t、r、x 什么都没说明

const MS_TO_KMH = 3.6

function calculateSpeedKmh(distanceMeters, timeSeconds) {
  const metersPerSecond = distanceMeters / timeSeconds
  return metersPerSecond * MS_TO_KMH
}

描述性的名称解释用途