First Code Academy exercise

calc.js

const readline = require('readline')

const prices = {
  MAX: 1000,
  MAC: 1500,
  MAE: 2000,
  MAL: 3000,
  TAX: 2700,
  TAC: 3900,
  TAE: 5100
}

const specials = {
  MAX: 1000, // quantity >= 2
  MAC: 1500, // quantity >= 3
  MAE: 2000, // quantity >= 2
  MAL: 2500  // Also bought MA[XCE]
}

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
})

rl.question(
`Please enter your order as <quantity><duration><code> separated by commas
E.g. 3MAX, 4MAE, 2TAC
> `,
handleOrder)

function handleOrder(answer) {
  const items = answer.split(',').map(s => s.trim())
  const total = items.reduce((total, item) => {
    return total + calculatePrice(item, items)
  }, 0)
  console.log(`The total price is HKD ${total}`)
  console.log('Thank you for choosing First Code Academy')
  rl.close()
}

function calculatePrice(item, items) {
  const quantity = +item.substr(0, 1)
  const code = item.substr(1)

  if (code === 'MAX') {
    return Math.floor(quantity / 2) * specials[code] + quantity % 2 * prices[code]
  }

  if (code === 'MAC') {
    return Math.floor(quantity / 3) * specials[code] + quantity % 3 * prices[code]
  }

  if (code === 'MAE') {
    return Math.floor(quantity / 2) * specials[code] + quantity % 2 * prices[code]
  }

  // String.match returns either null or non-empty array
  // so we can implicitly coerce it to a boolean
  if (code === 'MAL' && items.some(item => item.match(/MA[XCE]/))) {
    return quantity * specials[code]
  }

  return quantity * prices[code]
}