12DaysOfChristmas

12daysOfChristmas.js

#!/usr/bin/env node

const sumit = (sum, it) => sum + it
// Christmas is around us!
const christmasPresentsPerDays = (days = 12) => {
  const bag = [];
  for (let i = 0; i < days; i++) {
    bag.push(i + 1 + bag[i - 1] || 1);
  }
  return bag.reduce(sumit, 0);
}

const christmasPresentsPerDaysRec = (days = 12, day = 1, collect = [0]) => {
    if (day > days){
        day
        collect
        return collect.reduce(sumit)
    } else {
        day
        collect
        let nsum = collect.reduce(sumit) + day
        collect.push(nsum)
        let nday = day + 1
        return christmasPresentsPerDaysRec(days, nday, collect)
    }
}

const argvDays = process.argv.length > 2 ? process.argv.pop() : 12
console.log(christmasPresentsPerDays(argvDays)   )
console.log(christmasPresentsPerDaysRec(argvDays))
console.log(`For ${argvDays} days you got ${christmasPresentsPerDays(argvDays)} presents!`)

package.json

{"name": "12-days-of-christmas", "version": "0.0.0", "bin": "./12daysOfChristmas.js"}