generate the song "Twelve days of Christmas"

twelce-days-of-christmas.js

const gifts = {
  first: "a Partridge in a Pear Tree.",
  second: "two Turtle Doves",
  third: "three French Hens",
  fourth: "four Calling Birds",
  fifth: "five Gold Rings",
  sixth: "six Geese-a-Laying",
  seventh: "seven Swans-a-Swimming",
  eighth: "eight Mails-a-Milking",
  ninth: "nine Ladies Dancing",
  tenth: "ten Lords-a-Leaping",
  eleventh: "eleven Pipers Piping",
  twelfth: "twelve Drummers Drumming",
  and: "and"
};

const dayMap = {
  1: "first",
  2: "second",
  3: "third",
  4: "fourth",
  5: "fifth",
  6: "sixth",
  7: "seventh",
  8: "eighth",
  9: "ninth",
  10: "tenth",
  11: "eleventh",
  12: "twelfth",
  and: "and"
};

const days = 12;

const buildSentence = day => {
  const generateGifts = day => {
    const daysArray = Array.from(Array(day)).map((_, i) => i + 1);

    const sequence =
      day === 1
        ? daysArray
        : [...daysArray.slice(0, 1), "and", ...daysArray.slice(1)];

    const suffix = day => (day !== 1 && day !== "and" ? "," : "");

    return sequence
      .reverse()
      .map(dayOfGift => gifts[dayMap[dayOfGift]] + suffix(dayOfGift))
      .join(" ");
  };

  return (
    "On the " +
    dayMap[day] +
    " day of Christmas my true love gave to me: " +
    generateGifts(day)
  );
};

const recite = days => {
  const daysArray = Array.from(Array(days)).map((_, i) => i + 1);
  const song = daysArray.map(day => buildSentence(day));
  console.log(song.join("\n\n"));
};

recite(days);