Well-known Symbol.iterator example with roman numerals

symbol-iterator-roman-numerals.js

const tab = [1, 7, 14, 4];

tab[Symbol.iterator] = function () {
  let index = 0;
  const total = this.length;
  const values = this;
  return {
    next() {
      const romanize = num => {
        const dec = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
        const rom = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"];
        let output = "";

        for (let i = 0; i < dec.length; i++) {
          while (dec[i] <= num) {
            output += rom[i];
            num -= dec[i];
          }
        }

        return output;
      };

      return index++ < total ? {
        done: false,
        value: romanize(values[index - 1])
      } : {
        done: true
      };
    }

  };
};

for (let num of tab) {
  console.log(num);
}