JavaScript numbers to Words

Question

I\'m trying to convert numbers into english words, for example 1234 would become: \"one thousand two hundred thirty four\".

My Tact

Answer 1

Here is another version from me with some unit tests.

Don't use it with numbers larger than Number.MAX_SAFE_INTEGER.

describe("English Numerals Converter", function () {
  assertNumeral(0, "zero");
  assertNumeral(1, "one");
  assertNumeral(2, "two");
  assertNumeral(3, "three");
  assertNumeral(4, "four");
  assertNumeral(5, "five");
  assertNumeral(6, "six");
  assertNumeral(7, "seven");
  assertNumeral(8, "eight");
  assertNumeral(9, "nine");
  assertNumeral(10, "ten");
  assertNumeral(11, "eleven");
  assertNumeral(12, "twelve");
  assertNumeral(13, "thirteen");
  assertNumeral(14, "fourteen");
  assertNumeral(15, "fifteen");
  assertNumeral(16, "sixteen");
  assertNumeral(17, "seventeen");
  assertNumeral(18, "eighteen");
  assertNumeral(19, "nineteen");
  assertNumeral(20, "twenty");
  assertNumeral(21, "twenty-one");
  assertNumeral(22, "twenty-two");
  assertNumeral(23, "twenty-three");
  assertNumeral(30, "thirty");
  assertNumeral(37, "thirty-seven");
  assertNumeral(40, "forty");
  assertNumeral(50, "fifty");
  assertNumeral(60, "sixty");
  assertNumeral(70, "seventy");
  assertNumeral(80, "eighty");
  assertNumeral(90, "ninety");
  assertNumeral(99, "ninety-nine");
  assertNumeral(100, "one hundred");
  assertNumeral(101, "one hundred and one");
  assertNumeral(102, "one hundred and two");
  assertNumeral(110, "one hundred and ten");
  assertNumeral(120, "one hundred and twenty");
  assertNumeral(121, "one hundred and twenty-one");
  assertNumeral(199, "one hundred and ninety-nine");
  assertNumeral(200, "two hundred");
  assertNumeral(999, "nine hundred and ninety-nine");
  assertNumeral(1000, "one thousand");
  assertNumeral(1001, "one thousand and one");
  assertNumeral(1011, "one thousand and eleven");
  assertNumeral(1111, "one thousand and one hundred and eleven");
  assertNumeral(9999, "nine thousand and nine hundred and ninety-nine");
  assertNumeral(10000, "ten thousand");
  assertNumeral(20000, "twenty thousand");
  assertNumeral(21000, "twenty-one thousand");
  assertNumeral(90000, "ninety thousand");
  assertNumeral(90001, "ninety thousand and one");
  assertNumeral(90100, "ninety thousand and one hundred");
  assertNumeral(90901, "ninety thousand and nine hundred and one");
  assertNumeral(90991, "ninety thousand and nine hundred and ninety-one");
  assertNumeral(90999, "ninety thousand and nine hundred and ninety-nine");
  assertNumeral(91000, "ninety-one thousand");
  assertNumeral(99999, "ninety-nine thousand and nine hundred and ninety-nine");
  assertNumeral(100000, "one hundred thousand");
  assertNumeral(999000, "nine hundred and ninety-nine thousand");
  assertNumeral(1000000, "one million");
  assertNumeral(10000000, "ten million");
  assertNumeral(100000000, "one hundred million");
  assertNumeral(1000000000, "one billion");
  assertNumeral(1000000000000, "one trillion");
  assertNumeral(1000000000000000, "one quadrillion");
  assertNumeral(1000000000000000000, "one quintillion");
  assertNumeral(1000000000000000000000, "one sextillion");

  assertNumeral(-1, "minus one");
  assertNumeral(-999, "minus nine hundred and ninety-nine");

  function assertNumeral(number, numeral) {
    it(number + " is " + numeral, function () {
      expect(convert(number)).toBe(numeral);
    });
  }
});


function convert(n) {
  let NUMERALS = [
    {value: 1000000000000000000000, str: "sextillion"},
    {value: 1000000000000000000, str: "quintillion"},
    {value: 1000000000000000, str: "quadrillion"},
    {value: 1000000000000, str: "trillion"},
    {value: 1000000000, str: "billion"},
    {value: 1000000, str: "million"},
    {value: 1000, str: "thousand"},
    {value: 100, str: "hundred"},
    {value: 90, str: "ninety"},
    {value: 80, str: "eighty"},
    {value: 70, str: "seventy"},
    {value: 60, str: "sixty"},
    {value: 50, str: "fifty"},
    {value: 40, str: "forty"},
    {value: 30, str: "thirty"},
    {value: 20, str: "twenty"},
    {value: 19, str: "nineteen"},
    {value: 18, str: "eighteen"},
    {value: 17, str: "seventeen"},
    {value: 16, str: "sixteen"},
    {value: 15, str: "fifteen"},
    {value: 14, str: "fourteen"},
    {value: 13, str: "thirteen"},
    {value: 12, str: "twelve"},
    {value: 11, str: "eleven"},
    {value: 10, str: "ten"},
    {value: 9, str: "nine"},
    {value: 8, str: "eight"},
    {value: 7, str: "seven"},
    {value: 6, str: "six"},
    {value: 5, str: "five"},
    {value: 4, str: "four"},
    {value: 3, str: "three"},
    {value: 2, str: "two"},
    {value: 1, str: "one"}
  ];

  if (n < 0) {
    return "minus " + convert(-n);
  } else if (n === 0) {
    return "zero";
  } else {
    let result = "";
    for (let numeral of NUMERALS) {
      if (n >= numeral.value) {
        if (n < 100) {
          result += numeral.str;
          n -= numeral.value;
          if (n > 0) result += "-";
        } else {
          let times = Math.floor(n / numeral.value);
          result += convert(times) + " " + numeral.str;
          n -= numeral.value * times;
          if (n > 0) result += " and ";
        }
      }
    }
    return result;
  }
}