ilikelollies/agent-catalog/utils/numberSpelling.ts

export function convertNumberToWordsEN(value: number): string {
  value = Math.floor(value)
  const ones = [
    '',
    'one',
    'two',
    'three',
    'four',
    'five',
    'six',
    'seven',
    'eight',
    'nine',
    'ten',
    'eleven',
    'twelve',
    'thirteen',
    'fourteen',
    'fifteen',
    'sixteen',
    'seventeen',
    'eighteen',
    'nineteen'
  ];

  const tens = [
    '',
    '',
    'twenty',
    'thirty',
    'forty',
    'fifty',
    'sixty',
    'seventy',
    'eighty',
    'ninety'
  ];

  let numString = value.toString();
  let negative = '';

  if (value < 0) {
    negative = 'negative ';
    value = Math.abs(value);
    numString = value.toString();
  }

  if (value === 0) {
    return 'zero';
  }

  //the case of 1 - 20
  if (value < 20) {
    return negative + ones[value];
  }

  if (numString.length === 2) {
    return (
      negative +
      tens[Number(numString[0])] + ' ' +
      ones[Number(numString[1])]
    );
  }

  //100 and more
  if (numString.length == 3) {
    if (numString[1] === '0' && numString[2] === '0') {
      return (
        negative +
        ones[Number(numString[0])] + ' hundred'
      );
    } else {
      return (
        negative +
        ones[Number(numString[0])] +
        ' hundred and ' +
        convertNumberToWordsEN(+(numString[1] + numString[2]))
      );
    }
  }

  if (numString.length === 4) {
    let end = +(numString[1] + numString[2] + numString[3])
    if (end === 0) {
      return (
        negative +
        ones[Number(numString[0])] + ' thousand'
      );
    }
    if (end < 100) {
      return (
        negative +
        ones[Number(numString[0])] +
        ' thousand and ' +
        convertNumberToWordsEN(end)
      );
    }

    return (
      negative +
      ones[Number(numString[0])] + ' thousand ' +
      convertNumberToWordsEN(end)
    );
  }

  return '';
}