numerica/packages/core/src/locales/common/en/index.ts

import {BLANK_DIGIT} from '../../../utils/numeric';

const config = {
  onesNames: ['zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'],
  onesOrdinalNames: ['zeroth', 'first', 'second', 'third', 'fourth', 'fifth', 'sixth', 'seventh', 'eighth', 'ninth'],
  teensNames: [
    'ten',
    'eleven',
    'twelve',
    'thirteen',
    'fourteen',
    'fifteen',
    'sixteen',
    'seventeen',
    'eighteen',
    'nineteen',
  ],
  teensOrdinalNames: [
    'tenth',
    'eleventh',
    'twelfth',
    'thirteenth',
    'fourteenth',
    'fifteenth',
    'sixteenth',
    'seventeenth',
    'eighteenth',
    'nineteenth',
  ],
  tensNames: ['zero', 'ten', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'],
  tensOrdinalNames: [
    'zeroth',
    'tenth',
    'twentieth',
    'thirtieth',
    'fortieth',
    'fiftieth',
    'sixtieth',
    'seventieth',
    'eightieth',
    'ninetieth',
  ],
  hundredName: 'hundred',
  hundredOrdinalName: 'hundredth',
  grouping: 3,
};

export const getGroupDigitsName = (digitsRaw: string, ordinal: boolean) => {
  const digits = digitsRaw.padStart(config.grouping, BLANK_DIGIT);
  const [hundreds, tens, ones] = digits.split('').map(s => Number(s));
  const names = [];
  if (hundreds !== 0) {
    names.push(config.onesNames[hundreds]);
    if (!ordinal || (tens > 0 || ones > 0)) {
      names.push(config.hundredName);
    }
  }
  if (tens === 1) {
    names.push(ordinal ? config.teensOrdinalNames[ones] : config.teensNames[ones]);
  } else if (tens > 1) {
    if (ones > 0) {
      names.push(config.tensNames[tens]);
      names.push(ordinal ? config.onesOrdinalNames[ones] : config.onesNames[ones]);
    } else {
      names.push(ordinal ? config.tensOrdinalNames[tens] : config.tensNames[tens]);
    }
  } else {
    if (hundreds === 0) {
      names.push(ordinal ? config.onesOrdinalNames[ones] : config.onesNames[ones]);
    } else if (ones > 0) {
      names.push(ordinal ? config.onesOrdinalNames[ones] : config.onesNames[ones]);
    } else if (ordinal) {
      names.push(config.hundredOrdinalName);
    }
  }
  return names.join(' ');
};