n2words/src/en-KE.js

Convert numbers to words in 70+ languages with zero dependencies. Supports BigInt, decimals, and browser/Node.js environments.

/**
 * Kenyan English language converter
 *
 * CLDR: en-KE | English as used in Kenya
 *
 * Exports:
 * - toCardinal(value)            - Cardinal numbers: 42 → "forty-two"
 * - toOrdinal(value)             - Ordinal numbers: 42 → "forty-second"
 * - toCurrency(value, options?)  - Currency: 42.50 → "forty-two shillings and fifty cents"
 *
 * Kenyan English conventions:
 * - Follows British English style
 * - "and" after hundreds: "one hundred and twenty-three"
 * - "and" before final segment: "one million and one"
 * - Hyphenated tens-ones: "twenty-one", "forty-two"
 * - Western numbering system (short scale: billion = 10^9)
 * - Currency: Kenyan Shilling (KES) - shilling/shillings, cent/cents
 */

import { parseCardinalValue } from './utils/parse-cardinal.js'
import { parseCurrencyValue } from './utils/parse-currency.js'
import { parseOrdinalValue } from './utils/parse-ordinal.js'
import { checkMax } from './utils/check-max.js'
import { western } from './utils/scale.js'
import { resolveOptions } from './utils/resolve-options.js'

// ============================================================================
// Vocabulary (module-level constants)
// ============================================================================

const ONES = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
const TEENS = ['ten', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen']
const TENS = ['', '', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety']

const SCALES = [
  'thousand', 'million', 'billion', 'trillion', 'quadrillion',
  'quintillion', 'sextillion', 'septillion', 'octillion', 'nonillion',
  'decillion', 'undecillion', 'duodecillion', 'tredecillion', 'quattuordecillion',
  'quindecillion', 'sexdecillion', 'septendecillion', 'octodecillion', 'novemdecillion',
  'vigintillion',
]

export const cardinalMax = western(SCALES.length)
export const ordinalMax = western(SCALES.length)
export const currencyMax = western(SCALES.length)

const HUNDRED = 'hundred'
const ZERO = 'zero'
const NEGATIVE = 'minus'
const DECIMAL_SEP = 'point'

// Ordinal vocabulary
const ORDINAL_ONES = ['', 'first', 'second', 'third', 'fourth', 'fifth', 'sixth', 'seventh', 'eighth', 'ninth']
const ORDINAL_TEENS = ['tenth', 'eleventh', 'twelfth', 'thirteenth', 'fourteenth', 'fifteenth', 'sixteenth', 'seventeenth', 'eighteenth', 'nineteenth']
const ORDINAL_TENS = ['', '', 'twentieth', 'thirtieth', 'fortieth', 'fiftieth', 'sixtieth', 'seventieth', 'eightieth', 'ninetieth']

// Currency vocabulary (Kenyan Shilling)
const SHILLING = 'shilling'
const SHILLINGS = 'shillings'
const CENT = 'cent'
const CENTS = 'cents'

// ============================================================================
// Segment Building
// ============================================================================

const segmentResult = { word: '', hasHundred: false }

/**
 * @param {number} n The 0-999 group value to convert
 * @returns {{word: string, hasHundred: boolean}} The segment words and whether it includes a hundreds place
 */
function buildSegment(n) {
  if (n === 0) {
    segmentResult.word = ''
    segmentResult.hasHundred = false
    return segmentResult
  }

  const ones = n % 10
  const tens = Math.trunc(n / 10) % 10
  const hundreds = Math.trunc(n / 100)

  let tensOnes = ''
  if (tens === 1) {
    tensOnes = TEENS[ones]
  }
  else if (tens >= 2) {
    tensOnes = ones > 0 ? TENS[tens] + '-' + ONES[ones] : TENS[tens]
  }
  else if (ones > 0) {
    tensOnes = ONES[ones]
  }

  if (hundreds > 0) {
    if (tensOnes) {
      segmentResult.word = ONES[hundreds] + ' ' + HUNDRED + ' and ' + tensOnes
    }
    else {
      segmentResult.word = ONES[hundreds] + ' ' + HUNDRED
    }
    segmentResult.hasHundred = true
  }
  else {
    segmentResult.word = tensOnes
    segmentResult.hasHundred = false
  }

  return segmentResult
}

// ============================================================================
// Conversion Functions
// ============================================================================

/**
 * @param {bigint} n The non-negative integer to convert
 * @returns {string} The integer in English words
 */
function integerToWords(n) {
  if (n === 0n) return ZERO

  if (n < 1000n) {
    return buildSegment(Number(n)).word
  }

  if (n < 1_000_000n) {
    const thousands = Number(n / 1000n)
    const remainder = Number(n % 1000n)

    const { word: thousandsWord } = buildSegment(thousands)
    let result = thousandsWord + ' ' + SCALES[0]

    if (remainder > 0) {
      const { word: remainderWord, hasHundred } = buildSegment(remainder)
      result += hasHundred ? ' ' + remainderWord : ' and ' + remainderWord
    }

    return result
  }

  return buildLargeNumberWords(n)
}

/**
 * @param {bigint} n The integer of one million or greater to convert
 * @returns {string} The integer in English words
 */
function buildLargeNumberWords(n) {
  const segments = []
  let temp = n
  while (temp > 0n) {
    segments.push(Number(temp % 1000n))
    temp = temp / 1000n
  }

  let firstNonZeroIdx = -1
  for (let i = 0; i < segments.length; i++) {
    if (segments[i] !== 0) {
      firstNonZeroIdx = i
      break
    }
  }

  let result = ''
  let prevWasScale = false

  for (let i = segments.length - 1; i >= 0; i--) {
    const segment = segments[i]
    if (segment === 0) continue

    const { word, hasHundred } = buildSegment(segment)
    const isLastSegment = (i === firstNonZeroIdx)

    if (result && isLastSegment && prevWasScale && !hasHundred) {
      result += ' and'
    }

    if (result) result += ' '
    result += word

    if (i > 0) {
      result += ' ' + SCALES[i - 1]
      prevWasScale = true
    }
    else {
      prevWasScale = false
    }
  }

  return result
}

/**
 * @param {string} decimalPart The fractional digits as a string
 * @returns {string} The decimal digits in English words
 */
function decimalPartToWords(decimalPart) {
  let result = ''

  let i = 0
  while (i < decimalPart.length && decimalPart[i] === '0') {
    if (result) result += ' '
    result += ZERO
    i++
  }

  const remainder = decimalPart.slice(i)
  if (remainder) {
    if (result) result += ' '
    result += integerToWords(BigInt(remainder))
  }

  return result
}

/**
 * Converts a numeric value to Kenyan English words.
 * @param {number | string | bigint} value - The numeric value to convert
 * @returns {string} The number in English words
 * @throws {TypeError} If value is not a valid numeric type
 * @throws {Error} If value is not a valid number format
 */
function toCardinal(value) {
  const { isNegative, integerPart, decimalPart } = parseCardinalValue(value)
  // Both the integer part and the decimal's significant digits are spelled via
  // the scale builder, so both must clear the ceiling.
  checkMax(integerPart, cardinalMax, decimalPart)

  let result = ''

  if (isNegative) {
    result = NEGATIVE + ' '
  }

  result += integerToWords(integerPart)

  if (decimalPart) {
    result += ' ' + DECIMAL_SEP + ' ' + decimalPartToWords(decimalPart)
  }

  return result
}

// ============================================================================
// ORDINAL
// ============================================================================

/**
 * @param {number} n The 0-999 group value to convert
 * @returns {string} The segment as ordinal English words
 */
function buildOrdinalSegment(n) {
  const ones = n % 10
  const tens = Math.trunc(n / 10) % 10
  const hundreds = Math.trunc(n / 100)

  let tensOnesOrdinal = ''
  if (tens === 1) {
    tensOnesOrdinal = ORDINAL_TEENS[ones]
  }
  else if (tens >= 2) {
    if (ones > 0) {
      tensOnesOrdinal = TENS[tens] + '-' + ORDINAL_ONES[ones]
    }
    else {
      tensOnesOrdinal = ORDINAL_TENS[tens]
    }
  }
  else if (ones > 0) {
    tensOnesOrdinal = ORDINAL_ONES[ones]
  }

  if (hundreds > 0) {
    if (tensOnesOrdinal) {
      return ONES[hundreds] + ' ' + HUNDRED + ' ' + tensOnesOrdinal
    }
    else {
      return ONES[hundreds] + ' hundredth'
    }
  }

  return tensOnesOrdinal
}

/**
 * @param {bigint} n The non-negative integer to convert
 * @returns {string} The integer as ordinal English words
 */
function integerToOrdinal(n) {
  if (n < 1000n) {
    return buildOrdinalSegment(Number(n))
  }

  if (n < 1_000_000n) {
    const thousands = Number(n / 1000n)
    const remainder = Number(n % 1000n)

    if (remainder === 0) {
      return buildSegment(thousands).word + ' ' + SCALES[0] + 'th'
    }

    const { word: thousandsWord } = buildSegment(thousands)
    return thousandsWord + ' ' + SCALES[0] + ' ' + buildOrdinalSegment(remainder)
  }

  return buildLargeOrdinal(n)
}

/**
 * @param {bigint} n The integer of one million or greater to convert
 * @returns {string} The integer as ordinal English words
 */
function buildLargeOrdinal(n) {
  const segments = []
  let temp = n
  while (temp > 0n) {
    segments.push(Number(temp % 1000n))
    temp = temp / 1000n
  }

  let lowestNonZeroIdx = 0
  for (let i = 0; i < segments.length; i++) {
    if (segments[i] !== 0) {
      lowestNonZeroIdx = i
      break
    }
  }

  let result = ''

  for (let i = segments.length - 1; i >= 0; i--) {
    const segment = segments[i]
    if (segment === 0) continue

    const isLowestSegment = (i === lowestNonZeroIdx)

    if (result) result += ' '

    if (isLowestSegment) {
      if (i === 0) {
        result += buildOrdinalSegment(segment)
      }
      else {
        result += buildSegment(segment).word + ' ' + SCALES[i - 1] + 'th'
      }
    }
    else {
      result += buildSegment(segment).word
      if (i > 0) {
        result += ' ' + SCALES[i - 1]
      }
    }
  }

  return result
}

/**
 * Converts a numeric value to Kenyan English ordinal words.
 * @param {number | string | bigint} value - The numeric value to convert
 * @returns {string} The ordinal in English words
 */
function toOrdinal(value) {
  const integerPart = parseOrdinalValue(value)
  checkMax(integerPart, ordinalMax)
  return integerToOrdinal(integerPart)
}

// ============================================================================
// CURRENCY
// ============================================================================

/**
 * @typedef {object} CurrencyOptions
 * @property {boolean} [and] - Use "and" between shillings and cents
 */

/** @type {Required<CurrencyOptions>} */
export const currencyDefaults = { and: true }

/**
 * Converts a numeric value to Kenyan English currency words.
 * @param {number | string | bigint} value - The numeric value to convert
 * @param {CurrencyOptions} [options] - Optional configuration
 * @returns {string} The currency in English words
 */
function toCurrency(value, options) {
  const { isNegative, dollars: shillings, cents } = parseCurrencyValue(value)
  checkMax(shillings, currencyMax)
  const { and: useAnd } = resolveOptions(options, currencyDefaults)

  let result = ''
  if (isNegative) result = NEGATIVE + ' '

  if (shillings > 0n || cents === 0n) {
    result += integerToWords(shillings)
    result += ' ' + (shillings === 1n ? SHILLING : SHILLINGS)
  }

  if (cents > 0n) {
    if (shillings > 0n) {
      result += useAnd ? ' and ' : ' '
    }
    result += integerToWords(cents)
    result += ' ' + (cents === 1n ? CENT : CENTS)
  }

  return result
}

export { toCardinal, toOrdinal, toCurrency }