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Handle Roman Numerals

convertToRomanNumerals​

info

Converts an integer into its equivalent Roman numeral representation.

Converts any valid number from 1 to 3999 into a Roman numeral.

Function Signature​

convertToRomanNumerals(value: Numeric): RomanNumeralCap;

Parameters​

  • value — The numeric input (either number or numeric string) to be converted.

Returns​

  • A string representing the Roman numeral form of the number. Type RomanNumeralCap represents up to 5 characters in Roman.

Throws​

  • RangeError — If the number is less than 1 or greater than 3999.

Examples​

convertToRomanNumerals(29); // "XXIX"
convertToRomanNumerals("1987"); // "MCMLXXXVII"
convertToRomanNumerals(3999); // "MMMCMXCIX"
convertToRomanNumerals(0); // throws RangeError

Aliases​

convertToRomanNumerals can also be imported via the following aliases:

  • toRoman
  • numberToRoman
  • arabicToRoman
  • integerToRoman
  • numericToRoman
  • toRomanNumeral

Notes​

  • Roman numerals were used in ancient Rome for counting and notation. This implementation supports only traditional Roman numerals (1``–3999).
  • The conversion follows standard subtractive notation rules: e.g., 4 = IV, 9 = IX, 40 = XL, 90 = XC.
  • This function does not support numbers ≥ 4000 due to limitations in classical Roman numeral representation.

Conclusion​

Use convertToRomanNumerals when you need to represent numbers in Roman format — useful for page numbers, date stylization, clocks, or decorative number displays.

romanToInteger​

info

Converts a Roman numeral into its equivalent Arabic integer representation.

Converts any valid Roman numeral from I to MMMCMXCIX (1 to 3999) into an integer.

Function Signature​

romanToInteger(roman: RomanNumeral): number;

Parameters​

  • roman — The Roman numeral input (case-insensitive string) to be converted. Type RomanNumeral represents up to 5 characters (case-insensitive) in Roman and any other string.

Returns​

  • A number representing the integer form of the Roman numeral.

Throws​

  • TypeError — If the input is not a non-empty string.
  • Error — If the Roman numeral contains invalid characters or is malformed.
  • RangeError — If the resulting number is less than 1 or greater than 3999.

Examples​

romanToInteger("XXIX"); // 29
romanToInteger("MCMLXXXVII"); // 1987
romanToInteger("MMMCMXCIX"); // 3999
romanToInteger(""); // throws TypeError
romanToInteger("ABC"); // throws Error: Invalid Roman numeral character

Aliases​

romanToInteger can also be imported via the following aliases:

  • romanToArabic
  • romanToNumeric
  • convertRomanToArabic
  • convertRomanToNumeric
  • convertRomanToInteger

Notes​

  • This function validates the input Roman numeral by:
    1. Checking for invalid characters
    2. Ensuring proper subtractive notation rules are followed
    3. Reconverting the result back to Roman numerals to verify correctness
  • The function is case-insensitive but will normalize input to uppercase.
  • Only supports traditional Roman numerals in the range 1–3999.

Conclusion​

Use romanToInteger when you need to convert Roman numerals back to standard Arabic numbers — useful for parsing historical documents, clock faces, or any application that displays numbers in Roman format.