roman-numerals

Roman Numerals

A Roman numeral represents an integer using letters. Examples are XVII to represent 17, MCMLIII for 1953, and MMMCCCIII for 3303. By contrast, ordinary numbers such as 17 or 1953 are called Arabic numerals. The following table shows the Arabic equivalent of all the single-letter Roman numerals:

• M 1000
• D 500
• C 100
• L 50
• X 10
• V 5
• I 1

When letters are strung together, the values of the letters are just added up, with the following exception. When a letter of smaller value is followed by a letter of larger value, the smaller value is subtracted from the larger value. For example, IV represents 5 - 1, or 4. And MCMXCV is interpreted as M + CM + XC + V, or 1000 + (1000 - 100) + (100 - 10) + 5, which is 1995. In standard Roman numerals, no more than three consecutive copies of the same letter are used. Following these rules, every number between 1 and 3999 can be represented as a Roman numeral made up of the following one- and two-letter combinations:

• M 1000
• CM 900
• D 500
• CD 400
• C 100
• XC 90
• L 50
• XL 40
• X 10
• IX 9
• V 5
• IV 4
• I 1

Getting Started

Install using npm

npm install js-roman-numerals

Import the library

const RomanNumeral = require("js-roman-numerals")

To create a new roman numeral use

let num = new RomanNumeral(10)

or

let num = new RomanNumeral('IX')

Display as Roman Numeral

num.toString()

Display as Integer

num.toInt()

Testing

To run the tests

npm test