RomanJS

Javascript roman numeral library with robust unicode support.

Usage

Recommended: Install @sguest/roman-js from npm

Alternative: Download and use roman.js

A global object roman will be created with functions toRoman and parseRoman.

roman.parseRoman('I');  //1
roman.toRoman(1);       //I

These functions will also be available exported as an AMD module or a CommonJS module if those environments are present.

parseRoman(numeral)

Takes a string representing a roman numeral and converts to its' number representation. Returns NaN on any invalid input.

Supports basic latin letters as well as symbols from the Unicode Number Forms block (U+2160 - U+2188).

Wikipedia has a handy Reference on Unicode roman numerals.

Supports both multiple number forms glyphs, as well as the combined-symbol glyphs from 1-12 (U+1260 - U+216B).

Parsing is case-insensitive, lower-case input works the same as uppercase.

roman.parseRoman('VIII');   //8
roman.parseRoman('ⅤⅠⅠⅠ');    //8
roman.parseRoman('Ⅷ');     //8
roman.parseRoman('viii');   //8

toRoman(number, [options])

Convert a number to its' roman numeral representation. Default behavior is to use basic latin letters where possible for maximum compatibility. The exception is for symbols for 5,000 and greater which do not have basic latin letter representations and therefore use symbols from the Unicode Number Forms block.

roman.toRoman(8);     //VIII
roman.toRoman(11111); //ↂMCXI

Maximum value that can be converted is 399,999 because any higher value would require a symbol for 500,000 which does not have a commonly-accepted representation and therefore does not have a unicode glyph.

Any provided value that is not an integer from 1 to 399,999 inclusive will return NaN

This function will also accept an optional options hash, which supports 3 boolean options: thousand, combined, and forms

thousand: Uses the symbol ↀ (U+2180) instead of M for the thousands indicator for consistency with the 5000+ symbols

roman.toRoman(1111, {thousand: true});  //ↀCXI

combined: Uses the combined glyphs (U+1260 - U+216B) for numbers 1-12

roman.toRoman(8, {combined: true});   //Ⅷ

forms: Uses symbols from the Unicode Number Forms block instead of basic latin letters for all values. This option has a lower precedence than thousand or combined in cases where both could apply.

roman.toRoman(8, {forms: true});  //ⅤⅠⅠⅠ

toRoman() will always return upper-case results. In order to get a lower-case representation, simply call toLowerCase() on the result. toLowerCase() behaves as expected even when using symbols from the Number Forms block.

roman.toRoman(8, {forms: true}).toLowerCase();    //ⅴⅰⅰⅰ
roman.toRoman(8, {combined: true}).toLowerCase(); //ⅷ

Environment/Browser support

The library has no dependencies and should work across a variety of environments (including Node) and all modern browsers.

The library does make use of Array#indexOf and some old browsers (such as IE8 and below) do not support this method, therefore such browsers will need a polyfill, which is not part of this library. MDN has an example polyfill for this function.

License

[MIT License] (http://opensource.org/licenses/MIT)