Question: Have you considered using ECMAScript's Intl NumberFormat extension?

[renoirb]

Maybe what I'm going to say is overkill, maybe you haven't thought about it.

Hi,

Seeing your project made me wonder if ECMAScript's Intl/NumberFormat extensions do actually support Roman Numeral system natively.

For instance, we can get Thai numbers using the following method;

const someNumber = 123
let localeName = 'th-TH-u-nu-thai'
console.log((someNumber).toLocaleString(localeName)); // ๑๒๓
const localeName = 'ar-EG' // Arab from 
console.log((someNumber).toLocaleString(localeName)); // ١٢٣

Issue is just to find the proper notation.

I've had a quick search and a polyfill do make reference to "roman", in common/bcp47/number.xml and there is a notation to add Unicode numeral (see also u-extension) that should match foo-bar-u-nu-roman.

Meaning it might be possible to get roman numerals as easily as it is to get Hindi, or Hant numbers from Intl natively in the ECMAScript runtime engine (see locale identification, Number.toLocaleString()).

What are your thoughts about this?

See also

• MDN at Intl Extension
• MDN at Intl.NumberFormat Extension
• Unicode CLDR GitHub repository
• Unicode reports/tr35
• Unicode CLDR downloads
• Unicode Number "2" in Roman

[holtalanm]

That's pretty cool! I'll be honest, I just whipped this up in my free time last weekend, and the Intl.NumberFormat Extension wasn't even on my radar for it.

Now that it is, I'd be interested to see if you can effectively get the same functionality of romanum via this native support of locale numbers.

[renoirb]

Quick experiments for fun are the best! It always remind me how quick things can move when you start green-field :)

In relation to supporting all possible number formatting patterns. Roman has no standard notation for 0, fractions, floats, etc. Here's why, from ES Discuss it's not supported natively.

[holtalanm]

Well, that makes sense. I used nulla in romanum to denote 0, but fractions/floats aren't really supported. To be honest, I kind of completely forgot about floats when testing this. Although, since there isn't really a notation for floats/decimals in roman numerals, probably the best course of action is to treat that as an invalid number for parsing. i.e. toNumeral(12.5) -> 'nulla'