Read codes and names

Use the native API

import { isCountryCode,COUNTRY_CODES } from "@johnmorrisdotca/kuni/codes";
import { country,countryByName,fold } from "@johnmorrisdotca/kuni";
console.log(isCountryCode("JP"),isCountryCode("jp"),COUNTRY_CODES.length);
console.log(country("jp")?.numeric,countryByName("Holland")?.alpha2,fold("ＴＯＫＹＯ"));

true false 250
392 NL tokyo

isCountryCode requires the exact capital-letter alpha-2 spelling. country is forgiving about the documented code forms/case; countryByName uses stored names and aliases. Numeric codes remain strings so leading zeros survive. A name alias is not a new country or a subdivision. Do not use current-country validation to reinterpret a withdrawn code.

Preserve language choices

Choose English or Japanese through the native name functions. Short forms exist only where the stored source gives them. Core ordering and folding do not depend on the host’s Intl locale. For subdivisions, a Japanese name can be null; keep the source’s absence rather than copying an English name into its place. See missing results and the preserved name rules.