@nacelle/compatibility-connector/src/utils/toIetfLocale.ts

Connect @nacelle/client-js-sdk to Nacelle's v2 back end with minimal code changes

/**
 * @param inputLocale A dash-delimited language-region pair
 * @returns an IETF language tag
 */
export function toIetfLocale(
  inputLocale?: string,
  defaultLocale = 'en-US'
): string {
  if (!inputLocale) return defaultLocale;

  const [lang, region] = inputLocale.split('-');

  if (!region) return lang.toLowerCase();

  return lang.toLowerCase() + '-' + region.toUpperCase();
}