JavaScript/Node.js Get Country from iOS or Android locale string

countryAndLanguageFromIosOrAndroidLocale.js

/**
 * Get the country code (ISO 3166-1 alpha-2) from a valid locale string from Android or iOS.
 * Valid locale strings are described here:
 * ios: https://developer.apple.com/library/content/documentation/MacOSX/Conceptual/BPInternational/LanguageandLocaleIDs/LanguageandLocaleIDs.html
 * android: https://developer.android.com/reference/java/util/Locale.html
 * 
 * Tested with ava.
 * 
 * @param {*string} localeString The locale string from android or ios
 */
function getCountryFromLocaleString(localeString){
    var hit = localeString.match("(^|[a-z])_[A-Z]{2}"); 
    if(hit){
        return hit[0].split("_")[1];
    } 
}

function getLanguageFromLocaleString(localeString) {
	var hit = localeString.match("^[a-z]{2}(-|_|$)");
	if (hit) {
		return hit[0].substring(0,2);
	}
}

//AVA TESTS:


import test from 'ava';

test(t => {
    t.is(getCountryFromLocaleString("en"), undefined);
    t.is(getCountryFromLocaleString("de_DE"), "DE");
    t.is(getCountryFromLocaleString("_GB"), "GB");
    t.is(getCountryFromLocaleString("en_US_WIN"), "US");
    t.is(getCountryFromLocaleString("de__POSIX"), undefined);
    t.is(getCountryFromLocaleString("zh_CN_#Hans"), "CN");
    t.is(getCountryFromLocaleString("zh_TW_#Hant-x-java"), "TW");
    t.is(getCountryFromLocaleString("th_TH_TH_#u-nu-thai"), "TH");
    t.is(getCountryFromLocaleString("en"), undefined);
    t.is(getCountryFromLocaleString("fr"), undefined);
    t.is(getCountryFromLocaleString("en_GB"), "GB");
    t.is(getCountryFromLocaleString("zh_HK"), "HK");
    t.is(getCountryFromLocaleString("az-Arab"), undefined);
    t.is(getCountryFromLocaleString("zh-Hans"), undefined);
    t.is(getCountryFromLocaleString("zh-Hans_HK"), "HK");
    t.is(getCountryFromLocaleString("nb_NO"), "NO");
    t.is(getCountryFromLocaleString("en_US"), "US");
    t.is(getCountryFromLocaleString("en_GB"), "GB");
});

test(t => {
    t.is(getLanguageFromLocaleString("en"), "en");
    t.is(getLanguageFromLocaleString("de_DE"), "de");
    t.is(getLanguageFromLocaleString("_GB"), undefined);
    t.is(getLanguageFromLocaleString("en_US_WIN"), "en");
    t.is(getLanguageFromLocaleString("de__POSIX"), "de");
    t.is(getLanguageFromLocaleString("zh_CN_#Hans"), "zh");
    t.is(getLanguageFromLocaleString("zh_TW_#Hant-x-java"), "zh");
    t.is(getLanguageFromLocaleString("th_TH_TH_#u-nu-thai"), "th");
    t.is(getLanguageFromLocaleString("en"), "en");
    t.is(getLanguageFromLocaleString("fr"), "fr");
    t.is(getLanguageFromLocaleString("en_GB"), "en");
    t.is(getLanguageFromLocaleString("zh_HK"), "zh");
    t.is(getLanguageFromLocaleString("az-Arab"), "az");
    t.is(getLanguageFromLocaleString("zh-Hans"), "zh");
    t.is(getLanguageFromLocaleString("zh-Hans_HK"), "zh");
    t.is(getLanguageFromLocaleString("nb_NO"), "nb");
    t.is(getLanguageFromLocaleString("en_US"), "en");
    t.is(getLanguageFromLocaleString("en_GB"), "en");
});


// For the semi-golfers
// function golfatron(l){
//     return (hit = l.match("(^|[a-z])_[A-Z]{2}")) ? hit[0].split("_")[1] : undefined;
// }

This works for all the test examples on the respective websites, but in the case some locales does not work, let me know!