IsWellFormedCurrencyCode = function (code) {
        code = Internal.ToString(code);

        if (!CURRENCY_CODE_RE) {
            InitializeCurrencyRegExp();
        }

        return platform.builtInRegexMatch(code, CURRENCY_CODE_RE) !== null;
    }
Returns an object representing the language, script, region, extension, and base of a language tag,
or null if the language tag isn't valid.

@param {String} langtag a candidate BCP47 langtag