wikimedia/mediawiki-extensions-MobileFrontend

/**
 * Return the language code of the device in lowercase
 *
 * @ignore
 * @param {window.navigator} navigator
 * @return {string|undefined}
 */
function getDeviceLanguage( navigator ) {
    const lang = navigator.languages ?
        navigator.languages[ 0 ] :
        navigator.language || navigator.userLanguage ||
                navigator.browserLanguage || navigator.systemLanguage;

    return lang ? lang.toLowerCase() : undefined;
}

module.exports = getDeviceLanguage;