JS detect system language

var lang;
    if (navigator
            && navigator.userAgent
            && (lang = navigator.userAgent
                    .match(/android.*\W(\w\w)-(\w\w)\W/i))) {
        lang = lang[1];
    }

    if (!lang && navigator) {
        if (navigator.language) {
            lang = navigator.language;
        } else if (navigator.browserLanguage) {
            lang = navigator.browserLanguage;
        } else if (navigator.systemLanguage) {
            lang = navigator.systemLanguage;
        } else if (navigator.userLanguage) {
            lang = navigator.userLanguage;
        }
        lang = lang.substr(0, 2);
    }