const languageStrings = {
    'thesis_name': {
        'en': 'Thesis',
        'de': 'These',
        'fr': 'asdf',
    }
};

function translate123(lng) {
    $("[data-translate]").each((i, e) => {
        let key = $(e).data('translate');
        $(e).html(languageStrings[key][lng] || 'N/A');
    });
}

/**
 * Usage:
 *
 * <span data-translate="thesis_name"></span>
 */