function getLanguage() {
    var $langMap = {
      en: 'English',
      es: 'Spanish'
    };
    var $lang = $('html').attr('lang');
    return '//cdn.datatables.net/plug-ins/1.10.13/i18n/' + $langMap[$lang] + '.json';
  }

  // Build Datatable
  $('#example').DataTable({
    language: {
      url: getLanguage() // works perfectly, but I need to overwrite with a few custom text options
    }
  });

en: {
    // Overwrite defaults with this string
    "lengthMenu": "Display _MENU_ records per page - custom test",
  },
  es: {
    // Overwrite Spanish defaults with this string
    "lengthMenu": "Mostrar _MENU_ registros - algo muy especial...",
  }