https://xbext.com/js/lang_select.js

1(function() {
2  'use strict';
3
4  var Cookies = window.Cookies.noConflict();
5
6  function changeLang() {
7    var lang = this.value;
8    
9    var canonical = this.dataset.canonical;
10    var path = '/';
11    var href;
12    var e = document.querySelector("link[hreflang=" + lang +"]");
13    if(e) {    
14      href = e.href;
15    } else {
16      href = path + canonical;
17    }
18    
19    Cookies.set('nf_lang', lang, { expires: 365 });
20   
21    location.href = href;
22  }
23
24  document.getElementById('lang-select').addEventListener('change', changeLang);
25  document.getElementById('mobile-lang-select').addEventListener('change', changeLang);
26}());