LocalStorage multilanguage

HTML

<select id="changelocation" name="language">
  <option value="">Please select</option>
  <option value="ja">Japanese</option>
  <option value="en">English</option>
  <option value="de">Frensh</option>
</select>
<label for="firstname">First Name</label><input id="firstname">
<label for="lastname">Last Name</label><input id="lastname">
<label for="message">Message</label><textarea id="message"></textarea>

JavaScript

// declarer la variable
var language = localStorage.getItem('language');

//si la variable existe changer la valeur du select box avec celle enregistre
if (language) {
  var lang1 = $('#changelocation').val(language);
  
}
// si elle n'existe pas encore affecter la valeur par defaut du select a la variable
else {
  var language = $('#changelocation option:selected').val();
  
  localStorage.setItem('language', language);
}
$.i18n = function(options){
    options = $.extend({}, {
        lang: 'en',
        data: $.i18n,
        sliceLang: false
    }, options);

    

    
    var storeData = function(data){
        if(!data) return;
        if(window.localStorage) {
        
            localStorage.setItem( "langStore", JSON.stringify(data) );
            langStore = data;          
        } else {
            langStore = data;
        }
    };

    if(window.localStorage) {
        var localLangStore = localStorage.getItem("langStore");
        storeData( localLangStore !== null ? JSON.parse(localLangStore) : langStore);
    } else {
        storeData( langStore );
    }

    this.getLang = function(){ return lang; };
    this.setLang = function(l){ lang = l; storeData(options.data[l]); };

    this.getItem = function(key){ return langStore[key]; };
    this.setItem = function(key, value){ options.data[lang][key] = value; storeData(langStore); };

    return this;
};

$.i18n.en = {
    firstname: 'First Name',
    lastname: 'Last Name',
    message: 'Message'
    
};

$.i18n.de = {
    firstname: 'Vorname',
    lastname: 'Nachname',
    message: 'Nachricht'
   
};
var i18n = $.i18n();
var changeLabels = function(){
    $('label').each(function(){
        var forLabel = $(this).attr('for');
        this.innerText = i18n.getItem(forLabel);
    });
};
changeLabels();
// si on modifie la valeur du select il faut mettre a jour la valeur de la variable
$('#changelocation').on('change', function(e) {
  var language = $(this).val();
  alert('language'+language);
 ...