带有Nodejs和Pugjs的i18next：无法读取属性＆＃39; t＆＃39;未定义的

Question

我是i18next的初学者，我想在使用Nodejs + Pugjs开发的小应用程序上管理多种语言。

尝试在pugjs中声明密钥时出现以下错误：Cannot read property 't' of undefined

我的代码：

app.js

i18n
.use(i18nFsBackend)
.use(i18nMiddleware.LanguageDetector)
.init({
  fallbackLng: 'en',
  debug: true,
  ns: ['translation', 'traduction'],
  defaultNS: 'translation',
  backend: {
    loadPath: __dirname + '/locales/{{lng}}/translation.json',
    addPath: __dirname + '/locales/{{lng}}.missing.json'
  },
  interpolation: {
    format: function(value, format, lng) {
      if (format === 'uppercase') return value.toUpperCase();
      if(value instanceof Date) return moment(value).format(format);
      return value;
    }},
    lowerCaseLng: true,
    preload: ['en', 'fr'],
    sendMissingTo: 'en',
    useCookie: false,
    detectLngFromHeaders: false,
    saveMissing: true}
  });
//Routes that should be ignored
  app.use(i18nMiddleware.handle(i18n, {
    ignoreRoutes: ['images/', 'public/', 'css/', 'js/'],
    removeLngFromUrl: false
  }));

routes.users.js

//Access i18n inside your route:
app.get("/", function(req, res) {
  // current language
  var currentLng = req.locale; 
  // access i18n
  var i18n = req.i18n; 
  // translate
  var t = i18n.t("applog.login"); // Comment renseigner my.key
  res.send(t);
});

default.pug

doctype
html(lang="fr")
  head       
    meta(charset="utf-8")      
    link(rel="stylesheet", href="/css/bootstrap.css")
    link(rel="stylesheet", href="/css/style.css")     
    block title
      title i18n.t(login)
  body
    .container                                  
      block index
      block login
      block register          
      footer
        p Login App - JPM2017
      script(src="/js/bootstrap.js")
      script(src="https://unpkg.com/i18next/i18next.js") 

login.pug

extends default

block title
  title i18n.t('applog.logapp') 
block login
  include nav   
  include flashmess

  h2.page-header #{i18n.t('applog.aclog')} 
  form(method="post", action="/users/login")
    .form-group
      label Username
      input.form-control(type="text", name="username", placeholder="+ #{i18n.t('applog.Uname')}+")

    .form-group
      label Password
      input.form-control(type="password", name="password", placeholder="+ #{i18n.t('applog.Pword')}+")

    button(type="submit").btn.btn-default="+ #{i18n.t('applog.submit')}"