req.flash() 返回空的 flash object 而不是成功消息

Question

如果用户的 email 已经存在，我正在尝试在注册期间进行检查。 如果是这样，我正在尝试 flash 一条错误消息，如果它没有成功消息。 相反，我返回的是一个空的 flash object。 res.redirect function 确实有效，但它仍然将我重定向到正确的页面（/register 或 /login）。 如果我 console.log(req) 我得到以下信息：

  sessionID: 'Qyhl4HA1mdr3-pRW1vSewYvPm7ffXkqg',
  session: Session {
    cookie: { path: '/', _expires: null, originalMaxAge: null, httpOnly: true },
    flash: { 'error-message': [Array] }
  },
  flash: [Function: _flash],
  originalMethod: 'POST',
  route: Route {
    path: '/register',
    stack: [ [Layer], [Layer] ],
    methods: { get: true, post: true }
  },
  [Symbol(kCapture)]: false,
  [Symbol(RequestTimeout)]: undefined

这是我的 controller：

registerGet: (req, res) => {
      res.render('default/register')
    },

    registerPost: (req, res) => {
      let errors = [];

      if(!req.body.firstName) {
        errors.push({message: 'First name is mandatory'});
      }

      if(!req.body.lastName) {
        errors.push({message: 'Last name is mandatory'});
      }

      if(!req.body.email) {
        errors.push({message: 'Email field is mandatory'});
      }

      if(req.body.password !== req.body.passwordConfirm) {
        errors.push({message: 'Passwords do not match'});
      }

      if(errors.length > 0) {
        res.render('default/register', {
          errors: errors,
          firstName: req.body.firstName,
          lastName: req.body.lastName,
          email: req.body.email
        });
      }

      else {

        User.findOne({email: req.body.email}).then(user => {
          if(user){
            req.flash('error-message', 'Email already exists, try to login');
            res.redirect('/register');
            console.log(req);
          }

          else {
          const newUser = new User(req.body);
           bcrypt.genSalt(10, (err, salt) => {
                bcrypt.hash(newUser.password, salt, (err, hash) => {
                  newUser.password = hash;
                  newUser.save().then(user => {
                    req.flash('success-message', 'You are now registered');
                    res.redirect('/login'); 
                  });
            });
          });
      }
    })
      }
    }

这是我的 regsiter.handlebars 文件：

{{#if errors}}
{{#each errors}}
<div class="alert alert-danger alert-dismissible fade show" role="alert">
  <strong>{{message}}</strong>
</div>
{{/each}}
{{/if}}


<div class="card card-register mx-auto my-5">
    <div class="card-header">Register an Account</div>
    <div class="card-body">
        <form action="/register" method="post">
            <div class="form-group">
                <div class="form-row">
                    <div class="col-md-6">
                        <label for="exampleInputName">First name</label>
                        <input name="firstName" class="form-control" id="exampleInputName" type="text" aria-describedby="nameHelp" placeholder="Enter first name">
                    </div>
                    <div class="col-md-6">
                        <label for="exampleInputLastName">Last name</label>
                        <input name="lastName" class="form-control" id="exampleInputLastName" type="text" aria-describedby="nameHelp" placeholder="Enter last name">
                    </div>
                </div>
            </div>
            <div class="form-group">
                <label for="exampleInputEmail1">Email address</label>
                <input name="email" class="form-control" id="exampleInputEmail1" type="email" aria-describedby="emailHelp" placeholder="Enter email">
            </div>
            <div class="form-group">
                <div class="form-row">
                    <div class="col-md-6">
                        <label for="exampleInputPassword1">Password</label>
                        <input name="password" class="form-control" id="exampleInputPassword1" type="password" placeholder="Password" >
                    </div>
                    <div class="col-md-6">
                        <label for="exampleConfirmPassword">Confirm password</label>
                        <input name="passwordConfirm" class="form-control" id="exampleConfirmPassword" type="password" placeholder="Confirm password">
                    </div>
                </div>
            </div>
            <button type="submit" class="btn btn-primary btn-block">Register</button>
        </form>
        <div class="text-center">
            <a class="d-block small mt-3" href="/login">Login Page</a>
            <a class="d-block small" href="forgot-password.html">Forgot Password?</a>
            <a class="d-block small" href="/">Home Page?</a>
        </div>
    </div>
</div>

我的路由器：

const express = require('express');
const router = express.Router();
const defaultController = require('../controllers/defaultController');


router.all('/*', (req, res, next) => {
    
    req.app.locals.layout = 'default';

    next();
})

router.route('/')
      .get(defaultController.index);

router.route('/login')
    .get(defaultController.loginGet)
    .post(defaultController.loginPost);

router.route('/register')
    .get(defaultController.registerGet)
    .post(defaultController.registerPost);

module.exports = router;

非常感谢您的帮助，我已经尝试调试了几个小时！