Express-sessions不在不同的路由上保存会话数据

Question

我正在使用Express和Express会话来保存当前用户的ID。登录时，在会话中设置了用户ID，但是，如果我要切换到另一个页面，则会发现该用户ID被设置为undefined。为什么会这样？

下面是API。每当加载页面以检查用户是否登录时，身份验证路由就会运行。

const express = require('express');
const router = express.Router();
const bodyParser = require('body-parser');
const session = require('express-session');
const user = require('../components/user');

let sess;

router.post('/createUser', (req, res) => {
    user
        .createUser({
            username: req.body.username,
            password: req.body.password,
            email: req.body.email
        })
        .then(() => res.sendStatus(200))
});
router.post('/login', (req, res) => {
  sess = req.session;
    user
        .authenticate({
            username: req.body.username,
            password: req.body.password
        })
        .then(({ success, user }) => {
            if (success) {res.sendStatus(200); sess.userID = user;}
            else res.sendStatus(401)
        })
});

router.post('/auth', (req, res) => {
  sess = req.session;
    if (sess.userID === undefined){
      res.redirect('/');
    }else{
      res.sendStatus(200);
    }
});

router.post('/auth/logout', (req, res) => {
  sess = req.session;
  sess.userID = undefined;
  res.redirect('/');
});

router.post('/auth/createCheck', (req, res) => {
  sess = req.session;
  console.log(sess.userID);
    if (!sess.userID === undefined){
      res.redirect('/');
    }else{
      res.sendStatus(200);
    }
});


module.exports = router;

Answer 1

结果是因为我在每条路由上都定义了sess，因为它应该只在登录路由中定义。