I am so confused while using express 4. I use express-generator to generate my project. And there are app.js in root and index.js in router file. However, the tutorial on internet about express are using router directly in app.js. So when I want to set some variables in index.js(in router file), I use app.locals, but it doesn't work. But when I change to the other two, my ejs template works... I am very confused. Anybody can tell me the difference between them and how to use correctly, please?

<!-- language: index.js in router file -->



    var app = require('express');

    var router = express.Router();



    ....



router.get('/', function(req, res, next) {

    var _user = req.session.user;

    if (_user) {

      //does't work!!

      //app.locals.user=_user;

      //I am not sure about which usage is correct below

      //1.

      req.app.locals.user = _user;

      //2.

      // res.locals.user=_user;

    }

}



<!-- language: lang-ejs -->



    <% if (user) { %>

      <li><a class=navbar-link>Welcome <%= user.name %></a>

      </li>

      <span>&nbsp;|&nbsp;</span>

      <li><a href=/logout class=navbar-link id=logoutBtn>Logout</a>

      </li>

      <% } else { %>

        <li><a href=# class=navbar-link data-toggle=modal data-target=#signinModal>登录</a>

        </li>

        <span>&nbsp;|&nbsp;</span>

        <li><a href=# class=navbar-link data-toggle=modal data-target=#signupModal>注册</a>

        </li>

      <% } %>