title: Cant get all response data from fetch
body: <p>So I'm trying to store some info in the session, for later use. But when I fetch it in react, it doesn't all come back. Despite the get route having all of the data. </p>
  
  <p>My thought process is on the serverside, when a user logs in store their id in the session. I'll then have a <code>/userinfo</code> route that dumps all the data i need in json. I can then fetch that <code>/userinfo</code> route and get the data in the response. My code is as follows:</p>
  
  <p>Heres the post code to sign in, I <code>console.log</code> to verify the session is modified. It is.</p>
  
  <pre><code>User.authenticate(req.body.logemail, req.body.logpassword, function (error, user) {
     if (error || !user) {
       var err = new Error('Wrong email or password.');
       err.status = 401;
       return next(err);
    } else {
       req.session.userId = user._id;
       console.log(req.session);
       return res.redirect('/');
     }
   });
  </code></pre>
  
  <p>Then I have this route:</p>
  
  <pre><code>app.get('/userinfo', (req, res)=&gt;{
    res.json(req.session);
  });
  </code></pre>
  
  <p>If I simply go to <code>localhost:3000/userinfo</code> the json looks like:</p>
  
  <pre><code>{
    "cookie": {
      "originalMaxAge": null,
      "expires": null,
      "httpOnly": true,
      "path": "/"
    },
    "userId": "blahblahblah"
  }
  </code></pre>
  
  <p>so UserID is indeed there.
  However, when I finally go to fetch it in react with:</p>
  
  <pre><code>fetch('http://localhost:3000/userinfo')
    .then(res =&gt; res.json())
    .then(data =&gt; console.log(data));
  </code></pre>
  
  <p>All I get back is the cookie. I dont get <em>UserId</em>. I've tried adding UserId to the cookie as well, just to see if it'd work, and likewise I just get the plain cookie.</p>