AJAX loaded page doesn't see data from 'parent-page'

I have an HTML page (index.ejs) with tabs.

 <div class="tab-content">
   <div role="tabpanel" class="tab-pane active" id="first"></div>
   <div role="tabpanel" class="tab-pane" id="second"></div>
 </div>

and javaScript for these tabs:

$.get("firsttabpage.html", function(res, req) {
    $("#first").html(res, req);
});
$.get("secondtabpage.html", function(res, req) {
    $("#second").html(res, req);
});

It's Node.js here as you can see at first. And I have

    app.get('/', function(req, res) {
        res.render('index.ejs', {
            user : req.user
        });
    });

for authentication. I can use

<%= user.local.email %>

on index.ejs and it's ok, but I can't use this code for secondtabpage.html or secondtabpage.html - "user" is not available here. What I do wrong?