cookie-session doesn't save session modification - node.js

Question

I wanted to remember the last page someone visited (like here)
I tried to do it with cookie-session but It's doesn't work as I a suppose.
I saw this and I tried this example for extending the session without success.
Here the code :
var session = require('cookie-session');
var express = require('express');
var app = express();
app.use( session({ secret: 'secret' }) );
app.get('/a', function (req, res) {
if(req.session.last) {
res.write("the last page was " + req.session.last + ". ");
}
req.session.last = "a";
res.end("Page A");
});
app.get('/b', function (req, res) {
if(req.session.last) {
res.write("the last page was " + req.session.last + ". ");
}
req.session.last = "b";
res.end("Page B");
});
app.get('/c', function (req, res) {
if(req.session.last) {
res.write("the last page was " + req.session.last + ". ");
}
req.session.last = "c";
res.end("Page C");
});
app.listen(8080);

Answer 1

Are you sure you are not getting an error in your logs along the line of "cannot write to headers after they have been sent"? Can you try moving the assigning of the session to before the res.write call? From your first link, in the comments...
"I kept getting an error that the headers couldn't be set after they'd been sent.
I modified the code so that lastPage was set before sending any body eg:
var responseText;
if(req.session.lastPage)
responseText = 'Last page was: ' + req.session.lastPage + '. ';
else
responseText = 'You\'re Awesome';
req.session.lastPage = '/awesome';
res.send(responseText);