sessionTest.js

var express = require('express');
var session = require('express-session');
var bodyParser = require('body-parser');
var app = express();

app.set('views', __dirname + '/views');
app.engine('html', require('ejs').renderFile);

app.use(session({secret: 'ssshhhhh'}));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: true}));

var sess;

app.get('/',function(req,res){
    sess=req.session;
//Session set when user Request our app via URL
    if(sess.email)
    {
        /*
         * This line check Session existence.
         * If it existed will do some action.
         */
        res.redirect('/admin');
    }
    else{
        res.render('index.html');
    }
});

app.post('/login',function(req,res){
    sess=req.session;
//In this we are assigning email to sess.email variable.
//email comes from HTML page.
    sess.email=req.body.email;
    res.end('done');
});

app.get('/admin',function(req,res){
    sess=req.session;
    if(sess.email)
    {
        res.write('<h1>Hello '+sess.email+'</h1>');
        res.end('<a href="+">Logout</a>');
    }
    else
    {
        res.write('\
        <h1>Please login first.</h1>\
    ');
        res.end('<a href="+">Login</a>');
    }

});

app.get('/logout',function(req,res){

    req.session.destroy(function(err){
        if(err){
            console.log(err);
        }
        else
        {
            res.redirect('/');
        }
    });

});
app.listen(3000,function(){
    console.log("App Started on PORT 3000");
});