title: how to display flash message in html view for nodejs
body: <p>this function is for login authentication.i want to display alert message in browser when authentication failed.i cant use alert because in node alert is not defined so i am trying to use flash for display alert message.how can i use it please suggest if there is any other method to do this.</p>
  
  <pre><code>login : function(req, res) {
          var sess;
          sess = req.session;
          sess.user = req.body.username;
          if (sess.user) {
  
              /*
               * This line check Session existence. If it existed will do some
               * action.
               */
              var db = req.app.get('db')();
              // console.log(db);
              var Username = req.body.username;
              var Password = req.body.password;
              console.log('u r here');
  
              if (!Username.trim())
              {
                  console.log('Incorrect username');
                  // res.end('Incorrect username');
                  res.redirect('/login');
              }
              else if (!Password.trim())
              {
                  console.log('Incorrect Password');
                  // res.end('Incorrect Password');
                  res.redirect('/login');
              }
              else
              {
                  var queryString = 'SELECT * from admin_info where user_name= ? And password=?';
                  console.log(queryString);
                  db.query(queryString, [ Username, Password ], function(error, rows, fields) 
                  {
                      if (error) 
                      {
                          console.log(error);
                          res.end(error);
                      } 
                      else 
                      {
                          console.log('u r in function');
  //                      console.log(Username + " " + Password);
          //              console.log(rows[0].id);
                          if(rows.length&gt;0)
                          req.session.user_type_id=rows[0].user_type_id;
  //                      req.session.userName =rows[0].username;
                          if (rows.length &gt; 0) {
                              var str = '';
  
                              for (var i = 0; i &lt; rows.length; i++) {
                                  str = str + rows[i].Username + '\n';
                              }
  
                              module.exports.user(req,res);
  
                          } else {
                              // dialog.info('invalid username or password');
                              // res.end('Invalid username or password');
                              // res.redirect('/login');
                              res.render('login', { messages: req.flash('info','hello') });
  
                          }
                      }
  
                  });
  
              }
          } else {
              res.redirect('/login');
          }
  
      },
  </code></pre>