此功能用于登录身份验证。我希望在身份验证失败时在浏览器中显示警报消息。我无法使用警报，因为在节点警报中未定义所以我正在尝试使用闪存来显示警报消息。我可以使用它吗如果还有其他方法，请建议。
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>0)
req.session.user_type_id=rows[0].user_type_id;
// req.session.userName =rows[0].username;
if (rows.length > 0) {
var str = '';
for (var i = 0; i < 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');
}
},