How to use res.send in passport strategy? - node.js

Question

I'm trying to make Node.js ajax authentication with passport.js, I want to show messages in /login page. I should use res.send in my passport strategy, then ajax call ended successfully will display success data to its page. But I can't guess how can I use res. in strategy. Please see below code,
login.ejs
<div id="messages"></div>
<!-- and there is a form, when form submitted, the ajax call executed.-->
<!-- ...ajax method : POST, url : /login, data: {}, success:... -->
<!-- If ajax call success, get 'result' data and display it here -->
app.js
// and here is ajax handler
// authentication with received username, password by ajax call
app.post('/login', passport.authenticate('local'),
function(req, res, next){
res.redirect('/');
});
// and here is passport strategy
passport.use(new passportLocal.Strategy(function(userid, password, done) {
Members.findOne({'user_id' : userid}, function(err, user){
// if user is not exist
if(!user){
// *** I want to use 'res.send' here.
// *** Like this :
// *** res.send('user is not exist');
// *** If it is possible, the login.ejs display above message.
// *** That's what I'm trying to it. How can I do it?
return done(null, null);
}
// if everything OK,
else {
return done(null, {id : userid});
}
})
}));
I searched some document on google, people usually use 'flash()' in connect-flash module, but I thought this module needed to reload page, this is not what I want to, So please help me and let me know if there is better way. Thanks.

Answer 1

Instead of directly inserting the Passport middleware, you can use a custom callback in order to pass the req, res, next objects to the Passport function.
You could do something similar in your route handler/controller (this is taken directly from the Passport docs):
app.post('/login', function(req, res, next) {
passport.authenticate('local', function(err, user, info) {
if (err) { return next(err); }
if (!user) { return res.redirect('/login'); }
req.logIn(user, function(err) {
if (err) { return next(err); }
return res.redirect('/users/' + user.username);
});
})(req, res, next);
});