What the difference between these two programs segments

Question

When I try to create a middleware 'Passport' then this issue occurs.

This Program segment works good:

router.post('/login',function(req,res,next) {
   passport.authenticate('local', function(err,user,message){
      res.send(message.message);    
   }) (req, res, next);
});

But when I changed this to:

router.post('/login', function (req, res, next) {
  passport.authenticate('local',(err, user,message) => {
    res.send(message.message);  
  });
}, function(req, res, next){

});

The post request doesn't end. Loading doesn't stop.

What's the difference between these code snippets? I think both programs are the same.

Answer 1

passport.authenticate() returns a middleware function. So in the first snippet, what you are doing is,

router.post('/login',function(req,res,next) {
  var middleware = passport.authenticate('local',(err, user,message) => {
    res.send(message.message);  
  }); // middleware is now a function. You can call it!

  middleware(req, res, next);
});

In the second snippet, the middleware function which is returned is never used. Thus, your (err, user,message) => {} is never executed.

And that is why the request does not end.

Try:

router.post('/login', passport.authenticate('local', function(err,user,message) {
  res.send(message.message);    
}));