res.redirect is not a function in promise then

Question

I use node v8.11.1 with express 4.16.3 and postgresql as my database, so I use the pg module. I am new to promises and then. This is my code that should work

the route

 router.post('/save',
(req, res)=>{
  req.checkBody('email', 'put email').notEmpty().trim();
  let errors = req.validationErrors();
  if (errors) {
    req.session.msgs = errors;
    res.redirect('/signup');
   }
   else {
     var user = {email:req.body.email};
     signup.signup(user)
     .then((res)=>{           
       req.session.msgs = [{msg: res}];
       res.redirect('/events');
       },
       (rej)=>{
         res.redirect('/signup');
         req.session.msgs = [{msg: 'err'}];
       }
     )
     .catch((err)=>{
       res.redirect('/signup');
       req.session.msgs = [{msg: 'err'}];
     });
   }
});

the function

const signup = (user) => {
  return new Promise((res, rej)=>{
    pool.connect( //connect to db
      (err, client, done) => {
        if (err) {
          return rej(err); //rej
        }
        client.query('insert into user (email) values($1)',[user.email]);
        done();
        res(user.email);
      }// pool anonumous funct
    );//pool connect
  })//promise
};
exports.signup = signup;

So , I guess this should work right away, but I am getting err TypeError: res.redirect is not a function that refers to my route, in this part

     signup.signup(user)
     .then((res)=>{           
       req.session.msgs = [{msg: res}];
       res.redirect('/events'); // <= REFERS HERE
       },

What am I missing? Why is this not a function? How to fix this? Thank you

score 2 · Accepted Answer · answered May 19 '18 at 15:57

2

You're using a res in the then callback, and that one shadows the res from the router.post.

So you need to rename one of those.

answered May 19 '18 at 15:57

Tudor Ilisoi

2,934
23
25

great catch, i would never think of that. it worked. thanks – slevin May 19 '18 at 17:52

desoares · Answer 2 · 2018-05-19T16:02:18.543

1

You are shadowing "res" in the database response:

router.post('/save',
(req, res)=>{ // one "res" here!
  req.checkBody('email', 'put email').notEmpty().trim();
  let errors = req.validationErrors();
  if (errors) {
    req.session.msgs = errors;
    res.redirect('/signup');
   }
   else {
     var user = {email:req.body.email};
     signup.signup(user)
     .then((res)=>{  // SHADOWS "res" in here !          
       req.session.msgs = [{msg: res}];
       res.redirect('/events');
       },
       (rej)=>{
         res.redirect('/signup');
         req.session.msgs = [{msg: 'err'}];
       }
     )
     .catch((err)=>{
       res.redirect('/signup');
       req.session.msgs = [{msg: 'err'}];
     });
   }
});

edited May 19 '18 at 16:02

answered May 19 '18 at 16:01

desoares

861
7
15

it's called shadowing, not overwriting – Tudor Ilisoi May 19 '18 at 16:02
Really? I'm not familiarized with the term. Gonna research. – desoares May 19 '18 at 16:03
Technically both variables exist, but the outer one is not accesible in the inner scope https://stackoverflow.com/questions/11901427/an-example-of-variable-shadowing-in-javascript – Tudor Ilisoi May 19 '18 at 16:06
He calls res.redirect right after "signup.signup(user)", in this scope res is not Express res but signup.signup(user) result. – desoares May 19 '18 at 16:08
That's right, and that is what I'm pointing at, but in other words. – Tudor Ilisoi May 19 '18 at 16:10

res.redirect is not a function in promise then

2 Answers2