'TypeError: Cannot read property 'then' of undefined when using JWT token and refresh token

Sorry I'm new to backend (nodejs) and I'm trying to build a JWT token and refresh token but I stumbled across an error that I cannot fix when I try to run an endpoint in insomnia.

TypeError: Cannot read property 'then' of undefined

This is the code snippet from the area the error came from in my app.js file

app.post('/users/login', (req, res) => {
   let email = req.body.email;
   let password = req.body.password;

   User.findByCredentials(email, password)
      .then((user) => {
         return user.createSession()
            .then((refreshToken) => {
               return user.generateAccessAuthToken()
               .then((accessToken) => {
                  return { accessToken, refreshToken };
               });
            })
            .then((authTokens) => {
               res
                  .header('x-refresh-token', authTokens.refreshToken)
                  .header('x-access-token', authTokens.accessToken)
                  .send(user);
            })
   }).catch((e) => {
      res.status(400).send(e);
   });
});

And this is the code for the method "findByCredentials" in my user.model.js file

UserSchema.statics.findByCredentials = function(email, password) {
    let User = this;
    User.findOne({ email }).then((user) => {
        if(!user) return Promise.reject();

        return new Promise((resolve, reject) => {
            bcrypt.compare(password, user.password, (err, res) => {
                if (res) resolve(user);
                else {
                    reject();
                }
            })
        })
    });
}

Please help me

Error solved: I just needed to return the value of the findByCredentials method to solve the problem

node.jsjwtrefresh-token


Solution 1:[1]

Since the error isn't posted, it's hard to pinpoint the error line & cause. But I would suggest using .catch blocks along with the end of every .then chain and get the spot/line of error

Recommendation:
You are creating a callback hell by using nested .then chains what is call back hell.
Try using async/await syntax to achieve the same functionality in a simplified way - Ref.

Regards,
Muhamed

Solution 2:[2]

As if you didn't send any code snippet, it is quite clear. But after going through your code it seems after resolving the "user" you are calling two methods createSession and generateAccessAuthToken. And as you also didn't send any code snippet of these methods I'm assuming you are having error from one of the functions.

And a piece of advice:

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Muhamed Salih
Solution 2

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