无法通过承诺从 nodejs 中的 bcrypt.compare() function 返回数据

Question

I'm currently buildung an application with nodejs (10.15.2) but I'm running into some problems with the login function.

Snippet from my "dbconnector.js" file:

login(email, password) {
    return userModel.findOne({
      email: email
    }).lean().then(function(user) {
      // return user;
      return bcrypt.compare(password, user.password, function(err, res) {

           if (res) {
              console.log(user); //prints the userinfo - works fine
              return user;
          }
        });
    });
};

Snippet from my serve.js file:

app.post('/login', async (req, res) => {

    var { email, password } = req.body;
    var user = await dbconnector.login(email,password);
    console.log(user) //returns undefined

    if (user != false) {
      console.log("loggedin");
        const accessToken = jwt.sign({ email: user.email,  id: user.id }, key.tokenKey);

        res.json({
            accessToken
        });
    } else {
        res.send('Username or password incorrect');
    }
});

My problem is that the login() -function returns undefined. However, when I change it to the following, it works perfect (just without checking the password...):

  login(email, password) {
    return userModel.findOne({
      email: email
    }).lean().then(function(user) {
    return user;
    });
};

So I know something's wrong with the bcrypt / promise part but I couldn't find a solution.

Answer 1

My Fellow brother, the problem lives in the fact that a promise will only return you another promise and the compare callback that you have there as its name says callback is not apromise. Lets make it a promise

login(email, password) {
    return userModel.findOne({
      email: email
    }).lean().then(function(user) {
      // return user;
      return new Promise((resolve, reject) => {
          return bcrypt.compare(password, user.password, (err, res) => {
              if (err) {
                  return reject(err);
              }

              return resolve(res);
        })
};

BUT!!! if by any means the bcrypt package u are using is this one https://www.npmjs.com/package/bcrypt then you dont event have to promisify the method, it has it as promise already

login(email, password) {
    return userModel.findOne({
      email: email
    }).lean().then(function(user) {
      return bcrypt.compare(password, user.password);
    }).then(isEquals => {
        if (isEquals) {
            return true
        }

        return false
    }).catch(error => {
        throw error;
    })
};