JavaScript无法获取从then（）调用返回到另一个then（）调用的返回值

Question

I am trying to execute this code:

UserSchema.methods.generateAuthToken = function () {
    const user = this;
    const access = 'auth';
    const token = jwt.sign({_id: user._id.toHexString(), access}, 'abc123');

    user.tokens.push({access, token});

    user.save().then(() => {
        return token;
    });
};

In my express file, I have following code:

app.post('/users', (req, res) => {
    const body = _.pick(req.body, ['email', 'password']);
    const user = new User(body);

    user.save().then(() => {
        return user.generateAuthToken();
    }).then((token) => {
        res.header('x-auth', token).send(user);
    }).catch((err) => {
        console.log(err);
        res.status(400).send(err);
    });
});

The problem is that the token returned from the user.save().then() call in first file never reaches the express code user.generateAuthToken() . What is the reason and how should I solve it?

Answer 1

generateAuthToken has no return statement.

If you want to return the promise that then returns, then you have to do so explicitly.

Answer 2

you need to update your schema to the following:

 UserSchema.methods.generateAuthToken = function () { const user = this; const access = 'auth'; const token = jwt.sign({_id: user._id.toHexString(), access}, 'abc123'); user.tokens.push({access, token}); user.save().then(() => { return token; }); }; 

The generateAuthToken does not return a Promise in your code