How to response data after create data "model.save()" in MongoDB? - node.js

Question

I try the response model after create data but it doesn't work. It shows data on "console.log" and it didn't respond when I use "resolve({})".
In the routers.js:
const register = require('./functions/register');
module.exports = router => {
router.get('/', (req, res) => res.end('Welcome to Idol Fan With your Idol !'));
//======REGISTER & LOGIN WITH SOCIAL =====
router.post('/socialuser', (req, res) => {
const social_id = req.body.social_id;
const token = req.body.token;
const name = req.body.name;
const email = req.body.email;
const photoprofile = req.body.photoprofile;
const tokenfirebase = req.body.tokenfirebase;
if (!social_id) {
res.status(400).json({message: 'Invalid Request !'});
} else {
register.registerUser(social_id, name, email, photoprofile, token, tokenfirebase)
.then(result => {
res.status(result.status).json({status: result.status, message: result.message, user: result.user})
})
.catch(err => res.status(err.status).json({message: err.message}));
}
});
}
Function Register.js:
const userfan = require('../models/user');
exports.registerUser = (social_id, name, email, photoprofile, token,
tokenfirebase) =>
new Promise((resolve, reject) => {
const d = new Date();
const timeStamp = d.getTime();
userfan.find({social_id: social_id})
.then(users => {
if (users.length == 0) {
let newUser = new userfan({
social_id: social_id,
name: name,
email: email,
photoprofile: photoprofile,
token: token,
tokenfirebase: tokenfirebase,
created_at: timeStamp
});
newUser.save()
.then(doc => {
console.log("run... " + doc);
resolve({
status: 200,
message: 'User Register Sucessfully !',
user: doc
});
})
.catch(err => {
console.error(err)
if (err.code == 11000) {
reject({status: 409, message: 'User Already Registered !'});
} else {
reject({status: 500, message: 'Internal Server Error !'});
}
});
} else {
return users[0];
}
})
.then(usertemp => resolve({status: 200, message: "Login Successfully !", user: usertemp}))
.catch(err => {
console.log(err.message);
reject({status: 500, message: err.message});
});
});
This is my result after run on server:
As a result and code above. I have a question Why "user: doc" no response?. Thank you so much!

Answer 1

userfan.find.then.then (synchronous since nothing requires waiting) is called before newUser.save.then (asynchronous since under the hood it waits for the DB to answer).
So both resolve are called, but only the first call is considered, and the first one to be called is the one using usertemp. And this one receives undefined as argument, because of the implicit return undefined at the end of userfan.find.then.
Your flow should be:
userfan.find().then(users => {
if (!users.length) {
let newUser = ...
// explicitly return the promise, which will give the created user
return newUser.save().then(doc => {
// format and return the value you want
return {user: doc, message: 'registered'};
});
} else {
// another explicitly returned value, but you already have this
return {user: users[0], message: 'login'};
}
// it's not possible here because we returned before it, but your code reached this point
// and, implicitly, any function ending with no return does:
return undefined;
// this .then receives *either* the promise from newUser.save *or* the object from the else block
}).then(structure => {
structure.status = 200;
return structure; // here structure is {status: 200, message: 'registered'|'login', user: document}
});
Also, note that using the syntax shortcut (without curly braces around the function body) for arrow functions implies the one-line body is returned:
singleArgument => doSomething();
// is actually *strictly* equivalent to
(singleArgument) => { return doSomething(); }
With these ways of writing, it's easy to lose the reflex of writing return when it's needed.