Ggtcf

I want to do find an user, whose model contains an array of cities (for example:[Madrid, London, Moscow, Buenos Aires, etc])

This is the model:

var UserSchema = Schema(
 name: String,
 surname: String,
 userName: String,
 email: String,
 password: String,
 rol: String,
 suscriptionDate: Date,
 cities:[String],
 citiesPopulate:[]
);

Once I've found the user, I want to iterate through this array to use each city as the parameter in order to find the info that I have on the model City just to add coords to user.citiesPopulate

function findUsersCities(req,res)
 let id=req.body._id;

 User.findById(id,function(err,userFound)
 if(err)
 console.log(err)
 else

 for(let i=0;i<userFound.cities.length;i++)

 City.findOne('city':userFound.cities[i],function(err,citiesFound)
 if(err)
 console.log(err)
 else
 userFound.citiesPopulate.push(citiesFound.coords);
 console.log(userFound)
 
 )
 

 
 )

And, once all the info of every single city has been added to userFound.citiesPopulate (by now just arrays with a pair of coordinates), I want to use res.status(200).send(userFound) to see the result on my postman console, something like this(three cities and three pairs of coordinates):

 cities: [ 'Bilbao', 'Madrid', 'Barcelona' ],
 citiesPopulate: [ [ -3.68, 40.4 ], [ -2.97, 43.25 ], [ 2.18, 41.38 ] ],
 _id: 5c82c2e5cfa8d543d0133dd6,
 name: 'pruebas35',
 surname: 'pruebas35',
 userName: 'pruebas35',
 email: 'pruebas35@prueba.es',
 password: '$2a$10$eSue5gw7r4dFPtwD8qzJhODcvvNFaRkeQYRAOPO9MCBsy3Djhkffq',
 rol: 'user',
 suscriptionDate: 2019-03-08T19:30:45.075Z,
 __v: 0 

But if I type the res.status into the loop, it is sent and I can´t get the whole information.

I'd like to know a solution for this, please.

As pointed out by Carlos, this won't work because of the asynchronous nature of database requests. The way I would do it is to use async/await to make the code synchronous, like this:

function findUsersCities(req,res)
 let id=req.body._id;

 User.findById(id,async function(err,userFound)
 if(err)
 console.log(err)
 else
 try 

 for(let i=0;i<userFound.cities.length;i++)

 let cityFound = await City.findOne('city':userFound.cities[i]);

 userFound.citiesPopulate.push(cityFound.coords);
 

 //complete userFound
 console.log(userFound);

 catch (e) 
 console.log(e);
 

 
 )

Notice the use of the keyword async in the callback function from User.findById. You can only use the await feature if it is inside a function marked with the async keyword.

Also, when you doesn't specify a callback function to any Mongoose query funcion, it returns a Promise, and you can only use the await keyword on promises.

If the promise resolves, the code will continue to run, and the resolved value will be in the variable cityFound, otherwise (if the promise rejects), it will throw an execption, so the code will fall into the catch statement, and the rejected value will be in variable e.