mongoose document.save not working - node.js

Question

I am trying to create a very simple forum using nodejs, mongo and mongoose.
So far I created a mongoose Schema for users:
var mongoose = require('mongoose');
var user = {
_id: { type: String, required: true },
password: { type: String, required: true }
};
var schema = new mongoose.Schema(user);
module.exports = schema;
module.exports.user = user;
Then created the Model:
var mongoose = require('mongoose');
var url = 'mongodb://localhost:27017/forum'
mongoose.connect(url);
mongoose.connection.on('connected', function() {
console.log('Stablished connection on ' + url);
});
mongoose.connection.on('error', function(error) {
console.log('Something wrong happened: ' + error);
});
mongoose.connection.on('disconnected', function() {
console.log('connection closed');
});
var User = mongoose.model('User', require('./user'));
module.exports.User = User;
Finally, there is the file that contains all the models (currently just one) and its methods:
var models = require('./models');
var User = models.User
exports.addUser = function(user, password) {
var data = new User({ _id: user, password: password });
data.save(function(error) {
console.log('inside');
if(error) { console.log('ERROR: ' + error); return true; }
else { console.log('User ' + user + ' added'); return false; }
});
};
exports.getUserList = function() {
User.find().lean().exec(function(error, users) {
if(error) { console.log('ERROR: ' + error); }
else { return JSON.stringify(users); }
});
}
The problem comes when I execute this file:
var mongodb = require('mongodb');
var mongoose = require('mongoose');
var dm = require('./dm');
var users = { 'user1': '1234',
'user2': '1234',
'user3': '1234',
'user4': '1234'
};
console.log('Initial user list');
dm.getUserList();
for(var user in users) {
dm.addUser(user, users[user]);
}
console.log('Final user list');
dm.getUserList();
process.exit(0);
It seems that it does nothing and does not save the users. Output:
Initial user list
Final user list
Thanks!

Answer 1

Remove the process.exit() part, or wrap it in a timeout. You don't give your database enough time to execute. E.g. put this at the end instead:
...
setTimeout(() => process.exit(0), 2000);
Edit: or add promises, like somebody commented:
exports.addUser = function(user, password) {
var data = new User({ _id: user, password: password });
return data.save()
.then(() => console.log('User ' + user + ' added'))
.catch(function(error) {
console.log('ERROR: ' + error);
else { return false; }
});
};
Then in your main loop:
const promises = users.map(userData => addUser(userData));
Promise.all(promises)
.then(() => {
console.log('All users added.');
// .. do another async operation here, or process.exit();
});