Return mongojs query result from function - node.js

Question

I made the function below for getting usernames from ids. It is not working well.
I can write console.log(result.first_name); within the query function, and the usernames shows up in my terminal, but not the browser. I tried adding “return 'something';” at the end of the function, to see if that showed up in the browser – It did. How can I write the function so that the query result is returned?
function (global function in app.js)
function usernameFromId(id, callback){
db.users.findOne({ _id: ObjectId(id.toString()) }, function(err, result) {
var first_name = result.first_name;
console.log(first_name); // names show up in the console…
callback(first_name);
});
};
page handler (in app.js)
app.get('/books', function(req, res){
function timeSince(dato){
moment.lang('nb');
return moment(dato).fromNow();
};
db.books.find().sort({ added:-1 }, function(err, docs) {
var books = docs;
db.activity.find().limit(9).sort({ time:-1 }, function(err, docs) {
var activity = docs;
res.render('books', {
books: books,
activity: activity,
timeSince: timeSince,
usernameFromId: usernameFromId
})
});
});
});
template (books.jade)
- each a in activity
p=usernameFromId(a.user_id, function(name){return name;})

Answer 1

No because of the asynchronous nature of JavaScript. I have added some comments to your code to indicate the actual order of execution. This is why you are getting the error.
function usernameFromId(id){
var id = id.toString(); // 1
db.users.findOne({ _id: ObjectId(id) }, function(err, result) {
var first_name = result.first_name; // 3
});
return first_name; // 2
};
Edit: you probably want something like the following
function usernameFromId(id, callback){
var id = id.toString();
db.users.findOne({ _id: ObjectId(id) }, function(err, result) {
var first_name = result.first_name;
callback(first_name);
});
};

Answer 2

Okay, I found a solution. Not sure whether it’s any good, but it works. No need for a function.
page handler (in app.js):
app.get('/books', function(req, res){
db.activity.find().limit(9).sort({ time:-1 }, function(err, docs) {
var activity = docs;
db.users.find(function(err, docs) {
var users = docs;
res.render('books', {
page_title:'books',
activity: activity,
users: users
})
});
});
});
template (books.jade):
- each a in activity
- for u in users
- if (a.user_id == u._id.toString())
| #{u.first_name}