Node.js module to fetch data from MongoDB database - node.js

Question

I want to use an module to get and process data from my MongoDB database. (It should generate an object that represents my Express.js site's navbar)
I thought of doing something like this:
var nav = { Home: "/" };
module.exports = function() {
MongoClient.connect(process.env.MONGO_URL, function(err, db) {
assert.equal(err, null);
fetchData(db, function(articles, categories) {
combine(articles, categories, function(sitemap) {
// I got the data. What now?
console.log("NAV: ", nav);
})
});
});
};
var fetchData = function(db, callback) {
db.collection('articles').find({}).toArray(function(err, result) {
assert.equal(err);
articles = result;
db.collection('categories').find({}).toArray(function(err, result) {
assert.equal(err);
categories = result;
db.close();
callback(articles, categories);
});
});
};
var combine = function(articles, categories, callback) {
categories.forEach(function(category) {
nav[category.title] = {};
articles.forEach(function(article) {
if(article.category == category.name) {
nav[category.title][article.title] = "link";
}
})
});
callback(nav);
};
As of line 6, I do have all data I need.
(An object, currenty like { Home: '/', Uncategorized: { 'Hello world!': 'link' } })
But since I'm in an anonymous function, I don't know how to return that value. I mean, return would just return it the function that called it... And in the end, MongoClient.connect would receive my data.
If I set a variable instead, it would be set as module.exports returned before Node can even query the data from the database, right?
What can I do in order to make this work?
It should result in some kind of function, like
var nav = require('nav');
console.log(nav());
Thanks in advance!

Answer 1

Add another callback:
var nav = { Home: "/" };
module.exports = function(cb) {
MongoClient.connect(process.env.MONGO_URL, function(err, db) {
assert.equal(err, null);
fetchData(db, function(articles, categories) {
combine(articles, categories, function(sitemap) {
cb(sitemap);
})
});
})
});
And then use this way:
var nav = require('nav');
nav(function(sitemap){ console.log(sitemap); });

Answer 2

You can use mongoose module or monk module. These modules have been tested properly .
Just use
npm install mongoose or monk

Answer 3

The suggestion about mongoose is great and you can look into it, however I think you've already done the job with the fetching of the data from the db. You just need to access it in your main node flow.
You can try this:
module.exports.generateNav = function() {
MongoClient.connect(process.env.MONGO_URL, function(err, db) {
assert.equal(err, null);
var output = fetchData(db, function(articles, categories) {
combine(articles, categories, function(sitemap) {
})
});
return (output);
});
};
And then in your main application you can call it in the following way:
var nav = require('nav');
navigation = nav.generateNav();
console.log(navigation);