Node.js module to fetch data from MongoDB database

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!

I have posted an answer. Hopefully correct as I don't have an ability to test it right now. Write a comment if you encounter any errors. — Nonemoticoner
– Nonemoticoner, Commented Jun 19, 2016 at 17:55

Nonemoticoner · Accepted Answer · 2016-06-19 17:51:37Z

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); });

answered Jun 19, 2016 at 17:51

Nonemoticoner

6485 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

user6485949 · Accepted Answer · 2016-06-19 17:24:54Z

1

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

Just use

npm install mongoose or monk

answered Jun 19, 2016 at 17:24

user6485949

1 Comment

sk22 Over a year ago

That should still work with the official module, somehow. If I can't find an solution, I'll try mongoose. Thanks for the suggestion!

Neekoy · Accepted Answer · 2016-06-19 17:34:05Z

0

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);

answered Jun 19, 2016 at 17:34

Neekoy

2,5625 gold badges36 silver badges54 bronze badges

3 Comments

sk22 Over a year ago

That was also my idea. But, you seem to not really understand my problem... If I add a return statement to fetchData, the data is passed to db.collection('categories').find({}).toArray, which does not make any sense...

Nonemoticoner Over a year ago

fetchData function is asynchronous. I hardly see that work the way you written that here. output will be most likely undefined.

sk22 Over a year ago

@Nonemoticoner Correct.

Collectives™ on Stack Overflow

Node.js module to fetch data from MongoDB database

3 Answers 3

Comments

1 Comment

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related