Node.js模块从MongoDB数据库中获取数据

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

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

Just use

npm install mongoose or monk

Answer 2

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 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);