Query mongodb and pass results to to http server in node.js

Question

I am fairly new to javascript, and I want to use node.js to query a mongodb database in order to pass it to an http server.

So far, I have successfully set up a "Hello, world!" http server using this script:

var http = require('http');

http.createServer(function (req, res) {
       res.write('Hello World!');
       res.end();
}).listen(8080);

I've also been able to query my mongodb database and print the results to the console:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/MYDB";

MongoClient.connect(url, function(err, db) {
        if (err) throw err;
        db.collection("collection").find({}).toArray(function(err, result) {
                if (err) throw err;
                console.log(result);
                db.close();
        })
});

However, I am unable to pass the results of my query to the res object of the http server. I would like to do something like this:

var http = require('http');
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/MYDB";

http.createServer(function (req, res) {
    MongoClient.connect(url, function(err, db) {
        if (err) throw err;
        db.collection("collection").find({}).toArray(function(err, result) {
            if (err) throw err;
            var query = result;
            db.close();
        })
    });

    res.write(query);
    res.end();

}).listen(8080);

When I try to create the query variable inside of the the MongoClient connection and use it later, I get an error that query is not defined . I can't find any examples of MongoClient.connect that don't simply print the result to the console, so I'm stuck.

Thanks for the help.

Answer 1

db.collection("collection").find({}) is async function, you should send the result to the client inside of the callback:

http.createServer(function (req, res) {
    MongoClient.connect(url, function(err, db) {
        if (err) throw err;
        db.collection("collection").find({}).toArray(function(err, result) {
            if (err) throw err;
            var query = result;
            db.close();
            res.write(query);
            res.end();
        });
    });
}).listen(8080);