Retrieving data from MongoDB using NodeJS with Express

Question

Okay, so in the past few days I started messing with Node (because I think I should learn something that is actually useful and might get me a job). Right now, I know how to serve pages, basic routing and such. Nice. But I want to learn how to query databases for information.

Right now, I'm trying to build an app that serves as a webcomic website. So, in theory, the application should query the database when I type in the url http://localhost:3000/comic/<comicid>

I have the following code in my app.js file:

router.get('/', function(req, res) {  
    var name = getName();
    console.log(name); // this prints "undefined"

    res.render('index', {
        title: name,
        year: date.getFullYear()
    });
});

function getName(){
    db.test.find({name: "Renato"}, function(err, objs){
    var returnable_name;
        if (objs.length == 1)
        {
            returnable_name = objs[0].name;
            console.log(returnable_name); // this prints "Renato", as it should
            return returnable_name;
        }
    });
}

With this setup I get console.log(getName()) to output "undefined" in the console, but I have no idea why it doesnt get the only element that the query can actually find in the database.

I have tried searching in SO and even for examples in Google, but no success.

How the hell am I supposed to get the parameter name from the object?

Answer 1

NodeJs is async. You need a callback or Promise.

router.get('/', function(req, res) {
    var name = '';
    getName(function(data){
        name = data;
        console.log(name);

        res.render('index', {
            title: name,
            year: date.getFullYear()
        });
    });
});

function getName(callback){
    db.test.find({name: "Renato"}, function(err, objs){
        var returnable_name;
        if (objs.length == 1)
        {
            returnable_name = objs[0].name;
            console.log(returnable_name); // this prints "Renato", as it should
            callback(returnable_name);
        }
    });
}