I am trying get value from database. Trying it out with a demo example. But I am having problem to synchronize the calls, tried using callback function. I am beginner in node.js, so don't know if this is the right way.

FILE 1 : app.js

var data;



var db = require('./db.js');



var query = 'SELECT 1 + 1 AS solution';



var r = db.demo(query, function(result) { data = result; });



console.log( 'Data : ' + data);

FILE 2 : db.js

var mysql      = require('./node_modules/mysql');



var connection = mysql.createConnection({

    host     : 'localhost',

    user     : 'root',

    password : 'root',

});



module.exports.demo = function(queryString, callback) {

    try {

        connection.connect();

        console.log('Step 1');



        connection.query(queryString, function(err, rows, fields) {

            console.log('Step 2');

            if (err) {

                console.log(ERROR :  + err);

            }

            console.log('The solution is: ', rows[0].solution);



            callback(rows[0].solution);



            return rows[0].solution;

        });

        callback();



        connection.end();

        console.log('Step 3');

    }

    catch(ex) {

        console.log(EXCEPTION :  + ex);

    }

};

OUTPUT :

Step 1

Step 3

Data : undefined

Step 2

The solution is:  2

Referred to this question also, but it didnt solve my problem :
nodeJS return value from callback