Node.js Export Troubles

Question

I'm curious about the way NodeJS exports it's modules. I know to export a method, we write the exports keyword.methodname.

However, my module is a connection:

//Require mysql connector that you installed with npm
var mysql      = require('mysql');

var conn_conf = {
    host     : 'localhost',
    port     : 3306,
    user     : 'root',
    password : 'root',
    database : 'nutrition_tracker'
}

var connection = mysql.createConnection(conn_conf);

connection.connect(function(err) {
    if(err) console.log("Could not connect to DB");
    else{
        console.log("Connected to "+conn_conf.database+' on '+conn_conf.host );

    }
});

Then in the file that requires it:

var db2 = require('../db/mysql_conn');

console.log(db2)

But everytime, db2 is {}. I can't understand why - shouldn't me requiring the module give me the connection? I even tried returning the connection within the module, but the same thing - db2 was {}.

Answer 1

Add this line at the end of your module file:

exports = module.exports = connection;

Note that your approach is flawed as you don't know what is the status of the connection returned by your require() call. You might send a query before the connection was opened.

A better approach would be to export a factory function instead:

exports = module.exports = function(cb) {
   // your code as above
   // ...

   connection.connect(function(err) {
     if(err) {
       console.log("Could not connect to DB");
       cb(err);
     } else {
       console.log("Connected to "+conn_conf.database+' on '+conn_conf.host );
       cb(null, connection);
     }
   });
};

And use it this way:

var createDb = require('../db/mysql_conn');
createDb(function(err, db2) {
   console.log(db2);
});