How to reference a variable inside a module.exports in Node.js

Question

I have a module written like below:

module.exports = {
    port: '1337',
    facebook: {
        clientID: '123456789',
        clientSecret: 'a1b2c3d4e5f6g7h8i9j0k',
        callbackURL: 'http://localhost:1337/oauth/facebook/callback'
    }
};

What I would like to do is use the port variable in the callbackURL:

callbackURL: 'http://localhost:1337/oauth/facebook/callback'

I tried:

callbackURL: 'http://localhost:'+ this.port +'/oauth/facebook/callback'

but obviously that's not correct since the facebook is another object. So, can someone solve this one, and please any additional reading that you have (in terms of deeper understanding) is welcome.

Answer 1

Just declare it above the module.exports as an ordinary variable:

var port = '1337';
module.exports = {
    port,
    facebook: {
        clientID: '123456789',
        clientSecret: 'a1b2c3d4e5f6g7h8i9j0k',
        callbackURL: 'http://localhost:'+ port + '/oauth/facebook/callback'
    }
};

You can put module.exports wherever you want in your file, you can even perform some logic (like retrieving settings from a file or another resource).