Node.js Module.Exports Undefined Empty Object

I have the following files.

index.js

module.exports = {
    "first": require('./1.js'),
    "second": require('./2.js'),
    "third": require('./3.js')
};

1.js

module.exports = "Hello";

2.js

module.exports = "World";

3.js

const utils = require('./');
module.exports = `${utils.first} ${utils.second}`;

run.js

const utils = require('./');
console.log(utils.first);
console.log(utils.second);
console.log(utils.third);

Why is it that when I run node run.js that it prints the following?

Hello
World
undefined undefined

I expect it to print

Hello
World
Hello World

Answer

This is because at the time of running 3.js the index.js file has not been fully defined yet. In order to fix this you have to require the files specifically. For example changing 3.js to the following will work.

const first = require('./1.js');
const second = require('./2.js');
module.exports = `${first} ${second}`;