console.md

first.js

var first = global.first = {
	foo: 'bar'
};

var second = require('./second');
var third = require('./third');

console.log();
second();
third();

first.foo = 'baz';

console.log();
second();
third();

second.js

module.exports = function () {
	console.log('second - first.foo:', first.foo);
	first.baz = 'bang';
};

third.js

module.exports = function () {
	console.log('third - first.foo:', first.foo);
	console.log('third - first.baz:', first.baz);
};