Node.js - how to attach properties to one single object in multiple files?

I want to attach a lot of properties to a single object. I do not want to do this in one single file. Is the example below a correct and good way to break this into multiple files?

For example, in main.js,

var obj = {};

obj = require('./utils');
obj = require('./part1');
// other requires omitted...

obj.init = function() {
  obj.util1();
  obj.helper1();
};

module.exports = obj;

in utils.js,

var obj = require('./main');

obj.util = function() {
  console.log('util1');
};

// other methods omitted...

module.exports = obj;

in part1.js,

var obj = require('./main');

obj.helper1= function() {
  obj.util1();
  console.log('helper1');
};

// other methods omitted...

module.exports = obj;

and there are part2.js, part3.js, etc.

You see there is circular dependency in the files. Is there a better way than the example above?