app.js

"use strict";

var contrivedFoo = require('./contrivedFoo');

contrivedFoo.foo();

contrivedBar.js

"use strict";

exports.bar = bar;

var contrivedFoo = require('./contrivedFoo');

function bar() {
  return contrivedFoo.contrived + 'bar';
}

contrivedFoo.js

"use strict";

exports.id = 0;
exports.contrived = 'foo';
exports.foo = foo;

var contrivedBar = require('./contrivedBar');

function foo() {
  exports.id++;
  return {
    id: exports.id,
    bar: contrivedBar.bar()
  };
}