a.js

exports.getC = function () {
    return c;
};

var c = require("./c");

b.js

exports.getC = function () {
    return c;
};

var c = require("./c");

c.js

require("./b");
module.exports = "Hello, Dave.";

d.js

var a = require("./a");
var b = require("./b");
var sys = require("sys");
sys.puts(a.getC());
sys.puts(b.getC());