gistfile1.js

// base.js
var base = function() {
};
base.prototype = { 
};
exports.base = base;

// test.js
var base = require("./base").base, 
    sys = require("sys");

sys.puts(base.prototype);
base.prototype.test = function() {
  return "yes."
};

var t = new base();
sys.puts(t.test());

/*
tmpvar@tmpvar:/tmp$ node test.js 
undefined
TypeError: Cannot set property 'test' of undefined
    at Object.<anonymous> (/tmp/test.js:6:21)
    at [object Object].<anonymous> (node.js:938:23)
    at [object Object].emitSuccess (node.js:241:15)
    at [object Object].<anonymous> (node.js:655:21)
    at [object Object].emitSuccess (node.js:241:15)
    at node.js:511:29
    at node.js:995:9
*/