How to manage multiple JS files server-side with Node.js

You do not want a common namespace because globals are evil. In node we define modules

// someThings.js

(function() {
    var someThings = ...;

    ...

    module.exports.getSomeThings = function() {
        return someThings();
    }

}());

// main.js

var things = require("someThings");
...
doSomething(things.getSomeThings());

You define a module and then expose a public API for your module by writing to exports.

The best way to handle this is dependency injection. Your module exposes an init function and you pass an object hash of dependencies into your module.

If you really insist on accessing global scope then you can access that through global. Every file can write and read to the global object. Again you do not want to use globals.