How can I share code between Node.js and the browser?

I am creating a small application with a JavaScript client (run in the browser) and a Node.js server, communicating using WebSocket.

I would like to share code between the client and the server. I have only just started with Node.js and my knowledge of modern JavaScript is a little rusty, to say the least. So I am still getting my head around the CommonJS require() function. If I am creating my packages by using the ‘export’ object, then I cannot see how I could use the same JavaScript files in the browser.

I want to create a set of methods and classes that are used on both ends to facilitate encoding and decoding messages, and other mirrored tasks. However, the Node.js/CommonJS packaging systems seems to preclude me from creating JavaScript files that can be used on both sides.

I also tried using JS.Class to get a tighter OO model, but I gave up because I couldn’t figure out how to get the provided JavaScript files to work with require(). Is there something am I missing here?

Answer

If you want to write a module that can be used both client side and server side, I have a short blog post on a quick and easy method: Writing for Node.js and the browser, essentially the following (where this is the same as window):

(function(exports){

    // Your code goes here

   exports.test = function(){
        return 'hello world'
    };

})(typeof exports === 'undefined'? this['mymodule']={}: exports);

Alternatively there are some projects aiming to implement the Node.js API on the client side, such as Marak’s gemini.

You might also be interested in DNode, which lets you expose a JavaScript function so that it can be called from another machine using a simple JSON-based network protocol.