Node for Front-End Developers

Sharing Modules Between the Client and Server

Files within your application’s public directory can be served by your application, of course, by they can also be used by it. If there’s a module providing some business logic you need for both the client and server, it’s fragile to try and store it in two places—the better strategy is to reference it from a single location. If you’re using Require.js or similar on the client-side this is very easy because you can import the module the same way in both places, but even if you’re not, you can share code.

Because of the possibilities that reusing client-side code offers, there are numerous utilities to create an unrendered DOM in Node, enabling client-side code to run unmodified on the server. These things aren’t likely to disappear—they can be necessary for scraping or spidering content, for example. Because window or document objects may be created on the server by these tools, in shared modules it’s safer to test whether we’re on the server-side than whether we’re on the client. One way to do this is to look for the process object:

(function(ns) {
  ns.modul = function() {
    console.log("works!");
  };
  return ns;
}((typeof process !== "undefined" && process.title === "node")
    ? exports : myapp));

On the server, this will pass exports into our function to use as a parent object. On the client, we can hardcode the global namespace being used there. Our module will attach whatever it exposes to that object without having to worry about the context ...