There's plenty of cool stuff Node offers purely in terms of server-side architectures, but it also offers a way to solve a problem we've been wrestling with since client-side applications became a big deal: writing everything twice. Rather than having the templates that produce markup exist in one backend language and in JavaScript, you can reuse them. Instead of validating in JavaScript on the client for the user's convenience and then again in some other language on the server for security, you can share a validation module that can be used in both scenarios. And so on. We'll look at some of the ways to stop repeating ourselves in Node apps and focus on getting the most out of existing client-side code.