One of the most distinctive patterns in Node.js is definitely middleware. Unfortunately, it's also one of the most confusing for the inexperienced, especially for developers coming from the enterprise programming world. The reason for the disorientation is probably connected to the meaning of the term middleware, which in enterprise architecture jargon represents the various software suites that help to abstract lower-level mechanisms such as OS APIs, network communications, memory management, and so on, allowing the developer to focus only on the business case of the application. In this context, the term middleware recalls topics such as CORBA, Enterprise Service Bus, Spring, JBoss, but in its more generic meaning it can also define any kind of software layer that acts like a glue between lower-level services and the application (literally the software in the middle).
Express (http://expressjs.com) popularized the term middleware in the Node.js world, binding...