Some principles and design patterns literally define the Node.js platform and its ecosystem; the most peculiar ones are probably its asynchronous nature and its programming style that makes heavy use of callbacks. However, there are other fundamental components that characterize the platform; for example, its module system, which allows multiple versions of the same dependency to coexist in an application, and the observer pattern, implemented by the EventEmitter class, which perfectly complements callbacks when dealing with asynchronous code. It's therefore important that we first dive into these fundamental principles and patterns, not only for writing correct code, but also to be able to take effective design decisions when it comes to solving bigger and more complex problems.

Another aspect that characterizes Node.js is its philosophy. Approaching Node.js is in fact way more than simply learning a new technology; it's also embracing a culture and a community. We will see how this greatly influences the way we design our applications and components, and the way they interact with those created by the community.

In this chapter, we will learn the following topics: