Node: Up and Running

Chapter 3. Building Robust Node Applications

To make the most of the server-side JavaScript environment, it’s important to understand some core concepts behind the design choices that were made for Node.js and JavaScript in general. Understanding the decisions and trade-offs will make it easier for you to write great code and architect your systems. It will also help you explain to other people why Node.js is different from other systems they’ve used and where the performance gains come from. No engineer likes unknowns in her system. “Magic” is not an acceptable answer, so it helps to be able to explain why a particular architecture is beneficial and under what circumstances.

This chapter will cover the coding styles, design patterns, and production know-how you need to write good, robust Node code.

The Event Loop

A fundamental part of Node is the event loop, a concept underlying the behavior of JavaScript as well as most other interactive systems. In many languages, event models are bolted onto the side, but JavaScript events have always been a core part of the language. This is because JavaScript has always dealt with user interaction. Anyone who has used a modern web browser is accustomed to web pages that do things “onclick,” “onmouseover,” etc. These events are so common that we hardly think about them when writing web page interaction, but having this event support in the language is incredibly powerful. On the server, instead of the limited set of events based on the user-driven ...