You already know how to use JavaScript in the browser, so we will first focus on getting you acclimated to this different environment. When we are done, you will have a much better sense of how to separate the JS programming language from browser-specific and Node-specific features.

Node is not just a server-side JavaScript runtime, it also includes a robust collection of libraries or “core modules” for managing the filesystem, streaming data, events and more! We will get some hands-on experience with a broad array of commonly-used libraries, so you know what is available and when to reach for it.

Node comes with some great foundational support for both low and high-level networking. We will begin with writing a program that manages a TCP socket directly, then upgrade it to a turnkey HTTP server to build a simple web application.

Node applications run on a single thread, but they can start new processes and communicate with them to form a distributed system. We will look at several use cases for doing something like this, and study how the Actor Concurrency Model helps keep inter-process communication simple and cheap.

Express is, by a fairly large margin, the most popular web application framework for Node.js. It can be used to respond to HTTP requests with JSON, HTML, or pretty much anything else.

You may already be using some Node-friendly testing tools and assertion libraries. We will focus mostly on Mocha, a flexible and straightforward testing framework that works equally well for server and client-side code.