Node.js is a server-side JavaScript platform that allows developers to build fast and scalable applications using JavaScript outside of web browsers. It is playing an ever-wider role in the software development world, having started as a platform for server applications but now seeing wide use in command-line developer tools and even in GUI applications, thanks to toolkits such as Electron. Node.js has liberated JavaScript from being stuck in the browser.
It runs on top of the ultra-fast JavaScript engine at the heart of Google's Chrome browser, V8. The Node.js runtime follows an ingenious event-driven model that's widely used for concurrent processing capacity despite using a single-thread model.
The primary focus of Node.js is high-performance, highly scalable web applications, but it is seeing adoption in other areas. For example, Electron, the Node.js-based wrapper around the Chrome engine, lets Node.js developers create desktop GUI applications and is the foundation on which many popular applications have been built, including the Atom and Visual Studio Code editors, GitKraken, Postman, Etcher, and the desktop Slack client. Node.js is popular on Internet of Things devices. Its architecture is especially well suited to microservice development and often helps form the server side of full-stack applications.
The key to providing high throughput on a single-threaded system is Node.js's model for asynchronous execution. It's very different from platforms that rely on threads for concurrent programming, as those systems often have high overheads and complexity. By contrast, Node.js uses a simple event dispatch model that originally relied on callback functions but today relies on the JavaScript Promise object and async functions.
Because Node.js is on top of Chrome's V8 engine, the platform is able to quickly adopt the latest advances in the JavaScript language. The Node.js core team works closely with the V8 team, letting it quickly adopt new JavaScript language features as they are implemented in V8. Node.js 14.x is the current release and this book is written for that release.
