Node.js实践 is a document about Node.js. It discusses how Node.js allows JavaScript to be used for server-side applications by providing a fast, scalable, and flexible environment. Node.js uses a single thread with non-blocking I/O and the V8 JavaScript engine. It also uses an event-driven architecture. This allows JavaScript to be used beyond just client-side applications in the browser. It also discusses how libraries like YUI3 and jQuery can be used in Node.js applications both on the front-end and back-end.