Node.js is a JavaScript interpreter and runtime system which has made the use of JavaScript a feasible and attractive option for server-side programming. Its combination of an efficient interpreter with an event-driven library makes Node.js especially suitable for Web applications that deal with many requests. Express is a Web application framework built on top of Node.js that relieves developers of the burden of some of the repetitive tasks of Web development. Written for professional and student Web developers, this book provides a clear and concise introduction to the kind of JavaScript programming that will allow readers to take advantage of Node.js and Express to create Web applications. Drawing on a deep understanding of programming languages and many years of practical experience in Web application development, the authors explain functions and objects, Node.js's system of modules, and the use of callbacks in asynchronous programming. A small complete application, using Express and a relational database, is built and described in detail. The two final chapters are devoted to the important topic of testing. Clear key points summarize each section, links to relevant Web sites are included, and technical terms are defined in an 8-page glossary. Topics covered include: • Functions and closures • Objects and prototypes • Modules • Asynchronous callbacks and events • Building a simple application using Express • Unit testing and integration testing This is not a general introduction to JavaScript. It is assumed that readers already have some experience using JavaScript for client-side scripting and are familiar with the basic syntax, built-in data types and control structures. A short book in the "Web Development Topics" series, by the well-known authors Nigel and Jenny Chapman.