The book is the authoritative reference guide to the language. Without using the formal and inaccessible language of the W3C specifications, it tells the reader exactly what every construct in the language does, and how it is intended to be used. It is a reference rather than a tutorial; it is designed for the professional programmer who is using the language every day. It is the book that people quote when they claim that a particular product is giving the wrong answer, and the book that implementers of the language turn to when they want clarification of the specifications. At the same time, the book is readable. Reviews of the previous editions show that readers appreciate the background material on the design thinking behind the language, the essay on functional programming, the occasional dry wit, the gentle criticism of the language specification when appropriate, and the fact that the examples stray into a diverse range of interesting application areas.