Part III is the reference section for the core API.
“Array” in this part of the book, for example. Part IV is
“Canvas” in this part of the book to read about the graphics API defined
by the HTML5
<canvas> element, for example.
This book covers low-level fundamentals first, and then builds on those to more advanced and higher-level abstractions. The chapters are intended to be read more or less in order. But learning a new programming language is never a linear process, and describing a language is not linear either: each language feature is related to other features and this book is full of cross-references—sometimes backward and sometimes forward to material you have not yet read. This chapter makes a quick first pass through the core language and the client-side API, introducing key features that will make it easier to understand the in-depth treatment in the chapters that follow.