1 About this book

1.1 Where is the homepage of this book?

The homepage of “Deep JavaScript” is exploringjs.com/deep-js/

1.2 What is in this book?

This book dives deeply into JavaScript:

• It teaches practical techniques for using the language better.
• It teaches how the language works and why. What it teaches is firmly grounded in the ECMAScript specification (which the book explains and refers to).
• It covers only the language (ignoring platform-specific features such as browser APIs) but not exhaustively. Instead, it focuses on a selection of important topics.

1.3 What do I get for my money?

If you buy this book, you get:

• The current content in four DRM-free versions:
  • PDF file
  • ZIP archive with ad-free HTML
  • EPUB file
  • MOBI file
• Any future content that is added to this edition. How much I can add depends on the sales of this book.

The current price is introductory. It will increase as more content is added.

1.4 How can I preview the content?

On the homepage of this book, there are extensive previews for all versions of this book.

1.5 How do I report errors?

• The HTML version of this book has a link to comments at the end of each chapter.
• They jump to GitHub issues, which you can also access directly.

1.6 Tips for reading

• You can read the chapters in any order. Each one is self-contained but occasionally, there are references to other chapters with further information.
• The headings of some sections are marked with “(optional)” meaning that they are non-essential. You will still understand the remainders of their chapters if you skip them.

1.7 Notations and conventions

1.7.1 What is a type signature? Why am I seeing static types in this book?

For example, you may see:

Number.isFinite(num: number): boolean

That is called the type signature of Number.isFinite(). This notation, especially the static types number of num and boolean of the result, are not real JavaScript. The notation is borrowed from the compile-to-JavaScript language TypeScript (which is mostly just JavaScript plus static typing).

Why is this notation being used? It helps give you a quick idea of how a function works. The notation is explained in detail in a 2ality blog post, but is usually relatively intuitive.

1.7.2 What do the notes with icons mean?

1.8 Acknowledgements

• Thanks to Allen Wirfs-Brock for his advice via Twitter and blog post comments. It helped make this book better.

• More people who contributed are acknowledged in the chapters.