This chapter answers questions you may have and gives tips for reading this book.
This book is three books in one:
The quizzes and exercises play an important part in helping you practice and retain what you have learned.
As your knowledge evolves, you can later come back to some or all of the advanced content.
The bonus chapters are only available in the paid versions of this book (print and ebook). They are listed in the full table of contents.
The home page of this book describes how you can buy them.
The HTML version of this book (online, or ad-free archive in the paid version) has a link at the end of each chapter that enables you to give feedback.
The receipt email for the purchase includes a link. You’ll always be able to download the latest version of the files at that location.
If you opted into emails while buying, then you’ll get an email whenever there is new content. To opt in later, you must contact Payhip (see bottom of
For example, you may see:
That is called the type signature of
Number.isFinite(). This notation, especially the static types
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.
Explains how to best read the content.
Points to additional, external, content.
Gives a tip related to the current content.
Asks and answers a question pertinent to the current content (think FAQ).
Warns about pitfalls etc.
Provides additional details, complementing the current content. It is similar to a footnote.
Mentions the path of a test-driven exercise that you can do at that point.
Indicates that there is a quiz for the current (part of a) chapter.