JavaScript for impatient programmers (beta)
Please support this book: buy it or donate
(Ad, please don’t block.)

2. FAQ: book

This chapter answers questions you may have and gives tips for reading this book.

2.1. What should I read if I’m really impatient?

Do the following:

Then this book should be a fairly quick read.

2.2. Why are some chapters and sections marked with “(advanced)”?

Several chapters and sections are marked with “(advanced)”. The idea is that you can initially skip them. That is, you can get a quick working knowledge of JavaScript by only reading the basic (non-advanced) content.

As your knowledge evolves, you can later come back to some or all of the advanced content.

2.3. Why are some chapters marked with “(bonus)”?

Bonus chapters are only available in the paid versions of this book (print and ebook). They are listed in the full table of contents.

2.4. How do I submit feedback and corrections?

The HTML version of this book (online, or ad-free archive in paid version) has a link at the end of each chapter that enables you to give feedback.

2.5. How do I get updates for the downloads I bought at Payhip?

2.6. I’m occasionally seeing type annotations – how do those work?

For example, you may see:

Number.isFinite(num: number): boolean

Type annotations such as “: number” and “: boolean” are not real JavaScript. They are a notation for static typing, 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 type notation is explained in detail in a blog post on 2ality.

2.7. What do the notes with icons mean?


Explains how to best read the content or points to additional reading elsewhere (in the book or externally).


Gives tips related to the current content.


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.