Despite the author’s idiocy regarding software licencing, and his sometimes opinionated… well, opinion on certain things’ evilness, this is a rock-solid book (if you ignore the hints to use his nōn-free software) explaining, to a somewhat versed programmer new to ECMAscript, about the intricacies of the almost-a-bit-functional programming language, and what language constructs to best avoid (“==” (use “===” instead), or the stuff added to make it look like Java™).

For example, you will learn why code breaks when you add or remove the “var” in front of an assignment, and what these “(function () { return function () {…}})();” are for, and why.

This is a pocket reference every programmer that has to touch any ECMAscript code ought to be required to read and understand first. Granted (as per Chad’s review), nowadays (in 2017) most everyone uses some framework(s) to abstract from the foundation of both the language and the runtime environment (browser — which the book does not handle in detail, it concentrates on the language itself), but even to cobble those things together, perhaps adding a dash of business logic in the process, or to understand the “why” behind a framework (especially when inspecting its source code during debugging), I consider this still a required read.