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You Don't Know JS: Types & Grammar

(You Don't Know JS #4)

4.49  ·  Rating details ·  614 ratings  ·  26 reviews
No matter how much experience you have with JavaScript, odds are you don't fully understand the language. As part of the "You Don't Know JS" series, this compact guide explores JavaScript types in greater depth than previous treatments, defining the problems of coercion, demonstrating why types work, and showing developers how to take advantage of those features.

The type s
Paperback, 182 pages
Published February 21st 2015 by O'Reilly Media (first published August 25th 2014)
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Aug 17, 2017 rated it it was amazing
Essential reading for anyone working with JavaScript.

Beginners will get a good grounding in the basics of the language types and grammar and it goes into enough detail for experts to learn something too.

I think this is the third or fourth book in the series, but in my opinion, it should be the second. There's nothing in here that you need the second or third books (Scope and Closure, and this & Object Prototypes) to understand.

It's all quite basic, but very important if you want to really unde
Daniel Gormly
Feb 16, 2017 rated it really liked it
Still an important read but less mind-blowing and more frustrating than the other books due to the persnickety nature of coercion in JS. Kyle's ardent defense of the language is no less admirable but slightly more difficult to stomach here!
Hưng Đặng
Jan 22, 2019 rated it really liked it
Shelves: it-books
The first part of this book is about data types and some quirks of the language with data type. Let me give an evil example:
`0.1 + 0.2 === 0.3 // false`
To be able to understand this peculiarity, we must dig somewhat deeper into floating-point value which IEEE 754 (I can't stand it the first time I heard this name, now I come to term with it) document would mention.
Each data types has their own weirdness that I would not spoil it here.
One thing I like about the book is its recommendations about b
May 23, 2019 rated it it was amazing
This book is not as interesting or intriguing as other books in the series because it goes through the basic stuff then it's basically a list of Gotchas and quirks in the language logic. I gave it 5 stars because Kyle's explanations and examples are amazing even if the material itself is dull.
Jon Jones
Dec 25, 2019 rated it it was amazing
All books in this series are essential reads of any Javascript developer. Types are the basic building block of every programming language, so understanding them properly is key. The part of the book I learn the most from was around coercion, how it works and the difference between implicit and explicit conversations. The bok has definitely changed the way I think about some of the 'bad patterns' other books have recommended avoiding completely.
This is a usefull book which helps you to understand the type system lying in foundation of the language. You will understand what a mess js types are but you'll be able to navigate through that mess easyly. There is a side-effect: you may become resistant to JS type coersion WTF jokes because coresion rules will become straightforward and reasonable for you.
Dec 01, 2017 rated it it was amazing
Excellent and comprehensive.

Although the content isn't organized in a strict way. I would also urge people not to follow author's advices always in terms of style (=== vs ==) and make their own opinions. Also the authors sometimes is too defensive about JS.

But definitely recommended. Did I mention it is free?
Ryan Day
Jul 12, 2017 rated it it was amazing
I've never read a book about JavaScript like this. Simpson puts aside everything you've learned about JavaScript over the years and digs into the spec to find out how the language really works. You Don't Know JS makes JavaScript feel like a new and exciting language again.
Yanjia Li
Jun 21, 2017 rated it it was amazing  ·  review of another edition
Solid and well rounded introduction of low level JS

Literally JavaScript: The Bad Part. However, it helps you understand how JS works underneath those fancy ES5/6/7 syntax. Recommend for experienced JS developers.
Pankaj Phartiyal
May 10, 2017 rated it it was amazing
A must read for Javascript Developers
Oct 18, 2017 rated it it was amazing
Seriously Guys, If you want to learn Javascript this book-series is the best ......
Stop whatever you are doing and read this book if you haven't yet.
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Basics for Java Script... essential for those beginners...
Dec 01, 2017 rated it it was amazing
Recommend this to any JS developer.
May 23, 2018 rated it really liked it
Solid overview on the language semantics and grammar. Sometimes a lot of this goes over my head, but I came out with a lot to think about. Overall a solid read!
Ten Zhi
Jan 09, 2019 rated it it was amazing
very good examples and easy pacing for people who are slow to understand concepts.
Apr 01, 2019 rated it really liked it
This book is as great as JavaScript isn't...
Divyanshu Maithani
Feb 08, 2020 rated it it was amazing
Always bet on JavaScript!
Anh Trinh
Apr 08, 2020 rated it really liked it
Many helpful information, especially Natives and Coercion.
Franco Risso
Jun 15, 2016 rated it it was amazing  ·  review of another edition
Shelves: programming
Exceptionally well explained book about the nuances of JS for types and grammar. You can learn here that using implicit coercion is not as bad as you can imagine right now, and remove that lint rule of forcing strict comparison from your project!
Jan 30, 2017 rated it it was amazing  ·  review of another edition
This book is very in-depth to the workings of type coercion and the grammar of javascript. However, it does not go too far to the low level implementation of javascript. Just explained the different standards and how they affect the usage of the language.
Marc Udoff
Nov 25, 2015 rated it really liked it
A good read on JS to understand each of the primitive types, boxing and unboxing, comparison (== vs. ===), and other got you's of the language. Geared towards an intermediate JS programmer more than anyone else. Good to have read once.
Abdulfattah Popoola
Feb 01, 2017 rated it it was amazing
Great insights! Great read!!
Oct 09, 2014 rated it really liked it
Shelves: 2016_read
Good review of fundamentals related to types, coercion and grammar.
Eder Sanchez
Apr 25, 2016 rated it really liked it
Como en todos sus libros hay gotchas interesantes y explicaciones detalladas de los mecanismos del lenguaje, pero la actitud del autor me hace querer odiarlo.
Dave Peticolas
Dec 13, 2015 rated it liked it
Another solid work in this series.
Jul 22, 2015 rated it really liked it
Shelves: coleccion
clarifies trivial misconceptions about JS (especially with castings, operator precedence, etc)
rated it it was amazing
Jun 26, 2016
Rafael Paulo
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Jul 06, 2019
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Oct 24, 2018
Ankit Goel
rated it really liked it
Dec 26, 2019
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Kyle Simpson is an Open Web Evangelist from Austin, TX, who's passionate about all things JavaScript. He's an author, workshop trainer, tech speaker, and OSS contributor/leader.

Other books in the series

You Don't Know JS (6 books)
  • You Don't Know JS: Up & Going
  • You Don't Know JS: Scope and Closures (You Don't Know JS, #2)
  • You Don't Know JS: this & Object Prototypes
  • You Don't Know JS: Async & Performance
  • You Don't Know JS: ES6 & Beyond

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