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You Don't Know JS: Async & Performance
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You Don't Know JS: Async & Performance

(You Don't Know JS #5)

4.28  ·  Rating details ·  318 Ratings  ·  20 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 concise yet in-depth guide focuses on new asynchronous features and performance techniques--including Promises, generators, and Web Workers--that let you create sophisticated single-page web applications and escape callba ...more
Paperback, 296 pages
Published March 9th 2015 by O'Reilly Media (first published September 25th 2014)
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Daniel R.
Jun 24, 2015 rated it liked it
This book dives deep into various techniques for handling asynchronous operations in JavaScript. In particular the simplicity and drawbacks of callbacks are outlined with suggestions to address them as the cost of added code complexity. The chapter on promises is one of the best that I've read and walks through great examples of chaining and the power of composing. The chapter on generators focuses on modeling asynchronous code in a more synchronous manner. I was unconvinced and found the code e ...more
Ilya Ivanov
Sep 12, 2016 rated it it was amazing
I have never imagined that there are so many concerns not with callbacks, but regarding promises as well.

Wonderful book on handling async requests via callbacks, promises and handling them via generators. Kyle looks ahead a bit into ES7 async\await features.

Last two chapters cover web performance, from general topics: Web Workers, SIMD, asm.js, to very specific ones: benchmarking pieces of js code, figuring out crucial path. I will definitely take a look at

Eder Sanchez
Jun 27, 2016 rated it really liked it
La primera mitad se puede saltar si se entiende bien como funcionan las promesas, la segunda se pone mas interesante con los generadores y performance.
Aug 26, 2018 rated it liked it
This book should have ended with chapter 4.

Chapters 1-4 deal with the "Async" stuff.
Chapter 1 starts with a general introduction to concurrency and asynchrony and how it is managed in JavaScript via the event queue.
chapter 2 describes callbacks: the pre-ECMAScript 6 way to manage asynchrony and focuses on its limitations.
Chapter 3 details every possible aspect of Promises and how they solve the limitations of callbacks.
Chapter 4 deals with Generators: another welcome new feature of ECMAScript 6
Sathish Paul
Aug 09, 2017 rated it really liked it
A fantastic exploration of what "async" means in the context of JavaScript. I was amazed at the depth of explanation provided especially for the Promises chapter. It is a gold mine in my opinion, one that I expect to be returning to again and again.

The author's take on Generators is pretty interesting. Though I must confess, after a while, it started going a little above my head. This only means that the text is dense and needs re-reading. This also makes me think how much of this can I apply in
Aug 09, 2018 rated it really liked it
The first appendix was unnecessary (perhaps the second one as well), the Promise's chapter did get repetitive (but it was still good), and I wish he had gone deeper into performance. Still not a bad book though, worth reading.
Dec 11, 2017 rated it really liked it
The last chapter on performance is a complete dud which could be summarized in a single paragraph. Some of the chapters are overtly long but still exhaustive so 4 stars unless I find a better book on this topic.
Heba Atallah
Nov 27, 2017 rated it liked it
Shelves: javascript
*To re-read some chapters
Jun 20, 2018 rated it really liked it
Shelves: technical
The book itself is good. The only the part I didn't like was about the asyncquence library. I felt it was out of the scope of JavaScript core features. Apart from this book is amazing.
Mar 30, 2018 rated it it was amazing
Shelves: ebooks
I don't know why I didn't read this book earlier, for weeks I've been lost with all the "Async-Await" tech talks and now this book, eloquently written offers a clear and consice explanation.
Aug 15, 2018 rated it it was amazing
One of the best resources for learning the ins and outs of JS asynchronous programming and Promises. Some really great insight about JS performance and benchmarking too!
Oct 16, 2016 rated it really liked it
Author is right. If you think you know, you're probably wrong.
Abdulfattah Popoola
Feb 15, 2017 rated it liked it
Long book, some parts felt like filler material. Still had some gems though.
Marc Udoff
Nov 07, 2015 rated it it was amazing
This author does a great job walking you through why and how for promises and generators. He touches on a few other concepts at the end, but not in as much depth. Overall this is a great read for learning to write async JS code that is reliable and readable. I would also say a must read for the subject.
Michal Paszkiewicz
Mar 07, 2016 rated it really liked it
A great guide to ES6, promises, generators and so much more, with glimpses into ES7 potential updates. Very easy to read and gives a pretty good understanding of Async programming. A must read for any JS developer.
Matthew (Skip) Moore
May 26, 2016 rated it really liked it
if you want to understand Async in the ES6 world this is the book to read
Feb 06, 2016 rated it really liked it  ·  review of another edition
Shelves: javascript
Like the other books in this series it is dense, goes into extreme detail, will probably require you to read it at least twice, and it is required reading for serious Javascript developers.
Zach Smith
Jan 24, 2016 rated it liked it
Shelves: non-fiction
Just as good as the previous ones, but the subject matter is much more complex. This is the crux of Javascript though, so worth a read (+ re-read)
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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.

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