High Performance JavaScript (Inglese) Copertina flessibile – 13 apr 2010

Working at a mobile advertising startup, I've been looking for new ways to make our code as high-performing as possible. So, naturally, I came to this book.

After reading it, there are perhaps four tips from the entire book that are relevant to developers today. The rest are based off micro-benchmarks of browsers like IE 6 and Firefox 4 - needless to say, how browsers handle JS has changed a lot since then, so these benchmarks are useless.

In conclusion: if you absolutely /need/ to write the absolute fastest JS possible, this book might be worth a quick skim and should not be taken too seriously. If you aren't concerned about shaving off a couple of ms from your code, you can find much of this advice for free, online, with up-to-date benchmarks and comparisons.

While reading Nicholas Zakas' "High Performance JavaScript", it occurred to me that there were actually two different reviews that I wanted to write. So, rather than try to reconcile them into one review, I'll simply apply them here as an ordered list.

(1) To continue with the JavaScript University metaphor (from my review of Zakas' Professional JavaScript for Web Developers (Wrox Programmer to Programmer)): Finals are coming up in Prof. Crockford's upper-division JavaScript class. You've been a diligent student all semester and although you're not failing, it always seems like you're somewhere in the middle of the pack. You want desperately to ace the final exam, so you reach out for some help. Zakas (the graduate student/teaching assistant for the class) offers to show you the thesis he is working on. Then It hits you like a bolt from the blue -- every bit of it resonates with you. "It's so simple! so clear!" you exclaim. The inner machinations of the language snap together in a way that makes it all feel new and exciting -- the possibilities are boundless! You go back over your notes. You were close -- oh so close -- the whole time. But the last little bits drop in. A refinement here, a re-factor there... and the next thing you know, things are blazing. Your pages load 60% faster, execution time is down an average of 40%. You're amazed at yourself. And when the grades for the final exam come back, you're pleased to see that you aced it (aside from that little Oops on scoping closures -- but you try to think of that as a conscious trade-off). Prof. Crockford is pleased (if a little disappointed that it took you this long to Get It) and you're the envy of your peers. At least until next semester's RegEx class with Prof. Levithan. [Rated: 5 of 5]

(2) The frustrating part about working at a well-organized shop is that you get yourself all excited for a book like this and then half the recommendations in there are things that you're already doing. Put scripts at the bottom of the document? Check. Minify and compress? Check. Concatenate and package? Check. So on the one hand you say: "I guess I can sleep a little easier at night knowing that our build system adheres to the best practices recommended by the experts out there." But on the other hand, you're a little disappointed because you were hoping for some startling revelations. Again: not that this makes it without merit. From this perspective, what is noteworthy about this book is that these best practices and techniques are all gathered up in one place and presented in a logical order; even if "you're already doing it right", it is still a worthwhile exercise to meditate on the specifics, and to really go deep on why these best practices are important. (Plus, it's great to see the data -- nothing beats a little chartporn for proving the point.) [Rated: 4 of 5]

There are things covered in this book that I haven't seen elsewhere but I have often wondered about. Highlights were string processing optimization, techniques in adding non-blocking scripts, and in-depth look at array processing.. I also really enjoyed detailed look at different ways to implement a javascript String trim() method - made me realise again how bad the advice a google search can return sometimes. The most disappointing was Ch9. It's rather confusing and wordy. I didn't think it did a great job of explaining how to package up scripts into one file - it probably needs a few more chapters to explain it better and the author may have been struggling to squash it all in there.
Having said that. LOVED how small the book was - it was very refreshing and I got through it in less than a week. If you already have Nicolas other book Professional JavaScript and you're wondering whether to get this book - I would recommend you do. There is more than enough variation and new content and the chapters by other authors are a real bonus.

Zakas does a brilliant job covering all the bases for the modern Javascript developer. Optimizing Javascript performance is often difficult, if done at all, and now there are a lot of good tips conveniently in one reference. The topics are well thought out and organized in a natural way. And while the lines on the charts were a bit difficult to distinguish from one another, I liked how the various techniques were backed up with cross-browser analysis.

I would highly recommend this book to the intermediate JS developer. For those of us who follow front-end optimization discussions regularly, some of the topics covered in this book have been covered elsewhere. Nevertheless, there is still a lot useful material here.

Front-end performance is currently a hot topic and I'm glad Zakas et. al. are nudging developers in the right direction.

Can run old because the browsers versions were uses, mostly mentions old IE versions tweaks and those may no longer be used