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This Week in JavaScript Performance

by | Mar 30, 2012

This Week in JavaScript Performance summarizes recent web postings related to JavaScript performance. Watch for it at the beginning of each week.

Progressive Enhancement 2.0

Presenter: Nicholas Zakas.   Publisher: yuilibrary.This 50 minute presentation is from the March 5 BayJax event. Zakas shares his vision of progressive enhancement.

Cache them if you can

Author: Steve Souders.   Publisher: Steve Souders.This revealing article examines the current usage of the Cache-Control: max-age header, which is essential for website performance. It shows that more than half of the resources downloaded from the most-used websites in the world are not cached. It then examines whether uncached resources could benefit from caching or whether they are truly dynamic.Third party content is also covered. The most popular 30 are listed along with their max-age. The analysis is informative.

Cache compressed? or uncompressed?

Author: Steve Souders.   Publisher: Steve Souders.This article is a follow-on to the above. It asks whether compressed data is stored in compressed or uncompressed form in the browser’s cache, then proceeds to answer that question. It also notes the tradeoff between disk space usage and CPU cycles when reading compressed data from a cache. It doesn’t offer definitive answers because there are no definitive answers (yet).

CSS Reflow

Author: Pixeln3rd.   Publisher: Pixeln3rd.This short video helps us visualize the CSS reflow process. As different regions of the page are written over and over and over again, we can’t help but wonder why the computer is doing all that extra work. It’s less than two minutes long, so check it out.

Why Minify JavaScript?

Author: Matt Farina.   Publisher: Matt Farina.This article tests some .js files from Drupal and jQuery to show by example that minification is better than compression in some cases, and that minification + compression is better in all cases. It then describes how minification + compression saves on round trip times by reducing the number of round trips.

JavaScript Performance: You like it, it likes you

Author: Rodrigo Castilho.   Publisher: Rodrigo Castilho.This slideshow lists a number of JavaScript performance tips, including sample code where appropriate. A few slides on jQuery are included.

Putting Performance In Perspective

Author: ajpiano.   Publisher: GitHub.This short comment is an invitation to discuss how to put the myriad of website/webapp performance tips into perspective. As of March 30th, there has been no discussion, but it’s only been two days. Perhaps you would like to add your two cents worth.It looks like ajpiano read my recent article, Performance Perspectives. I can’t say that for sure, of course, but the content of my article almost cries out for additional discussion.

JavaScript: avoid overuse and enhance accessibility

Author: Gabriele Romanato.   Publisher: Gabriele Romanato.This short article describes how overuse and/or misuse of JavaScript can create accessibility issues for the visually-impaired. We may need a paradigm-shift in our thinking, friends.

jsPerf JavaScript Performance Playground

Author: contributors.   Publisher: Mathias Bynens.Here are some of this week’s JavaScript tests/measurements:

  • o.p vs. a[i]. Which is a faster read: arrays or objects?
  • x.toFixed(2) vs. Math.round(x*100)/100. There’s a very clear winner here, but it’s not what I expected.
  • Extra parentheses may improve readability, but will they affect performance?
  • If a value won’t be used in an expression, should I store it as a number or as a string?
  • Is a string all uppercase? The two options in this test are not equivalent. They will not give the same results if text is set to “abc123″.
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About Warren Gaebel

Warren wrote his first computer program in 1970 (yes, it was Fortran).  He earned his Bachelor of Arts degree from the University of Waterloo and his Bachelor of Computer Science degree at the University of Windsor.  After a few years at IBM, he worked on a Master of Mathematics (Computer Science) degree at the University of Waterloo.  He decided to stay home to take care of his newborn son rather than complete that degree.  That decision cost him his career, but he would gladly make the same decision again. Warren is now retired, but he finds it hard to do nothing, so he writes web performance articles for the Monitor.Us blog.  Life is good!