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Octopress, PageSpeed, jQuery and fancyBox

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Goal

To improve the Google PageSpeed scores of this site.

Background

I use MathJax and fancyBox for displaying math equations and images respectively.

Problem

As shown in the following two pictures, the PageSpeed scores of the homepage of this blog for “Mobile” and “Desktop” were very low.

pagespeed score mobile pagespeed score desktop

Solution

I followed the advice of Google Developers, and deferred loading of JavaScripts.

Results

After a week’s work, the PageSpeed has risen.

mobile pagespeed score

pagespeed score desktop

HTML Headers

I removed render-blocking JavaScripts and stylesheets in the HTML Headers.

  1. Deleted all <script> and <link rel="stylesheet" ... /> tags in source/_includes/custom/head.html, except <link src="/stylesheets/print.css" ... />.
  2. Deleted the lines which loads jQuery, Modernizr, /javascripts/octopress.js and /stylesheets/screen.css.
Lines to be removed from the default HTML head
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<link href="/stylesheets/screen.css" media="screen,
projection" rel="stylesheet" type="text/css">
<script src="/javascripts/modernizr-2.0.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">
</script>
<script>!window.jQuery && document.write(unescape('%3Cscript
src="/javascripts/libs/jquery.min.js"%3E%3C/script%3E'))</script>
<script src="/javascripts/octopress.js" type="text/javascript">
</script>

Combine and compress fancyBox JavaScripts

I used the online JavaScript compressor at http://jscompress.com. First, I clicked the “Upload Javascript Files” tabbed pane. After that, uploaded the three JavaScripts for fancyBox helpers:1

  1. /fancybox/source/helpers/jquery.fancybox-buttons.js?v=1.0.5
  2. /fancybox/source/helpers/jquery.fancybox-media.js?v=1.0.6
  3. /fancybox/source/helpers/jquery.fancybox-thumbs.js?v=1.0.7

I then downloaded the compressed output.

To load the scripts, especially Google hosted jQuery (or a local copy of it in case that the remote library can’t load) and fancyBox, and the stylesheets after the contents in the <body> tag has been loaded, I added the following lines to source/_includes/custom/after_footer.html.

Defer loading of JavaScripts and stylesheets
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<script type="text/javascript" charset="utf-8">
// For loading JavaScripts
(function() {
    function getScript(url,success){
	var script=document.createElement('script');
	script.src=url;
	var head=document.getElementsByTagName('head')[0],
	done=false;
	script.onload=script.onreadystatechange = function(){
	if ( !done && (!this.readyState || this.readyState == 'loaded' || this.readyState == 'complete') ) {
	    done=true;
	    success();
	    script.onload = script.onreadystatechange = null;
	    head.removeChild(script);
	}
	};
	head.appendChild(script);
    }

    // Any scripts independent of jQuery
    getScript("/javascripts/modernizr-2.0.js",function() {});
    getScript("https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"+
    ",https://vincenttam.github.io/javascripts/MathJaxLocal.js",function() {});

    // Google hosted jquery and fancyBox JavaScripts
    getScript("//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js",function(){
      getScript("/javascripts/octopress.js",function() {});
      getScript("/fancybox/source/jquery.fancybox.pack.js?v=2.1.5", function() {
	getScript("/fancybox/source/helpers/all.js", function() {
	  getScript("/javascripts/FancyBoxLocal.js", function() {});
	  });
	});
      });

    // jquery fallback local copy and fancyBox JavaScripts
    window.onload = function() {
      if (typeof jQuery == "undefined") {
	var jqri = document.createElement("script");
	jqri.src = "/javascripts/libs/jquery.min.js";
	jqri.type = "text/javascript";
	document.body.appendChild(jqri);
	jqri. onload = function () {
	  var fbjs = document.createElement("script");
	  fbjs.src = "/fancybox/source/jquery.fancybox.pack.js?v=2.1.5";
	  fbjs.type = "text/javascript";
	  document.body.appendChild(fbjs);
	  var fball = document.createElement("script");
	  fball.src = "./octopress/source/fancybox/source/helpers/all.js";
	  fball.type = "text/javascript";
	  document.body.appendChild(fball);
	  fbjs.onload = function () {
	    fball.onload = function () {
	      var fblocjs = document.createElement("script");
	      fblocjs.src = "/javascripts/FancyBoxLocal.js";
	      fblocjs.type = "text/javascript";
	      document.body.appendChild(fblocjs);
	    }
	  }
	}
      }
    }
})();

// For loading CSS files
var cb = function() {
  var h = document.getElementsByTagName('head')[0];

  // Fonts from Google's Web font directory
  var font1 = document.createElement("link");
  font1.href = "//fonts.googleapis.com/css?family=PT+Serif:regular,italic,bold,bolditalic";
  font1.rel = "stylesheet";
  font1.type = "text/css";
  h.parentNode.insertBefore(font1, h);

  var font2 = document.createElement("link");
  font2.href = "//fonts.googleapis.com/css?family=PT+Sans:regular,italic,bold,bolditalic";
  font2.rel = "stylesheet";
  font2.type = "text/css";
  h.parentNode.insertBefore(font2, h);

  // any other external CSS

  // CSS files for FancyBox
  var fbcss = document.createElement("link");
  fbcss.href = "/fancybox/source/jquery.fancybox.css?v=2.1.5";
  fbcss.rel = "stylesheet";
  fbcss.type = "text/css";
  fbcss.media = "screen, projection";
  document.body.appendChild(fbcss);
  var fbbtncss = document.createElement("link");
  fbbtncss.href = "/fancybox/source/helpers/jquery.fancybox-buttons.css?v=1.0.5";
  fbbtncss.rel = "stylesheet";
  fbbtncss.type = "text/css";
  fbbtncss.media = "screen, projection";
  document.body.appendChild(fbbtncss);
  var fbthmcss = document.createElement("link");
  fbthmcss.href = "/fancybox/source/helpers/jquery.fancybox-thumbs.css?v=1.0.7";
  fbthmcss.rel = "stylesheet";
  fbthmcss.type = "text/css";
  fbthmcss.media = "screen, projection";
  document.body.appendChild(fbthmcss);
};

var raf = requestAnimationFrame || mozRequestAnimationFrame ||
    webkitRequestAnimationFrame || msRequestAnimationFrame;
if (raf) raf(cb);
else window.addEventListener('load', cb);
</script>

Improve user experience

Google PageSpeed Insights said that my homepage was too wide for mobile devices whose width were 320 px. Therefore, I’ve tried preparing different pictures for windows of different width by <picutre> tags with <source srcset=...> inside. Although this pure HTML 5 approach is now supported in Google Chrome only, I find this method simple and beautiful.2 Due to its elegance, I believe that this feature will soon be implemented in all major browsers, such as Mozilla Firefox.

Part of pages/posts contents
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<picture class="fancybox center" title="Custom search failed">
  <source srcset="/images/big.png" media="(min-width: 880px)" />
  <!-- a fallback for browsers that don't support the source tag -->
  <img alt="alt text" src="/images/small.png" />
</picture>

The simplest way to avoid getting the message “Optimize images” in a PageSpeed test is to optimize the images. OptiPNG can be used for this. Before compressing the images, I issued the following command to create a diminished image of width 300 px of the original image.

$ optipng big.png
$ convert big.png -resize 300 small.png
$ optipng small.png

How to enable fancyBox for <picture> elements? I did a bit of “guided coding” — I copied Erv Walter’s function and changed a few lines.3

Part of my "/javascripts/FancyBoxLocal.js"
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$(document).ready(function() {
  $('.entry-content').each(function(i){
    var _i = i;
    $(this).find('img.fancybox').each(function(){
      // Erv Walter's function ...
    }

    $(this).find('picture.fancybox').each(function(){
      var picture = $(this);
      var title = picture.attr("title");
      picture.removeClass("fancybox");
      var url = picture.children("source").eq(0).attr("srcset");
      picture.wrap('<a href="'+url+'" class="fancybox" rel="galleryp'+_i+'" />');
      if (title != "") {
	picture.parent().attr("title", title);
      }
    });
  });

  // settings found on fancyBox's homepage ...
});

View the file at commit 29d86dd for a working example.

Lastly, to ensure that the contents wouldn’t fall outside the viewport on the screen of mobile devices, I embedded an inline CSS.

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<style>article img {max-width:100%;}</style>

Though this wasn’t good, it enabled me to get rid of the above message about image optimization in a PageSpeed test.

Lessons learnt

My first way to load JavaScripts from a script

Due to my homework and exams in early December and my limited knowledge on JavaScripts, I didn’t have time to understand the section “Defer loading of JavaScript” in a suggestion page on Google Developers. On Dec 20, 2014, I found an article on feedthebot useful.4 I copied the codeblock and changed defer.js to other files.

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<script type="text/javascript">
function downloadJSAtOnload() {
  var element = document.createElement("script");
  element.src = "defer.js";
  document.body.appendChild(element);
}
if (window.addEventListener)
  window.addEventListener("load", downloadJSAtOnload, false);
else if (window.attachEvent)
  window.attachEvent("onload", downloadJSAtOnload);
else window.onload = downloadJSAtOnload;
</script>

In M$ I.E., one has to use window.attachEvent instead of window.addEventListener. The last line acts as a fallback for old browsers.

This works for MathJax. However, for fancyBox, which depends on jQuery, strange things happened, and I got trapped for two days. I had wrote a function which worked in Google Chrome, but when I opened Mozilla Firefox to test the results, no box popped out and I was taken to a page containing merely the picture. I was puzzled and made a Git commit.5

My second way to load JavaScripts from a script

I googled “defer jquery fancybox”, and found a question on Stack Overflow.6 I made use of Jamed Donnelly’s functions, and had successfully made a popped up image, which meant that the loading of JavaScripts for fancyBox had been deferred.

Just before the closing body tag
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<script>
(function() {
    function getScript(url,success){
	var script=document.createElement('script');
	script.src=url;
	var head=document.getElementsByTagName('head')[0],
	done=false;
	script.onload=script.onreadystatechange = function(){
	if ( !done && (!this.readyState || this.readyState == 'loaded'
	  || this.readyState == 'complete') ) {
	    done=true;
	    success();
	    script.onload = script.onreadystatechange = null;
	    head.removeChild(script);
	}
	};
	head.appendChild(script);
    }

getScript("jquery-1.8.3.min.js",function(){
    getScript("jquery.fancybox-1.3.4/fancybox/jquery.fancybox-1.3.4.pack.js", function() {});
    getScript("myCustomScript.js", function() {});
});

})();
</script>
A separate file "myCustomScript.js"
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$(document).ready(function(){
    $(".example3").fancybox({
	'transitionIn'  : 'none',
	'transitionOut' : 'none'
    });
});

Nonetheless, the image title and the close icon were missing.

View loaded resources and the timeline

I had tried using “Network” in the developer toolbar in both Google Chromium and Mozilla Firefox to view the time taken for loading the scripts and CSS files. I contrasted the timelines of working sites and my failed trials, and then made changes to the above script before the </body> tag.

Test Javascript functions using the web console

While testing the script in source/_includes/custom/after_footer.html, the scripts often failed to work. The error console in web browsers spotted out the missing brackets and other syntax errors. Moreover, it told me whether jQuery had been loaded if I typed typeof jQuery.

Access the children of an HTML element with jQuery

While writing the anonymous function in /javascripts/FancyBoxLocal.js, I tried to extract the URL of the <source> element inside a <picture> element. In the web console, if typeof jQuery returns "function", $('picture').children('source').length returns a non-negative integer. If the integer returned is positive, $('picture').children('source')[0].srcset returns "/images/foo.png" and "undefined" in Google Chromium and Mozilla Firefox respectively.

I played with the example on W3Schools about the children() method in jQuery.7 After re-writing the code and seeing the result repeatedly, I’ve learnt to use the eq(n) and attr(source) methods to access the n-th element and the source attribute.

Load CSS files from a script

Google Developers has already provided a script for doing so.8 At first, I didn’t understand it and I tried injecting a <link> element inside the downloadJSAtOnload() method. Unluckily, this method failed. Without /stylesheets/screen.css, the Solarized theme disappeared, and was “replaced by a black-and-white theme”. After that, I re-read Google’s page on CSS delivery optimization, and extracted the script which grabbed external stylesheets.

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<script>
  var cb = function() {
    var l = document.createElement('link'); l.rel = 'stylesheet';
    l.href = 'small.css';
    var h = document.getElementsByTagName('head')[0]; h.parentNode.insertBefore(l, h);
  };
  var raf = requestAnimationFrame || mozRequestAnimationFrame ||
      webkitRequestAnimationFrame || msRequestAnimationFrame;
  if (raf) raf(cb);
  else window.addEventListener('load', cb);
</script>

From “Network” in the web developer toolbar, in an up-to-date version of modern browsers, this anonymous function which loads external CSS files should be executed before script.onload and window.onload.

In addition, unlike Javascripts, I don’t use something like stylesheet.onload. Simply put the relative path or URL of the external CSS files inside the anonymous function will do.

After I grabbed the stylesheets before the external Javascripts loaded, the missing components of the pop up window were still missing. It took me half an hour to figure out that l.rel = 'stylesheet' couldn’t be omitted. I then pushed commit 1d40cea to GitHub and claimed that I’d found a way for both Google Chrome and Mozilla Firefox.

The next day, I tested it with M$ I.E., and older versions of Google Chrome and Mozilla Firefox. In older versions, my configurations had failed, but they worked fine in the recent ones. For example, the method of loading external Javascripts in a non-render-blocking manner as suggested by Google Developers didn’t work in Mozilla Firefox 14, which didn’t support requestAnimationFrame. Though mozRequestAnimationFrame was supported, if they’re put together, the whole thing would collapse. Since I’m not a web designer/programmer, I won’t consider fixing this problem since

  • the old versions of browsers will be eventually upgraded, and more importantly,
  • I’ve other (non-technical) problems to solve.

Onload and createElement()

I’ve read a question on Stack Overflow, and understood that even though a <script> element with the src='/javascripts/foo.js' attribute had been created by the createElement() function, the functions defined in the external script /javascripts/foo.js could be unusable if one doesn’t make proper use of script.onload.

A fallback for Google hosted jQuery


(Added on AUG 3RD, 2015)

Unluckily, this failed on mobile devices. I was told that I should have this problem fixed. Due to the difficulty described below and the enormous number of mobile device users, I decided to remove the part of JavaScript source code which was responsible for loading a local copy of jQuery. This would reduce over 9,600 lines of code in the master branch.


In my opinion, this is the most difficult part, which has taken me a whole day.

I observed that loading both the local and remote copy of jQuery was incorrect. Since jQuery is relatively large, leaving this problem unsolved is like leaving a black dot on a whiteboard.

One can’t simply remove the local copy of jQuery since Google is blocked in some regions.9 There’re some political reasons behind. Unlike Zigang Xiao’s blog, I’m not going to write any articles on politics.10 I’ll just seek a technical solution to this political problem.

This problem is extremely difficult for me since I’m not a student of IT, and there’s no direct solution from the Internet. Inside and outside the function triggered by an onload event, code aren’t executed sequencially, but in parallel. Therefore, if I put if (typeof jQuery == 'undefined') after getScript(...), then even though the Google hosted jQuery library can be downloaded, the if statement returns true. Google Chromium and Mozilla Firefox showed different results for the same JavaScript. This increased the difficulty of the task.

While coming up with a solution, I looked at source/_includes/head.html, and found the following line.

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<script>!window.jQuery && document.write(unescape('%3Cscript
src="./javascripts/libs/jquery.min.js"%3E%3C/script%3E'))</script>

Not being familiar with JavaScript syntax, I searched for the meaning of the unescape() function and that of the ‘.’ in front of /javascripts/.... After viewing a question on Stack Overflow, I decided to create the pull request #1699 of Octopress. Luckily, it was accepted and merged into the master branch of Octopress.

After doing some off-topic stuff, I curiously reproduced the error described in the first subsection of this section, and figured out a way to fix this error. During the process, I’ve learnt the dependence of difference scripts Therefore, the correct sequence should be

  1. Load jquery.min.js.
  2. Load octopress.js and /fancybox/source/jquery.fancybox.js.
  3. Load /fancybox/source/helpers/jquery.fancybox-*.js.
  4. Load FancyBoxLocal.js.

For example, appendChild(octopress) should be inside jquery.onload = function() {...}.

Finally, using “Network” in the web developer toolbar in Google Chromium, I observed that before the window.onload event, the getScript(...) method had already got the scripts. I combined the two ways, and solved the problem.


  1. I didn’t use the mousewheel plugin. If one uses a mouse click to get the popped up window, then he/she can also view the next/previous picture with a click.

  2. See, for example, Built-in Browser Support for Responsive Images by Pearl Chen on HTML 5 Rocks, for an introduction to the <picture> element.

  3. See Octopress Customizations by Erv Walter on ewal.net.

  4. Defer Loading Javascript by Patrick Sexton on feedthebot.

  5. See commit e7e6743 for details.

  6. See How to defer javascript on Stack Overflow for the function.

  7. The online example is available at http://www.w3schools.com/jquery/tryit.asp?filename=tryjquery_children2

  8. See Optimize CSS delivery on Google Developers for details.

  9. Google Is Blocked In 25 Of The 100 Countries They Offer Products In by MG Siegler on TechCrunch.

  10. 精英主義與投票考試 by Zigang Xiao.

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