In HTML, it’s perfectly valid to write something like this:

<p class=alpha>Lorem ipsum dolor sit amet etc.</p>

Indeed, Internet Explorer 7 and 8 favour this approach. Whereas Firefox, for example, would return the above as

<p class="alpha">Lorem ipsum dolor sit amet etc.</p>

when retrieving it using innerHTML, IE 7 & 8 only quotes attributes that satisfy certain criteria:

• Any attributes that contain spaces;
• Some magic set of standard attributes, such as href;
• Any custom attributes you may have specified.

Unfortunately, however, this doesn’t constitute well-formed XML. In the software I develop at work, we produce PDFs that can include user-generated HTML. To do this, we use XSL:FO — an XML-based system. You can see where this is going: the backend requires valid XML, but the frontend is sending through HTML. The simplest way to fix this is with a simple regex, like so:

var s = '<p class=alpha>Lorem ipsum dolor sit amet etc.</p>';
s = s.replace(/=([^"'`>\s]+)/g, '="$1"');
// s === '<p class="alpha">Lorem ipsum dolor sit amet etc.</p>'

Bear in mind that this regex is by no means perfect. It will, for example, convert this:

<p class=alpha>Lorem ipsum</p>
<p>dolor sit=amet</p>

into this:

<p class="alpha">Lorem ipsum</p>
<p>dolor sit="amet</p">.

…which is obviously not what we want. I spent a while trying to come up with a regex that would solve this problem, but I stopped pretty soon. What’s really needed here is a parser: something that can take in the tag soup that Internet Explorer produces, and produce valid XHTML (which is valid XML). A quick search reveals myriad implementations in various languages — Python, Java, even JavaScript.

So, after all that, what’s the take-away from this post? Just this: web browsers (slightly older versions of Internet Explorer in particular) are imperfect. XML was borne out of HTML, and is much less forgiving; whether or not its strictness is a good thing is up for debate. I guess that it’s a bit like reading Shakespeare nowadays: you can pretty much understand it, but every now and then you have to reach for a dictionary to make sense of what’s going on. Of course, when you don’t understand something in Shakespeare, you don’t fall over in a heap, but let’s not stretch the analogy too far.

In brief

When retrieving the innerHTML of an element (or using contenteditable), Internet Explorer doesn’t always wrap attribute values in quotes. The solution to this is not a magnificently obtuse regex, but a tag-soup parser that can return valid XML.

And so, for the third time this year, I’ve completely re-themed this site. Taking a very different tack from the last theme, I’ve tried to keep this one as simple as possible, with just a few subtle touches here and there to add interest. The palette is more subdued, which hopefully means that reading the text is a more pleasant experience. I’ve also done away with the multi-column body text in favour of a fixed-width design.

At the same time, though, I have endeavoured to use some of the new features available in modern web browsers — gradients, shadows, transitions, generated content, and so on. I’m fairly happy with the result — I think it’s a clean, unobtrusive theme that’s not too in your face. Feedback and criticism welcome!

Continuing my HTML5 and canvas experiments, I’ve put together a generative music system. Essentially, a series of particles move across a field, occasionally triggering sounds — the sound triggered depends on their location in the field.

There is, of course, a little bit more to it than that. Under the hood, I’ve got a series of HTML5 Audio objects that are used to provide polyphonic audio using a simple round-robin algorithm (I encoded the audio in OGG, so you’ll need to use an OGG-friendly browser, like Firefox). The particles are much simpler than those in my previous canvas dalliance, in that they don’t swarm, and their motion is more linear.

View (and hear!) it live

I’ve been meaning to start playing with the HTML5 <canvas> element for a while now, and yesterday I took the opportunity. I translated a Processing sketch I made a while ago into JavaScript (with a few minor enhancements).

View it live

Essentially, 1 to 3 swarms of particles move around the canvas, reproducing when the conditions are just right, and dying of old age. Quite simple, but the patterns produced can be really quite pretty.

One interesting thing that I discovered whilst doing this is that you can’t pass around a canvas’ context at the instantiation of a MooTools class — it complains about wrapped natives. That’s why, if you like in the source JavaScript, you’ll see me pass the actual context around to various functions. I’d be interested in hearing if anyone has a workaround for this, because this is, well, a bit clunky.