QuirksBlog - Coding techniques
| Contest | Memory leaks | XMLHTTP |
Today I spent about an hour in writing a few very simple Intersection Observer tests, two hours in running them in a few browsers, and now an hour in writing down the results.
I’ve only just started my research, but can already draw a few odd conclusions, which make me fear Intersection Observers are not yet ready to be deployed on a large scale, particularly on mobile.
A quick note on styling placeholder texts. Although it’s very easy, it turns out that both MDN and the usual go-to CSS Tricks article leave out one important bit of data: when setting the
color you should add
opacity: 1 for Firefox.
I’m currently working on my first real paid coding project in ages: PvdApp, a project of a friend of mine. (He paid for this research, so he deserves a link.)
Among other things, this project requires me to style and script sliders. There are several interesting points I would like to bring to your attention, such as a few underreported IE problems, the solution to Android WebKit’s appearance bug, and the proper use of the input and change events. And a quick syntax overview is always useful.
Today I rant about undocumented Chrome features and unreadable W3C specs. There’s too much of both nowadays, and I’m getting VERY tired of both. Google and W3C should clean up their act.
Yesterday I found that proper hyphenation of text is now supported by Firefox, IE10, and Safari. So I added it to my main style sheet and it should work in these browsers across my site. I also advise you to add it to your sites straight away.
During my media query test I found out that
min-resolution: 0[unit] does not work in any browser for any unit. I find this weird.
For my DIBI presentation
I need a dropdown menu (in order to compare it on desktop and mobile), so I wrote one.
and three of which deal with the fact that bloody Firefox still doesn’t support
Net amount of lines: 18. Can somebody please remind me why we all used to think dropdowns
are so extremely complicated? I can’t for the life of me figure it out.
Yesterday I walked into the local phone store because the “Temporarily Unavailable” sign had been removed from their “Get your iPhone here” poster. To my utter surprise they had six (6!) entire iPhones for sale, and no, there was no waiting list. I walked back home with a shiny new gadget, impatient to start testing it.
Meanwhile I’ve done some tests; now it’s time for a report.
Before we continue, let’s get the bad CSS news out of the way: Safari on the iPhone does not support
position: fixed. Certain Other Browsers were ridiculed for this lack; Safari won’t be.
Event delegation is especially useful in effects like dropdown menus, where lots of events on links may take place that can easily be handled at the root level (an
<ul> in this case).
There used to be one problem, though: although event delegation works fine for the mouse events, it does not work for the focus and blur events we need to make dropdown menus keyboard-accessible.
In the course of my ongoing event research, however, I found a way to delegate the focus and blur events, too. Maybe one of those
will use this technique to shave off a few milliseconds of computing time
For all I know they're already aware of this technique; but it was new to me so I publish it anyway.
The previous version of the Find Position script didn't work quite correctly,
since it often ignored the last step in position calculations: the one from the
<html> element. Part of the reason was that its code was too complicated.
The problems with this script used to generate a lot of comments. Eight months ago I changed the
script somewhat, and comments dropped off to zero, meaning I'd done it right. Meanwhile I've taken another
look at it and changed it a bit more.
In any case, the changed script now uses a new approach (that is, it was new to me eight months ago).
It now uses the assignment operator
= instead of the equality operator
that you'd expect:
while (obj = obj.offsetParent)
I always planned to write a blog entry about this approach, because I feel this little trick should
become general knowledge. So here it is (eight months too late, but anyway):
While attending Brian Fling's presentation on desiging for a mobile phone, I suddenly had an idea that might solve one of the problems he mentioned. I thought I'd document it immediately, before tonight's beer will cloud my mind and make me forget all about it.
I added a new page about importing the site navigation on all QuirksMode.org pages. The page is mostly about why I do what I do, and less about the how (besides, technically it's quite easy). The site navigation is a perfect example of what Jeremy calls Hijax.
I also put my trusty XMLHttpRequest functions online for future reference. No explanations on this page; I already treated them in section 10A of the book.
Just now I delivered a project during the making of which I noted a feature of event bubbling that, though totally logical, came as a surprise to me. No doubt someone else will be surprised, too, and may even be able to use it in a project.
I'm already regretting the publication of my Browser Detect 2.0. From one of the comments I learned that there's a new script making the rounds of blogs, a script that neatly highlights the dangers of using browser detects, but that's been received with glad cries by otherwise sensible sites.
Combine the release of this script with my release, and it might seem to the unaware web developer that browser detects are back in fashion. It's necessary to repeat why browser detects are dangerous, unprofessional and usually badly written, even though those facts have been general knowledge since at least 1998.
Well, I'm back from @media, and it was as wonderful as last year. I met lots of interesting people, talked about lots of geeky stuff, drank the amount of beer required by British law, and went on stage at a web conference for the first time—but I hope not for the last.
Well, my previous entry Is asynchronous communication really being used? has certainly elicited some interesting comments. The answer was a resounding "Yes"; and the replies allow me to take a first stab at defining a few Ajax use patterns.
Yesterday I attended the 10th Sigchi.nl conference in Amsterdam, during which I had the pleasure of seeing
Jesse James Garrett,
Martijn van Welie,
and Steven Pemberton in real live action. (Note to self: Jared and Steven are stiff competitors of Joe when it comes to being The Funniest Man at Web Conferences).
I'm not going to describe the conference in detail. Instead, I'd like to discuss an asynchronous communication question that popped into my head during Jesse James' presentation.
In a project I'm currently working on I encountered an Explorer bug that depends on the window you open a page with.
I post it here because I know that MSIE team members occasionally read my blog, and I have the faint hope that can they solve this bug, especially since it's messing up one of my projects (and, after all, what in the world is more important than my projects going smoothly <grin>, particularly when I have another important and exciting project that should be finished quickly but is held up by this bug).
One of my minor irritations with Mozilla is that it doesn't support a few DOM methods and properties that, though not officially a part of the spec, are nonetheless extremely useful and supported by all other browsers. I'm especially thinking of the
contains() method and the
children nodeList. While going through the more abstruse parts of the Level 3 Core spec today I found a way to add
contains() to Mozilla.
Sounds fascinating? You bet. There's just one slight problem: the actual data is totally inaccessible.
My last entry The AJAX response generated a few interesting comments, as well as a thoroughly non-scientific and non-representative poll on the use of the various output formats.
In the rest of this article I'd like to reply to some points that were made: the name "AJAX", rendering speed, error handling, the "evilness" of
innerHTML and some other remarks.
(This article has been translated into Spanish.)
In the past two weeks I've again created an Ajax-driven interface, and as usual I discovered quite a few interesting XMLHTTP bugs and problems. This entry contains three Explorer and one Safari bug, and it talks about cloning nodes from HTML to XML, from XML to XML, appending HTML that contains a form, and extremely agressive caching.
In my ongoing quest for memory leaks I've come upon a mystery. A script that should leak memory according to the definitions and the experts, doesn't. Why not? I have no idea.
Since the comments to my previous posts contain a few useful links to memory leaks and closure resources, I thought I'd create a linkdump for future reference. Note that I only included those articles that explain what they're doing and why and give code examples. I ignored the pages that just throw scripts over the fence and leave it to the reader to figure out what they're all about.
I made an obvious error in my previous round of experiments. We're going to start afresh.
The plot thickens. I now have succesfully created a simple function that causes memory leaks. The problem is, I don't understand why.
Update: Incorrect experiments. This entry is closed.
It becomes more and more apparent that creating the new
addEvent() function is not for the fainthearted. I underestimated the many problems, and in the comments to my previous entry compelling arguments were raised against the winning code.
I've decided to take a few steps back and study the problem before messing about with the solution. I want to write a script that leaks memory. I'd like to judge how bad it is in practice and I'd like to see some practical code examples. Unfortunately I just can't get any function to leak memory. I'm afraid I just don't get it.
Well, that wasn't what anyone would call fast. Scott, Dean and I all had trouble making time to judge the contest. Besides, the quality of most of the entries was less and their length far greater than we'd expected. We had to wade through dozens of lines of script that didn't really make much sense to us, and that weren't really necessary to perform the job at hand.
Despite this disappointment we have determined a winner.
I know, I know. I'm terribly late, not to say distinctly overdue, in judging the addEvent() recoding contest. The main reasons are that my clients now actively gang up on me to prevent me working on anything but their projects, and that the bit of spare time I've managed to squeeze from them is almost entirely taken by a very exciting new project that I hope to unveil within the next few weeks.
That said, today I finally found the time for the first round. I took a quick look at all the entries and judged them on formal grounds.
On Thursday my Windows XP computer died. This was not entirely unforeseen, since it had taken to crashing at random instances, and also when I wanted to restart it after a night of inactivity. But now it didn't want to start up at all, and reinstalling Windows XP brought on yet another crash. Time for a new computer.
This thrilling episode of "My glorious life as a web developer" has played havoc on my schedule, which was rather tight to begin with. The main victim turns out to be the addEvent() recoding contest.
As we all know an xmlhttp script requires the use of the
readystatechange event. In theory, using the
load event is also possible, but Explorer doesn't support it on xmlhttp requests.
Both these events, and the
readyState property, have a few odd quirks when used in an xmlhttp environment, though. These quirks don't impact standard xmlhttp scripts too much, but as soon as you want to use the event objects or
readyStates other than 4 you need to know about them.
Remember that the addEvent() recoding contest closes in three days. Thursday is your last chance to submit your script, since I'm going to close comments on my Friday morning and start working on the judging.
In my continuing quest to understand XMLHTTP I gathered some very intriguing material that I'm quite sure will save somebody else's ass. Today I offer a closer look at the
abort() method, as well as an as yet unexplained bug in Mozilla which causes the
responseXML to go missing.
My recent entry addEvent() considered harmful generated many interesting comments and technical pointers. It's clear that the original
addEvent() function doesn't quite cut the cake any more, and it's equally clear that we badly need a function such as this to keep our scripts simple.
Hence I'd like to take the opportunity to launch an
addEvent() recoding contest. Write your own version of
In a recent article on the IE Blog, Justin Rodgers talks about further CSS improvements in the ever more impatiently awaited IE 7 beta 2. His message is that CSS hacks will start to break in IE 7, and I fully agree.
Nearly two years ago I warned against the excessive use of CSS hacks, because I envisioned a situation like this. Web developers who rely on CSS hacks are going to have serious problems.
Currently I'm working on debugging a very complicated script that's supposed to xmlhttprequest a few pages to be shown in a "Dashboard". I already wrote about another aspect of the project in my previous entry, but now that I'm concentrating on the XMLHTTP aspects of this project I found out a few very interesting things about
responseXML, as well as a complicated Explorer bug.
This entry treats these two points, since they should be documented.
Back in 2001 Scott Andrew LePera published the cross browser event handler script
addEvent(), which was subsequently copied, revised, and used in many, many websites. I never used it, because I felt — and feel — it is wrong to assume that the W3C
addEventListener and the Microsoft
attachEvent methods are the same. They aren't, and the slight but important difference can trip up the unwary web developer.
Today I found excellent evidence that
addEvent() can be harmful if it's used without intimate knowledge of the differences between the W3C and Microsoft event registration models.
When I first read Jesse James Garrett's article Ajax: A New Approach to Web Applications my reactions were "What a silly name", and "Not really new, is it?" Although both points of critique have been repeatedly and heatedly mentioned in the ensuing discussion, the concept seems to be taking the Web development community by storm. This can mean one of two things: either it's a promise or it's a hype. To decide the case, I offer an annotated link dump.
Since XMLHTTP is becoming more and more important I thought I'd create a linkdump, both for my own future reference and for other developers. Additions and comments will be gratefully accepted.