David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C

D

David Mark

David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C

In an (X)HTML DOM, don't read/manipulate DOM attributes (e.g.
"class"). Use the corresponding properties (e.g. "className"). It's
more intuitive, with less code, less calls and no legacy IE nonsense
(e.g. broken get/setAttribute, no hasAttribute, etc.) to worry about.
This has been the rule forever.

In all the time I've worked with DOM elements, there is only one
exception that comes to mind. Something like this, IIRC:-

var elButton = document.createElement('button');
//elButton.type = 'button';
elButton.setAttribute('type', 'button');

....was required in Webkit-based browsers at the time. From a quick
console session, it appears this is still the case as the "type" set
on the BUTTON fails silently, so the default of "submit" remains. Not
sure if this is a bug or if there is an allowance for such behavior in
the recommendation for BUTTON elements. Doesn't seem reasonable to
make the "type" property of a button write-once unless the caller is
afforded a chance to write it once.

I normally use INPUT of type "button", which has no such ambiguity, so
don't really care one way or the other. Whether due to a browser bug
or recommendation shortcoming; it's the one time I can think of where
I had to resort to using setAttribute in an HTML DOM operation.
Operative word is "one". :)

Buttons created with innerHTML will not have this problem as the
parser will take care of setting the "type" property to "button".

Anyway, in an XML DOM (e.g. XHR result), there are only attributes, so
you must use the attribute-related methods.

So there is really nothing to worry about, is there? :)

It's unfortunate that most of the "major" JS libraries feature an
"attr" method that attempts to deal with *both* HTML and XML (though
not normally XHTML). Even worse, they seem to have been written with
little understanding of the above concepts, IE bugs and shortcomings,
etc., ending up as gobbledygook after years of guesswork and patching.

The documentation for the recently added "prop" function demonstrates
just how confused that effort is.

http://api.jquery.com/prop/

First off, it says it returns a string. :(

Then there's this:-

"Concerning boolean attributes, consider a DOM element defined by the
HTML markup <input type="checkbox" checked="checked" />, and assume it
is in a JavaScript variable named elem:"

The DOM element defined by the "HTML markup" is "in a JavaScript
variable". Never mind the awkward wording and XHTML; it's clear what
they are trying to say. But would it be clear to a beginner trying to
forget the "troubles" of basic DOM scripting?

And this is their result matrix:-

elem.checked true (Boolean) Will change with
checkbox state
$(elem).prop("checked") true (Boolean) Will change with
checkbox state
elem.getAttribute("checked") "checked" (String) Initial state of the
checkbox; does not change
$(elem).attr("checked")(1.6) "checked" (String) Initial state
of the checkbox; does not change
$(elem).attr("checked")(1.6.1+) "checked" (String) Will change with
checkbox state
$(elem).attr("checked")(pre-1.6) true (Boolean) Changed with checkbox
state

Third one down is not going to yield anything close to consistent
results in their "core browsers". Does change too, just not by the
user.

After that, the wheels fall off. No mention of 1.6.2, either.

http://pengbos.com/blog/a-bug-in-jquery-latest-releasev1-6-2

There's no mention of how XML DOM's are handled. Certainly "prop" does
nothing with those, yet it is often pitched as a "better" replacement
for "attr". The "attr" method requires *attribute* names (as it
sometimes uses attribute-related methods). The "prop" method requires
property names. Studying such "documentation" and following such
recommendations will only lead to worse confusion.

http://sunnyarpit.wordpress.com/2011/06/06/jquery-removeprop-vs-removeattr/

What could be the effect of all this waffling on plug-ins, widgets and
such? The effect on the libraries is to cause them to scrap their
previous efforts and start anew. jQuery has indicated they are going
down that path too. Of course, there's nothing good down that path;
will divide the project in two, sapping any momentum it had left. :(

http://www.cinsoft.net/
http://www.twitter.com/cinsoft/
http://jsperf.com/browse/david-mark
 
D

Denis McMahon

David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C

I tried dropping gentle hints. Obviously there's some high density
material in your skull.

We have a faq server, we have Thomas 'pointed ears' Lahn, we don't need a
(nother) self appointed wannabe guru trying to build a rep by spouting
twaddle that we're not interested in reading on a daily basis.

Rgds

Denis McMahon
 
S

SteveYoungTbird

David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C
[snip]

The indexing of this new "service" is confusing. Could you please
explain it?

So far we have had:

Volume 1 - Tip 1 ---------David Mark 5th Nov.2011
Volume 1 - Tip 3A --------David Mark 7th Nov.2011
Volume #1 - #Tip 14-C ----David Mark 8th Nov.2011
 
D

David Mark

David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C
[snip]

The indexing of this new "service" is confusing. Could you please
explain it?

So far we have had:

Volume 1 - Tip 1 ---------David Mark 5th Nov.2011
Volume 1 - Tip 3A --------David Mark 7th Nov.2011
Volume #1 - #Tip 14-C ----David Mark 8th Nov.2011

It's designed to confuse morons. ;)
 
D

David Mark

I tried dropping gentle hints. Obviously there's some high density
material in your skull.

We have a faq server, we have Thomas 'pointed ears' Lahn, we don't need a
(nother) self appointed wannabe guru trying to build a rep by spouting
twaddle that we're not interested in reading on a daily basis.

Who the hell is "we"? I own this dump. ;)
 
T

Thomas 'PointedEars' Lahn

Denis said:
David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C

[…]
We have a faq server,

It is spelled _FAQ_, and the server is frequently down, unfortunately.
Also, I do not think that the FAQ covers this subject.

I value David's pointing out that the Webkit bug with dynamically created
`button' elements can be worked around with setAttribute(), as I had
problems with that when creating widgets (for a quick solution I had opted
to use `input[type="button"]' elements instead of `button' elements, but the
latter are more flexible).

Also, it is important to realize that the value of an attribute as retrieved
with getAttribute() can be misleading. For a practical example, there is
(was?) a jQuery UI component which attempted to provide a fallback for
HTML5's type="date". But it used jQuery's attr() method for detection.
Since the attr() method always uses the getAttribute() method in Gecko-based
browsers, the plugin was unable to detect that Firefox did not support the
attribute's `date' value (the attribute property yielded "text" which would
have shown that), and that applying the fallback was indicated. As a
result, the corresponding `input' element stopped working in Firefox (text-
based date input impossible, as all keyboard events had been canceled by the
plugin) until that jQuery plugin had been eliminated from the project's code
base.
we have Thomas 'pointed ears' Lahn,

_PointedEars_, please.
 
R

RobG

David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C

In an (X)HTML DOM, don't read/manipulate DOM attributes (e.g.
"class"). Use the corresponding properties (e.g. "className"). It's
more intuitive, with less code, less calls and no legacy IE nonsense
(e.g. broken get/setAttribute, no hasAttribute, etc.) to worry about.
This has been the rule forever.

Yes, but if you want to use non-standard attributes, get/setAttribute
is the only way to go.

I don't think non-standard attributes should be used, but as soon as
the design heads down that route, get/setAttribute looms large.

Also, there seem to be many programmers from other languages who like
using a function call like get/setAttribute rather than direct
property access. It seems to give them comfort and is a difficult
habit to shake.

[...]
It's unfortunate that most of the "major" JS libraries feature an
"attr" method that attempts to deal with *both* HTML and XML (though
not normally XHTML). Even worse, they seem to have been written with
little understanding of the above concepts, IE bugs and shortcomings,
etc., ending up as gobbledygook after years of guesswork and patching.

The documentation for the recently added "prop" function demonstrates
just how confused that effort is.

http://api.jquery.com/prop/

Unfortunately the authors of various W3C specifications haven't made
life any easier with their muddled handling of the issue. HTML5 only
makes it worse, particularly as it introduces a heap of new
attributes. Anyone using them will prefer get/setAttribute to property
access to deal with older browsers where:

element.getAttribute('data-foo');

"works" but

element.data-foo;

does not.
 
E

Erwin Moller

I tried dropping gentle hints. Obviously there's some high density
material in your skull.

We have a faq server, we have Thomas 'pointed ears' Lahn, we don't need a
(nother) self appointed wannabe guru trying to build a rep by spouting
twaddle that we're not interested in reading on a daily basis.

Rgds

Denis McMahon

Denis, I, for one, like to read David's contributions.
He is an experienced Javascript/DOM programmer, hence I learn a lot (and
get warned for shitty practices) simply reading his posts.
I am glad David decided to participate more actively in this newsgroup
again.

And Thomas Lahn? When he has a good day, and takes the time to explain
something in detail, his post are very worth your while.
(Or at least my while.)

You are of course entitled to your own opinion, but don't say "we",
since that clearly doesn't include all lurkers/posters in here.

And one last thing: Why would you object to anybody writing a
daily/weekly/whatever opinion in here?
It keeps usenet alive. :)
I applaud the initiative.

Regards,
Erwin Moller
 
S

Scott Sauyet

Denis said:
We have a faq server, we have Thomas 'pointed ears' Lahn, we don't need a
(nother) self appointed wannabe guru trying to build a rep by spouting
twaddle that we're not interested in reading on a daily basis.

I know you've been around long enough to recognize that David Mark is
not new here. His posts are often repetitive, self-aggrandizing, and
bullying, but there is also a lot of useful content in them. His
manner is among the most obnoxious I've seen on USENET, and I've given
up on responding to him (a fact he celebrated [1].) But I'm not sorry
to have him participate here. When he does respond to requests for
help (as opposed to his more common messages promoting his library or
denigrating all others), he often does so with some skill and with
genuinely helpful responses.

If you're interested in discussions where his usual bluster is not
welcomed, try JSMentors. The discussion there is much more civilized,
generally helpful, and often more interesting than what's here. Some
of the more interesting and helpful participants from
comp.lang.javascript also participate there. But I find there is
still much to learn here and many fascinating dialogs, if you can
stomach the nonsense.

-- Scott

[1] http://groups.google.com/group/comp.lang.javascript/msg/2f0d6233dd2c8bf6
 
T

Tim Down

David Mark's Javascript Tip of the Day - Volume #1 - #Tip 14-C

In an (X)HTML DOM, don't read/manipulate DOM attributes (e.g.
"class"). Use the corresponding properties (e.g. "className"). It's
more intuitive, with less code, less calls and no legacy IE nonsense
(e.g. broken get/setAttribute, no hasAttribute, etc.) to worry about.
This has been the rule forever.

In all the time I've worked with DOM elements, there is only one
exception that comes to mind. Something like this, IIRC:-

var elButton = document.createElement('button');
//elButton.type = 'button';
elButton.setAttribute('type', 'button');

...was required in Webkit-based browsers at the time. From a quick
console session, it appears this is still the case as the "type" set
on the BUTTON fails silently, so the default of "submit" remains. Not
sure if this is a bug or if there is an allowance for such behavior in
the recommendation for BUTTON elements. Doesn't seem reasonable to
make the "type" property of a button write-once unless the caller is
afforded a chance to write it once.

I normally use INPUT of type "button", which has no such ambiguity, so
don't really care one way or the other. Whether due to a browser bug
or recommendation shortcoming; it's the one time I can think of where
I had to resort to using setAttribute in an HTML DOM operation.
Operative word is "one". :)

Buttons created with innerHTML will not have this problem as the
parser will take care of setting the "type" property to "button".

Another exception is getting hold of a property of a <form> element
such as "action" or "method" when a form input with the corresponding
name exists. The input wins.

<form id="test" action="somepage.html">
<input name="action" value="foo">
</form>

var form = document.getElementById("test");

form.action is a reference to the <input> element.
form.getAttribute("action") is "somepage.html", except in older IE
with its broken getAttribute().

Tim
 
R

RobG

   element.getAttribute('data-foo');
"works" but
   element.data-foo;
does not.

Right, but a little bit of research by these hypothetical developers
would reveal that the `dataset` object [0] houses connections to data-*
attributes. Ergo, the `data-bar` attribute in  `<div
data-bar="true"></div>` would be accessed via `[Element].dataset.bar`.

[0]:http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.....

It will be quite some time before that feature is sufficiently well
supported that it can be used without feature testing and fall-back to
getAttribute, something like:

if (element.dataset) {
alert(element.dataset[dataAtt]);
} else {
alert(element.getAttribute('data-' + dataAtt));
}

Since getAttribute works everyhwere (in regard to data- attributes at
least), it seems a better option to dispense with the feature test and
just use getAttribute.

Host objects have some quirks still, in Chrome 15:

alert(element.dataset)

reports in the console:

Uncaught TypeError: Cannot convert object to primitive value
 
D

David Mark

I know you've been around long enough to recognize that David Mark is
not new here.  His posts are often repetitive, self-aggrandizing, and
bullying, but there is also a lot of useful content in them.

In other words, you have no idea what you are talking about (and are
relatively new around here).
His
manner is among the most obnoxious I've seen on USENET, and I've given
up on responding to him (a fact he celebrated [1].)  But I'm not sorry
to have him participate here.  When he does respond to requests for
help (as opposed to his more common messages promoting his library or
denigrating all others), he often does so with some skill and with
genuinely helpful responses.

You are just pissed that your constant advice to use things like Dojo
and jQuery turned out so badly.
If you're interested in discussions where his usual bluster is not
welcomed, try JSMentors.  The discussion there is much more civilized,
generally helpful, and often more interesting than what's here.

I'll see you over there. ;) Hope you aren't doing your usual act.
Some
of the more interesting and helpful participants from
comp.lang.javascript also participate there.  But I find there is
still much to learn here and many fascinating dialogs, if you can
stomach the nonsense.

....And the stalkers. Get a life.
 
D

David Mark

Another exception is getting hold of a property of a <form> element
such as "action" or "method" when a form input with the corresponding
name exists. The input wins.

<form id="test" action="somepage.html">
    <input name="action" value="foo">
</form>

var form = document.getElementById("test");

form.action is a reference to the <input> element.
form.getAttribute("action") is "somepage.html", except in older IE
with its broken getAttribute().

Yes, so the best bet is not to name form controls "action" (or
anything else that clashes with properties of the form object).
 
D

David Mark

Yes, but if you want to use non-standard attributes, get/setAttribute
is the only way to go.

Absolutely as there are no corresponding properties.
I don't think non-standard attributes should be used, but as soon as
the design heads down that route, get/setAttribute looms large.

Right. Will create expando properties in IE5-7 (and compatibility
mode), but there's nothing that can be done for that.
Also, there seem to be many programmers from other languages who like
using a function call like get/setAttribute rather than direct
property access. It seems to give them comfort and is a difficult
habit to shake.

Yes and all of the ridiculous library "attr" functions and their bad
documentation aren't helping at all.
[...]


It's unfortunate that most of the "major" JS libraries feature an
"attr" method that attempts to deal with *both* HTML and XML (though
not normally XHTML). Even worse, they seem to have been written with
little understanding of the above concepts, IE bugs and shortcomings,
etc., ending up as gobbledygook after years of guesswork and patching.
The documentation for the recently added "prop" function demonstrates
just how confused that effort is.

Unfortunately the authors of various W3C specifications haven't made
life any easier with their muddled handling of the issue. HTML5 only
makes it worse, particularly as it introduces a heap of new
attributes. Anyone using them will prefer get/setAttribute to property
access to deal with older browsers where:

  element.getAttribute('data-foo');

"works" but

  element.data-foo;

does not.

Yes, hyphenated attribute names have traditionally been reflected by
camel-case property names. I assume the data-whatever attributes are
not reflected and should therefore be handled like custom attributes.

And HTML5 really screwed up the naming as well (DOM properties are now
some sort of attributes apparently). Given that for several years,
the most "advanced" JS efforts out there couldn't tell attributes from
properties, what chance will beginners have if both are now called
"attributes"?
 
S

Scott Sauyet

Andrew said:
I know you've been around long enough to recognize that David Mark is
not new here.  His posts are often repetitive, self-aggrandizing, and
bullying, but there is also a lot of useful content in them. [ ... ]

Funny, I read this post of yours in the same manner that you describe
many of the posts of DM.

I'm curious as to why. (I know that I once accused you of being a
David Mark pseudonym, and I know that some might find that insulting,
but you are clearly a fan, so I can't imagine you're terribly
offended.) I've been reading this group two years and posting two
months less. In that time, there is only one person who has publicly
suggested that my contributions were inappropriate or that my effect
on the group was less than salubrious. That was David Mark, of
course. Now he's accusing me of promoting jQuery, Dojo, etc, which is
not at all what I've posted. But if he stays true to form, he'll keep
saying it, acting as though if he says it enough, it'll be true.

Except when seriously provoked, I'm fairly mild-mannered in my
posting. David Mark, on the other hard, obviously works to draw
attention to himself, and has drawn the ire of many here in the
process. As I said earlier, I wish he was less abrasive and less
abusive. But I do think that he has also made significant positive
contributions in the time I've been watching.

-- Scott
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Members online

Forum statistics

Threads
473,754
Messages
2,569,516
Members
44,991
Latest member
Josephnag

Latest Threads

Top