By James Edwards

Internet Explorer doesn’t just suck, it also blows!

By James Edwards

I’m spending most of my time these days working on SitePoint’s upcoming Ultimate JavaScript Reference, a task that I can fairly say is eating my brain.

Unlike the authors of the imminent Ultimate CSS Reference, I didn’t have any particular inclination to be nice to Internet Explorer. And I knew I was going to run into bugs and quirks, none of which would be any different in IE7, because the DOM simply wasn’t on the development radar for that version.

Even so, I’ve been nothing short of staggered at the sheer amount of chaotic brokenness evident in its implementation of even the simplest of things.

You may remember, not so long ago, that I wrote about the behavior of href attributes in Internet Explorer, and how for links they come back as qualified URIs rather than literal attribute values. But, oh man … that is so the tip of the iceberg when it comes to getAttribute()

You wouldn’t have thought it was so hard

In addition to qualifying the value of href attributes on links, IE does the same thing for the src attribute of images.

When retrieving a style attribute, IE returns a style object, rather than an attribute value. Retrieving an event-handling attribute such as onclick, it returns the contents of the event handler wrapped in an anonymous function. Retrieving an attribute value which evaluates to boolean true (such as disabled or checked, when defined) it returns a boolean, and retrieving a value that evaluates to a number (such as tabindex), it returns a number. All of these values are supposed to be returned as strings.

But these attributes are considered by IE to have non-string values; and so if they’re not defined at all they return null, rather than an empty string. IE also returns null for non-defined attributes it doesn’t recognise (ie. custom attribute names).

In its defense, other non-defined but known attributes correctly return an empty string, which is according to specification; and IE is actually the only browser that does this (Firefox, Opera and Safari all return null). But that’s not really much of a defense, because it only does that for attributes it recognises — so it isn’t really implementing to specification, it just happens to be correct!


Pure class

To retrieve a class attribute in Internet Explorer you must refer to it as className; to retrieve a for attribute you must refer to it as htmlFor:

//these work in IE, null in others

Now this is a side-effect of the mapping of attributes to HTML DOM properties — for example, as a DOM property you always have to refer to element.className rather than element.class, because class is a reserved word in JavaScript. But while other browsers reconcile this by allowing string values to getAttribute() to use the original attribute name, Internet Explorer does not:

//these work in others, null in IE

And there are other attributes that can only be referred to by the camel-cased name they use for their DOM property equivalent, even though those names are not reserved words; I haven’t found a concrete pattern, but examples of this are tabIndex and accessKey.

And there’s more …

Internet Explorer implements a second, proprietary argument to getAttribute(), which is supposed to control the way it behaves. The second argument is a numerical flag which can take the value 0, 1 or 2. According to MSDN:

  • 0 (default): Performs a property search that is not case-sensitive, and returns an interpolated value if the property is found.
  • 1: Performs a case-sensitive property search.
  • 2: Returns the value exactly as it was set in script or in the source document.

When it says interpolated value it means it won’t necessarily return a string, as already noted. Notice also how it says if the property is found [my emphasis] — this would seem to imply that IE is not using getAttribute() as a getter for node values at all, it’s using it as a getter for DOM properties! If true, this goes a long way to explaining its aberrant behavior — if it’s retrieving property values, that’s why it requires property names, and why it returns a value of the applicable type; and when MSDN says that getAttribute() retrieves the value of the specified attribute, it is flat-out lying.

The difference between 0 and 1 appears to be implemented as documented — attribute names are treated as case-sensitive, so a search for onClick will not match onclick.

However the value 2 does not behave as documented. When this value is used, event-handling attributes are still returned as functions, the style attribute is an empty string, and values which evaluate to boolean true return 65535 (which is 216, the largest possible value of a 16-bit number. What’s up with that??) But hey — on a more positive note — href and src attributes do return their literal value, rather than a qualified URI. I suppose we should be grateful for small mercies!

You can see why I said it’s eating my brain … I mean, failing so comprehensively to implement the standards is one thing, and bad enough, but Internet Explorer doesn’t even implement its own proprietary stuff correctly!

  • I can imagine all those JavaScript library authors out there also have eaten brains from dealing with these issues to normalize browser differences.

  • php_penguin

    IE sucks eh?

    thanks for that shocker! I shall blog about it immediately…

  • Thats just a shocker, James. How is anyone meant to work with such badly documented JavaScript implementations. Least they could do is correct the documentation on MSDN

  • SchizoDuckie

    Now thát is why we have Javascript Frameworks, and that is why Javascript frameworks will *never* die…

  • Dezro

    Correction: 65535 is 2^16 – 1

  • justinbezanson

    Just when I think I know how bad IE is something else gets revealed. I keep wondering how it could possibly get any worse and IE keeps delivering. IE needs to dump Trident and start over with Gecko or WebKit.


  • tpetruzzi

    with all the javascript libraries out there like mootools, dojo, jquery, prototype; why the hell do you even need to know native javascript? Just use one of those libraries and it will take care out all the browser in compatibilities for you. No offense but your “Ultimate Javascript Reference” went out the door 5 years ago.

  • gwenhwyfaer

    with all the javascript libraries out there like mootools, dojo, jquery, prototype; why the hell do you even need to know native javascript?

    Seems like you need the obvious pointing out, tpetruzzi, so here goes – someone needs to know native javascript, in order to (a) write the libraries you list in the first place, and (b) figure out why they aren’t working on the latest browser updates the way they’re supposed to. Since you have clearly chosen the path of parasitic ignorance, why not delight that brothercake can be one of your knowledge hosts?

    (These tiresome people who pipe up “dude, just use a library” whenever anyone talks about writing any code that might possibly do something that someone else on the planet might ever have done – do they believe that these libraries evolve on server farms or something…?)

  • sapphirecat

    65535 is also -1, if it’s a signed 16-bit number being displayed as unsigned.

  • Dave

    values which evaluate to boolean true return 65535 (which is 216, the largest possible value of a 16-bit number. What’s up with that??)

    IE’s DOM functionality is implemented using Microsoft COM. The COM VT_BOOL defines VARIANT_TRUE in 16 bits is -1 or 0xFFFF. This was inherited from Visual Basic.

  • issesi sagawa

    Yes. I like Internet Explorer. God.

  • The Peach

    hopefully you didn’t talk about the marvellous js debugger made by MS!!! rotflmao

  • As others have mentioned, that is exactly why I use a javascript framework! I just don’t have time to deal with these kinds of inconsistencies when there are such easy ways around them (jQuery is only 21k and worth every last bit! [pun intended]). Frankly, I’m really not sure why you do seem to have time to mess around with and report on these kinds of issues when everyone else just fills the gaps in with a well tested cross-browser framework.

  • I’ve found Javascript to be quite a headache in Internet Explorer, too. In some DOM functions it supports only one argument, where every other browser supports two, so you have to use a try and catch block, and what this is about with the enctype, I do not know.

  • madr

    Great stuff! :D

    I, whom prefer to write my javascript by hand rather than trusting a library, really approciate these kind of articles. I surely bookmark this one and place it in my bookmarks toolbar. Might coming handy (last week, I tracked down JS/DOM bugs in IE for about 20 hours at work. Really sucks.)

  • Thanks for the comments, and for the COM info – that’s very helpful.

  • Unlike the authors of the imminent Ultimate CSS Reference, I didn’t have any particular inclination to be nice to Internet Explorer.

    Believe me, James, it wasn’t us authors who felt inclined to be nice to IE. SitePoint’s editorial staff didn’t want us to put ‘partial support’ for every CSS property in IE, although it doesn’t support the inherit value. The reason was that they didn’t want the book to appear as wanton IE bashing, since that could make parts of the target audience less inclined to buy the book. In the end it didn’t matter much, since IE has issues with most CSS properties anyway.

    I just wanted to set the record straight. I’m really looking forward to reading your book!

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