[whatwg] getElementsByClassName() feedback

Ian Hickson ian at hixie.ch
Mon Oct 8 14:25:01 PDT 2007

On Sat, 14 Jan 2006, Karoly Negyesi wrote:
> A getElementsByCSSSelector IMO would be great and introduces minimal 
> plus burden on browsers -- they have CSS selector code anyways.
> It's very unfriendly that I can do magic with CSS2/3 selectors and then 
> I need to translate them myself if I want to change them on-the-fly.

You may find this specification to be of interest:


On Tue, 24 Oct 2006, Dean Edwards wrote:
> > >
> > > Personally, I prefer a comma delimited list. Passing an array seems 
> > > yukky.
> > 
> > Really? I always thought the comma-separated argument to window.open() 
> > was one of the ugliest APIs ever...
> This isn't the same thing. We are faking varargs so whatever we do is 
> going to look a bit ugly. Nine times out of ten this method will be 
> called with one argument:
> var menus = document.getElementsByClassName("menu");
> That is much more intuitive for the most common case.


On Tue, 24 Oct 2006, Gervase Markham wrote:
> Why not allow a string in the single class name case, but require an 
> array for multiple class names?
> Alternatively, we could make it more obvious that it takes an array by 
> calling it document.getElementsByClassNames(["...", "..."]); This gives 
> a little hint, and is a more accurate description of what the function 
> does.

Also true...

On Sun, 5 Nov 2006, Anne van Kesteren wrote:
> I think this hasn't been suggested before. Perhaps the method should 
> accept a DOMTokenString as argument instead of an array. This allows 
> things like ele.getElementsByClassName(ele.className) etc. The only 
> problem is how to get a DOMTokenString without first getting .className 
> from somewhere. Perhaps it should be a constructor as well. 'x = new 
> DOMTokenString("aaa bbb")'

We could, though that's far more awkward.

> * The examples use a mix of accepting arrays and strings. This should be 
> fixed I assume.


> * In "HTML, XHTML, SVG and MathML elements" you can drop XHTML as it's 
> clearly defined in the specification what HTML elements means.


On Sun, 5 Nov 2006, Anne van Kesteren wrote:
> Hixie, the title attribute of the remove(token) definition says 
> dom-tokenstring-add rather than dom-tokenstring-remove...


On Fri, 2 Feb 2007, Robert Sayre wrote:
> I landed support for this on the Mozilla trunk, and it will appear in 
> upcoming Firefox alphas and betas. The array argument turned out to be 
> quite a pain to implement, so we cut it. If other implementors feel it's 
> worth it, we can put that support back in.

Ok. I've changed the spec to use a space-separated list.

On Sat, 7 Jul 2007, Lachlan Hunt wrote:
> It could be defined to accept either a space separated string or an 
> array. Using the [Overloads] extended attributed defined in the Language 
> Bindings for DOM Specifications draft [1], it could be defined like 
> this:
> NodeList getElementsByClassName(in DOMString classNames);
> [Overloads=getElementsByClassName]
>      NodeList getElementsByClassNameArray(in DOMString[] classNames);
> For ECMAScript, that effectively means that getElementsByClassName() can 
> be called with either a space separated string of class names or an 
> array.

I've dropped the array form altogether.

On Mon, 9 Jul 2007, Jonas Sicking wrote:
> I agree with Simon here. Allowing arrays to be passed in doesn't add any 
> extra value and complicates the implementation significantly. I think 
> that the by far most common case is going to be passing a single class 
> name, so adding multiple ways of passing multiple class names seems like 
> overkill.


On Tue, 10 Jul 2007, Dan Dorman wrote:
> Granted, the most common case will indeed be asking for a single class 
> name.  But, if we're going to the trouble of accepting multiple class 
> names, it seems shortsighted to restrict the parameter for the 
> multi-class case to a space-separated string, which is really just a 
> kludgey way of representing a list (or array).

Agreed as well, but implementation feedback seems to be that accepting an 
array is more expensive than it's worth.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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