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Re: Publishing Selectors API Level 2 as an FPWD?

From: Sean Hogan <shogun70@westnet.com.au>
Date: Tue, 12 Jan 2010 00:25:11 +1100
Message-ID: <4B4B26B7.90209@westnet.com.au>
To: Boris Zbarsky <bzbarsky@MIT.EDU>
CC: Lachlan Hunt <lachlan.hunt@lachy.id.au>, public-webapps <public-webapps@w3.org>
On 11/01/10 6:40 PM, Boris Zbarsky wrote:
> On 1/11/10 1:24 AM, Sean Hogan wrote:
>> That's correct. jQuery's $(element).find("div") is the equivalent of
>> SelectorsAPI2's element.querySelectorAll(":scope div") or
>
> So in fact jquery can simply implement Element.find in terms of 
> querySelectorAll by just prepending ":scope " to the selector string, 
> right?  Note that this happens to work even for the "> div" case (by 
> converting the selector to ":scope > div", which is what jquery means).
>
> So the "> div" thing doesn't seem to require preparsing (modulo commas 
> in the selector; was that the key point?).  Of course the jquery 
> selectors that aren't in CSS do (or possibly post-parsing depending on 
> how it's implemented).
>

If we could assume that commas only ever delimit selectors in a 
selector-string, and if jQuery didn't support selectors not implemented 
by the browser then something like the following conversion would be 
sufficient for all jQuery queries:

function preprocess(str) { return ":scope " + str.split(",").join(", 
:scope "); }

Hence no value is added by queryScopedSelector*().

If we can't assume those things then jQuery will still need its current 
selector parser.
Hence no value is added by queryScopedSelector*().


>> My point is that jQuery's $(element).find("> div") isn't supported
>> (without pre-processing by the JS lib) by 
>> element.queryScopedSelectorAll().
>
> ...
>
>> element.queryScopedSelectorAll(":scope > div") generally becomes
>> element.parentNode.querySelectorAll(":scope > div", element) which is
>> the same as
>> element.querySelectorAll(":scope > div", element) or even
>> element.querySelectorAll(":scope > div")
>
> That's what I'm confused about.  Does implementing element.find("> 
> div") as element.queryScopedSelectorAll(":scope > div") not do what 
> the current jquery code does?  If not, how do they differ?
>

They will select the same list of elements.
As will element.querySelectorAll(":scope > div")

> I'm still confused about queryScopedSelectorAll, though. It sounds 
> from your example like queryScopedSelectorAll just prepends ":scope " 
> to the whole query string and then calls querySelectorAll on the 
> parentNode of the scope node, with the scope node passed in as the 
> optional argument.  So:
>
>   element.queryScopedSelectorAll(myStr)
>
> is the same as:
>
>   element.parentNode.querySelectorAll(":scope " + myStr, element);
>
> is that correct?
>

For some selector-strings yes.
More specifically, the parsing rules for scoped selectors are at:
     http://dev.w3.org/2006/webapi/selectors-api2/#parse-a-scoped-selector

Scoped selectors must still be valid selectors, so "> div", "+ div", "~ 
div" will all throw exceptions.
They must be explicitly written as ":scope > div", etc in the call to 
element.queryScopedSelectorAll().
Thus the queryScopedSelectorAll call won't prepend them with ":scope ".
Received on Monday, 11 January 2010 13:25:58 GMT

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