It is clear, but you're misunderstanding the concept. I'll use a class
selector to exemplify it:
$('#people .name')
is the same as
$('#people .name', document)
.context = [object HTMLDocument]
$('.name', '#people') or $('.name', $('#people')) will simply
translate to $('#people').find('.name'), or $('#people .name'), where
the context is the *document* object. The context only changes if you
pass a HTMLElement as the second argument, then the native methods
will be called on that node, not the document:
$('.name', $('#people')[0] )
.context = [object HTMLDivElement]
For example (using common DOM methods):
$('#people') == $('#people', document);
what's happening is equivalent to
document.getElementById('people');
now in this case
$('div', document.getElementById('people'))
what is actually happening is
[#people node].getElementsByTagName('div');
In other words, jQuery objects and strings passed as a context will
act as filters, but the context will still be the document. The
context will only change if you pass in a DOM node.
It's a bit counter-intuitive but that's the way it works right now.
cheers,
- ricardo
On Mar 25, 9:30 pm, DBJ <dbj...@gmail.com> wrote:
> This is, of course, true and fine. Exactly the purpose of the context.
> To define the starting node BELLOW which it will look further. Fine.
> It is only that this is not what current documentation is saying :
>
> http://docs.jquery.com/Core/jQuery#expressioncontext
>
> At least NOT clearly and NOT unambigously...
>
> On top of that jQuery.selector and jQuery.context in this case are not
> what was originaly passed but what was processed inside jQ
>
> So:
>
> $("[name]","#people") which is equivalent to $("#people
> [name]").
>
> Results in :
>
> selector := "'#people [name]" // space in the middle
> context := DOMDocument
>
> After call to $() finsihes, and plugins can start using this properties.
> Above is wrong and should be :
>
> selector := "[name]"
> context := "#people " // space on the end
>
> This might seem as some nitpicking, but it is actually extrmely important.
> Because if context is always given , jQuery enabled pages will be faster.
> In some case much faster. So the context syntax should be crystal
> clear and consistent.
>
> In my mind context (as I said but I will repeat ;) should be only dom
> node, or single id string. If given by user. So these will be only
> three valid forms:
>
> $("'#people") // dom document default context
> $("[name], "#people") //single id
> $("[name]", domNode ) // element given as context
>
> I see no reason for anything else to act as context.
> This would be (as I also already said ;) excellent start for people to
> understand how to structure their pages and why. And why are properly
> strucutred pages faster to traverse with jQuery( selector, context )
> calls.
>
> 2009/3/25 Julian Aubourg <aubourg.jul...@gmail.com>:
>
>
>
> > $("[name]","#people") is equivalent to $("#people [name]").
> > Please note the spacing.
> > It then means every element with a name attribute BELOW the element of id
> > "people".
> > $("#people[name]") means the element of id "people" with a name attribute.
> > So, YES, this is quite different.
> > 2009/3/25 DBJ <dbj...@gmail.com>
>
> >> @Daniel
>
> >> You confuse me ;o)
>
> >> Aa I said : A quick sample I have made (quickly) is here:
> >>http://jsbin.com/avowu/edit
>
> >> Please use it now. It is extremely simple and it shows what is going
> >> on inside jQuery, regarding : this.selector and this.context.
>
> >> So when I say: $("[name]", "#people"); I can (and you) can see that
> >> inside jQuery selector (aka this.selector) is : "'#people[name]"
>
> >> So I am not "thinking" on this one I am just passing it on. This is
> >> also very confusing:
>
> >> > Thinking that $("[name]", "#people"); is the same as $("#people[name]");
> >> > is wrong on multiple levels.
>
> >> This is how I understood jQuery documentation describes the context,
> >> but this is not
> >> apparently how this.selector value is defined inside ... This might be
> >> "wrong on multiple levels" bi this is the value of this.selector , as
> >> we can clearly see.
>
> >> Also you say :
>
> >> > $("[name]", $("#people")); actually means $("#people [name]");
>
> >> Are you actually saying this is the proper usage? Ok, but why is than
> >> the "improper" usage allowed? If it is imporper that is. But the
> >> question (for the last snippet) is what is then the value of the
> >> this.slector going to be, when used by a plugin ? Currently it is :
> >> "#people [name]"
>
> >> Also, why are we in this mess ? Can we have consistent documentation
> >> and implementation that is folllowing it? Something like :
>
> >> "Context type can be a dom node or an jQuery instance. Everything else
> >> throws an exeception if passed as a context to the jQuery() function"
>
> >> This would be a really good start to the discussion on what is
> >> actually a "context" ;o)
>
> >> Regards.
>
> >> 2009/3/25 Daniel Friesen <nadir.seen.f...@gmail.com>:
>
> >> > Context is either a dom node, a document, or recently a jQuery object
> >> > with the like. Context is merely used for establishing a dom node as a
> >> > parent, and in the case of a document is necessary to know what document
> >> > to use to create new nodes for.
> >> > Thinking that $("[name]", "#people"); is the same as $("#people[name]");
> >> > is wrong on multiple levels. $("[name]", $("#people")); actually means
> >> > $("#people [name]"); and the contex is not meant to be used that way.
> >> > In fact trying to think that way makes things confusing and reduces code
> >> > readability because you are mixing up order. If you want to build
> >> > queries like this then I'd recommend you push for the inclusion of my
> >> > alternate proposed format:
> >> > $("#selector", "[selector]", ".selector", ...);
> >> > Which makes proper sense since you are building up selectors in order
> >> > (even has potential performance benefits if someone is adventurous since
> >> > I'd explicitly say to not rely on any consistent return for .end() when
> >> > using it). It's even more useful when you throw widget objects into the
> >> > mix.
>
> >> > ~Daniel Friesen (Dantman, Nadir-Seen-Fire)
>
> >> > DBJDBJ wrote:
> >> >> My question/comment : What is a CONTEXT LOGIC in jQ ? I think it
> >> >> should be : dom node inside which is the result set to be found?
> >> >> The dom node inside which is jQuery to use the selector given. Default
> >> >> is document.
>
> >> >> If I read it right , jQ doc says that context type can be (only?) dom
> >> >> node or jQuery instance. So I expected that if I give context as a
> >> >> string it will be takens as selector for the jQuery, which will
> >> >> eventualy spill out a single dome node to be used as a context. And
> >> >> that
> >> >> way one can speed up her code, because querying inside the known dom
> >> >> element must be quicker than querying inside the whole document, each
> >> >> time. finding on the branch is faster that finding from the root of
> >> >> the tree.
>
> >> >> But it seems that if string is given as a context , the selector get's
> >> >> it as a prefix and context is a dom document ? So :
>
> >> >> $("[name]", "#people") is the same as saying $("#people[name]",
> >> >> document ) , because jQ makes it into this.
>
> >> >> While one might expect the above to be translated to : $("[name]",
> >> >> document.getElementById("people") ) , which could considerably speed
> >> >> up the slection ...
>
> >> >> A quick sample I have made (quickly) is here:
> >> >>http://jsbin.com/avowu/edit
>
> >> >> // context is correctly reported by jQ
> >> >> $("[name]", document.getElementById("people")).formula( log ) ;
>
> >> >> // this.context is reported by jQ as HTMLDocument ?
> >> >> // this.selector is prefixed with context
> >> >> $("[name]", "#people") ;
>
> >> >> Is this "by design" ? Maybe jQ does this :
>
> >> >> 1 :: jQuery("#people").find("[name]")
> >> >> 2 :: this.context = "#people" + "[name]"
>
> >> >> So that plugins can see the context which actually was used ? So the
> >> >> line :
> >> >> $("[name]", "#people")
> >> >> after all IS actually making things faster ? And I am (or I was)
> >> >> confused with the value of this.context and this.selector, available
> >> >> to me inside a plugin ? But then I think I can;t be right here,
> >> >> because it would be much better to have the selector and context, as
> >> >> originaly
> >> >> given by the user :
>
> >> >> 1 :: this.context = "#people" ; this.selector = "[name]" ;
> >> >> 2 :: jQuery(context).find(selector)
>
> >> >> After this plugins will see the original selector and context.
> >> >> Provided my assumptions are correct.
>
> >> --
> >> Dusan Jovanovic
> >>http://dbj.org
> >> -------------------------
> >> "html e-mail is expensive" ™
>
> >> This email originates from Dusan B. Jovanovic. It, and any
> >> attachments, may contain confidential information and may be subject
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> >> use of the addressee(s). You may not copy, forward, disclose, save or
> >> otherwise use it in any way if you are not the addressee(s) or
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>
> --
> Dusan Jovanovichttp://dbj.org
> -------------------------
> "html e-mail is expensive" ™
>
> This email originates from Dusan B. Jovanovic. It, and any
> attachments, may contain confidential information and may be subject
> to copyright or other intellectual property rights. It is only for the
> use of the addressee(s). You may not copy, forward, disclose, save or
> otherwise use it in any way if you are not the addressee(s) or
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> advise the sender and cancel it immediately. Dusan B. Jovanovic may
> monitor the content of emails within its network to ensure compliance
> with its policies and procedures. Any email is susceptible to
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