On 24 juin, 11:46, Paul Schwarz <paulsschw...@gmail.com> wrote:
> In Mootools et al. it is really easy to select all elements in the DOM
> with a given attribute, such as CSS class. In Mootools this is
> var listOfDivsWithClassRED = $$(".RED")
>
> I have a need to select all the elements on a page with a given
> attribute and value and I'm trying to mimic Mootools functionality AND
> speed!
>
> I
> found:http://stackoverflow.com/questions/2406002/find-an-element-by-css-sel...
> and then saw Robert
> Hanson's:http://gwt-widget.sourceforge.net/docs/xref/org/gwtwidgets/client/uti...
>
> Robert Hanson's recursion idea seems correct to me, except in my case
> the execution time is 5500ms for a typical page. Due to the structure
> of my markup I know that the elements I am interested in will not
> occur deeper than a certain depth on the DOM tree, so I put a
> recursionMaxDepth concept into my recursion and now I'm down to
> 3000ms.
>
> That's still too long, but I know how to solve it. The problem is (see
> Robert's code) we are dealing with GWT Elements. For example, see the
> lines:
> c = DOM.getAttribute(element, "className");
> Element child = DOM.getChild(element, i);
>
> So in my case the recursive function is inspecting about 1000 elements
> on the page (which is fine) but then GWT is turning each child element
> into an Element just to inspect an attribute and value pair, and then
> it discards the Element if it doesn't match my criteria. That's VERY
> expensive.
>
> I need a way to spin through those 1000ish elements quickly, treating
> them as "raw DOM elements", maybe Nodes, and then do the attribute
> matching on those light-weight objects. If one of them matches then
> GWT can turn it into a full blown Element object.
They *are* "raw DOM elements"... when compiled!
(Element inherits JavaScriptObject)
Of course in DevMode, you're then switching many times between Java
(in DevMode) and JavaScript (in the browser), with TCP communication
in between!
The "workaround" would be implement everything in a single JSNI
method, but then you'd have to duplicate your method with tweaks for
each supported user.agent, or lose the advantage of deferred-binding
for com.google.gwt.dom.client.* (compiling only the browser-specific
code).
I'd however use GwtQuery, as suggested instead of trying to re-
implement it. AFAICT, it even uses querySelectorAll in browsers that
supports it (i.e. recent versions of all of them, including IE8).
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