Hi,
> But can anyone explain what my conceptual failure was here?
Elements can have at most *one* parent element. What you were
expecting would have resulted in an element having two parents, which
the tree-like structure of the DOM does not allow. This isn't a
Prototype thing, it goes at least back to the first formal DOM
specification (and probably farther):
"appendChild: Adds the node newChild to the end of the list of
children of this node. If the newChild is already in the tree, it is
first removed."[1]
Conveniently, though, there's cloneNode[2], which would have done
pretty much what you were expecting:
$('bar').update(this.down('p').cloneNode());
Be careful if you clone a node that has an ID attribute, though; you
have to change the ID before adding it back to the tree (since IDs
*must* be unique).
[1] http://www.w3.org/TR/REC-DOM-Level-1/level-one-core.html#method-appendChild
[2] http://www.w3.org/TR/REC-DOM-Level-1/level-one-core.html#method-cloneNode
HTH,
--
T.J. Crowder
Independent Software Consultant
tj / crowder software / com
www.crowdersoftware.com
On Mar 3, 8:02 pm, Walter Lee Davis <[email protected]> wrote:
> I was trying to do a very simple image-swap effect:
>
> <div id="foo">
> <p><img ... /></p>
> </div>
>
> <div id="bar">
> <p><img ... /></p>
> </div>
>
> $('foo').observe('click',function(evt){
> $('bar').update(this.down('p'));
>
> });
>
> I expected both #foo and #bar to contain the same image, but instead,
> #foo was empty, and #bar contained the image originally in #foo.
>
> I resolve the problem by changing my method from copying the P to
> simply making the two images have the same src attribute.
>
> But can anyone explain what my conceptual failure was here? Why did
> update() seem to do what I would have expected the following
> construction to do:
>
> $('bar').update(this.down('p').remove());
>
> ???
>
> Thanks in advance,
>
> Walter
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