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My code to get Y position of anchor - always null?

I wrote the function below to get the vertical scroll position of an
anchor. That is, a URL of the form
http://www.example.com/mypage.html#anchorname
should scroll to the point on the page that has an anchor
<a name="anchorname">...</a>).

Doing this in Javascript is necessary in the presence of a dynamic
HTML page having some hidden blocks. DHTML messes up the scroll
position in Opera and Mozilla (but not IE) so I'm trying to fix
it with javascript. Can anyone tell me why this function always
returns zero? What am I doing wrong?

=====================================
function getAnchorYPos(s) { /* s = string name of anchor */
/* get anchor object o */
var o=null;
if (document.getElementsByName && document.getElementsByName(s))
o = document.getElementsByName(s);
else if (document.all && document.all[s])
o = document.all[s];
else if (document.anchors && document.anchors.length
&& document.anchors[0].y) {
for (var i=0; i<document.anchors.length; i++)
if (document.anchors[i].name==s) o = document.anchors[i];
}
if (o==null) return null;

/* get anchor object Y position */
var ypos = 0;
var offset_parent = null;
offset_parent = o.offsetParent;
var el = o;
while (el.parentNode != null) {
el = el.parentNode;
if (el == offset_parent) {
ypos += o.offsetTop;
if (el.clientTop && el.nodeName != "TABLE") ypos += el.clientTop;
o = el;
if (o.offsetParent==null && o.offsetTop) ypos += o.offsetTop;
offset_parent = o.offsetParent;
}
}
return ypos;
}

var anchorname = document.location.hash.substr(1);
ypos = getAnchorYPos(anchorname); // ALWAYS ZERO ?!
=====================================

What I've observed:

1. The var anchorname has the correct value from the document URL.
2. The object o gets set by getElementsByName(s), however ALL of
the properties of o seem to be undefined after that.
3. document.all is never null, but document.all[s] has no properties.
4. document.anchors is never null, but document.anchors[0] and
document.anchors[s] have no properties.
2. Should I use getElementByID? document.getElementByID is never null,
but document.getElementByID(s) is.

What am I missing?

-Alex
Jun 13 '06 #1
3 3871
axlq wrote:
I wrote the function below to get the vertical scroll position of an
anchor. That is, a URL of the form
http://www.example.com/mypage.html#anchorname
should scroll to the point on the page that has an anchor
<a name="anchorname">...</a>).

Doing this in Javascript is necessary in the presence of a dynamic
HTML page having some hidden blocks. DHTML messes up the scroll
position in Opera and Mozilla (but not IE) so I'm trying to fix
it with javascript. Can anyone tell me why this function always
returns zero? What am I doing wrong?

=====================================
function getAnchorYPos(s) { /* s = string name of anchor */
/* get anchor object o */
var o=null;
if (document.getElementsByName && document.getElementsByName(s))
o = document.getElementsByName(s);


getElementsByName returns a collection, not a single element. Try:

if ( document.getElementsByName
&& document.getElementsByName(s).length)
o = document.getElementsByName(s)[0];

which will set the value of 'o' as a reference to the first element in
the collection (hopefully that's the one you want).

Or give it an ID and use getElementById, which returns a reference to a
single element.

[...]

I haven't tested the rest of your code...
--
Rob

Jun 14 '06 #2
In article <11**********************@u72g2000cwu.googlegroups .com>,
RobG <rg***@iinet.net.au> wrote:
getElementsByName returns a collection, not a single element. Try:

if ( document.getElementsByName
&& document.getElementsByName(s).length)
o = document.getElementsByName(s)[0];

which will set the value of 'o' as a reference to the first element in
the collection (hopefully that's the one you want).
Hmm... it returns null. And I know the argument (s) is the name of an
element of the form <a name="FL" ...>, and s="FL";
Or give it an ID and use getElementById, which returns a reference to a
single element.


Strange... that comes out null too, for <a name="FL" id="FL" ...>.
Funny thing is, *other* code using getElementById on the exact same
page (to hide a bunch of other elements in the un-expanded list)
work just fime.

-A
Jun 15 '06 #3
In article <e6**********@blue.rahul.net>, axlq <ax**@spamcop.net> wrote:
In article <11**********************@u72g2000cwu.googlegroups .com>,
RobG <rg***@iinet.net.au> wrote:
getElementsByName returns a collection, not a single element. Try:

if ( document.getElementsByName
&& document.getElementsByName(s).length)
o = document.getElementsByName(s)[0];

which will set the value of 'o' as a reference to the first element in
the collection (hopefully that's the one you want).


Hmm... it returns null. And I know the argument (s) is the name of an
element of the form <a name="FL" ...>, and s="FL";
Or give it an ID and use getElementById, which returns a reference to a
single element.


Ignore my last message. That worked. I was testing for the wrong
ID. Oddly, getElementsByName(s)[0] always returns null, when
testing with an element name that I know exists. Anyway, I have it
working now.

Thanks!!

-A
Jun 15 '06 #4

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