x and y coordinates

How can I find out (using JavaScript) the x and y coordinates of a HTML
element, e.g. an image, an anchor, a div?


Thanks for the help.
Derek

re: x and y coordinates

Derek wrote:[color=blue]
> How can I find out (using JavaScript) the x and y coordinates of a HTML
> element, e.g. an image, an anchor, a div?
>
>[...][/color]

Search for "findPosX" posted in the last couple of days.

Have a poke around quirksmode.org:

<URL:http://www.quirksmode.org/js/findpos.html#>


--
Fred

re: x and y coordinates

Derek wrote:[color=blue]
> How can I find out (using JavaScript) the x and y coordinates of a HTML
> element, e.g. an image, an anchor, a div?[/color]

This little function should do the trick (credit to jumper on
http://eksperten.dk):

function getPos(elm) {
for(var
zx=zy=0;elm!=null;zx+=elm.offsetLeft,zy+=elm.offse tTop,elm=elm.offsetParent);
return {x:zx,y:zy}
}

To use the function you should use an object (an image, div etc.) as the
argument. The function returns another object with the x and y coordinates:

elm = document.getElementById("divElement");
pos = getPos(elm);
alert(pos.x); // this is the x-coordinate
alert(pos.y); // ..and the y-coordinate
// You can also do something like this:
coordinateX = getPos(elm).x;
// or
coordinateY = getPos(document.getElementById("divElement")).y;

re: x and y coordinates

Ulrik Skovenborg wrote:
[color=blue]
> Derek wrote:[color=green]
> > How can I find out (using JavaScript) the x and y coordinates of a HTML
> > element, e.g. an image, an anchor, a div?[/color]
>
> This little function should do the trick (credit to jumper on
> http://eksperten.dk):
>
> function getPos(elm) {
> for(var
> zx=zy=0;elm!=null;zx+=elm.offsetLeft,zy+=elm.offse tTop,elm=elm.offsetParent);
>
> return {x:zx,y:zy}
> }
>
> To use the function you should use an object (an image, div etc.) as the
> argument. The function returns another object with the x and y coordinates:
>
> elm = document.getElementById("divElement");
> pos = getPos(elm);
> alert(pos.x); // this is the x-coordinate
> alert(pos.y); // ..and the y-coordinate
> // You can also do something like this:
> coordinateX = getPos(elm).x;
> // or
> coordinateY = getPos(document.getElementById("divElement")).y;[/color]

Does that take into consideration absolutely positioned elements when
using CSS?

--
Justin Koivisto - justin@koivi.com
http://koivi.com

re: x and y coordinates

Justin Koivisto wrote:

(snip)
[color=blue]
> Does that take into consideration absolutely positioned elements when[/color]
[color=blue]
> using CSS?[/color]

Yes. The offset[Left/Top/Width/Height] properties are calculated by the
browser when laying out the page; they're read-only, and available
regardless of whether CSS was even used to position the object. There
are a few browser-specific wrinkles that crop up, but the accumulated
offsets are reasonably accurate. Here's an alternative if you only need
one coordinate (takes id or object ref):

function getLeft(obj)
{
if ('string' == typeof obj)
obj = document.getElementById(obj);
var x = 0;
while (obj != null)
{
x += obj.offsetLeft;
obj = obj.offsetParent;
}
return x;
}

function getTop(obj)
{
if ('string' == typeof obj)
obj = document.getElementById(obj);
var y = 0;
while (obj != null)
{
y += obj.offsetTop;
obj = obj.offsetParent;
}
return y;
}

re: x and y coordinates

RobB wrote:
[color=blue]
> Justin Koivisto wrote:
>
> (snip)
>
>[color=green]
>>Does that take into consideration absolutely positioned elements when[/color]
>
>[color=green]
>>using CSS?[/color]
>
>
> Yes. The offset[Left/Top/Width/Height] properties are calculated by the
> browser when laying out the page; they're read-only, and available
> regardless of whether CSS was even used to position the object. There
> are a few browser-specific wrinkles that crop up, but the accumulated
> offsets are reasonably accurate. Here's an alternative if you only need
> one coordinate (takes id or object ref):
>
> function getLeft(obj)
> {
> if ('string' == typeof obj)
> obj = document.getElementById(obj);
> var x = 0;
> while (obj != null)
> {
> x += obj.offsetLeft;
> obj = obj.offsetParent;
> }
> return x;
> }
>
> function getTop(obj)
> {
> if ('string' == typeof obj)
> obj = document.getElementById(obj);
> var y = 0;
> while (obj != null)
> {
> y += obj.offsetTop;
> obj = obj.offsetParent;
> }
> return y;
> }
>[/color]

Oops... I was thinking of something slightly different.

I used a (likely inefficient) way to find the position of an object
relative to its absolutely positioned parent (or root if there was no
CSS positioning involved) which worked out to just under 30 lines. I was
hoping to replace it all with that piece. ;)

--
Justin Koivisto - justin@koivi.com
http://koivi.com