x and y coordinates

Discussion in 'Javascript' started by Derek, Apr 7, 2005.

  1. Derek

    Derek Guest

    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
     
    Derek, Apr 7, 2005
    #1
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  2. Derek

    Fred Oz Guest

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


    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
     
    Fred Oz, Apr 7, 2005
    #2
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  3. Derek wrote:
    > How can I find out (using JavaScript) the x and y coordinates of a HTML
    > element, e.g. an image, an anchor, a div?


    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.offsetTop,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;
     
    Ulrik Skovenborg, Apr 7, 2005
    #3
  4. Ulrik Skovenborg wrote:

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

    >
    > 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.offsetTop,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;


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

    --
    Justin Koivisto -
    http://koivi.com
     
    Justin Koivisto, Apr 7, 2005
    #4
  5. Derek

    RobB Guest

    Justin Koivisto wrote:

    (snip)

    > Does that take into consideration absolutely positioned elements when


    > using CSS?


    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;
    }
     
    RobB, Apr 7, 2005
    #5
  6. RobB wrote:

    > Justin Koivisto wrote:
    >
    > (snip)
    >
    >
    >>Does that take into consideration absolutely positioned elements when

    >
    >
    >>using CSS?

    >
    >
    > 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;
    > }
    >


    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 -
    http://koivi.com
     
    Justin Koivisto, Apr 7, 2005
    #6
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