Question

To get an elements offset I use:

function(el) {
    if(el && el.parentNode) {
        var x = 0;
        var y = 0;
        while(el) {
            x += el.offsetLeft;
            y += el.offsetTop;
            el = el.offsetParent;
        }
        return {x: x, y: y};
    }
    return null;
}

and to get its scroll offset I use:

function(el) {
    if(el && el.parentNode) {
        var x = 0;
        var y = 0;
        while(el) {
            if(el && el.parentNode) {
                x += el.scrollLeft;
                y += el.scrollTop;
                el = el.parentNode;
            } else {
                el = null;
            }

        }
        return {x: x, y: y};
    }
    return null;
}

Problem is I can’t figure out how to merge these two functions together so I can get an elements offset including any scrolling thats been done on the page. When setting an elements position I usually just have to reference both functions, but it seems like it makes sense to just get the total offset in one function. How can I achieve this? Is it event a good idea to do this all in one function, or are there specific use cases when it would be a good idea to get the offset without the scroll?

Answer 1

You mean something like this?

function f (el) {
  var offset = (function(el) {
    if(el && el.parentNode) {
      var x = 0;
      var y = 0;

      while(el) {
        x += el.offsetLeft;
        y += el.offsetTop;
        el = el.offsetParent;
      }

      return {x: x, y: y};
    }

    return null;
  })(el);

  var scroll = (function(el) {
    if(el && el.parentNode) {
      var x = 0;
      var y = 0;

      while(el) {
        if(el && el.parentNode) {
          x += el.scrollLeft;
          y += el.scrollTop;
          el = el.parentNode;
        } else {
          el = null;
        }
      }

      return {x: x, y: y};
    }

    return null;
  })(el);

  return { x: offset.x + scroll.x, y: offset.y + scroll.y }
}