find_position_of_element.js

来自「源码JAVASCRIPT精粹」· JavaScript 代码 · 共 58 行

addLoadListener(init);

function init()
{
  var heading = document.getElementsByTagName("h1")[0];
  var position = getPosition(heading);
  
  alert("The X position of the h1 is: " + position[0] + "px\nThe Y position of the h1 is: " + position[1] + "px");
  
  return true;
}

function getPosition(theElement)
{
  var positionX = 0;
  var positionY = 0;

  while (theElement != null)
  {
    positionX += theElement.offsetLeft;
    positionY += theElement.offsetTop;
    theElement = theElement.offsetParent;
  }
  
  return [positionX, positionY];
}

function addLoadListener(fn)
{
  if (typeof window.addEventListener != 'undefined')
  {
    window.addEventListener('load', fn, false);
  }
  else if (typeof document.addEventListener != 'undefined')
  {
    document.addEventListener('load', fn, false);
  }
  else if (typeof window.attachEvent != 'undefined')
  {
    window.attachEvent('onload', fn);
  }
  else
  {
    var oldfn = window.onload;
    if (typeof window.onload != 'function')
    {
      window.onload = fn;
    }
    else
    {
      window.onload = function()
      {
        oldfn();
        fn();
      };
    }
  }
}