get-scrolling-position.js

来自「《JavaScript精粹》 源文件下载」· JavaScript 代码 · 共 78 行

addLoadListener(init);

function init()
{
  window.onscroll = function()
  {
    var scrollpos = getScrollingPosition();
    document.title = 'left=' + scrollpos[0] + ' top=' + scrollpos[1];
  };

  return true;
}

function getScrollingPosition()
{
  var position = [0, 0];

  if (typeof window.pageYOffset != 'undefined')
  {
    position = [
        window.pageXOffset,
        window.pageYOffset
    ];
  }

  else if (typeof document.documentElement.scrollTop != 'undefined'
      && (document.documentElement.scrollTop > 0 ||
      document.documentElement.scrollLeft > 0))
  {
    position = [
        document.documentElement.scrollLeft,
        document.documentElement.scrollTop
    ];
  }

  else if (typeof document.body.scrollTop != 'undefined')
  {
    position = [
        document.body.scrollLeft,
        document.body.scrollTop
    ];
  }

  return position;
}

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();
      };
    }
  }
}