前提条件是当前元素必须设置为绝对定位。

<h2 id="id" style=" position: absolute">当前元素</h2>

设置:

    document.getElementById('id').style.width=value
    document.getElementById('id').style.height=value
    document.getElementById('id').style.top=value
    document.getElementById('id').style.left=value

获取:
 

    value=document.getElementById('id').offsetLeft
    value=document.getElementById('id').offsetTop
    value=document.getElementById('id').offsetWidth
    value=document.getElementById('id').offsetHeight

找一个元素的坐标：

function findPosition( oElement )
{
  var x2 = 0;
  var y2 = 0;
  var width = oElement.offsetWidth;
  var height = oElement.offsetHeight;
  alert(width + "=" + height);
  if( typeof( oElement.offsetParent ) != 'undefined' )
  {
    for( var posX = 0, posY = 0; oElement; oElement = oElement.offsetParent )
    {
      posX += oElement.offsetLeft;
      posY += oElement.offsetTop;     
    }
    x2 = posX + width;
    y2 = posY + height;
    return [ posX, posY ,x2, y2];
   
    } else{
      x2 = oElement.x + width;
      y2 = oElement.y + height;
      return [ oElement.x, oElement.y, x2, y2];
  }
}

alert (findPosition(document.getElementById('id')));