// Find the horizontal positioing of an element within its parent
  function parentX(elem) {
      // If the offsetParent is the element’s parent, break early
      return elem.parentNode == elem.offsetParent ?
          elem.offsetLeft :
  
          // Otherwise, we need to find the position relative to the entire
          // page for both elements, and find the difference
          pageX( elem ) - pageX( elem.parentNode );
  }
  
  // Find the vertical positioing of an element within its parent
  function parentY(elem) {
      // If the offsetParent is the element’s parent, break early
      return elem.parentNode == elem.offsetParent ?
          elem.offsetTop :
  
          // Otherwise, we need to find the position relative to the entire
          // page for both elements, and find the difference
          pageY( elem ) - pageY( elem.parentNode );
  }