Selected Object Group row wise or column wise in javascript

I just implemented my idea step by step and I think it totally fullfills your objective.

absqua is wrong -- overlaps are important. Here is a before–after screenshot; larger objects may overlap previously defined groups ('buckets'), and if they do they have to be added to that bucket and its information updated. Initially I saved both top and bottom extremas, but after some more consideration that's not even necessary, and I could write it out exactly as I suggested earlier.

//DESCRIPTION:Group by horizontal extent
// A Jongware Script 26-Dec-2011
// grab selection
elements = app.selection;
// sort on tops
elements.sort (function(x,y)
 {
    return x.geometricBounds[0] - y.geometricBounds[0];
 }
);
// put in simple buckets, saving bottom and contains:array of elements
buckets = [ ];
for (i=0; i<elements.length; i++)
{
  e_top = elements.geometricBounds[0];
  e_bottom = elements.geometricBounds[2];
  b = 0;
  while (b < buckets.length && (e_top > buckets.bottom) )
    b++;
  // not in an available bucket? add one!
  if (b == buckets.length)
    buckets.push ( {bottom:e_bottom, contains:[ elements ] } );
  else
  {
    // put in bucket
    buckets.contains.push ( elements );
    // update range
    if (e_bottom > buckets.bottom)
      buckets.bottom = e_bottom;
    }
}
// add label for debugging purposes:
for (i=0; i<buckets.length; i++)
{
  app.activeDocument.textFrames.add ({geometricBounds:[ buckets.contains[0].geometricBounds[0], 0, buckets.bottom, 20 ], contents:String(i)+" => "+String(buckets.contains.length) } );
}
// deselect all
app.select(null);
// convert to groups and re-select
for (i=0; i<buckets.length; i++)
{
  if (buckets.contains.length > 1)
    app.select ([app.activeDocument.groups.add (buckets.contains)], SelectionOptions.ADD_TO);
  else
    app.select(buckets.contains, SelectionOptions.ADD_TO);
}