How do I modify this script , make it duplicates the currently selected rows

How do I modify this script , make  it duplicates the currently selected rows
Then add a empty at the table top

//first table in the active document
var table=app.activeDocument.textFrames[0].parentStory.tables[0]
dupeTopRow(table);
table.rows.add(LocationOptions.BEFORE, table.rows[0]);

/**
* duplicate the first row af a table 
* @ param the table 
* @ return void 
*/
function dupeTopRow(t){
    var nr = t.rows.add(LocationOptions.BEFORE, t.rows[0]);
    var c = nr.cells
    var lr = t.rows[1].cells
    for (var i = 0; i < c.length; i++){
        c[i].properties = lr[i].properties;
    };   
}