I am looking for a quick way to select all rows on the client. I am using the following function and it seems very slow.

function checkAll() {
  var grid = $find("WebDataGrid1");
  var rows = grid.get_rows();
  var selection = grid.get_behaviors().get_selection();
  var selectedRows = selection.get_selectedRows();
  var rowCount = rows.get_length();

  grid.beginUpdate();
           
  for (var i = 0; i < rowCount; i++) {
     var row = rows.get_row(i);
     selectedRows.add(row);
  }
  grid.endUpdate();
        
}

Any help would be greatly appreciated.