Changing name attribute using jQuery

Karim is right,

$("#" + id).attr('classname', 'selected');
$("#" + id).attr('id', 'sel' + rowIndex);
$("#" + id).attr('name', 'sel' + rowIndex);

could be changed to

$("#" + id).attr('name', 'sel' + rowIndex);
$("#" + id).attr('classname', 'selected');
$("#" + id).attr('id', 'sel' + rowIndex);

to change the name first, $("#" + id) is the same as getElementById and once you change the id, its no longer the element you meant to refer to

Instead of chaining you can pass into .attr()

{
    "id" : "sel" + rowIndex ,
    "name" : "sel" + rowIndex
}

A lot of jQuery functions accept objects like above when you have to pass in (string comma string) data like .css() and .animate()

The name cannot be changed because once you have modified the id, the selector in the subsequent expression (which uses the unmodified id) is selecting nothing :)

$("#" + id).attr('id', 'sel' + rowIndex);
$("#" + id).attr('name', 'sel' + rowIndex); // this can't ever work

Try chaining them together like this, to keep the reference to the current selection:

$("#" + id).attr('id', 'sel' + rowIndex)
           .attr('name', 'sel' + rowIndex);

Alternatively, reorder the statements such that you change the name (and/or whatever else) before changing the id:

$("#" + id).attr('name', 'sel' + rowIndex);
$("#" + id).attr('id', 'sel' + rowIndex);

You can also assign the selection to a variable:

var $el = $("#" + id);
$el.attr("id", 'sel' + rowIndex);
...