Apply css class on tr and th jquery

Question

I try to apply class on tr and th i try this but effect did not reflect when i run this

html

<table id="tabledata">  </table>

and

success: function (result) {
var final = JSON.parse(result.d).response;
console.log(JSON.parse(result.d).response)
$("#tabledata").empty();
$("th").addClass("GridviewScrollHeader");
$("td").addClass("GridviewScrollItem");
if (final.length > 0) {
$("#tabledata").append(
"<tr><th>ID</th><th>OwnerName</th><th>RegNo</th><th>MileageAccumlation</th><th>MaxSpeed</th></tr>");
for (var i = 0; i < final.length; i++) {
if (final[i] !== null) {
$("#tabledata").append("<tr><td>" +
final[i][0] + "</td> <td>" +
final[i][1] + "</td> <td>" +
final[i][2] + "</td> <td>" +
final[i][3] + "</td> <td>" +
final[i][4] + "</td></tr>");
}
}
}

any solution?>