how to select the first div in jQuery

JavaScript
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>first demo</title>
  <style>
  td {
    color: blue;
    font-weight: bold;
  }
  </style>
  <script src="https://code.jquery.com/jquery-3.5.0.js"></script>
</head>
<body>
 
<table>
  <tr><td>Row 1</td></tr>
  <tr><td>Row 2</td></tr>
  <tr><td>Row 3</td></tr>
</table>
 
<script>
$( "tr:third" ).css( "font-style", "italic" );
</script>
 
</body>
</html>
Source

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