<!DOCTYPE html> <html> <head> <title></title> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <script language="javascript" src="https://code.jquery.com/jquery-3.1.1.min.js"></script> <style type="text/css"> .active{ color:red; } </style> <script language="javascript"> $(document).ready(function(){ $('input').click(function(){ $('div span:only-child').addClass('active'); }); }); </script> </head> <body> <div> <p>Real Madrid</p> <p>Barcelona</p> <p>Manchester United</p> <span>Liverpool </span> <p>Paris Saint-Germain</p> </div> <div> <span>Chelsea</span> </div> <input id="bt01" type="button" value=":only-child"/> </body> </html>