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<!doctype html> <html lang="vi"> <head> <meta charset="utf-8"> <title>Học web chuẩn</title> <script src="https://code.jquery.com/jquery-latest.js"></script> <style> .test { background-color: yellow; } </style> <script> $(function(){ $('div').addClass('test'); }); </script> </head> <body> <div>Thành phần div</div> </body> </html>