<!DOCTYPE html> <body onload="f()"> <p>First</p> <p> <style scoped> p { text-decoration: underline } </style> Second </p> <p>Third</p> <script> function f() { var p = document.getElementsByTagName("p")[1]; var style = document.createElement("style"); style.setAttribute("scoped", ""); style.textContent = "p { color: green }"; p.appendChild(style); } </script> </body>