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<html><body><p><a id="myAnchor" href="https://johnsmith:smith123@www.example.com">Example link</a></p><p>Click the button to change the username part of the link above.</p><button onclick="myFunction()">Try it</button><p id="demo"></p><script>function myFunction() { document.getElementById("myAnchor").username = "newUsername"; document.getElementById("demo").innerHTML = "The username was changed from 'johnsmith' to 'newUsername'.";}</script></body></html>