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<!DOCTYPE html>

<html lang=en>

<head>

  <meta charset=UTF-8>

  <meta name=viewport content="width=device-width,initial-scale=1">

  <title>onfocus — addEventListener</title>

  <style>body{font-family:system-ui,sans-serif;margin:0;padding:1.5rem;background:#f8fafc;color:#334155;line-height:1.7}h1{margin:0 0 .75rem;font-size:1.25rem;color:#0f172a}input{display:block;width:100%;max-width:280px;padding:.5rem .75rem;border:1px solid #cbd5e1;border-radius:8px;font-size:.875rem;margin-bottom:.75rem}.log{padding:.75rem 1rem;background:#f0fdf4;border:1px solid #bbf7d0;border-radius:8px;font-size:.8125rem;max-width:420px}</style>

</head>

<body>

  <h1>dynamicInput + addEventListener</h1>

  <p>Focus the field — handler registered in script, not in HTML.</p>

  <input type=email id=dynamicInput placeholder=you@example.com>

  <div class=log id=log>Tab or click into the input…</div>



  <script>var input=document.getElementById("dynamicInput"),log=document.getElementById("log");input.addEventListener("focus",(function(){log.innerHTML="<strong>focus event:</strong> input is in focus!",input.style.outline="2px solid #2563eb"})),input.addEventListener("blur",(function(){log.textContent="blur event — focus left the input.",input.style.outline=""}))</script>

</body>

</html>

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HTML onfocus Attribute — addEventListener