HTML Code

<!DOCTYPE html>
<html lang=en>
<head>
  <meta charset=UTF-8>
  <meta name=viewport content="width=device-width,initial-scale=1">
  <title>hidden — optional form section</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 1rem;font-size:1.25rem;color:#0f172a}form{max-width:420px;padding:1.25rem;background:#fff;border:1px solid #e2e8f0;border-radius:8px}label{display:block;margin:.65rem 0 .25rem;font-size:.875rem;font-weight:500;color:#475569}label:first-of-type{margin-top:0}label.check{display:flex;align-items:center;gap:.35rem;font-weight:400}input[type=text]{width:100%;box-sizing:border-box;padding:.45rem .6rem;border:1px solid #cbd5e1;border-radius:6px;font:inherit}.hint{margin-top:1rem;font-size:.8125rem;color:#64748b;max-width:420px}code{background:#e2e8f0;padding:.1rem .35rem;border-radius:4px}</style>
</head>
<body>
  <h1>hidden — optional form fields</h1>
  <form action=# onsubmit=return!1>
    <label for=name>Name:</label>
    <input id=name name=name placeholder="Your name">

    <label class=check>
      <input type=checkbox id=shipToggle>
      Add shipping address
    </label>

    <div id=addressPanel hidden>
      <label for=street>Street:</label>
      <input id=street name=street placeholder="123 Main St">
    </div>
  </form>
  <p class=hint>When shown, remove <code>hidden</code> (or set <code>hidden = false</code>) so the fields become visible and keyboard-accessible.</p>

  <script>var toggle=document.getElementById("shipToggle"),panel=document.getElementById("addressPanel");toggle.addEventListener("change",(function(){panel.hidden=!toggle.checked}))</script>
</body>
</html>

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HTML hidden Attribute — Optional Form Section