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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>novalidate — custom validation</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}label{display:block;margin:.75rem 0 .35rem;font-weight:500;font-size:.875rem}input{width:100%;max-width:320px;padding:.5rem .65rem;font:inherit;border:1px solid #cbd5e1;border-radius:6px}input.invalid{border-color:#ef4444;background:#fef2f2}button{margin-top:1rem;padding:.5rem 1rem;font:inherit;cursor:pointer;border-radius:6px;border:1px solid #1d4ed8;background:#2563eb;color:#fff}.error{margin-top:.35rem;font-size:.8125rem;color:#dc2626;max-width:320px}.success{margin-top:1rem;padding:.75rem 1rem;background:#f0fdf4;border:1px solid #bbf7d0;border-radius:8px;font-size:.8125rem;max-width:420px}code{background:#e2e8f0;padding:.1rem .35rem;border-radius:4px}</style>



</head>



<body>



  <h1>Custom validation with novalidate</h1>



  <p>Browser validation is off; JavaScript checks the email format instead.</p>







  <form id=customForm novalidate>



    <label for=email>Email:</label>



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



    <div class=error id=emailError hidden>Enter a valid email address.</div>



    <button type=submit>Submit with custom check</button>



  </form>



  <div class=success id=success hidden>Valid email — form would submit to server.</div>







  <script>var form=document.getElementById("customForm"),email=document.getElementById("email"),emailError=document.getElementById("emailError"),success=document.getElementById("success");form.addEventListener("submit",(function(e){e.preventDefault(),success.hidden=!0,email.classList.remove("invalid"),emailError.hidden=!0;var i=email.value.trim();if(!/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(i))return email.classList.add("invalid"),void(emailError.hidden=!1);success.hidden=!1}))</script>



</body>



</html>
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HTML novalidate Attribute — Custom JavaScript Validation
