HTML Document File : input.html

<title>input with validity checks</title>

<meta name="viewport" content="width=device-width, initial-scale=1.0">

<input id=email type=email placeholder=email oninput="validity_indicator()">
<button onclick="alert('input was: '+email.value)">invia</button>
<script>
function validity_indicator(){
  email.style.backgroundColor=email.validity.valid?"yellowgreen":"red"
}
</script>

<!-- mostra source code -->
<script src="show-source.js"></script>