<!DOCTYPE html>
<html>
<body>
E-mail: <input type="email" id="myEmail"><br><br>
<button onclick="disableBtn()">Disable Email Field</button>
<button onclick="undisableBtn()">Undisable Email Field</button>
<script>
function disableBtn() {
document.getElementById("myEmail").disabled = true;
}
function undisableBtn() {
document.getElementById("myEmail").disabled = false;
}
</script>
</body>
</html>