Select option constantly blink when doesn’t field. And you can also follow JQuery if else condiotion.
<!DOCTYPE html>
<html lang="en" >
<head>
<meta charset="UTF-8">
<title></title>
<style>
.blinkanimat {
animation: blinker 1s linear infinite;
}
select.blinkanimat.open{
animation: inherit;
}
@keyframes blinker {
50% {
opacity: 0;
}
}
</style>
</head>
<body>
<select class="blinkanimat">
<option value="">Select</option>
<option value="a">A</option>
<option value="b">B</option>
<option value="c">C</option>
</select>
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js'></script>
<script>
$('.blinkanimat').on('click', function () {
var numberX = $(this).val();
if (numberX == '') {
$(this).removeClass('open');
} else {
$(this).addClass('open');
}
});
</script>
</body>
</html>