Below snippet how to make alert message on the input field when its in empty and unfilled
<script type='text/javascript'>
$.validator.addMethod("pan", function(value, element)
{
return this.optional(element) || /^[A-Z]{5}\d{4}[A-Z]{1}$/.test(value);
}, "Invalid Pan Number");
$("#myform").validate({
rules: {
"pan": {pan: true},
},
});
</script>