How is it possible to display an alert with jQuery if I click the submit button and the value of the input field is empty?
Also you can try this, if you want to focus on same text after error.
If you wants to show this error message in a paragraph then you can use this one:
$(document).ready(function () {
$("#submit").click(function () {
if($('#selBooks').val() === '') {
$("#Paragraph_id").text("Please select a book and then proceed.").show();
$('#selBooks').focus();
return false;
}
});
});