How to select empty inputs (value=“”) using jQuery

Question

How can I check for empty values of (required) input fields within a section, and then add a class to them on an event, using jQuery? So far, I have tried:

Answer 1

to get all fields inspected this might help.

$('#sender_container [required]').each(function(index)
{
       if (!($(this).val())) $(this).addClass('error');
}

});