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

jQuery('#sender_container input.required[value=""]').addClass("error");

You can try this:

$('input:not([value!=""])').addClass('error');

DEMO

Note: This answer should not be used, and the only reason it wasn't deleted is so it can be learned from.