Making an Entityform field required using jQuery I have an Entityform and defined dependencies to where if a particular value is selected from one of the drop downs, the resume field (file upload) should be required. 

I don't know why, but it's currently not working. It marks the resume field as required, but still lets the application submitted with no error. 

I noticed all the required fields (that do work) have a class of required in their markup. Is it possible I can do this in jQuery? Meaning that I check that dropdown and if a certain value is selected, I'll add the required class to the file upload (resume) field.
Javascript can only handle soft (client-side) validation, unless you start looking into AJAX validation.

You need to alter the form on the server side to ensure that the data is validated properly - never rely on JS validation, it should only be used for UI/display purposes, and form data can easily be overridden by the user.