// Get all form fields that are hidden
var hidden_fields = $( this ).find( 'input:hidden' );
// Filter those which have a specific type
hidden_fields.attr( 'text' );
<input type="hidden" id="hiddenField" name="hiddenField" class="hiddenField"/>
$("#hiddenField").val(); //by id
$("[name='hiddenField']").val(); // by name
$(".hiddenField").val(); // by class