How do I close a modal window after AJAX success

Question

I have a button which opens a modal but I have prevented the modal close by clicking background or ESC key.

My button looks like this:

Answer 1

success :function(){
              console.log("success");
              $('#contact_modal').html("").delay(3000).fadeOut(450);
              $('body').removeClass('modal-open');
              $('.modal-backdrop.show').css('opacity','0');
              $('.modal-backdrop').css('z-index','-1')
          }