Function renderUnknownOption

test/angular/1.4/angular.js:27044–27049

()

      var renderUnknownOption = function() {
        selectElement.prepend(unknownOption);
        selectElement.val('?');
        unknownOption.prop('selected', true); // needed for IE
        unknownOption.attr('selected', true);
      };

      var removeUnknownOption = function() {
        unknownOption.remove();