code: function (index) {
              var choices = this.results.find(".select2-result-selectable").not(".select2-disabled");
  
              if (arguments.length === 0) {
                  return indexOf(choices.filter(".select2-highlighted")[0], choices.get());
              }
  
              if (index >= choices.length) index = choices.length - 1;
              if (index < 0) index = 0;
  
              choices.removeClass("select2-highlighted");
  
              $(choices[index]).addClass("select2-highlighted");
              this.ensureHighlightVisible();
  
          }
docs: abstract