Function selectPreLink

test/angular/1.6/angular.js:34200–34283

(scope, element, attr, ctrls)

  };

  function selectPreLink(scope, element, attr, ctrls) {

      var selectCtrl = ctrls[0];
      var ngModelCtrl = ctrls[1];

      // if ngModel is not defined, we don't need to do anything but set the registerOption
      // function to noop, so options don't get added internally
      if (!ngModelCtrl) {
        selectCtrl.registerOption = noop;
        return;
      }


      selectCtrl.ngModelCtrl = ngModelCtrl;

      // When the selected item(s) changes we delegate getting the value of the select control
      // to the `readValue` method, which can be changed if the select can have multiple
      // selected values or if the options are being generated by `ngOptions`
      element.on('change', function() {
        selectCtrl.removeUnknownOption();
        scope.$apply(function() {
          ngModelCtrl.$setViewValue(selectCtrl.readValue());
        });
      });

      // If the select allows multiple values then we need to modify how we read and write
      // values from and to the control; also what it means for the value to be empty and
      // we have to add an extra watch since ngModel doesn't work well with arrays - it
      // doesn't trigger rendering if only an item in the array changes.
      if (attr.multiple) {
        selectCtrl.multiple = true;

        // Read value now needs to check each option to see if it is selected
        selectCtrl.readValue = function readMultipleValue() {
          var array = [];
          forEach(element.find('option'), function(option) {
            if (option.selected && !option.disabled) {
              var val = option.value;
              array.push(val in selectCtrl.selectValueMap ? selectCtrl.selectValueMap[val] : val);
            }
          });
          return array;
        };

        // Write value now needs to set the selected property of each matching option
        selectCtrl.writeValue = function writeMultipleValue(value) {
          forEach(element.find('option'), function(option) {
            var shouldBeSelected = !!value && (includes(value, option.value) ||
                                               includes(value, selectCtrl.selectValueMap[option.value]));
            var currentlySelected = option.selected;

            // Support: IE 9-11 only, Edge 12-15+
            // In IE and Edge adding options to the selection via shift+click/UP/DOWN
            // will de-select already selected options if "selected" on those options was set
            // more than once (i.e. when the options were already selected)
            // So we only modify the selected property if necessary.
            // Note: this behavior cannot be replicated via unit tests because it only shows in the
            // actual user interface.