Function ngOptionsPostLink

test/angular/1.7/angular.js:32440–32725

(scope, selectElement, attr, ctrls)

      optGroupTemplate = window.document.createElement('optgroup');

    function ngOptionsPostLink(scope, selectElement, attr, ctrls) {

      var selectCtrl = ctrls[0];
      var ngModelCtrl = ctrls[1];
      var multiple = attr.multiple;

      // The emptyOption allows the application developer to provide their own custom "empty"
      // option when the viewValue does not match any of the option values.
      for (var i = 0, children = selectElement.children(), ii = children.length; i < ii; i++) {
        if (children[i].value === '') {
          selectCtrl.hasEmptyOption = true;
          selectCtrl.emptyOption = children.eq(i);
          break;
        }
      }

      // The empty option will be compiled and rendered before we first generate the options
      selectElement.empty();

      var providedEmptyOption = !!selectCtrl.emptyOption;

      var unknownOption = jqLite(optionTemplate.cloneNode(false));
      unknownOption.val('?');

      var options;
      var ngOptions = parseOptionsExpression(attr.ngOptions, selectElement, scope);
      // This stores the newly created options before they are appended to the select.
      // Since the contents are removed from the fragment when it is appended,
      // we only need to create it once.
      var listFragment = $document[0].createDocumentFragment();

      // Overwrite the implementation. ngOptions doesn't use hashes
      selectCtrl.generateUnknownOptionValue = function(val) {
        return '?';
      };

      // Update the controller methods for multiple selectable options
      if (!multiple) {

        selectCtrl.writeValue = function writeNgOptionsValue(value) {
          // The options might not be defined yet when ngModel tries to render
          if (!options) return;

          var selectedOption = selectElement[0].options[selectElement[0].selectedIndex];
          var option = options.getOptionFromViewValue(value);

          // Make sure to remove the selected attribute from the previously selected option
          // Otherwise, screen readers might get confused
          if (selectedOption) selectedOption.removeAttribute('selected');

          if (option) {
            // Don't update the option when it is already selected.
            // For example, the browser will select the first option by default. In that case,
            // most properties are set automatically - except the `selected` attribute, which we
            // set always

            if (selectElement[0].value !== option.selectValue) {
              selectCtrl.removeUnknownOption();