AngularJS directive using bootstrap-multiselect

angular-bootstrap-multiselect.ts

// AngularJS: 1.5.8
// bootstrap-multiselect: 0.9.13

angular.module('SocoApp')
    .directive('multiSelect', function () {
        return {
            link: function (scope, element, attrs: any) {

                var options: any = {
                    onChange: function (optionElement, checked) {
                        if (optionElement != null) {
                            $(optionElement).removeProp('selected');
                        }
                        if (checked) {
                            $(optionElement).prop('selected', 'selected');
                        }
                        element.change();
                    }
                };

                //attrs are lowercased by Angular, but options must match casing of bootstrap-multiselect
                if (attrs.enablehtml) options.enableHTML = JSON.parse(attrs.enablehtml); //default:  false
                if (attrs.buttonclass) options.buttonClass = attrs.buttonclass; //default:  'btn btn-default'
                if (attrs.inheritclass) options.inheritClass = JSON.parse(attrs.inheritclass); //default:  false
                if (attrs.buttonwidth) options.buttonWidth = attrs.buttonwidth; //default:  'auto'
                if (attrs.buttoncontainer) options.buttonContainer = attrs.buttoncontainer; //default:  '<div class="btn-group" />'
                if (attrs.dropright) options.dropRight = JSON.parse(attrs.dropright); //default:  false
                if (attrs.dropup) options.dropUp = JSON.parse(attrs.dropup); //default:  false
                if (attrs.selectedclass) options.selectedClass = attrs.selectedclass; //default:  'active'
                if (attrs.maxheight) options.maxHeight = attrs.maxheight; //default:  false,  // Maximum height of the dropdown menu. If maximum height is exceeded a scrollbar will be displayed.
                if (attrs.includeselectalloption) options.includeSelectAllOption = JSON.parse(attrs.includeselectalloption); //default:  false
                if (attrs.includeselectallifmorethan) options.includeSelectAllIfMoreThan = attrs.includeselectallifmorethan; //default:  0
                if (attrs.selectalltext) options.selectAllText = attrs.selectalltext; //default:  ' Select all'
                if (attrs.selectallvalue) options.selectAllValue = attrs.selectallvalue; //default:  'multiselect-all'
                if (attrs.selectallname) options.selectAllName = JSON.parse(attrs.selectallname); //default:  false
                if (attrs.selectallnumber) options.selectAllNumber = JSON.parse(attrs.selectallnumber); //default:  true
                if (attrs.selectalljustvisible) options.selectAllJustVisible = JSON.parse(attrs.selectalljustvisible); //default:  true
                if (attrs.enablefiltering) options.enableFiltering = JSON.parse(attrs.enablefiltering); //default:  false
                if (attrs.enablecaseinsensitivefiltering) options.enablecaseinsensitivefiltering = JSON.parse(attrs.enableCaseInsensitiveFiltering); //default:  false
                if (attrs.enablefullvaluefiltering) options.enableFullValueFiltering = JSON.parse(attrs.enablefullvaluefiltering); //default:  false
                if (attrs.enableclickableoptgroups) options.enableClickableOptGroups = JSON.parse(attrs.enableclickableoptgroups); //default:  false
                if (attrs.enablecollapsibleoptgroups) options.enableCollapsibleOptGroups = JSON.parse(attrs.enablecollapsibleoptgroups); //default:  false
                if (attrs.filterplaceholder) options.filterPlaceholder = attrs.filterplaceholder; //default:  'Search'
                if (attrs.filterbehavior) options.filterBehavior = attrs.filterbehavior; //default:  'text', // possible options: 'text', 'value', 'both'
                if (attrs.includefilterclearbtn) options.includeFilterClearBtn = JSON.parse(attrs.includefilterclearbtn); //default:  true
                if (attrs.preventinputchangeevent) options.preventInputChangeEvent = JSON.parse(attrs.preventinputchangeevent); //default:  false
                if (attrs.nonselectedtext) options.nonSelectedText = attrs.nonselectedtext; //default:  'None selected'
                if (attrs.nselectedtext) options.nSelectedText = attrs.nselectedtext; //default:  'selected'
                if (attrs.allselectedtext) options.allSelectedText = attrs.allselectedtext; //default:  'All selected'
                if (attrs.numberdisplayed) options.numberDisplayed = attrs.numberdisplayed; //default:  3
                if (attrs.disableifempty) options.disableIfEmpty = JSON.parse(attrs.disableifempty); //default:  false
                if (attrs.disabledtext) options.disabledText = attrs.disabledtext; //default:  ''
                if (attrs.delimitertext) options.delimiterText = attrs.delimitertext; //default:  ', '

                element.multiselect(options);

                // Watch for any changes to the length of our select element
                scope.$watch(function () {
                    //debugger;
                    return element[0].length;
                }, function () {
                    scope.$applyAsync(element.multiselect('rebuild'));
                });

                // Watch for any changes from outside the directive and refresh
                scope.$watch(attrs.ngModel, function () {
                    element.multiselect('refresh');
                });
            }
        };
    });

Example: <select multi-select includeSelectAllOption="true" enableFiltering="true" enableClickableOptGroups="true" enableCollapsibleOptGroups="true" multiple ng-model="vm.selectedPlants" ng-options="plant.name group by plant.operatingCompanyName for plant in vm.plants"> </select>

element.multiselect is not a function , how to fix it?