怎么获取textarea中选中文字

//保存选中内容
            saveSelectionText: function () {
                var focusEle = document.activeElement.tagName;
                if (focusEle === ‘TEXTAREA‘) {
                    if (window.getSelection) {
                        $scope.mark.selectionText[0] = window.getSelection().toString();
                    } else if (document.selection && document.selection.type != "Control") {
                        $scope.mark.selectionText[0] = document.selection.createRange().text;
                    }
                    var ele = document.getElementById(‘textarea2‘);
                    if ($scope.mark.selectionText[0].length == 0) {
                        $scope.mark.selectionText[0] = ($scope.mark.Content || ‘‘).substring(ele.selectionStart, ele.selectionEnd)
                        if (!$scope.mark.selectionText[0]) {
                            $scope.mark.selectionText = [];
                            return false;
                        }
                    }
                    $scope.mark.selectionText[1] = ele.selectionStart.toString();
                    $scope.mark.selectionText[2] = (ele.selectionEnd - ele.selectionStart).toString();
                }
            },

//清空选中内容
            resetSelectionText: function () {
                $timeout(function () {
                    $scope.mark.selectionText = [];
                }, 500);
            },