Is there a way to prioritize items in a task list based on both their date of addition and their listed priority? I've managed to sort the tasks by date, but I'm looking for a solution that will organize items with the 'HIGH' priority at the top of the list.

UPDATE: Ideally, I want the sorting to occur based on the 'HIGH' property when it is selected from the 'Sort By' dropdown menu located above the task list.

Codepen: http://codepen.io/anon/pen/ryyQzy.

HTML:

<md-list class="md-padding">

                   <div layout="row">

                        <md-input-container class="md-block" flex="70">

                            <input type="text" ng-model="search" name="search" placeholder="Search by Task Name"></input>  

                        </md-input-container>

                        <md-input-container flex="30">

                            <md-select name="priority" ng-model="task.priority" placeholder="Sort By">

                                <md-option value="Low">Newest First</md-option>

                                <md-option value="HIGH">High Priority First</md-option>

                            </md-select>

                        </md-input-container>

                    </div>

                    <md-subheader class="md-no-sticky">Current Tasks ({{taskList.length}})</md-subheader> 

                    <md-list-item class="md-3-line" ng-repeat="task in taskList | orderBy:sortByNewest | filter:search">

                       <div class="md-list-item-text" layout="column">

                            <p>{{task.name}}</p>

                            <p>Priority: {{$location.path('/')}}</p>

                            <span class="weak">Added {{task.addedOn | date: 'medium'}}</span>

                        </div>

                        <md-checkbox class="md-secondary" ng-model="task.completed"></md-checkbox>

                        <md-divider ng-if="!$last"></md-divider>

                    </md-list-item>

                </md-list>

JS:

var app = angular.module('todoApp', ['ngMaterial']);

function menuController ($scope, $mdDialog) {
    var originatorEv;
    this.openMenu = function($mdOpenMenu, ev) {
        originatorEv = ev;
        $mdOpenMenu(ev);
    };
};  

app.controller('todoController', function($scope, $mdDialog, $mdToast, $filter) {

    $scope.sortByNewest = '-addedOn';
    //$scope.sortByPriority = ' ';

    $scope.taskList = [
        { name: 'Task 1', priority: 'Low', completed: false, addedOn: 1488722128000 },
        { name: 'Task 2', priority: 'HIGH', completed: false, addedOn: 1488722128000 },
    ];

    $scope.addTask = function() {
        if (angular.isUndefined($scope.taskName) || $scope.taskName.length === 0) {
            var alert =  $mdDialog.alert()
                .parent(angular.element(document.querySelector('#popupContainer')))
                .clickOutsideToClose(true)
                .title('Error')
                .textContent('You must enter a task name and select a priority level')
                .ok('Close');
            $mdDialog.show( alert )
                .finally(function() {
                    alert = undefined;
                });
        }
        else {
            $scope.taskList.push({name: $scope.taskName, priority: $scope.task.priority, addedOn: Date.now()});
            $scope.taskName = "";
            $scope.task.priority = "";
            var pinTo = $scope.getToastPosition();
            $mdToast.show (
                $mdToast.simple()
                .textContent('Task Added')
                .position(pinTo)
                .hideDelay(3000)
            )
        }
    };

    $scope.selectAll = function() {
        angular.forEach($scope.taskList, function(task) {
            task.completed = true;
        });  
    };

    $scope.selectNone = function() {
        angular.forEach($scope.taskList, function(task) {
            task.completed = false;
        });  
    };

    $scope.delete = function(ev) {

        var completedTasks = $filter('filter')($scope.taskList, { completed: true}, true);

        if (completedTasks.length > 0) {
            console.log('show dialog box to confirm');   
            var confirm = $mdDialog.confirm()
                .title ('Are you sure you want to delete the selected tasks?')
                .textContent ('Deleted tasks can\'t be recovered.')
                .targetEvent (ev)
                .ok ('Confirm')
                .cancel ('Cancel')
            clickOutsideToClose: false;
            $mdDialog.show(confirm).then(function() {
                if (completedTasks.length > 1) {
                    var pinTo = $scope.getToastPosition();
                    $mdToast.show (
                        $mdToast.simple()
                        .textContent('Tasks Deleted')
                        .position(pinTo)
                        .hideDelay(3000)
                    )
                }
                else {
                    var pinTo = $scope.getToastPosition();
                    $mdToast.show (
                        $mdToast.simple()
                        .textContent('Task Deleted')
                        .position(pinTo)
                        .hideDelay(3000)
                    )
                }
                $scope.status = 'Tasks Deleted';
                var i = $scope.taskList.length;
                while (i--) {
                    var task = $scope.taskList[i];
                    if(task.completed) {
                        $scope.taskList.splice(i, 1);
                    }
                }

            }, 
            function() {
                $scope.status = 'Deletion Cancelled';
            });
        } 

        else {
            $mdDialog.show(
                $mdDialog.alert()
                    .parent(angular.element(document.querySelector('#popupContainer')))
                    .clickOutsideToClose(true)
                    .title('Error')
                    .textContent('You must select at least one task to delete.')
                    .ok('Close')
                    .targetEvent(ev)
            );
        }
    };

    function DialogController($scope, $mdDialog) {
        $scope.hide = function() {
            $mdDialog.hide();
        };

        $scope.cancel = function() {
            $mdDialog.cancel();
        };

        $scope.answer = function(answer) {
            $mdDialog.hide(answer);
        };
    };

    var last = {
        bottom: false,
        top: true,
        left: false,
        right: true
    };

    $scope.toastPosition = angular.extend({},last);

    $scope.getToastPosition = function() {
        sanitizePosition();
        return Object.keys($scope.toastPosition)
        .filter(function(pos) { return $scope.toastPosition[pos]; })
        .join(' ');
    };

    function sanitizePosition() {
        var current = $scope.toastPosition;
        if ( current.bottom && last.top ) current.top = false;
        if ( current.top && last.bottom ) current.bottom = false;
        if ( current.right && last.left ) current.left = false;
        if ( current.left && last.right ) current.right = false;
        last = angular.extend({},current);
    };

});

app.controller('toastController', function($scope, $mdToast) {
    $scope.closeToast = function() {
        $mdToast.hide();
    }

});