Simple Async Service AngularJS

simple-async-service.js

angular.module('dep2', [])
.factory('ServiceTwo', function($q, $timeout){
    var timeStamp;

    return  {
        getTimeStamp: function(){
            var defer = $q.defer();

            if(typeof timeStamp === 'undefined'){
                $timeout(function(){
                    timeStamp = Date.now();
                    defer.resolve(timeStamp);
                }, 2000);
            }else{
                defer.resolve(timeStamp);
            }

            return defer.promise;
        }
    }
});