angular promise - Angularjs Implemet async task queue -

i have fiddle example, in i'm making 3 consecutive calls service function (emulating $http request interceptor function) returning promise, code below. want second , next calls wait until previous finishes, because second , next ones depend on previous response. im getting

message 1: value returned 6000,

message 2: value returned 600

message 3: value returned 30

but want get

message 1: value returned 10

message 2: value returned 200

message 3: value returned 6000

var myapp = angular.module('myapp', []);  myapp.factory('interceptor',['$q','$timeout',function($q,$timeout){   var _fact ={};   var asyntimeout;   var _intvalue = 1;   var _asynctask = function(time, value){      var deferred = $q.defer();       asyntimeout = $timeout(function(){           _intvalue = _intvalue*value           deferred.resolve(_intvalue);},time)       return deferred.promise; };    _fact.asynctask = _asynctask;   return _fact; }]);  myapp.controller('appctrl',['$scope', 'interceptor',function ($scope,interceptor) {      interceptor.asynctask(1500, 10).then(function(returnedval){      $scope.message1  = "the value returned " + returnedval;});         interceptor.asynctask(1000, 20).then(function(returnedval){      $scope.message2  = "the value returned " + returnedval;});      interceptor.asynctask(800, 30).then(function(returnedval){      $scope.message3  = "the value returned " + returnedval;});   }]) 

the template be:

 <div ng-controller="appctrl">    <div>message 1: {{message1}}</div>    <div>message 2: {{message2}}</div>    <div>message 3: {{message3}}</div>  </div>  

notice, solution should implemented in factory function -nested calls @ controller not solution scenario-, want follow @ interceptor side

myapp.factory('interceptor',['$q','$timeout',function($q,$timeout){    ...    var _asynctask = function(time, value){      var deferred = $q.defer();     ***if running previous call wait finishes , then(function(){***        asyntimeout = $timeout(function(){           _intvalue = _intvalue*value           deferred.resolve(_intvalue);},time)    ***}**     return deferred.promise;   };    ...    return _fact; }]); 

give try. stash away promise previous $timeout , use wait previous operations complete. simplified bit, removing deferred , using $timeout's promise instead...

myapp.factory('interceptor', ['$q', '$timeout', function ($q, $timeout) {     var _fact = {};     var _intvalue = 1;     var waitpromise = $q.when(true);      var _asynctask = function (time, value) {         waitpromise = waitpromise.then(function () {             return $timeout(function () {                 _intvalue = _intvalue * value;                 return _intvalue;             }, time);         });         return waitpromise;     };      _fact.asynctask = _asynctask;     return _fact; }]); 

fiddle