Angular synchronous http loop to update progress bar

Question

I'm trying to update a progress bar with a sequential http request inside a foreach, this works, but it's not synchronous by on complete, progress bar is being sync'd by the http call, what am I doing wrong?

angular.forEach(queue, function (item) {
    if (item.uid) {
        d.item = item;
        $http({
            url: BASE_URL + 'upp', 
            method: 'post',
            data: d                  
        }).then(function(res){
            x++;
            update_progress((x/queue_count)*100);
        });
    }
});

I would like to call the update_progress function just when the http returns as finished (200 OK), so the progress bar shows the actual progress correctly. Thanks!

Edit:

I tried checking the response status, before calling the *update_progress* function and it still does not work as expected. I wasn't aware that 200 was dispatched before the request is completed :| By logic, the res obj shouldn't be the response of the http request? I mean, if it's 200 and not an error code, that shouldn't mean that the request was completed?

angular.forEach(queue, function (item) {
if (item.uid) {
    d.item = item;
    $http({
        url: BASE_URL + 'upp', 
        method: 'post',
        data: d                  
    }).then(function(res){
        if(res.status == 200) {
          x++;
          update_progress((x/queue_count)*100);
        }
    });
}

Reading more on promises atm to see if I can make it work as stated by @josh-strange

Edit 2:

So promises was the way to do it, all requests are sent sequentially so the progress bar works as expected, here's the code:

var promise = $q.all({}); 
// Had to init $q.all with an empty obj, 'cause null was trowing errors

angular.forEach(queue, function(item){
  if (item.uid) {        
    promise = promise.then(function(){
      d.item = item;
      return $http({
        url: BASE_URL + 'upp', 
        method: 'post',
        data: d 
      }).then(function(res){
        x++;
        update_progress((x/queue_count)*100);
      });
    });
  }
});

promise.then(function(){
  end_js_update();
});

Thanks @josh-strange

Answer 1

Here is a working Plunker of a working example of sequential http requests. You could obviously package this up very nicely in a service but for your purposes I just put a simple example of it in a controller.

Here is the "meat" of the code:

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

app.controller('myController', function($scope, $http, $q){

  $scope.responses = [];
  $scope.doneLoading = false;
  var urls = [
    'http://httpbin.org/ip',
    'http://httpbin.org/user-agent',
    'http://httpbin.org/headers'
  ];

  var promise = $q.all(null);

  angular.forEach(urls, function(url){
    promise = promise.then(function(){
      return $http({
        method: 'GET', 
        url:url 
      }).then(function(res){
        $scope.responses.push(res.data);
      });
    });
  });

  promise.then(function(){
    //This is run after all of your HTTP requests are done
    $scope.doneLoading = true;
  })

});

EDIT: As Mike P says below: This is an example of chaining promises see $q documentation.