Angularjs loading screen on ajax request

Instead of setting up a scope variable to indicate data loading status, it is better to have a directive does everything for you:

angular.module('directive.loading', [])

    .directive('loading',   ['$http' ,function ($http)
    {
        return {
            restrict: 'A',
            link: function (scope, elm, attrs)
            {
                scope.isLoading = function () {
                    return $http.pendingRequests.length > 0;
                };

                scope.$watch(scope.isLoading, function (v)
                {
                    if(v){
                        elm.show();
                    }else{
                        elm.hide();
                    }
                });
            }
        };

    }]);

With this directive, all you need to do is to give any loading animation element an 'loading' attribute:

<div class="loading-spiner-holder" data-loading ><div class="loading-spiner"><img src="..." /></div></div>

You can have multiple loading spinners on the page. where and how to layout those spinners is up to you and directive will simply turn it on/off for you automatically.

Here's an example. It uses the simple ng-show method with a bool.

HTML

<div ng-show="loading" class="loading"><img src="...">LOADING...</div>
<div ng-repeat="car in cars">
  <li>{{car.name}}</li>
</div>
<button ng-click="clickMe()" class="btn btn-primary">CLICK ME</button>

ANGULARJS

  $scope.clickMe = function() {
    $scope.loading = true;
    $http.get('test.json')
      .success(function(data) {
        $scope.cars = data[0].cars;
        $scope.loading = false;
    });
  }

Of course you can move the loading box html code into a directive, then use $watch on $scope.loading. In which case:

HTML:

<loading></loading>

ANGULARJS DIRECTIVE:

  .directive('loading', function () {
      return {
        restrict: 'E',
        replace:true,
        template: '<div class="loading"><img src="..."/>LOADING...</div>',
        link: function (scope, element, attr) {
              scope.$watch('loading', function (val) {
                  if (val)
                      $(element).show();
                  else
                      $(element).hide();
              });
        }
      }
  })

PLUNK: http://plnkr.co/edit/AI1z21?p=preview