.controller('ArticlesCtrl', function($scope){
$scope.sum = function(value) {
  return value.reduce(function(total, article) {return total +
  article.price;}, 0); };
   })

[
  {"id": "1", "name": "Pizza Vegetaria", "price": 5 },
  {"id": "2", "name": "Pizza Salami",    "price": 5.5 },
  {"id": "3", "name": "Pizza Thunfisch", "price": 6 },
  {"id": "4", "name": "Pizza Salami",    "price": 5.5 },
  {"id": "5", "name": "Pizza Thunfisch", "price": 6 }
]

watch.js (строка 59)
GET http://192.168.1.136:6543/www/an/articles.json
angular.js (строка 10413)
Error: value is undefined
$scope.sum@http://192.168.1.136:6543/www/an/app.js:43:36
anonymous/fn@https://ajax.googleapis.com/ajax/libs/angularjs/1.4.0/angular.js line 13036 > Function:2:276
expressionInputWatch@https://ajax.googleapis.com/ajax/libs/angularjs/1.4.0/angular.js:14014:31
$RootScopeProvider/this.$get</Scope.prototype.$digest@https://ajax.googleapis.com/ajax/libs/angularjs/1.4.0/angular.js:15548:34
$RootScopeProvider/this.$get</Scope.prototype.$apply@https://ajax.googleapis.com/ajax/libs/angularjs/1.4.0/angular.js:15824:13
done@https://ajax.googleapis.com/ajax/libs/angularjs/1.4.0/angular.js:10263:36
completeRequest@https://ajax.googleapis.com/ajax/libs/angularjs/1.4.0/angular.js:10435:7
requestLoaded@https://ajax.googleapis.com/ajax/libs/angularjs/1.4.0/angular.js:10376:1


return logFn.apply(console, args);