angularjs factory service error - angularjs

Question

i am getting this error
...([c,d,arguments]);return k}}if(!e)throw Error("No module: "+d);var b=[],c=[],j=a...
can anyone please help on this issue.
<div ng-app="app">
<div ng-controller="booksCtrl">
<div ng-repeat="book in allBooks">
<ul>
<li>{{book.title}}</li>
<li>{{book.author}}</li>
<li>{{book.year}}</li>
</ul>
</div>
</div>
</div>
..............................
(function(){
angular.module('app').factory('dataService', dataService);
function dataService(){
return {
getAllBooks : getAllBooks,
};
function getAllBooks(){
return[
{
book_id:1,
title:"hari potter",
author:"J.K. Rowling",
year:2009
},
{
book_id:2,
title:"The Cat in the Hat",
author : "DR. Seuss",
year : 1967
},
{
book_id:3,
title:"Encyclopedia",
author : "Donald j Sobol",
year : 1940
}
];
};
};
}());
(function(){
angular.module('app').controller('booksCtrl', booksCtrl);
function booksCtrl($scope, dataService){
$scope.allBooks = dataService.getAllBooks();
}
}());

Answer 1

I think you have not initialized module app. You have to initialized your module once using syntax
angular.module('app', [])
in any one of js file.
(function(){
angular.module('app',[]).controller('booksCtrl', booksCtrl);
function booksCtrl($scope, dataService){
$scope.allBooks = dataService.getAllBooks();
}
}());
from official documentation https://docs.angularjs.org/guide/module
Beware that using angular.module('myModule', []) will create the module myModule and overwrite any existing module named myModule. Use angular.module('myModule') to retrieve an existing module.