Categories: JavascriptWeb

AngularJS – Two Ways to Initialize an Angular App

This article represents code samples along with related concepts for two different ways in which Angular app can be defined. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

Following are the key points described later in this article:

Automatic Initialization
Manual Initialization

Automatic Initialization

All that is needed for automatic initialization (as of current AngularJS version) is to define “ng-app” on an element and you should be all set. Take a look at following code sample. Pay attention to some of the following:

ng-app=”HelloApp” defined on div element
ng-controller=”HelloCtrl” defined on the same element. It could as well be defined within the inner elements.

<!DOCTYPE html>
<html>
<head>
 <title>Hello Angular</title>
 <link rel="stylesheet" type="text/css" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css"> 
</head>
<body>
  <div ng-app="HelloApp" ng-controller="HelloCtrl">
    <h1>Hello, {{name}}</h1>
   <form>
    <input type="text" ng-model="name" name="name">
   </form>  
  </div>
 <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/angularjs/1.3.3/angular.min.js"></script>
 <script type="text/javascript">
 angular.module('HelloApp', [])
 .controller('HelloCtrl', ['$scope', function($scope){
  $scope.name = "Calvin";
 }])
 </script>
</body>
</html>

As per the description on this page, Angular initializes automatically upon DOMContentLoaded event or when the angular.js script is evaluated if at that time document.readyState is set to ‘complete’. At this point, Angular looks for the ng-app directive which designates your application root. Read further on the given page.

Manual Initialization

One could also initialize the angular app manually. This seems to be suited more for existing/legacy web pages where you would want to initialize angular app for a particular set of “views” or, initialize the app conditionally. Following is the code sample. Pay attention to the following code snippet which is used to instantiate the angular app manually. angular.bootstrap(document, [‘HelloApp’]);. Read further on this page.

<!DOCTYPE html>
<html>
<head>
 <title>Hello Angular</title>
 <link rel="stylesheet" type="text/css" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css"> 
</head>
<body>
  <div ng-controller="HelloCtrl">
    <h1>Hello, {{name}}</h1>
   <form>
    <input type="text" ng-model="name" name="name">
   </form>  
  </div>
 <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/angularjs/1.3.3/angular.min.js"></script>
 <script type="text/javascript">
 angular.module('HelloApp', [])
 .controller('HelloCtrl', ['$scope', function($scope){
  $scope.name = "Calvin";
 }])
  angular.bootstrap(document, ['HelloApp']);
 </script>
</body>
</html>

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