Built-in Directives:-

ng-app Directive
ng-app AngularJS का एक built-in directive है।
इसका उपयोग AngularJS Application को शुरू (initialize) करने के लिए किया जाता है।
यह AngularJS को बताता है कि HTML page का कौन-सा भाग AngularJS Application है।
English
ng-app is a built-in directive of AngularJS.
It is used to start (initialize) an AngularJS application.
It tells AngularJS which part of the HTML page is an AngularJS application.
syntax:-
<html ng-app="myApp">
OR
<div ng-app="myApp">
Example (<html ng-app="myApp">):-
<!DOCTYPE html>
<html ng-app="">
<head>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.8.2/angular.min.js"></script>
</head>
<body>
<p>अपना नाम लिखिए:</p>
<input type="text" ng-model="name">
<h1>नमस्ते {{name}}</h1>
</body>
</html>
Example:-(<div ng-app="myApp">)
<!DOCTYPE html>
<html>
<head>
<title>ng-app Example</title>
<!-- AngularJS Library -->
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.8.2/angular.min.js"></script>
</head>
<body>
<div ng-app="myApp">
<h1>Hello Students</h1>
<p>Enter Your Name:</p>
<input type="text" ng-model="name">
<h2>Welcome {{name}}</h2>
</div>
<script>
// Create AngularJS Module
var app = angular.module("myApp", []);
</script>
</body>
</html>