New 100 Angular JS Interview Question

Introduction

AngularJS is a popular JavaScript framework developed by Google for building dynamic web applications. If you’re preparing for an AngularJS interview, it’s essential to have a good understanding of the framework and its key concepts. This user-friendly introduction to AngularJS interview questions will help you grasp the basics and prepare for a successful interview.

AngularJS offers several advantages that make it a preferred choice for web development:

1. Two-way data binding: AngularJS provides automatic synchronization between the model (data) and the view (UI), eliminating the need for manual DOM manipulation.
2. Modular architecture: AngularJS promotes modular development through components, directives, and services, making it easier to manage and scale complex applications.
3. Dependency injection: With AngularJS, you can easily inject dependencies into components, enabling better code organization, testability, and reusability.
4. Reusable components: AngularJS allows you to create reusable components that encapsulate functionality and can be easily used across multiple parts of an application.
5. Declarative templates: AngularJS uses HTML-based templates to define the UI, making it easier to understand and maintain the structure of your application.
6. Powerful data manipulation: AngularJS provides built-in filters and directives for manipulating and formatting data, simplifying common tasks such as sorting, filtering, and data binding.

The AngularJS interview questions covered here are suitable for individuals with varying levels of experience, including:

1. Beginners: If you’re new to AngularJS, these questions will help you gain a fundamental understanding of the framework and its core concepts.
2. Intermediate Developers: If you have some experience with AngularJS and want to expand your knowledge, these questions will help you delve deeper into advanced topics and best practices.
3. Experienced Developers: Even if you’re already proficient in AngularJS, these interview questions can serve as a valuable refresher and help you solidify your understanding of key concepts.

Whether you’re preparing for an entry-level AngularJS interview or aiming for a senior developer role, these questions will cover a range of topics to enhance your knowledge and boost your confidence during the interview process. Remember to practice implementing code examples and explanations to reinforce your understanding. Good luck with your AngularJS interview preparation!

Basic Questions

1. What is Angular JS?

AngularJS is a JavaScript-based open-source front-end web application framework developed by Google. It allows developers to build dynamic web applications by extending the functionality of HTML and providing a structured approach to application development. AngularJS follows the model-view-controller (MVC) architectural pattern and provides a set of tools and features for building single-page applications.

2. What are the key features of Angular JS?

• Two-way data binding
• Directives for extending HTML syntax
• Dependency injection for managing components
• Templating and declarative user interface
• Modular structure with reusable components
• Routing for building single-page applications
• Testing support with unit testing and end-to-end testing frameworks
• AJAX and RESTful API integration
• Form validation and error handling
• Internationalization and localization support

3. What are the advantages of using Angular JS?

• Enhanced productivity with declarative code and reusable components
• Two-way data binding simplifies the synchronization between UI and data models
• Modular architecture promotes code organization and maintainability
• Dependency injection enables easier testing and component isolation
• Powerful built-in features for form validation and error handling
• Efficient data binding and change detection mechanism
• Large and active community support with extensive documentation
• Seamless integration with other libraries and frameworks
• Improved performance through optimized rendering and caching

4. How does data binding work in Angular JS?

Data binding in AngularJS allows automatic synchronization of data between the model and the view. There are two types of data binding:

• One-way data binding: Changes in the model (JavaScript variables) are reflected in the view (HTML), but not vice versa. It is denoted by {{ expression }} in HTML templates.
  Example: <span>{{ message }}</span>
• Two-way data binding: Changes in the model are immediately propagated to the view, and vice versa. It uses the ng-model directive for two-way binding.
  Example: <input type="text" ng-model="name">

AngularJS uses a dirty checking mechanism to detect changes in the model and update the view accordingly. When a user interacts with the UI, the changes are automatically propagated to the model and vice versa, ensuring synchronization between the two.

5. Explain the concept of directives in Angular JS.

Directives in AngularJS are markers or attributes added to HTML elements that extend the functionality of HTML and define reusable components. They allow developers to create custom HTML tags and attributes, manipulate the DOM, attach behavior to elements, and encapsulate complex UI logic.

Directives can be used for various purposes, such as data binding, event handling, manipulating the DOM, rendering dynamic content, and creating reusable components.

Example of a directive usage:

<my-directive></my-directive>

AngularJS provides several built-in directives like ng-model, ng-repeat, ng-if, etc., and allows developers to create custom directives to suit specific application requirements.

6. What is dependency injection in Angular JS?

Dependency injection (DI) in AngularJS is a design pattern that allows components to be loosely coupled and makes it easier to manage dependencies between them. In DI, the dependencies of a component are provided from external sources, rather than being created within the component itself.

AngularJS provides an injector subsystem that resolves and injects dependencies automatically. Components declare their dependencies, and the injector takes care of providing the required dependencies when the component is instantiated.

Example of dependency injection in a controller:

app.controller('MyController', ['$scope', 'userService', function($scope, userService) {
  // $scope and userService are injected dependencies
  // Controller logic goes here
}]);

Dependency injection promotes modular and reusable code, improves testability, and enables easier component isolation and substitution.

7. How do you create a controller in Angular JS?

In AngularJS, controllers are used to define the behavior and logic of a specific part of the application. To create a controller, follow these steps:

1. Define the controller function and its logic:

app.controller('MyController', ['$scope', function($scope) {
  // Controller logic goes here
}]);

2. Attach the controller to a specific HTML element using the ng-controller directive:

<div ng-controller="MyController">
  <!-- HTML content controlled by the MyController -->
</div>

The ng-controller directive binds the controller’s scope to the HTML element, allowing access to the controller’s properties and methods within that scope.

8. What is the difference between one-way and two-way data binding?

9. How do you handle form validation in Angular JS?

In AngularJS, form validation can be handled using various built-in directives and validation attributes. Here’s an example of how to handle form validation:

1. Add the ng-form directive to a <form> element to enable form validation:

<form name="myForm" ng-submit="submitForm()" novalidate>
  <!-- Form elements and validation directives -->
</form>

2. Use validation directives such as ng-required, ng-minlength, ng-pattern, etc., to add validation rules to form fields:

<input type="text" name="name" ng-model="user.name" ng-required="true">

3. Display error messages based on validation states using the ng-messages directive:

<div ng-messages="myForm.name.$error">
  <div ng-message="required">Name is required.</div>
</div>

4. Add custom validation logic using the $validators property of the ngModelController:

app.directive('customValidator', function() {
  return {
    require: 'ngModel',
    link: function(scope, element, attrs, ngModelCtrl) {
      ngModelCtrl.$validators.customValidation = function(modelValue, viewValue) {
        // Custom validation logic
        return valid; // Return true or false based on validation result
      };
    }
  };
});

These steps demonstrate a basic approach to form validation in AngularJS. The framework provides more advanced features and customization options for handling complex form validation scenarios.

10. What are filters in Angular JS?

Filters in AngularJS are used to format and transform data in the view. They can be applied to expressions within double curly braces ({{ expression }}) or within directives like ng-repeat.

AngularJS provides several built-in filters for common data transformations, such as currency, date, uppercase, lowercase, orderBy, etc. Additionally, developers can create custom filters to suit specific formatting or transformation needs.

Example of using a built-in filter:

{{ amount | currency }} <!-- Displays amount in currency format -->

Example of using a custom filter:

{{ text | myCustomFilter }} <!-- Applies custom transformation to 'text' -->

Filters can also accept parameters to further customize their behavior. They can be chained together to perform multiple transformations on the data.

11. Explain the concept of routing in Angular JS.

Routing in AngularJS allows developers to build single-page applications where different views are loaded dynamically without full page refresh. It enables navigation within the application by mapping URLs to specific views and controllers.

To implement routing in AngularJS, follow these steps:

1. Include the angular-route.js script file in your application.
2. Configure the routes in the application’s module configuration:

app.config(['$routeProvider', function($routeProvider) {
  $routeProvider
    .when('/home', {
      templateUrl: 'views/home.html',
      controller: 'HomeController'
    })
    .when('/about', {
      templateUrl: 'views/about.html',
      controller: 'AboutController'
    })
    .otherwise({
      redirectTo: '/home'
    });
}]);

3. Define the corresponding views and controllers for each route.
4. Use the ng-view directive to specify the placeholder where the views will be rendered:

<div ng-view></div>

Now, when the user navigates to different URLs (e.g., /home, /about), the corresponding views are loaded dynamically into the ng-view placeholder without refreshing the entire page.

Routing allows developers to create a seamless user experience with navigation, bookmarking, and deep linking capabilities in AngularJS applications.

12. What is the use of ng-repeat directive?

The ng-repeat directive in AngularJS is used to iterate over a collection and generate HTML elements dynamically for each item in the collection. It allows developers to create repeated HTML structures based on the data in the model.

Example of using ng-repeat:

<ul>
  <li ng-repeat="item in items">{{ item }}</li>
</ul>

In the above example, the ng-repeat directive iterates over the items array in the model and generates <li> elements for each item, displaying the item’s value.

The ng-repeat directive can also be used with objects and key-value pairs, and it provides various features like index access, filtering, ordering, and tracking changes to optimize rendering.

13. How do you handle HTTP requests in Angular JS?

In AngularJS, HTTP requests can be handled using the $http service. The $http service allows developers to make AJAX requests to a server, send/receive data, and handle the responses.

Here’s an example of making an HTTP GET request using $http:

app.controller('MyController', ['$http', function($http) {
  $http.get('/api/data').then(function(response) {
    // Handle successful response
    var data = response.data;
  }, function(error) {
    // Handle error
  });
}]);

The example above demonstrates making a GET request to /api/data. The then function is used to handle the response asynchronously. In case of success, the response data is accessed through response.data. Error handling can be done within the error callback.

The $http service also supports other HTTP methods like POST, PUT, DELETE, etc., and provides options for request headers, data payloads, and more.

14. What is the purpose of services in Angular JS? in bullet points

• Services in AngularJS are used to encapsulate and share code, data, and functionality across different parts of an application.
• They provide a way to organize and separate concerns, promoting code reusability and maintainability.
• Services can be used to handle business logic, data manipulation, communication with servers, and other common tasks.
• AngularJS provides several built-in services like $http, $location, $timeout, etc., which offer pre-defined functionality.
• Custom services can be created using the .service or .factory methods of the AngularJS module.
• Services can be injected into controllers, directives, filters, or other services using dependency injection.
• They enable loose coupling and better unit testing, as dependencies can be easily mocked or replaced.

15. Explain the concept of scope in Angular JS.

In AngularJS, the scope is an object that serves as a context for data binding and maintains the state of the application. Scopes are hierarchical and closely tied to the DOM elements within the AngularJS application.

The scope acts as a glue between the view (HTML) and the controller. It holds the data and methods that can be accessed and manipulated in the view. Any changes made to the scope are automatically reflected in the view and vice versa, thanks to AngularJS’s two-way data binding.

Scopes are organized in a hierarchical structure, mirroring the structure of the DOM. Each AngularJS application has a root scope, and child scopes are created for individual controllers, directives, and other components.

Scopes provide the following functionalities:

• Data binding between the view and the model.
• Event propagation and handling.
• Observing changes and triggering digest cycles for efficient change detection.

By using scopes, AngularJS enables separation of concerns, promotes modularity, and provides a structured way to manage and synchronize data between the view and the model.

16. How do you perform unit testing in Angular JS?

AngularJS provides built-in support for unit testing through the use of tools like Jasmine and Karma. Here’s an outline of the steps involved in unit testing AngularJS code:

1. Set up the testing environment by installing Jasmine and Karma.
2. Write test cases (specs) for individual components like controllers, services, and directives.
3. Use dependency injection to provide mock or test-specific dependencies.
4. Use the describe and it functions of Jasmine to define test suites and individual test cases.
5. Create and initialize the component under test using $controller or $injector.
6. Manipulate the component, invoke methods, and simulate user interactions.
7. Use the expect function to make assertions and verify expected behavior.
8. Run the tests using Karma test runner and review the test results.

By writing comprehensive unit tests, developers can ensure the correctness and reliability of their AngularJS code, catch bugs early, and facilitate easier refactoring and maintenance.

17. What is the role of ng-model directive in Angular JS?

The ng-model directive in AngularJS is used for two-way data binding between HTML input elements and the model. It binds the value of an input element to a property in the model, ensuring that any changes made in the input element are reflected in the model and vice versa.

Example usage of ng-model:

<input type="text" ng-model="name">

In the above example, the ng-model directive binds the value of the input element to the name property in the model. If the user types something into the input field, the name property is updated automatically. Similarly, if the name property is updated programmatically, the input field’s value is also updated.

The ng-model directive can be used with various types of input elements, such as text, checkbox, radio buttons, select dropdowns, and more. It provides a powerful mechanism for data binding and synchronization between the view and the model.

18. What are the differences between AngularJS and Angular?

Please note that the information above is based on the general differences between AngularJS (1.x) and Angular (2.x and later). Angular has evolved significantly, and newer versions of Angular provide additional features, performance improvements, and enhanced tooling compared to AngularJS.

19. What is scope hierarchy?

In AngularJS, scopes are organized in a hierarchical structure known as the scope hierarchy. The scope hierarchy mirrors the structure of the DOM and is formed as components like controllers, directives, and other components are instantiated.

The scope hierarchy consists of the following components:

• Root Scope: The root scope is the top-level scope in an AngularJS application. It is associated with the <html> element and is created when the AngularJS application is bootstrapped.
• Child Scopes: Child scopes are created as AngularJS components like controllers, directives, or other services are instantiated. Each component has its own scope, which is a child scope of its parent component’s scope. The child scope inherits properties and methods from its parent scope.
• Isolate Scopes: Isolate scopes are special child scopes that do not prototypically inherit from their parent scope. They are typically used with directives to encapsulate and isolate scope properties for reusability.

The scope hierarchy allows data and behavior to be inherited and shared between components. It also ensures proper scoping and prevents scope pollution or conflicts between different components.

20. What is an AngularJS module?

In AngularJS, a module is a container that holds different parts of an application, such as controllers, services, directives, filters, and more. It provides a way to organize and separate concerns within an application.

A module is created using the angular.module function and typically has a unique name. Modules can depend on other modules, allowing the composition of larger applications from smaller, reusable parts.

Example of creating a module:

var app = angular.module('myApp', []);

In the example above, a module named myApp is created with an empty array as the second argument. The second argument can contain the names of other modules that myApp depends on.

Modules in AngularJS provide the following benefits:

• Encapsulation and modularity: Modules encapsulate related functionality and promote code organization and maintainability.
• Dependency management: Modules can depend on other modules, ensuring that dependencies are resolved and loaded correctly.
• Reusability: Modules can be easily reused across different applications.
• Testability: Modules facilitate unit testing by allowing the isolation and injection of dependencies.

An AngularJS application typically consists of one or more modules that work together to form a complete application.

21. Why is $watch used?

The $watch function in AngularJS is used to observe changes in a scope’s property or expression and execute a callback function whenever the observed value changes. It enables developers to react to changes in the model or other scope properties and perform necessary actions or updates.

The $watch function takes two parameters: the watchExpression and the listener function. The watchExpression is evaluated, and if its value changes, the listener function is invoked.

Example usage of $watch:

$scope.$watch('name', function(newValue, oldValue) {
  // Callback function executed when 'name' changes
  console.log('Name changed from ' + oldValue + ' to ' + newValue);
});

In the example above, $watch observes the name property in the scope, and whenever it changes, the callback function is executed.

$watch is useful for scenarios where you need to respond to changes in data and trigger actions accordingly. However, it is important to use $watch judiciously as it can impact performance, especially when used on complex or deeply nested properties.

22. Differentiate between ng-if and ng-show directives.

Both ng-if and ng-show are conditional directives in AngularJS that control the visibility of HTML elements based on a condition. However, they differ in their behavior and usage:

In summary, ng-if completely removes or recreates the element based on the condition, while ng-show toggles the CSS display property to show or hide the element. ng-if has a higher performance impact due to the creation/removal of the element and its watchers, while ng-show is more suitable for hiding/showing elements that are already present in the DOM.

23. What is auto bootstrap process in AngularJS?

The auto bootstrap process in AngularJS is the automatic initialization and compilation of the AngularJS application when the web page finishes loading. AngularJS automatically searches for the ng-app directive in the HTML document and bootstraps the application by creating the root scope and compiling the DOM elements.

The auto bootstrap process is triggered by adding the ng-app directive to an HTML element, typically the <html> or <body> tag. AngularJS identifies the element with the ng-app directive as the root element of the application.

Example usage of ng-app:

<!DOCTYPE html>
<html ng-app="myApp">
  <!-- HTML content -->
</html>

In the example above, the ng-app directive is added to the <html> element, and the value "myApp" corresponds to the name of the AngularJS module that will be bootstrapped.

During the auto bootstrap process, AngularJS performs the following steps:

1. Locates the element with the ng-app directive and identifies it as the root element of the application.
2. Creates the root scope associated with the root element.
3. Compiles the DOM starting from the root element, identifying AngularJS directives and applying their functionality.
4. Sets up data binding, watches for changes, and establishes the initial state of the application.
5. Triggers the digest cycle to perform the initial rendering and update the view based on the initial state of the model.

By automatically bootstrapping the application, AngularJS simplifies the initialization process and ensures that the application is ready to respond to user interactions and data changes.

24. What is a singleton pattern and where can we find it in AngularJS?

In software design patterns, the singleton pattern is a creational pattern that restricts the instantiation of a class to a single instance, ensuring that there is only one instance of the class throughout the application.

In the context of AngularJS, the singleton pattern can be observed in AngularJS services. When a service is defined and injected into various components of an AngularJS application, AngularJS creates a single instance of that service and shares it across all components. Any modifications made to the service within one component are immediately visible to other components that depend on the same service.

This behavior ensures that the service acts as a singleton and provides a consistent and shared state throughout the application. Singleton services are particularly useful for sharing data, managing application state, and facilitating communication between different parts of the application.

25. What are the basic steps to unit test an AngularJS filter?

Here are the basic steps to unit test an AngularJS filter:

1. Set up the testing environment by including the necessary libraries and test frameworks, such as Jasmine and AngularJS mocks.
2. Create a test suite (using describe) for the filter.
3. Inject the $filter service and retrieve an instance of the filter under test.
4. Write individual test cases (using it) to cover different scenarios and expected outcomes.
5. Use the expect function to make assertions and validate the behavior of the filter.
6. Invoke the filter with sample inputs and compare the output with the expected result.
7. Run the test suite and review the test results to ensure the filter behaves as expected.

Example test case for an AngularJS filter:

describe('myFilter', function() {
  var myFilter;

  beforeEach(inject(function($filter) {
    myFilter = $filter('myFilter');
  }));

  it('should return uppercase text', function() {
    var input = 'hello';
    var output = myFilter(input);
    expect(output).toBe('HELLO');
  });
});

In the example above, the test suite covers a filter named myFilter that converts text to uppercase. The test case checks whether the filter correctly transforms the input text to uppercase.

By following these steps, developers can ensure the correctness and reliability of their AngularJS filters and catch potential bugs or regressions.

26. Explain ng-init directive.

The ng-init directive in AngularJS is used to initialize values or evaluate expressions within the scope. It allows developers to set the initial state of variables or execute functions when the associated element is initialized.

The ng-init directive is typically used in conjunction with data binding to initialize the model data or perform some logic during the initialization phase.

Example usage of ng-init:

<div ng-init="count = 0">
  <button ng-click="count = count + 1">Increment</button>
  <span>Count: {{ count }}</span>
</div>

In the example above, the ng-init directive is used to initialize the count variable to 0. The value of count can be manipulated using the ng-click directive, and its value is displayed in the <span> element.

While ng-init can be useful for simple initialization scenarios, it is generally recommended to initialize variables or execute logic in the controller or a separate initialization function to maintain a clean separation between the view and the controller.

27. How to make an AJAX call using AngularJS?

In AngularJS, AJAX calls can be made using the $http service. The $http service provides a simple and consistent API for making HTTP requests to servers.

Here’s an example of making an AJAX GET request using $http:

app.controller('MyController', ['$http', function($http) {
  $http.get('/api/data').then(function(response) {
    // Handle successful response
    var data = response.data;
  }, function(error) {
    // Handle error
  });
}]);

In the example above, $http is injected into the controller, and the get method is used to make a GET request to the /api/data endpoint. The response can be handled within the success callback function, and error handling can be done in the error callback.

Similarly, the $http service provides methods like post, put, delete, etc., to make corresponding HTTP requests. Request headers, data payloads, and other options can also be configured using the $http service.

It’s worth noting that in newer versions of Angular (Angular 2+), the HttpClient module is recommended for making AJAX calls instead of $http. The HttpClient module provides an improved API and supports advanced features like interceptors, typed responses, and more.

28. What is a factory method?

In the context of AngularJS, a factory method is a function that produces and returns a service instance. It is one of the ways to define and create services in AngularJS.

A factory method is typically registered with an AngularJS module using the .factory method. The factory method is invoked by AngularJS when the service is requested (injected) into a component.

Example of creating a service using a factory method:

app.factory('userService', ['$http', function($http) {
  var service = {};

  service.getUser = function(userId) {
    return $http.get('/api/users/' + userId);
  };

  return service;
}]);

In the example above, a service named userService is created using a factory method. The factory method is registered with the AngularJS module using the .factory method. The factory function takes dependencies (e.g., $http) as arguments and returns an object with service methods.

Factory methods provide flexibility in creating services and allow developers to customize the creation logic or provide additional setup before returning the service instance.

29. What are the differences between service and factory methods?

| Definition | A constructor function that creates a new instance of the service. | A function that produces and returns a service instance. |
| Usage | Use when the service does not need any configuration or setup. | Use when customization or additional setup is required. |
| Instantiation | Uses the new keyword to create a new instance of the service. | Returns the value returned by the factory function. |
| Returning Value | this (the instance of the service) is implicitly returned. | The value returned explicitly by the factory function is returned. |
| Dependency Injection | Dependencies are injected into the constructor function. | Dependencies are injected into the factory function. |
| Flexibility | Less flexible in terms of customization or setup. | More flexible as the factory function can have custom logic. |
| Typical Use Cases | Services that do not require additional configuration. | Services that require customization or setup before returning. |

Both service and factory methods are used to create services in AngularJS. The choice between them depends on the specific requirements of the service and the desired level of customization or setup.

30. How do you handle exceptions in Angular JS?

In AngularJS, exceptions can be handled using the $exceptionHandler service. The $exceptionHandler service allows developers to define a custom exception handler function to catch and handle exceptions that occur within AngularJS.

To handle exceptions in AngularJS, follow these steps:

1. Define a custom exception handler function in your application’s module configuration:

app.config(['$provide', function($provide) {
  $provide.decorator('$exceptionHandler', ['$delegate', function($delegate) {
    return function(exception, cause) {
      // Custom exception handling logic
      console.error(exception);
      // Additional handling or logging
    };
  }]);
}]);

2. Implement the custom exception handling logic within the decorator function. In the example above, the exception and its cause are logged to the console for demonstration purposes.

By defining a custom exception handler, you can intercept and handle exceptions thrown within AngularJS, allowing you to perform additional logging, error reporting, or custom error handling specific to your application.

31. What are AngularJS expressions?

AngularJS expressions are JavaScript-like code snippets that are evaluated in the context of an AngularJS application’s scope. They are used to dynamically bind data and provide logic within HTML templates.

AngularJS expressions are typically enclosed within double curly braces ({{ expression }}) and can be used within HTML attributes or content to display dynamic data, perform calculations, invoke functions, and more.

Example usage of AngularJS expressions:

<p>Welcome, {{ user.name }}!</p>
<p>Total price: {{ quantity * price }}</p>
<button ng-click="submitForm()">Submit</button>

In the example above, AngularJS expressions are used to bind the value of user.name to the <p> element, perform a calculation using quantity and price, and invoke the submitForm() function when the button is clicked.

AngularJS expressions support various operators, filters, function calls, and access to scope properties and methods. However, expressions are intentionally limited to avoid complex logic and encourage a separation of concerns between the view and the controller.

Intermediate Questions

1. How can you integrate AngularJS with HTML?

To integrate AngularJS with HTML, you need to follow these steps:

1. Include the AngularJS library: Add a reference to the AngularJS library in your HTML file by including the <script> tag with the source URL.

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.8.2/angular.min.js"></script>

2. Define an AngularJS module: Use the ng-app directive to define the root module for your AngularJS application. You can attach it to the <html> or <body> tag.

<html ng-app="myApp">

3. Create AngularJS controllers: Define controllers using the ng-controller directive. Attach them to HTML elements where you want to bind the controller’s behavior.

<div ng-controller="myController">
  <!-- HTML content -->
</div>

4. Write AngularJS expressions: Use double curly braces {{}} to bind expressions to HTML elements. These expressions can include variables, function calls, and other AngularJS constructs.

<p>{{message}}</p>

5. Define AngularJS directives: AngularJS provides built-in directives like ng-model, ng-click, etc. These directives extend HTML with AngularJS-specific functionality.

<input type="text" ng-model="name">
<button ng-click="sayHello()">Say Hello</button>

By following these steps, you can integrate AngularJS with HTML and build dynamic web applications.

2. What is the restrict option in a directive?

The restrict option in a directive is used to define how the directive can be used in HTML templates. It specifies which types of DOM elements the directive can be attached to. The restrict option can have the following values:

• 'E': The directive can be used as an element.
• 'A': The directive can be used as an attribute.
• 'C': The directive can be used as a class.
• 'M': The directive can be used as a comment.

You can combine these values to allow the directive to be used in multiple ways. For example, 'EAC' means the directive can be used as an element, attribute, or class.

Here’s an example of a directive with the restrict option:

angular.module('myApp').directive('myDirective', function() {
  return {
    restrict: 'E', // Only as an element
    template: '<div>This is my directive</div>'
  };
});

In this example, the directive 'myDirective' can only be used as an element in the HTML template.

3. On which types of components can we create a custom directive?

In AngularJS, you can create custom directives that can be applied to various types of components:

1. Elements: You can create directives that are used as custom HTML elements. For example, <my-directive></my-directive>.
2. Attributes: Directives can be created as attributes that are added to existing HTML elements. For example, <div my-directive></div>.
3. Classes: Directives can be applied as classes to HTML elements. For example, <div class="my-directive"></div>.
4. Comments: Directives can be used as comments in HTML templates. For example, <!-- directive: my-directive -->.

By using different restrict options ('E', 'A', 'C', 'M'), you can specify on which types of components your custom directive can be used.

4. What is jQLite/jQuery Lite?

jQLite, also known as jQuery Lite, is a lightweight version of jQuery that is bundled with AngularJS. It provides a subset of jQuery’s functionality and can be used in AngularJS applications without requiring an additional jQuery library.

jQLite is a built-in feature of AngularJS and is automatically loaded when AngularJS is included in your project. It provides a simplified API for common DOM manipulations, event handling, and traversal.

Although jQLite is not as feature-rich as the full jQuery library, it includes essential features such as element selection, manipulation, CSS operations, event handling, and AJAX requests. It allows AngularJS developers to perform common tasks with ease, without the need for a separate jQuery dependency.

However, if your project requires advanced jQuery features that are not available in jQLite, you can still include the full jQuery library alongside AngularJS. AngularJS will automatically use the full jQuery library if it is detected on the page.

5. What is the difference between link and compile in AngularJS?

In AngularJS, both the link and compile functions are used in directives for manipulating the DOM and attaching behavior to elements. However, they serve different purposes:

• compile function: The compile function is called once during the directive’s compilation phase. It is responsible for transforming the DOM by modifying the template or adding additional elements or directives. The compile function returns a linking function that AngularJS will later execute.
• link function: The link function is called multiple times during the directive’s linking phase. It is responsible for registering event listeners, manipulating the DOM, and setting up the behavior associated with the directive. The link function is passed the scope, element, and attributes as arguments.

In summary, the main differences are:

• compile function is called once during the compilation phase, while link function is called multiple times during the linking phase.
• compile function is used to modify the DOM or add additional elements or directives, while link function is used to set up behavior and register event listeners.
• compile function returns a linking function, while link function is the actual linking function.

It’s important to note that in most cases, using the link function is sufficient for directive behavior. The compile function is typically used when you need to modify the directive’s template before the linking phase.

6. What is the role of ng-app, ng-init, and ng-model directives?

• ng-app: The ng-app directive is used to define the root element of an AngularJS application. It initializes the AngularJS framework and sets the scope for the application. It is typically applied to the <html> or <body> tag in an HTML document.

Example:

<html ng-app="myApp">

• ng-init: The ng-init directive allows you to initialize variables in the AngularJS scope. It is commonly used to set up initial values or execute expressions when a view is loaded. However, it is generally recommended to avoid using ng-init for complex logic and instead initialize variables in controllers.

Example:

<div ng-init="name='John'">
  <p>{{name}}</p>
</div>

• ng-model: The ng-model directive is used for two-way data binding between input controls and model values in AngularJS. It binds the value of an input field to a property in the scope, allowing changes in the input to be automatically reflected in the model, and vice versa.

Example:

<input type="text" ng-model="name">
<p>Hello, {{name}}!</p>

In this example, the value entered in the input field will be automatically updated in the name variable, and the greeting message will be updated accordingly.

7. List out the scope characteristics in AngularJS

In AngularJS, scopes play a vital role in connecting the view (HTML) with the controller and providing data binding. Some characteristics of scopes in AngularJS are:

• Hierarchical Structure: Scopes in AngularJS follow a hierarchical structure, which mirrors the DOM structure. Each AngularJS application has a root scope, and child scopes are created for each directive or controller. The scopes form a tree-like structure.
• Inheritance: Child scopes inherit properties and methods from their parent scopes. Changes made to properties in a child scope do not affect the parent scope directly but can be observed through prototypical inheritance.
• Two-way Data Binding: AngularJS supports two-way data binding, meaning changes in the model (scope) are automatically reflected in the view, and vice versa. This enables seamless synchronization between the UI and the underlying data.
• Event Propagation: Scopes propagate events in a hierarchical manner. Events emitted by a child scope are captured by its ancestors. This allows communication between different scopes in the application.
• Watchers: Scopes in AngularJS use watchers to track changes to model properties. When a property changes, AngularJS triggers the associated watcher, allowing for reactive updates in the view.
• Lifecycle Hooks: Scopes have lifecycle hooks such as $watch, $digest, and $destroy. These hooks enable fine-grained control over when and how changes are propagated and allow for resource cleanup.

These characteristics of scopes in AngularJS facilitate a smooth flow of data and behavior between controllers, directives, and the view, ensuring a responsive and dynamic user interface.

8. How can you reset a $timeout and disable a $watch()?

To reset a $timeout and cancel its execution before it triggers, you can use the cancel() method that is returned when setting the timeout. Here’s an example:

var timeoutPromise = $timeout(function() {
  // Timeout logic
}, 5000);

// Cancel the timeout
$timeout.cancel(timeoutPromise);

In this example, the $timeout function returns a promise, which can be stored in a variable (timeoutPromise). To cancel the timeout and prevent its execution, you can call cancel(timeoutPromise).

To disable a $watch() expression, you need to store the function returned by the $watch() call and then invoke it when you want to unregister the watcher. Here’s an example:

var watchFn = $scope.$watch('property', function(newVal, oldVal) {
  // Watcher logic
});

// Disable the watch
watchFn(); // Invoking the returned function unregisters the watcher

In this example, the $watch() function returns a deregistration function, which can be stored in the variable watchFn. Calling watchFn() disables the watch and unregisters it.

By canceling a $timeout or disabling a $watch(), you can control the execution of asynchronous operations and ensure efficient management of resources in your AngularJS application.

9. Is it possible for a parent controller to access the methods and properties of the child controller?

In AngularJS, controllers communicate with each other through scope inheritance. By default, a parent controller can’t directly access the methods and properties of a child controller. However, you can establish communication between parent and child controllers using different techniques:

1. Scope Inheritance: Child controllers inherit the properties and methods of their parent controller’s scope. By setting properties or methods on the scope of the parent controller, they become accessible to the child controller.
2. Sharing Data via Services: Create a service that can be injected into both the parent and child controllers. The service can hold shared data or provide methods to exchange information between controllers.
3. Emitting and Broadcasting Events: AngularJS provides $emit, $broadcast, and $on methods to emit and listen to events. The child controller can emit an event, and the parent controller can listen to it using $on. This allows indirect communication between controllers.

Here’s an example illustrating scope inheritance and sharing data via a service:

angular.module('myApp').controller('ParentController', function($scope, sharedService) {
  $scope.sharedData = sharedService.getData();
});

angular.module('myApp').controller('ChildController', function($scope, sharedService) {
  $scope.sharedData = sharedService.getData();
});

angular.module('myApp').factory('sharedService', function() {
  var data = 'Shared data';

  return {
    getData: function() {
      return data;
    },
    setData: function(newData) {
      data = newData;
    }
  };
});

In this example, the ParentController and ChildController both inject and use the sharedService to access shared data. Any changes made to sharedData in either controller will be reflected in the other.

10. What is a digest cycle in AngularJS?

In AngularJS, a digest cycle is the process by which AngularJS tracks changes in the model and updates the view accordingly. It is the mechanism behind the two-way data binding in AngularJS applications.

During a digest cycle, AngularJS iterates over all the registered $watch expressions and compares the current values of their associated properties with their previous values. If there are any differences, AngularJS updates the corresponding parts of the view affected by those changes.

The digest cycle continues until all $watch expressions are stable, meaning no further changes are detected. AngularJS performs a minimum of two digest cycles to ensure that all changes are propagated and any subsequent changes triggered by the previous ones are captured.

The digest cycle can be triggered in several ways:

• AngularJS automatically triggers a digest cycle when an event occurs, such as user interactions, $http requests, or timers (e.g., $timeout, $interval).
• Developers can explicitly trigger a digest cycle by calling $scope.$apply() or $scope.$digest().

It’s important to note that digest cycles are efficient because AngularJS optimizes them by using a process called dirty checking. Only the $watch expressions and their associated properties that have potentially changed are evaluated during each cycle, rather than the entire scope.

Understanding the digest cycle is crucial for working with AngularJS, as it allows you to comprehend how data binding is handled and how changes propagate between the model and the view.

11. What is an interceptor? What are common uses of it?

In AngularJS, an interceptor is a middleware-like mechanism that allows you to intercept and modify HTTP requests and responses. Interceptors are defined as services and can be registered globally or locally to intercept requests made by the $http service or the $resource service.

Common uses of interceptors include:

1. Authentication and Authorization: Interceptors can be used to attach authentication tokens or headers to outgoing requests and handle authorization errors in response interceptors.
2. Logging and Error Handling: Interceptors can log requests, responses, and errors for debugging purposes or integrate with error tracking systems.
3. Caching: Interceptors can implement caching mechanisms to store and retrieve responses, reducing the number of actual server requests.
4. Request/Response Transformation: Interceptors can modify request or response data, such as converting XML to JSON or vice versa, before it reaches the application.
5. Loading Indicators: Interceptors can show loading indicators during AJAX requests and hide them once the responses are received.

To create an interceptor, you define a service that implements one or more interceptor methods (request, requestError, response, responseError). These methods are called at different stages of the request/response lifecycle.

Here’s an example of an interceptor that adds an authorization token to each outgoing request:

angular.module('myApp').factory('authInterceptor', function(AuthService) {
  return {
    request: function(config) {
      var token = AuthService.getToken();
      if (token) {
        config.headers.Authorization = 'Bearer ' + token;
      }
      return config;
    }
  };
});

angular.module('myApp').config(function($httpProvider) {
  $httpProvider.interceptors.push('authInterceptor');
});

In this example, the authInterceptor service adds an Authorization header to each request if a token is available. The interceptor is registered globally using $httpProvider.interceptors.push('authInterceptor').

Interceptors provide a powerful way to modify HTTP requests and responses globally or selectively, allowing for centralized logic and cross-cutting concerns in an AngularJS application.

12. Is AngularJS extensible?

Yes, AngularJS is highly extensible, allowing developers to customize and extend its core functionalities. AngularJS provides several extension points that enable you to enhance and modify its behavior:

1. Directives: Directives are one of the key features of AngularJS and allow you to create reusable components with custom behaviors. Directives provide a way to extend HTML by creating new elements, attributes, or classes that encapsulate logic and enhance the presentation layer of an application.
2. Filters: Filters in AngularJS allow you to transform and format data in the view. You can create custom filters to suit your specific needs and apply them to data bindings.
3. Services: AngularJS provides a range of built-in services, such as $http, $timeout, and $rootScope, which can be extended or customized to add new functionalities. Additionally, you can create your own custom services to encapsulate and share reusable functionality across different parts of your application.
4. Interceptors: As mentioned earlier, interceptors provide a way to intercept and modify HTTP requests and responses. You can create custom interceptors to add custom logic or modify the default behavior of the $http service.
5. Decorators: AngularJS decorators allow you to modify the behavior of existing services, directives, or controllers. By decorating a built-in or custom component, you can add additional functionality or override certain aspects without modifying the original implementation.
6. Module Configuration: AngularJS modules provide a way to organize and configure your application. You can use the module configuration phase (config()) to set up and customize various aspects of AngularJS, such as route configurations, global settings, or third-party library integrations.

These extensibility points in AngularJS empower developers to tailor the framework to their specific needs, create reusable components, and enhance the functionality and behavior of their applications.

13. How to implement internationalization in AngularJS?

To implement internationalization (i18n) in AngularJS, you can utilize the built-in localization features and third-party libraries. Here’s an approach using AngularJS’s built-in support:

1. Configure AngularJS with the angular-translate module: Install the angular-translate module using Bower or npm and include it in your project. Then, configure it in your AngularJS module:

angular.module('myApp', ['pascalprecht.translate'])
  .config(function($translateProvider) {
    // Configure translations
    $translateProvider.translations('en', {
      'GREETING': 'Hello!',
      // ...
    });

    $translateProvider.translations('fr', {
      'GREETING': 'Bonjour!',
      // ...
    });

    $translateProvider.preferredLanguage('en'); // Set default language
  });

2. Create translation files: Create separate translation files for each supported language, such as en.json and fr.json. These files contain key-value pairs representing translations for different messages or labels.

Example en.json:

{
  "GREETING": "Hello!"
}

Example fr.json:

{
  "GREETING": "Bonjour!"
}

3. Implement translations in the views: In your HTML templates, use the translate directive or the translate filter to display translated content.

Using translate directive:

<div translate="GREETING"></div>

Using translate filter:

<div>{{'GREETING' | translate}}</div>

4. Switch languages dynamically: You can provide an interface for users to switch between languages. Use the $translate service to change the current language dynamically.

angular.module('myApp').controller('LanguageController', function($translate) {
  $scope.changeLanguage = function(langKey) {
    $translate.use(langKey);
  };
});

<select ng-model="selectedLanguage" ng-change="changeLanguage(selectedLanguage)">
  <option value="en">English</option>
  <option value="fr">French</option>
</select>

By following these steps, you can implement internationalization in your AngularJS application, allowing users to switch between different languages and display content in their preferred language.

14. Name the styling forms that ngModel adds to CSS classes.

When you use the ng-model directive in AngularJS, it automatically adds CSS classes to the associated HTML elements based on the state of the form control. These CSS classes can be used to provide visual feedback and styling. The ngModel CSS classes include:

• .ng-pristine: Applied to form controls that have not been interacted with (no changes made).
• .ng-dirty: Applied to form controls that have been interacted with (changes made).
• .ng-valid: Applied to form controls with valid input.
• .ng-invalid: Applied to form controls with invalid input.
• .ng-touched: Applied to form controls that have been blurred or focused and then blurred again.
• .ng-untouched: Applied to form controls that have not been blurred or focused.

You can use these CSS classes to define custom styles or apply pre-defined styles to provide visual cues to users about the state and validity of the form controls.

15. What is the role of services in AngularJS, and name any services made available by default?

Services in AngularJS play a crucial role in providing shared functionality and data across different parts of an application. They promote modularization, separation of concerns, and code reuse. Services are singleton objects that are instantiated only once per application and are typically injected into controllers, directives, or other services.

AngularJS provides several built-in services that offer common functionality out-of-the-box, including:

• $http: A service that facilitates AJAX requests and communication with remote servers.
• $timeout: A service that allows you to execute a function after a specified delay, similar to setTimeout.
• $interval: A service that repeatedly executes a function at specified intervals, similar to setInterval.
• $rootScope: The root scope object that serves as the parent for all other scopes in an application.
• $location: A service that provides methods for reading and modifying the URL of the current page.
• $filter: A service that allows you to format, filter, and manipulate data in views using filters.
• $log: A service that provides a simple logging mechanism for debugging and error handling.

These are just a few examples of the services available in AngularJS. You can also create your own custom services to encapsulate specific functionality and share data or behavior across different parts of your application.

16. What are the different types of modules in AngularJS?

In AngularJS, there are two types of modules:

1. Application Modules: Application modules are used to define and organize the components of an AngularJS application, such as controllers, services, filters, directives, and configuration blocks. These modules represent different parts of the application and are typically loaded by the AngularJS framework using the ng-app directive.

Example:

angular.module('myApp', []);

In this example, 'myApp' is the name of the application module, and [] is an empty array that can be used to define dependencies on other modules.

2. Third-Party Modules: Third-party modules are created by external developers or organizations to provide additional functionality or integrations for AngularJS applications. These modules extend the capabilities of AngularJS by providing pre-built components, directives, services, or utilities that can be easily integrated into your application.

Example (using a third-party module, angular-animate):

angular.module('myApp', ['ngAnimate']);

In this example, 'ngAnimate' is a third-party module that provides animation features, and it is added as a dependency to the application module 'myApp'.

By using application modules and third-party modules, you can organize your code, encapsulate functionality, and easily integrate external libraries into your AngularJS application.

17. Explain the concept of transclusion in AngularJS.

Transclusion is a feature in AngularJS that allows you to create reusable directives with flexible templates. It enables you to define a directive’s template in such a way that the content provided within the directive’s tags in the HTML is preserved and inserted into the template during the compilation process.

To enable transclusion in a directive, you need to use the transclude option and set it to true in the directive’s configuration object. Additionally, you need to include the ng-transclude directive in the directive’s template, specifying where the transcluded content should be inserted.

Here’s an example to illustrate the concept of transclusion:

angular.module('myApp').directive('myDirective', function() {
  return {
    restrict: 'E',
    transclude: true,
    template: '<div>This is my directive.<div ng-transclude></div></div>'
  };
});

In this example, the myDirective directive is created with transclusion enabled (transclude: true). The directive’s template includes a <div> with the ng-transclude directive, which serves as a placeholder for the transcluded content.

In HTML, you can use the directive and provide content between its tags:

<my-directive>
  <p>This content will be transcluded.</p>
</my-directive>

During the compilation process, the content <p>This content will be transcluded.</p> is preserved and inserted into the <div ng-transclude></div> of the directive’s template. As a result, the final rendered output will be:

<div>This is my directive.<div><p>This content will be transcluded.</p></div></div>

Transclusion allows you to create versatile and reusable directives that can incorporate custom content provided by the user, providing flexibility and customization options.

18. What is the role of $rootScope in AngularJS?

In AngularJS, $rootScope is a special scope that exists at the top of the scope hierarchy. It serves as the parent scope for all other scopes in an AngularJS application.

The role of $rootScope includes:

1. Global Data and Events: $rootScope allows you to define global data or variables that are accessible throughout the application. It provides a common scope for sharing data between different components, such as controllers, directives, and services. Events can also be broadcasted or emitted from $rootScope to trigger actions or communicate across scopes.
2. Lifecycle Events: $rootScope emits several lifecycle events, such as $routeChangeStart, $routeChangeSuccess, and $destroy. These events can be used to execute code at specific points during the application’s lifecycle, such as before or after route changes or before a scope is destroyed.
3. $apply() and $digest(): $rootScope provides the methods $apply() and $digest() that trigger the digest cycle and initiate the process of dirty-checking and updating the bindings in the application. They are typically used to ensure changes in $rootScope or its child scopes are propagated to the view.

While it is possible to use $rootScope for sharing data or handling global events, it is generally recommended to use it sparingly and favor more specific scopes whenever possible. Excessive use of $rootScope can lead to a less modular and maintainable codebase.

19. How do you communicate between controllers in AngularJS?

In AngularJS, there are several ways to communicate between controllers:

1. Scope Inheritance: AngularJS uses scope inheritance, where child controllers inherit properties and methods from their parent scope. By placing shared data or functions in a parent scope, child controllers can access and modify them. However, this approach can lead to tight coupling between controllers.
2. Shared Service: You can create a shared service that acts as a mediator between controllers. The service can hold shared data or provide methods for communication. Controllers can inject the service and interact with it to exchange information.
3. Event Broadcasting: AngularJS provides the $rootScope.$broadcast() method to broadcast events down the scope hierarchy, and the $rootScope.$on() method to listen for events. Controllers can broadcast events with relevant data, and other controllers can listen to those events and respond accordingly.
4. $emit() and $on(): In addition to broadcasting events down the scope hierarchy, you can also use $emit() to emit events upwards to parent scopes. Parent controllers can listen to these events using $on() to receive data or trigger actions.

Here’s an example illustrating communication between controllers using a shared service:

angular.module('myApp').service('sharedService', function() {
  var data = '';

  return {
    getData: function() {
      return data;
    },
    setData: function(newData) {
      data = newData;
    }
  };
});

angular.module('myApp').controller('Controller1', function($scope, sharedService) {
  $scope.data = sharedService.getData();
});

angular.module('myApp').controller('Controller2', function($scope, sharedService) {
  $scope.setData = function(newData) {
    sharedService.setData(newData);
  };
});

In this example, Controller1 and Controller2 both inject and use the sharedService to share data. Controller1 retrieves data using getData(), while Controller2 updates the data using setData(). The shared service acts as a bridge between the controllers, allowing them to communicate indirectly.

By utilizing these communication techniques, you can establish interaction and data exchange between controllers in AngularJS applications.

Advanced Questions

1. Can you define multiple restrict options on a directive?

Yes, it is possible to define multiple restrict options on a directive in AngularJS. The restrict option specifies how a directive can be invoked in the HTML template. It can have one or more of the following options:

• 'E' – Element name: The directive can be used as an HTML element.
• 'A' – Attribute: The directive can be used as an attribute of an HTML element.
• 'C' – Class: The directive can be used as a class name of an HTML element.
• 'M' – Comment: The directive can be used as an HTML comment.

To define multiple restrict options, you can provide a string containing the desired options. For example, if you want to restrict the directive to be used both as an attribute and an element, you can specify the restrict option as 'EA'.

angular.module('myApp').directive('myDirective', function() {
  return {
    restrict: 'EA',
    // Directive configuration...
  };
});

In the above example, the myDirective can be used as <my-directive></my-directive> as well as an attribute like <div my-directive></div>.

2. Explain what is a linking function and the types of linking functions.

In AngularJS, a linking function is a function that is invoked during the compilation phase of a directive. It allows you to manipulate the DOM, register event listeners, and perform other actions based on the directive’s behavior.

A linking function receives three parameters: scope, element, and attrs.

• scope: The scope object associated with the directive.
• element: The jqLite-wrapped element that the directive is attached to.
• attrs: An object containing the normalized attribute names and their corresponding values.

There are two types of linking functions in AngularJS:

1. Pre-linking function: It is executed before the child elements are linked. It is useful for tasks that need to operate on the DOM before the directives on the child elements are processed.
2. Post-linking function: It is executed after the child elements are linked. It is suitable for most directive logic as it allows you to interact with the fully rendered DOM.

To define a linking function, you include a link property in the directive’s configuration object. The link property can either be an object with separate pre and post properties for pre-linking and post-linking functions respectively, or a single function that serves as the post-linking function.

angular.module('myApp').directive('myDirective', function() {
  return {
    link: {
      pre: function(scope, element, attrs) {
        // Pre-linking logic...
      },
      post: function(scope, element, attrs) {
        // Post-linking logic...
      }
    }
  };
});

3. How do you achieve internationalization?

To achieve internationalization (i18n) in AngularJS, you can use the built-in AngularJS services and features in combination with external libraries. Here are the steps involved:

1. AngularJS i18n module: Include the angular-i18n.js file in your project, which provides AngularJS localization features.
2. Translation files: Create translation files for different languages. These files typically use JSON or JavaScript format and contain key-value pairs for translations. For example, you might have a translation file en_US.js for English (United States) with translations like { "greeting": "Hello!" }.
3. AngularJS $translate service: Use the $translate service to handle translations. Inject it into your controller or directive and configure it to load the appropriate translation files based on the selected language.
4. Markup translation: In your HTML templates, use the translate directive or filter provided by AngularJS to mark text for translation. For example, <h1 translate="greeting"></h1> would display the translated value of the greeting key.
5. Language selection: Implement a mechanism for users to select their preferred language. This can be done through a language dropdown or any other UI element. When the language changes, update the $translate service to load the corresponding translation files.

External libraries like Angular Translate or ngx-translate can also be used to enhance the i18n capabilities in AngularJS by providing features such as dynamic language switching and interpolation.

4. What is the difference between the $ and the $$ prefixes?

In AngularJS, the $ and $$ prefixes are conventions used to indicate different types of objects or variables.

• $ prefix: It is used for public objects and variables that are part of the AngularJS framework or its modules. These objects are intended to be used by developers and can be accessed and manipulated in AngularJS applications.
• $$ prefix: It is used for internal objects and variables that are part of the AngularJS framework. These objects are implementation details and are not intended to be used or manipulated directly by developers. They are subject to change without notice and may not have a stable API.

The $$ prefix serves as a convention to discourage developers from relying on or modifying internal AngularJS objects. It helps to maintain compatibility and stability of the framework by clearly distinguishing between public and internal components.

For example, $scope is a public object accessible in AngularJS controllers, while $$watchers is an internal object used by AngularJS for managing watchers internally.

5. What are the lifecycle hooks available?

In AngularJS, directives have a set of lifecycle hooks, also known as directive definition object (DDO) properties, which allow you to interact with the directive at various points in its lifecycle. The available lifecycle hooks are:

1. compile: This hook is used to manipulate the DOM before the directive is linked. It is executed only once during the directive’s compilation phase. It can return a link function or a pre- and post-linking functions.
2. controller: It is used to specify the directive’s controller, which contains the business logic and can be used to expose an API to other directives or controllers.
3. pre and post: These hooks are part of the linking function and are used for pre-linking and post-linking logic respectively. The pre-linking function is executed before the child elements are linked, and the post-linking function is executed after the child elements are linked.
4. compile (as a function): This hook is an alternative way to define the compile property. Instead of providing a separate compile function, you can define it as a function directly on the DDO. This function is called during the compilation phase and can return a linking function or an object with pre and post properties.
5. link: It is used to specify the post-linking function directly. This function is executed after the child elements are linked.
6. controller (as a string): Instead of providing a controller function directly, you can specify the name of an existing controller registered with AngularJS.

These hooks provide opportunities to perform custom logic at different stages of the directive’s lifecycle, such as manipulating the DOM, registering event listeners, or setting up data bindings.

6. Explain how $scope.$apply() works?

In AngularJS, the $scope.$apply() method is used to explicitly trigger the digest cycle, which is the process of checking for changes in data bindings and updating the view. It informs AngularJS that changes have been made and it needs to update the bindings and perform any necessary DOM manipulation.

When you call $scope.$apply(), AngularJS evaluates all the watchers registered on the current scope and its child scopes. It compares the current values of the watched expressions with their previous values and updates the view if necessary.

The $scope.$apply() method is typically used when you need to update the scope from outside of AngularJS, such as in asynchronous callbacks or event handlers that are not managed by AngularJS itself.

Here’s an example to illustrate its usage:

angular.module('myApp').controller('MyController', function($scope) {
  $scope.value = 'Initial value';

  // Simulating an asynchronous callback
  setTimeout(function() {
    $scope.$apply(function() {
      // Update the value within $apply to trigger the digest cycle
      $scope.value = 'Updated value';
    });
  }, 1000);
});

In the above example, the $scope.$apply() method is called inside a setTimeout callback. The callback modifies the value property within the $apply function to ensure that the changes are detected by AngularJS. This will trigger the digest cycle, updating the view with the new value.

It’s important to note that if you’re already inside an AngularJS context (such as within an AngularJS event handler), you don’t need to call $scope.$apply() explicitly, as AngularJS automatically triggers the digest cycle for you. The need for $scope.$apply() arises when you’re performing asynchronous operations outside of AngularJS’s awareness.

7. How is the mouse double-click event accomplished?

In AngularJS, you can accomplish the mouse double-click event using the ng-dblclick directive. The ng-dblclick directive allows you to specify an expression to be evaluated when a double-click event occurs on an element.

Here’s an example of how to use ng-dblclick:

<button ng-dblclick="handleDoubleClick()">Double-click me</button>

In the above example, the handleDoubleClick() function will be called when the button is double-clicked. You can define this function in your controller to perform any desired actions.

angular.module('myApp').controller('MyController', function($scope) {
  $scope.handleDoubleClick = function() {
    // Handle double-click event here
  };
});

When the button is double-clicked, the handleDoubleClick() function will be invoked, allowing you to execute the necessary logic or perform any desired operations in response to the double-click event.

8. Why is the findIndex() method used? What does it return in case the value is not found?

The findIndex() method in JavaScript is used to find the index of the first element in an array that satisfies a given condition. It is particularly useful when you want to locate the position of an element based on specific criteria.

The findIndex() method accepts a callback function that tests each element of the array. The callback function should return true if the element matches the desired condition or false otherwise. Once the callback function returns true for the first time, the findIndex() method stops iterating and returns the index of that element. If no element satisfies the condition, it returns -1.

Here’s an example to illustrate the usage of findIndex():

const numbers = [10, 20, 30, 40, 50];

const index = numbers.findIndex(function(number) {
  return number > 30;
});

console.log(index); // Output: 3

In the above example, the findIndex() method is used to find the index of the first number greater than 30 in the numbers array. The callback function number > 30 returns true when number is greater than 30. The findIndex() method stops at index 3, which corresponds to the value 40, and returns that index.

If no element satisfies the condition, the findIndex() method returns -1. For example:

const numbers = [10, 20, 30, 40, 50];

const index = numbers.findIndex(function(number) {
  return number > 100;
});

console.log(index); // Output: -1

In this case, there is no element greater than 100 in the numbers array, so findIndex() returns -1.

9. What can you tell about the given piece of code?

angular.module('myApp').controller('MyController', function($scope, $timeout) {
  $scope.message = 'Hello, AngularJS!';

  $timeout(function() {
    $scope.message = 'Delayed message';
  }, 2000);
});

The given piece of code defines an AngularJS controller named 'MyController' within the 'myApp' module. The controller depends on the $scope and $timeout services, which are injected as function parameters.

Inside the controller, a property named message is assigned the initial value 'Hello, AngularJS!'. This property is bound to the view and can be accessed within the corresponding template.

The $timeout service is used to introduce a delay before updating the message property. It invokes the provided callback function after a specified time (in this case, 2000 milliseconds or 2 seconds). When the callback function is executed, it changes the value of message to 'Delayed message'.

The purpose of using $timeout in this context is to demonstrate how asynchronous operations can be handled within AngularJS. By using $timeout, the delay ensures that the change to message occurs after the initial rendering of the view, allowing the updated value to be displayed to the user.

10. Write a syntax to send a sample HTTP POST request in AngularJS.

To send an HTTP POST request in AngularJS, you can use the $http service. Here’s an example syntax:

angular.module('myApp').controller('MyController', function($http) {
  var data = {
    name: 'John Doe',
    email: '[email protected]'
  };

  $http.post('/api/endpoint', data)
    .then(function(response) {
      // Success callback
      console.log('Request succeeded:', response.data);
    })
    .catch(function(error) {
      // Error callback
      console.log('Request failed:', error);
    });
});

In the above example, an HTTP POST request is sent to the /api/endpoint URL with the data object as the request payload. The $http.post() method returns a promise, which can be used to handle the response asynchronously.

The then() function is called if the request is successful, and it receives the response object as a parameter. You can access the response data using response.data and perform any desired actions.

The catch() function is called if the request encounters an error. The error parameter provides information about the error that occurred.

Remember to include the $http service as a dependency in your controller to be able to use it for making HTTP requests.

11. What is the importance of the $location service?

The $location service in AngularJS is used for URL manipulation and routing within an application. It provides an API to interact with the browser’s URL and enables navigation between different views or pages of the application.

The importance of the $location service can be summarized as follows:

1. URL management: The $location service allows you to read and modify the current URL of the application. You can retrieve information such as the current path, search parameters, or hash fragments. You can also modify the URL programmatically to update the displayed content dynamically.
2. Routing: The $location service plays a crucial role in implementing client-side routing in AngularJS. It works in conjunction with the $routeProvider service to define routes for different URLs and map them to corresponding views or controllers. By using $location and $routeProvider, you can create single-page applications with multiple views that can be navigated without a full page reload.
3. URL-based state: The $location service allows you to encode application state in the URL. This makes the application’s state bookmarkable and shareable. By configuring routes and using parameters in the URL, you can represent different states of your application and enable users to directly access specific states by visiting the corresponding URLs.
4. Programmatic navigation: The $location service provides methods for programmatic navigation. You can use functions like $location.path() or $location.url() to navigate to a different URL or modify the current URL. This allows you to create navigation links or implement actions that change the application’s state based on user interactions.

Overall, the $location service is essential for managing URLs, enabling client-side routing, and implementing navigation within an AngularJS application

12. How is AngularJS compilation different from other JavaScript frameworks?

AngularJS utilizes a unique approach to compilation compared to other JavaScript frameworks. Here are a few ways in which AngularJS compilation differs:

1. Declarative HTML: AngularJS uses declarative HTML markup with additional directives to define dynamic behavior and data bindings. During compilation, AngularJS parses the HTML templates and analyzes the directives to establish the necessary bindings and transformations. This differs from frameworks that may rely more on imperative code or manual DOM manipulation.
2. Two-way Data Binding: AngularJS supports two-way data binding, allowing changes in the model to automatically update the view, and vice versa. During compilation, AngularJS sets up the necessary watchers and listeners to facilitate this bidirectional data flow. Other frameworks may use different approaches to manage data binding, such as one-way data flow or explicit event handling.
3. Dependency Injection: AngularJS heavily utilizes dependency injection (DI) to manage dependencies between components. During compilation, AngularJS analyzes the DI annotations and constructs the necessary injection tree, ensuring that components have access to the required dependencies. In contrast, some other frameworks may use different dependency management mechanisms or rely on global state.
4. Directive Compilation: AngularJS treats directives as first-class citizens and compiles them separately. Directives in AngularJS have their own compilation process, which involves parsing the directive’s template or linking function, analyzing the associated scope, and resolving dependencies. This separate compilation phase allows AngularJS to handle directives efficiently and apply their behavior appropriately.
5. Dynamic Templates: AngularJS allows for the dynamic creation and compilation of templates. It provides mechanisms like $compile service or directives like ng-include to dynamically generate and compile templates based on runtime conditions. This flexibility enables dynamic UI generation, template switching, and code reuse.

AngularJS’s compilation process combines the power of HTML markup, two-way data binding, dependency injection, and directive-driven behavior to create a dynamic and expressive framework for building web applications. Its approach to compilation sets it apart from other JavaScript frameworks and contributes to its unique programming model.

13. Explain the concept of watchers in AngularJS with examples.

Watchers in AngularJS are an essential part of the digest cycle and play a key role in facilitating data binding and change detection. They monitor changes in the model and update the view when necessary. Watchers are established during the compilation phase of AngularJS and are associated with specific expressions or properties.

Here’s an example to illustrate the concept of watchers:

angular.module('myApp').controller('MyController', function($scope) {
  $scope.firstName = 'John';
  $scope.lastName = 'Doe';

  $scope.$watch('firstName', function(newValue, oldValue) {
    console.log('First name changed from', oldValue, 'to', newValue);
  });

  $scope.$watch('lastName', function(newValue, oldValue) {
    console.log('Last name changed from', oldValue, 'to', newValue);
  });
});

In the above example, the MyController sets up two watchers using the $watch function provided by the $scope object. The watchers monitor changes in the firstName and lastName properties of the scope, respectively.

When the value of firstName or lastName changes, the associated watcher functions are triggered. The watcher functions receive the new value (newValue) and the previous value (oldValue) as parameters. In this case, the watcher functions log the change to the console.

Whenever a change occurs, AngularJS runs the digest cycle, during which it evaluates all the watchers to determine if any values have changed. If a watcher’s associated expression has changed, AngularJS updates the corresponding view elements bound to that expression.

By establishing watchers, AngularJS enables automatic synchronization between the model and the view. Any changes made to the firstName or lastName properties in the example will trigger the respective watcher functions, providing an opportunity to perform additional logic or update other parts of the application as needed.

14. How do you optimize performance in AngularJS?

To optimize performance in AngularJS applications, you can employ several techniques and best practices. Here are some key strategies:

1. Minification and Concatenation: Minify and concatenate your JavaScript and CSS files to reduce their size. This reduces network overhead and improves load times.
2. One-time Binding: Use one-time binding ({{::expression}}) for data that doesn’t change after initial rendering. This avoids setting up unnecessary watchers, improving digest cycle performance.
3. ng-cloak: Use the ng-cloak directive to hide elements until AngularJS has finished rendering and compilation. This prevents the display of unstyled content and improves user experience.
4. Limit Watchers: Be mindful of the number of watchers in your application. Excessive watchers can impact performance. Use techniques like binding only to necessary properties, using track by in ng-repeat to minimize watchers, and using ng-if instead of ng-show or ng-hide to reduce unnecessary watchers.
5. Avoid Filters: Minimize the use of filters within data bindings, especially complex or stateful filters. Filters are re-evaluated during every digest cycle, impacting performance. Consider moving complex filtering logic to controller functions.
6. Debounce Events: For events that trigger frequent updates, like input events, debounce the event handlers to reduce unnecessary processing and digest cycles.
7. Use ng-bind: Instead of using {{expression}} data binding, use ng-bind directive for better performance. ng-bind directly updates the DOM with the value, eliminating the need for creating a watcher.
8. Optimize ng-repeat: Use track by with ng-repeat when iterating over collections. This helps AngularJS identify individual items and reduces the need to recreate DOM elements unnecessarily.
9. Asynchronous Loading: Use tools like lazy loading or asynchronous module loading to load AngularJS components and resources as needed. This speeds up the initial loading time and improves perceived performance.
10. Use ng-if Instead of ng-show/ng-hide: When conditionally showing or hiding elements, use ng-if instead of ng-show or ng-hide. ng-if removes the element from the DOM when the condition is false, reducing the number of watchers.
11. Avoid Excessive DOM Manipulation: Minimize direct DOM manipulation within AngularJS controllers and directives. Leverage AngularJS’s data binding and directives to update the DOM efficiently.

By following these performance optimization techniques, you can ensure that your AngularJS application runs smoothly, loads quickly, and provides a responsive user experience.

15. How do you implement authentication in AngularJS?

Implementing authentication in AngularJS typically involves the following steps:

1. Authentication Service: Create an authentication service that handles user authentication, login, logout, and token management. This service can communicate with a server-side authentication API to perform authentication-related tasks.
2. Login Page: Design a login page where users can enter their credentials. The login form can capture the username and password and call the authentication service to initiate the login process.
3. Token Storage: After successful authentication, obtain an authentication token from the server and store it securely, such as in the browser’s localStorage or sessionStorage. The token will be used for subsequent API calls to authenticate the user.
4. Route Protection: Configure route protection to restrict access to certain views or routes based on the user’s authentication status. This can be achieved using AngularJS’s route configuration and route resolvers. For example, you can define a route resolver that checks if the user is authenticated before allowing access to a protected route.
5. Authentication Interceptor: Implement an HTTP interceptor to attach the authentication token to outgoing requests. This interceptor intercepts each outgoing request, checks if the user is authenticated, and adds the token to the request headers before sending it to the server.
6. Authentication Guards: Implement authentication guards to prevent unauthorized access to specific components or features within your application. These guards can check the user’s authentication status and redirect them to the login page if necessary.
7. Logout: Provide a logout mechanism that clears the authentication token from storage and resets the user’s authentication status. This can be done by calling the authentication service’s logout method.

It’s important to note that while the above steps outline a general approach, the specific implementation may vary depending on the authentication mechanism you’re using (e.g., JWT, OAuth) and the backend server’s authentication API.

16. What is the difference between the scopes of a directive and the scopes of a controller? Explain with an example.

In AngularJS, directives and controllers have their own distinct scopes, and the way they create and interact with scopes differs. Here’s an explanation of the differences with an example:

1. Directive Scope: Directives can have their own isolated scope or inherit from the parent scope. An isolated scope is typically created using the 'scope' property in the directive’s definition object (DDO). It allows the directive to encapsulate its data and behavior independently of the surrounding scope.

Example:

<div ng-controller="MyController">
  <my-directive></my-directive>
</div>

angular.module('myApp').directive('myDirective', function() {
  return {
    scope: {},
    template: '<p>{{message}}</p>',
    controller: function($scope) {
      $scope.message = 'Directive Scope';
    }
  };
});

In this example, the my-directive directive is used within the MyController. The directive’s 'scope' property is set to an isolated scope using {}. It creates a new scope for the directive that is independent of the parent scope. The message property defined in the directive’s controller is specific to the directive’s scope and does not affect the MyController scope.

2. Controller Scope: Controllers, on the other hand, typically rely on the default scope or the parent scope. When a controller is defined within an HTML element using the ng-controller directive, it uses the scope of that element.

Example:

<div ng-controller="MyController">
  <p>{{message}}</p>
</div>

angular.module('myApp').controller('MyController', function($scope) {
  $scope.message = 'Controller Scope';
});

In this example, the MyController is defined using the ng-controller directive. The controller’s scope is the scope of the <div> element. The message property defined in the controller is accessible within the scope of the MyController and any child directives or components.

The key difference is that a directive’s scope can be isolated or inherited, allowing it to encapsulate its data and behavior independently. On the other hand, a controller operates within the scope of the element where it is defined and can access and modify the properties of that scope.

17. How can you maintain logs in AngularJS?

In AngularJS, you can maintain logs by utilizing the built-in $log service or by integrating external logging libraries. Here are a few approaches:

1. $log Service: AngularJS provides the $log service, which is a simple logging service that wraps the console object. It offers methods such as $log.debug(), $log.info(), $log.warn(), and $log.error() for different log levels. These methods write logs to the console and can be disabled or controlled via configuration.

Example:

angular.module('myApp').controller('MyController', function($log) {
  $log.debug('Debug message');
  $log.info('Info message');
  $log.warn('Warning message');
  $log.error('Error message');
});

2. Custom Logging Service: You can create a custom logging service tailored to your application’s specific requirements. This allows you to define additional functionalities such as log formatting, log storage, or log level filtering.

Example:

angular.module('myApp').service('Logger', function() {
  this.log = function(level, message) {
    // Custom logging implementation
    console.log('[' + level.toUpperCase() + '] ' + message);
  };
});

angular.module('myApp').controller('MyController', function(Logger) {
  Logger.log('debug', 'Debug message');
  Logger.log('info', 'Info message');
  Logger.log('warn', 'Warning message');
  Logger.log('error', 'Error message');
});

In this example, a custom Logger service is defined with a log() method. The method takes a log level and a message as parameters and performs a custom logging implementation.

3. External Logging Libraries: AngularJS can also be integrated with external logging libraries such as log4js or winston. These libraries provide advanced logging capabilities, including log levels, log formatting, log storage, and log filtering. Integrating such libraries allows you to leverage their features within your AngularJS application.

Choose an approach that suits your logging requirements and integrates well with your application’s logging ecosystem. Be mindful of the log levels, log verbosity, and log storage size to ensure efficient log management and effective debugging capabilities.

Coding Challenges

1. How will you hide an HTML tag element on the click of a button in AngularJS? Write a program for the same.

You can hide an HTML tag element on the click of a button in AngularJS by using the ng-hide directive. Here’s an example program that demonstrates this functionality:

<!-- wp:code -->
<pre class="wp-block-code"><code><div ng-controller="MyController">
  <button ng-click="toggleHide()">Toggle Hide</button>
  <p ng-hide="isHidden">This element will be hidden or shown based on button click.</p>
</div></code></pre>
<!-- /wp:code -->

angular.module('myApp', [])
  .controller('MyController', function($scope) {
    $scope.isHidden = false;
    $scope.toggleHide = function() {
      $scope.isHidden = !$scope.isHidden;
    };
  });

In the above example, clicking the “Toggle Hide” button will toggle the value of isHidden in the controller’s scope. The ng-hide directive is bound to this scope variable, so when isHidden is true, the paragraph element will be hidden, and when isHidden is false, the element will be shown.

2. Create a simple AngularJS application to display a list of users from a JSON API.

   <div ng-app="myApp" ng-controller="UserController">
     <ul>
       <li ng-repeat="user in users">{{ user.name }}</li>
     </ul>
   </div>

   <script>
     angular.module('myApp', [])
       .controller('UserController', function($scope, $http) {
         $http.get('/api/users')
           .then(function(response) {
             $scope.users = response.data;
           });
       });
   </script>

3. Implement a search filter to filter a list of items based on user input.

   <div ng-app="myApp" ng-controller="ItemController">
     <input type="text" ng-model="searchQuery" placeholder="Search...">
     <ul>
       <li ng-repeat="item in items | filter: searchQuery">{{ item.name }}</li>
     </ul>
   </div>

   <script>
     angular.module('myApp', [])
       .controller('ItemController', function($scope) {
         $scope.items = [
           { name: 'Item 1' },
           { name: 'Item 2' },
           { name: 'Item 3' }
         ];
       });
   </script>

4. Implement a form with validation to create a new user.

   <div ng-app="myApp" ng-controller="UserController">
     <form name="userForm" ng-submit="createUser()" novalidate>
       <input type="text" name="name" ng-model="user.name" required>
       <input type="email" name="email" ng-model="user.email" required>
       <button type="submit" ng-disabled="userForm.$invalid">Create User</button>
     </form>
   </div>

   <script>
     angular.module('myApp', [])
       .controller('UserController', function($scope) {
         $scope.user = {};

         $scope.createUser = function() {
           if ($scope.userForm.$valid) {
             // Create user logic here
           }
         };
       });
   </script>

5. How do you disable a button depending on a checkbox’s state?

You can use the ng-disabled directive to disable a button based on a checkbox’s state. Here’s an example:

<div ng-app="myApp" ng-controller="MyController">
  <input type="checkbox" ng-model="isChecked">
  <button ng-disabled="!isChecked">Submit</button>
</div>

<script>
  angular.module('myApp', [])
    .controller('MyController', function($scope) {
      $scope.isChecked = false;
    });
</script>

In the above example, the button will be disabled when the checkbox is not checked (isChecked is false) and enabled when the checkbox is checked (isChecked is true).

6. How would you make an Angular service return a promise?

You can use the $q service in AngularJS to create and return a promise from a service. Here’s an example:

angular.module('myApp', [])
  .service('MyService', function($q) {
    this.getData = function() {
      var deferred = $q.defer();

      // Perform asynchronous operation
      setTimeout(function() {
        var data = 'Some data';
        deferred.resolve(data);
      }, 2000);

      return deferred.promise;
    };
  });

In the above example, the getData method returns a promise that resolves with the data after a 2-second delay. You can then use the promise in the controller to handle the resolved data.

7. When creating a directive, it can be used in several different ways in the view. Which ways for using a directive do you know? How do you define the way your directive will be used?

In AngularJS, a directive can be used in different ways in the view, such as element, attribute, class, or comment. You can define the way your directive will be used by specifying the restrict option in the directive definition. Here’s an example:

angular.module('myApp', [])
  .directive('myDirective', function() {
    return {
      restrict: 'E', // Element usage
      template: '<div>This is my directive</div>'
    };
  });

In the above example, the directive is restricted to be used as an element (<my-directive></my-directive>) only. You can change the value of restrict to 'A' for attribute usage (<div my-directive></div>), 'C' for class usage (<div class="my-directive"></div>), or 'M' for comment usage (<!-- directive: my-directive -->).

8. How would you implement application-wide exception handling in your Angular app?

You can implement application-wide exception handling in AngularJS by using the $exceptionHandler service. Here’s an example:

angular.module('myApp', [])
  .factory('$exceptionHandler', function() {
    return function(exception, cause) {
      // Perform error handling logic here
      console.error('Exception:', exception);
      console.error('Cause:', cause);
    };
  });

In the above example, the $exceptionHandler the factory function is defined to handle any uncaught exceptions that occur within the Angular app. You can customize the error-handling logic inside the function according to your application’s requirements.

MCQ Questions

1. Which of the following is a JavaScript framework?

a) React
b) AngularJS
c) Vue.js
d) All of the above
Answer: d) All of the above

2. AngularJS is developed and maintained by which company?

a) Google
b) Microsoft
c) Facebook
d) Apple
Answer: a) Google

3. AngularJS is based on which design pattern?

a) Model-View-Controller (MVC)
b) Observer
c) Singleton
d) Decorator
Answer: a) Model-View-Controller (MVC)

4. Which directive is used to bind the value of an input element to a property in the AngularJS controller?

a) ng-model
b) ng-bind
c) ng-repeat
d) ng-click
Answer: a) ng-model

5. Which directive is used to conditionally display an element based on an expression?

a) ng-if
b) ng-switch
c) ng-show
d) ng-hide
Answer: a) ng-if

6. Which directive is used to repeat a set of HTML elements for each item in an array?

a) ng-repeat
b) ng-model
c) ng-bind
d) ng-class
Answer: a) ng-repeat

7. Which service is used to make HTTP requests in AngularJS?

a) $http
b) $timeout
c) $q
d) $interval
Answer: a) $http

8. In AngularJS, which symbol is used as a placeholder for data binding expressions?

a) #
b) $
c) @
d) {{}}
Answer: d) {{}}

9. Which directive is used to include an external HTML template file in AngularJS?

a) ng-include
b) ng-template
c) ng-src
d) ng-href
Answer: a) ng-include

10. In AngularJS, what is the role of the $scope object?

a) It represents the current state of the application.
b) It is used to define the structure of the application’s data.
c) It provides a way to communicate between the controller and the view.
d) It handles the routing of the application.
Answer: c) It provides a way to communicate between the controller and the view.

11. In AngularJS, which directive is used to create custom reusable components?

a) ng-controller
b) ng-directive
c) ng-component
d) ng-custom
Answer: c) ng-component

12. What is the purpose of dependency injection in AngularJS?

a) To reduce code duplication
b) To improve performance
c) To modularize the application
d) To make components more testable and maintainable
Answer: d) To make components more testable and maintainable

13. Which of the following is NOT a valid way to declare a module in AngularJS?

a) angular.module(‘myApp’, [])
b) angular.module(‘myApp’)
c) var myApp = angular.module(‘myApp’, [])
d) angular.module(‘myApp’, [‘ngRoute’])
Answer: b) angular.module(‘myApp’)

14. What is the purpose of the $rootScope in AngularJS?

a) It represents the root element of the HTML document.
b) It is used to create global variables accessible throughout the application.
c) It provides a scope for all other scopes in the application.
d) It handles the authentication and authorization of the application.
Answer: c) It provides a scope for all other scopes in the application.

15. Which directive is used to handle user input events in AngularJS?

a) ng-click
b) ng-change
c) ng-keydown
d) ng-mouseover
Answer: b) ng-change

16. What is the purpose of the $watch function in AngularJS?

a) To trigger a digest cycle and update the view when a specific value changes
b) To create a new scope for a directive
c) To handle routing in the application
d) To perform data binding between the model and the view
Answer: a) To trigger a digest cycle and update the view when a specific value changes

17. Which of the following is true about two-way data binding in AngularJS?

a) It allows changes in the model to automatically update the view, and changes in the view to automatically update the model.
b) It is only supported in AngularJS version 2 and above.
c) It requires explicit synchronization between the model and the view.
d) It is not recommended as it can lead to performance issues.
Answer: a) It allows changes in the model to automatically update the view, and changes in the view to automatically update the model.

18. What is the purpose of the ng-init directive in AngularJS?

a) To initialize the AngularJS application module
b) To define a new controller in the application
c) To set initial values to variables in the scope
d) To include an external HTML template in the view
Answer: c) To set initial values to variables in the scope

19. In AngularJS, how do you make an AJAX call to a server?

a) Using the $http service
b) Using the ng-ajax directive
c) Using the ng-resource module
d) Using the $ajax function
Answer: a) Using the $http service

20. What is the purpose of the ng-model directive in AngularJS?

a) It defines the structure of the application’s data.
b) It handles the routing of the application.
c) It creates a new module in the application.
d) It binds the value of an input element to a property in the scope.
Answer: d) It binds the value of an input element to a property in the scope.

21. What is the purpose of the $injector service in AngularJS?

a) To handle dependency injection
b) To manipulate the DOM
c) To handle routing
d) To create custom directives
Answer: a) To handle dependency injection

22. Which of the following is true about the digest cycle in AngularJS?

a) It updates the view with the changes in the model.
b) It updates the model with the changes in the view.
c) It is triggered manually using $digest().
d) All of the above
Answer: d) All of the above

23. What is the purpose of the $compile service in AngularJS?

a) To compile HTML templates into JavaScript code
b) To optimize the performance of the application
c) To handle AJAX requests
d) To create custom directives
Answer: a) To compile HTML templates into JavaScript code

24. In AngularJS, what is the role of the $routeProvider?

a) To handle routing in the application
b) To create custom filters
c) To perform data binding
d) To handle AJAX requests
Answer: a) To handle routing in the application

25. What is the purpose of the $interpolate service in AngularJS?

a) To handle internationalization
b) To evaluate expressions in the view
c) To create custom directives
d) To manipulate the DOM
Answer: b) To evaluate expressions in the view

26. What is the difference between $timeout and $interval in AngularJS?

a) $timeout executes the callback function once, while $interval executes it repeatedly at a specified interval.
b) $interval executes the callback function once, while $timeout executes it repeatedly at a specified interval.
c) $timeout and $interval are the same and can be used interchangeably.
d) $timeout and $interval are used for handling different types of timeouts.
Answer: a) $timeout executes the callback function once, while $interval executes it repeatedly at a specified interval.

27. What is the purpose of the ng-transclude directive in AngularJS?

a) To include an external HTML template in the view
b) To create custom directives
c) To transclude the content of a directive
d) To handle internationalization
Answer: c) To transclude the content of a directive

28. Which of the following is true about filters in AngularJS?

a) Filters are used for data validation.
b) Filters can be applied to expressions in the view to format the output.
c) Filters can only be used with the ng-model directive.
d) Filters are used for handling AJAX requests.
Answer: b) Filters can be applied to expressions in the view to format the output.

29. What is the purpose of the $animate service in AngularJS?

a) To handle animations in the application
b) To manipulate the DOM
c) To handle AJAX requests
d) To create custom directives
Answer: a) To handle animations in the application

30. What is the purpose of the $cacheFactory service in AngularJS?

a) To cache HTTP responses
b) To cache JavaScript files
c) To cache template files
d) To handle routing in the application
Answer: a) To cache HTTP responses