Infosys AngularJS Interview Questions

Infosys AngularJS Interview Questions

On September 21, 2024, Posted by CRS Info Solutions , In Angular, With Comments Off

What is AngularJS, and how does it differ from Angular?
Explain the concept of data binding in AngularJS?
How do you create a new AngularJS application?
How does AngularJS handle dependency injection?
How do you use filters in AngularJS?
How do you create a new AngularJS application?
What are custom directives, and how do you create one?
How do you handle routing in AngularJS?
How can you implement form validation in AngularJS?

AngularJS, a powerful JavaScript framework developed by Google, is a key technology for building dynamic and interactive web applications. Infosys, a leading global consulting and IT services company, frequently hires developers proficient in AngularJS to create scalable and high-performance solutions for their clients. In the interview process at Infosys, candidates are often asked a variety of AngularJS-related questions to assess their understanding of the framework’s core concepts, practical skills, and problem-solving abilities. These questions typically address fundamental topics such as directives, data binding, dependency injection, and routing, providing insight into how well candidates can leverage AngularJS for real-world application development.

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When preparing for an AngularJS interview at Infosys, it’s crucial to not only grasp theoretical concepts but also to demonstrate hands-on experience with the framework. Questions may delve into tasks such as setting up AngularJS applications, managing routes, handling asynchronous operations, and implementing custom directives. By addressing these areas, candidates can showcase their ability to apply AngularJS principles effectively and solve practical problems, reflecting their readiness to contribute to Infosys’s diverse range of projects and client needs.

This section offers a detailed exploration of several AngularJS interview questions tailored for Infosys. Ranging from beginner to advanced levels, these questions cover essential aspects of AngularJS development. By reviewing these questions and their answers, candidates can better prepare for interviews, gain a deeper understanding of AngularJS, and improve their chances of success in securing a position at Infosys. This preparation not only enhances technical skills but also demonstrates the ability to handle real-world challenges in a high-stakes environment.

1. What is AngularJS, and how does it differ from Angular?

AngularJS is a JavaScript-based framework developed by Google to build dynamic web applications. It follows the MVC (Model-View-Controller) architecture and helps in creating single-page applications with a rich user experience. AngularJS provides two-way data binding, which means that changes in the UI automatically update the application data and vice versa.

On the other hand, Angular (commonly referred to as Angular 2+) is a complete rewrite of AngularJS. Angular uses TypeScript as its primary language, which offers better performance, a more robust development environment, and more features compared to AngularJS. While AngularJS uses controllers and $scope, Angular uses components and services.

Example Code Snippet:

// AngularJS Code
app.controller('MyController', function($scope) {
    $scope.message = 'Hello, AngularJS!';
});

// Angular Code
@Component({
  selector: 'app-my-component',
  template: '<h1>{{ message }}</h1>'
})
export class MyComponent {
  message: string = 'Hello, Angular!';
}

Read more about Introduction to Angular: A Beginner’s Guide

2. Explain the concept of data binding in AngularJS.

Data binding in AngularJS is a powerful feature that allows automatic synchronization between the model (JavaScript objects) and the view (HTML). This means that any changes in the data model automatically reflect in the view, and any changes in the view update the model. AngularJS provides two-way data binding, which ensures that the UI and the data are always in sync.

For example, if a user updates a form input field, AngularJS automatically updates the corresponding model property. Similarly, if the model property changes due to some other logic, AngularJS updates the view to reflect the new value.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <input type="text" ng-model="name">
    <p>Hello, {{ name }}!</p>
</div>

// AngularJS Code
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.name = 'John';
});

See also: Data Binding in Angular

3. What are directives in AngularJS? Can you name a few built-in directives?

Directives in AngularJS are special tokens in the HTML that tell the library to do something to the DOM. They can be used to extend HTML capabilities by creating custom HTML tags or attributes. AngularJS provides a set of built-in directives, including:

ng-model: Binds the value of HTML controls (like input fields) to application data.
ng-bind: Binds the inner text of an HTML element to application data.
ng-repeat: Repeats a set of HTML elements for each item in a collection.
ng-if: Conditionally includes an HTML element based on an expression.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <p ng-bind="message"></p>
    <ul>
        <li ng-repeat="item in items">{{ item }}</li>
    </ul>
</div>

// AngularJS Code
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.message = 'Hello, AngularJS!';
    $scope.items = ['Item 1', 'Item 2', 'Item 3'];
});

4. How do you create a new AngularJS application?

To create a new AngularJS application, you need to include the AngularJS library in your HTML file and define a module. A module in AngularJS is a container for different parts of the application, such as controllers, services, and directives. You then create a controller to manage the data and logic for your application.

Here’s a basic setup:

Include the AngularJS library in your HTML file.
Define an AngularJS module.
Create a controller within the module.
Use AngularJS directives to bind data and behavior to the HTML view.

Example Code Snippet:

var app = angular.module('myApp', []);
        app.controller('myCtrl', function($scope) {
            $scope.message = 'Welcome to AngularJS!';
        });

5. What is the role of the `$scope` object in AngularJS?

In AngularJS, the $scope object acts as the glue between the controller and the view. It holds the data and functions that the view (HTML) can bind to. The $scope object allows the controller to communicate with the view and vice versa. Changes made to $scope in the controller are automatically reflected in the view, and user interactions in the view can modify $scope data.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <p>{{ message }}</p>
    <button ng-click="updateMessage()">Change Message</button>
</div>

// AngularJS Code
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.message = 'Hello, AngularJS!';
    
    $scope.updateMessage = function() {
        $scope.message = 'Message Updated!';
    };
});

I hope these explanations and examples help clarify the basics of AngularJS! Let me know if you need more details or have other questions.

6. How does AngularJS handle dependency injection?

Dependency injection (DI) in AngularJS is a design pattern used to manage dependencies in an application. It allows you to inject services, objects, or values into components, controllers, and other services. AngularJS’s DI system helps in creating more modular and testable code by providing dependencies in a structured way.

When I define a component or service, I can list its dependencies as parameters. AngularJS’s injector then automatically provides the required services. For example, if a controller needs to use a service, I simply list the service as a parameter in the controller’s function, and AngularJS takes care of the rest.

Example Code Snippet:

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

// Define a service
app.service('myService', function() {
    this.getMessage = function() {
        return 'Hello from myService!';
    };
});

// Define a controller with dependency injection
app.controller('myCtrl', function($scope, myService) {
    $scope.message = myService.getMessage();
});

7. Explain the concept of services in AngularJS and give an example.

In AngularJS, services are singleton objects used to organize and share code across an application. They can be used to encapsulate business logic, make HTTP requests, manage data, or perform other tasks. Services are created using the .service(), .factory(), or .provider() methods of an AngularJS module. Each service is instantiated only once during the lifetime of the application, ensuring a single source of truth.

I often use services to separate concerns and make my code more modular and reusable. For instance, if I need to fetch data from an API, I can create a service to handle the HTTP requests and then inject this service into controllers that need the data.

Example Code Snippet:

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

// Define a service
app.service('dataService', function($http) {
    this.getData = function() {
        return $http.get('https://api.example.com/data');
    };
});

// Define a controller that uses the service
app.controller('myCtrl', function($scope, dataService) {
    dataService.getData().then(function(response) {
        $scope.data = response.data;
    });
});

8. What is the purpose of the `ng-model` directive?

The ng-model directive in AngularJS is used to bind the value of HTML form elements to a property in the AngularJS $scope. This creates a two-way data binding between the model and the view. When the user changes the value in the form element, the model property is updated automatically. Conversely, if the model property changes, the view updates to reflect the new value.

I find ng-model particularly useful for handling user inputs and keeping my data synchronized with the UI. For example, if I have a text input field that should reflect the value of a property in my controller, I use ng-model to link the input field to that property.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <input type="text" ng-model="username">
    <p>Welcome, {{ username }}!</p>
</div>

// AngularJS Code
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.username = 'John Doe';
});

9. How do you use filters in AngularJS?

Filters in AngularJS are used to format data displayed in the view. They can be applied to expressions in HTML to transform data in various ways, such as formatting dates, numbers, or text. Filters are typically used in conjunction with directives like ng-repeat and ng-bind.

I use filters to make data presentation more user-friendly. For example, if I need to display a date in a specific format or limit the number of characters in a text string, I apply the appropriate filter in the HTML.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <p>Current date: {{ today | date:'fullDate' }}</p>
    <p>Limited text: {{ longText | limitTo: 20 }}</p>
</div>

// AngularJS Code
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.today = new Date();
    $scope.longText = 'This is a long text that will be truncated by the filter.';
});

10. What are AngularJS modules, and why are they used?

AngularJS modules are containers for different parts of an AngularJS application. They help organize and manage the application by grouping related components, such as controllers, services, and directives. Each AngularJS application has at least one module, known as the root module, which can depend on other modules.

Modules provide a way to modularize the application code, making it more maintainable and scalable. They also allow for better separation of concerns and reusability. By defining different modules for different functionalities, I can keep my application organized and modular.

Example Code Snippet:


// AngularJS Code
var app = angular.module('myApp', []); // Define a module

// Define a controller in the module
app.controller('myCtrl', function($scope) {
    $scope.message = 'Hello, AngularJS Modules!';
});

I hope these explanations and examples help clarify these AngularJS concepts! Let me know if you have any more questions or need further details.

Read more about Directives in Angular

11. How do you create a new AngularJS application?

To create a new AngularJS application, you need to start by including the AngularJS library in your HTML file and then set up your AngularJS module and controller. The AngularJS module is the core of the application, where you define different components such as controllers, services, and directives.

Here’s a simple step-by-step approach to create a basic AngularJS application:

Include the AngularJS library in your HTML file.
Define an AngularJS module using angular.module().
Create a controller within the module using .controller().
Bind data and functionality to the view using AngularJS directives.

By following these steps, I can set up a basic AngularJS application and start building its components.

Example Code Snippet:

 var app = angular.module('myApp', []);
        app.controller('myCtrl', function($scope) {
            $scope.message = 'Welcome to AngularJS!';
        });

12. How does AngularJS handle asynchronous operations?

AngularJS handles asynchronous operations using services like $http and $q. The $http service is used to make AJAX requests to retrieve data from a server, while $q is a promise-based service that

var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope, $http) {
$http.get('https://api.example.com/data')
.then(function(response) {
$scope.data = response.data;
})
.catch(function(error) {
console.error('Error occurred:', error);
});
});

13. What are custom directives, and how do you create one?

Custom directives in AngularJS are user-defined directives that allow you to create reusable components or extend HTML capabilities. Directives can be used to create custom HTML tags or attributes that encapsulate specific behavior or templates.

To create a custom directive, I use the .directive() method on an AngularJS module. In the directive definition object, I specify properties like restrict, template, and link to define how the directive behaves and interacts with the DOM.

Example Code Snippet:

// AngularJS Code
var app = angular.module('myApp', []);
app.directive('myCustomDirective', function() {
    return {
        restrict: 'E', // Element name
        template: '<div><h2>{{ message }}</h2></div>',
        link: function(scope, element, attrs) {
            scope.message = 'Hello from custom directive!';
        }
    };
});

<!-- HTML Code -->
<my-custom-directive></my-custom-directive>

Read more about routing and navigation in Angular

14. Describe the difference between `$http` and `$resource` services in AngularJS.

Both $http and $resource are AngularJS services used for making HTTP requests, but they serve different purposes and have distinct features.

$http: This is a lower-level service that provides a flexible way to make HTTP requests. It allows me to configure requests and handle responses using promises. $http is suitable for making simple requests and handling responses directly.
$resource: This is a higher-level service that provides a more structured approach to interacting with RESTful APIs. It simplifies common tasks like querying and saving data by abstracting the HTTP methods into a more convenient API. $resource is ideal for working with RESTful resources and provides built-in support for actions like get, save, query, and delete.

Example Code Snippet Using $http:

// AngularJS Code
app.controller('myCtrl', function($scope, $http) {
    $http.get('https://api.example.com/data')
        .then(function(response) {
            $scope.data = response.data;
        });
});

Example Code Snippet Using $resource:

// AngularJS Code
var app = angular.module('myApp', ['ngResource']);
app.factory('Data', function($resource) {
    return $resource('https://api.example.com/data/:id', { id: '@id' }, {
        'update': { method: 'PUT' }
    });
});
app.controller('myCtrl', function($scope, Data) {
    $scope.data = Data.query();
});

How to Set up the Development Environment for Angular Application?

15. How do you manage state and handle form validations in AngularJS?

Managing state and handling form validations in AngularJS involves using built-in directives and services to control the state of form inputs and ensure that user input meets certain criteria.

For form validation, AngularJS provides built-in directives like ng-model, ng-required, and ng-pattern to validate user input. I can use these directives to specify validation rules and display error messages when the input does not meet the criteria.

AngularJS also offers form control objects like $valid, $invalid, $pristine, and $dirty to manage the form’s state. These objects help track whether the form is valid or invalid, and whether it has been interacted with.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <form name="myForm">
        <input type="text" name="username" ng-model="username" ng-required="true" ng-pattern="/^[a-zA-Z0-9]+$/" />
        <span ng-show="myForm.username.$error.required">Username is required.</span>
        <span ng-show="myForm.username.$error.pattern">Username must be alphanumeric.</span>
        
        <button ng-disabled="myForm.$invalid">Submit</button>
    </form>
</div>


// AngularJS Code
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    // Controller logic
});

I hope these explanations and examples help you understand these AngularJS concepts better! Let me know if you need more details or have any other questions.

Read more about Angular Material and UI Components

16. How do you handle routing in AngularJS?

Routing in AngularJS is managed by the ngRoute module, which allows me to create single-page applications with multiple views. With routing, I can define different URLs for different views or states of the application and navigate between them without reloading the entire page.

To set up routing, I first include the ngRoute module in my application. Then, I configure routes using the $routeProvider service, specifying the routes and their associated views and controllers. This setup enables seamless navigation and dynamic content loading within my application.

Example Code Snippet:

 var app = angular.module('myApp', ['ngRoute']);
        
        app.config(function($routeProvider) {
            $routeProvider
                .when('/', {
                    templateUrl: 'home.html',
                    controller: 'HomeCtrl'
                })
                .when('/about', {
                    templateUrl: 'about.html',
                    controller: 'AboutCtrl'
                })
                .otherwise({
                    redirectTo: '/'
                });
        });
        
        app.controller('HomeCtrl', function($scope) {
            $scope.message = 'Welcome to the Home page!';
        });
        
        app.controller('AboutCtrl', function($scope) {
            $scope.message = 'Learn more About us!';
        });

17. Explain the role of `ng-repeat` directive in AngularJS.

The ng-repeat directive in AngularJS is used to iterate over a collection (such as an array or object) and create a new DOM element for each item in the collection. This is particularly useful for displaying lists of items or generating repeated elements based on the data in the scope.

When I use ng-repeat, it creates a new instance of the specified HTML element for each item in the collection, binding each instance to the current item in the loop. This helps in dynamically rendering lists and other repeated structures in the view.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <ul>
        <li ng-repeat="item in items">{{ item }}</li>
    </ul>
</div>

<br><br><code><br></code>// AngularJS Code<br>var app = angular.module('myApp', []);<br>app.controller('myCtrl', function($scope) {<br>    $scope.items = ['Item 1', 'Item 2', 'Item 3'];<br>});<br>

18. What are AngularJS expressions, and how do they differ from JavaScript expressions?

AngularJS expressions are similar to JavaScript expressions but are used within AngularJS templates to bind data to the view. They are enclosed in double curly braces ({{ }}) and can be used to evaluate and display dynamic data in the HTML.

While JavaScript expressions can be used directly in JavaScript code, AngularJS expressions are evaluated in the context of the AngularJS $scope. They can include simple expressions, filters, and even function calls that return values. AngularJS expressions do not support statements like loops or conditionals, unlike JavaScript expressions.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <p>Username: {{ username }}</p>
    <p>Today is: {{ today | date:'fullDate' }}</p>
</div>

<br><br>// AngularJS Code<br>var app = angular.module('myApp', []);<br>app.controller('myCtrl', function($scope) {<br>    $scope.username = 'John Doe';<br>    $scope.today = new Date();<br>});<br>

This blog offers a deep dive into Pipes in Angular—find out what you need to know.

19. How can you implement form validation in AngularJS?

Form validation in AngularJS is implemented using built-in directives and form control properties. AngularJS provides directives like ng-required, ng-minlength, ng-maxlength, and ng-pattern to enforce validation rules on form fields.

I can also use form control properties such as $valid, $invalid, $pristine, and $dirty to manage the state of the form and provide feedback to users. By combining these directives and properties, I can create robust validation rules and ensure that user input meets the required criteria before form submission.

Example Code Snippet:

<!-- HTML Code -->
<div ng-app="myApp" ng-controller="myCtrl">
    <form name="myForm">
        <label for="email">Email:</label>
        <input type="email" name="email" ng-model="user.email" ng-required="true" />
        <span ng-show="myForm.email.$error.required">Email is required.</span>
        <span ng-show="myForm.email.$error.email">Invalid email address.</span>
        
        <button ng-disabled="myForm.$invalid">Submit</button>
    </form>
</div>

// AngularJS Code
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    // Controller logic
});

Read these Advanced Topics in Angular: Pushing the Boundaries of Web

20. What is the purpose of the `$digest` cycle in AngularJS?

The $digest cycle in AngularJS is the process by which AngularJS checks for changes in the model and updates the view accordingly. This cycle is triggered whenever AngularJS needs to update the DOM to reflect changes in the application state.

The $digest cycle involves comparing the current values of the model with the previous values to detect any changes. If a change is detected, AngularJS updates the view. This process ensures that the view remains synchronized with the model, providing a seamless user experience.

In most cases, I don’t need to manually invoke the $digest cycle as AngularJS handles it automatically. However, in situations where changes occur outside AngularJS’s scope (e.g., third-party libraries), I might use $scope.$apply() to trigger a digest cycle.

Example Code Snippet:

// AngularJS Code
var app = angular.module(‘myApp’, []);
app.controller(‘myCtrl’, function($scope) {
$scope.message = ‘Initial message’;

// Manually trigger a digest cycle
$scope.changeMessage = function() {
    $scope.message = 'Message updated!';
    $scope.$apply(); // Forces AngularJS to update the view
};
});