In this case, the {{item.name}} expression is evaluated for each item in the items array, and displays the name property of each item.

7. What is dependency injection in Angular? How is it useful?

Dependency injection is a design pattern used to manage dependencies between different components of an application. 

It is the process of providing a dependent object with the objects it needs to function, rather than having the dependent object create those objects itself. It is implemented using the $injector service, which is responsible for resolving dependencies and providing the necessary objects to components.

Dependency injection is useful in several ways:

– Modularity

Dependency injection promotes modularity by allowing components to be developed and tested in isolation. This makes it easier to maintain and update the code, as each component can be developed and tested independently.

– Reusability

By injecting dependencies into a component, it becomes easier to reuse that component in different parts of the application, or even in different applications.

– Testability

Dependency injection makes it easier to test components, as the dependencies can be easily mocked or replaced with test doubles.

– Separation of concerns

By separating the creation of objects from their use, dependency injection helps to separate concerns and promote cleaner, more maintainable code.

8. How do you handle errors in AngularJS?

Errors can be handled using several techniques:

a) Exception Handling

Angular provides a built-in exception handler service $exceptionHandler, which can be used to handle exceptions that occur during the execution of an AngularJS application. 

This service can be used to log errors, display error messages to the user, or perform other error-handling tasks.

b) Promises

It is a powerful feature of Angular that can be used to handle errors in asynchronous code. Promises allow developers to handle errors in a consistent way across the entire application, and provide a way to propagate errors up the call stack.

c) Interceptors

These allow developers to intercept and modify HTTP requests and responses. Interceptors can be used to handle errors that occur during HTTP requests, and can be used to provide consistent error handling across the entire application.

d) Custom Error Handling

In addition to the built-in error-handling mechanisms provided by AngularJS, developers can also implement custom error-handling logic in their applications. This can include custom error messages, logging, and other error-handling tasks.

It is one of the most asked Angular interview questions. Make sure to be prepared well for it. 

9. Explain the concept of services in AngularJS. 

Services in Angular are objects that are used to organize and share code across different components of an application. These are used to provide functionality that can be shared across different controllers, directives, filters, and other services.

A built-in example of a service in AngularJS is the $http service. It is used to make HTTP requests to a server and returns a promise that is resolved with the response data from the server. This service is commonly used to fetch data from a server and update the application’s state accordingly.

10. Give an example of a built-in service in Angular.

Here’s an example of how to use the $http service in AngularJS:

angular.module('myApp', [])

  .controller('myCtrl', function($http) {

    $http.get('/api/data').then(function(response) {

      // handle the response data here

    }, function(error) {

      // handle the error here

    });

  });

In this example, the $http service is injected into the myCtrl controller, and is used to make a GET request to the /api/data endpoint. When the request is successful, the then method is called with the response data, which can be used to update the application’s state. 

If an error occurs, the catch method is called with the error object, which can be used to handle the error appropriately.

11. What is the purpose of ng-repeat in AngularJS? Give an example.

The ng-repeat directive is used to repeat a set of HTML elements for each item in an array or an object. The purpose of ng-repeat is to create dynamic content based on the data provided by the controller.

Example

Here is an example of how ng-repeat can be used to generate a list of items in an HTML template:

  


    
{{item}}

  

Here, ng-repeat is used to iterate over an array of items in the $scope.items object and generate an HTML list element for each item. The syntax item in items specifies that each item in the items array should be assigned to the item variable during each iteration. The double curly braces {{item}} indicate that the value of the item should be interpolated into the HTML template.

Suppose the $scope.items array contains the following values: [‘apple’, ‘banana’, ‘orange’]. The resulting HTML output generated by ng-repeat would be:

  


    
apple

    
banana

    
orange

  

This is just a basic example, but ng-repeat can be used for more complex scenarios, such as generating tables, nested lists, or even custom directives.

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12. Explain the concept of digest cycle in AngularJS.

The digest cycle is a process that keeps track of changes to a scope and updates the view accordingly. It is triggered automatically by Angular whenever it detects a change to the model, which could be the result of user input or updates made by the application logic.

The digest cycle consists of several steps, which are executed in order until all changes have been detected and applied:

a) Dirty checking: 

Angular checks the current state of the model to see if any values have changed since the last digest cycle.

b) Watchers: 

AngularJS iterates through all registered watchers, which are functions that are called whenever a specific model value changes. These watchers may update other parts of the model, which triggers additional digest cycles.

c) Model update: 

If any changes are detected during the previous steps, AngularJS updates the model with the new values.

d) View update: 

AngularJS updates the view to reflect any changes to the model.

The digest cycle continues until no further changes are detected, at which point the cycle is complete.

The digest cycle is an essential part of AngularJS because it ensures that the view is always up-to-date with the model. Without the digest cycle, changes made to the model would not be reflected in the view, and the application would not behave as expected.

While preparing for Angular interview questions and answers for experienced professional, you can’t ignore core topics like the digest cycle. 

13. What are filters in AngularJS? 

Filters are functions that can be used to format and transform data within a view. Filters are applied to expressions using the | character, and they can be chained together to create more complex transformations.

AngularJS provides several built-in filters that can be used out of the box, such as:

• currency: formats a number as a currency string.
• date: formats a date object into a string.
• filter: filters an array based on a given criteria.
• orderBy: orders an array by a specified property.

Custom filters can also be defined by creating a new filter factory function using the filter() method on the module object. 

Example

For example, the following code defines a custom filter that capitalizes the first letter of a string:

angular.module('myApp', []).filter('capitalize', function() {

  return function(input) {

    if (input) {

      return input.charAt(0).toUpperCase() + input.slice(1);

    }

    return input;

  };

});

Once defined, the capitalize filter can be used in an expression like this:

{{ myString | capitalize }}

Filters can also accept arguments by including them in the expression after the filter name, separated by a colon. For example:

{{ myDate | date:'yyyy-MM-dd' }}

This applies the date filter to myDate, using the format string ‘yyyy-MM-dd’.

14. Give an example of a built-in filter.

An example of a built-in filter in Angular is the currency filter. This filter formats a number into a currency string based on the locale specified in the application.

Example

Here’s an example usage of the currency filter:

{{ price | currency }}

Here, price is a variable in the current scope that contains a number, such as 42.99. When the currency filter is applied to price, it formats the number as a currency string based on the default locale.

For example, if the default locale is set to US English, the output of the above expression would be:

$42.99

The currency filter can also take an optional argument to specify the currency symbol, as well as other options such as the number of decimal places to include.

Here’s an example that specifies the currency symbol as “€” and sets the decimal places to 2:

{{ price | currency:'€':2 }}

In this case, assuming price is still 42.99, the output would be:

€42.99

15. What is the difference between ng-show and ng-hide in AngularJS?

ng-show and ng-hide are two directives used to show or hide elements in the view based on a condition.

The primary difference between ng-show and ng-hide is in the way they work:

• ng-show displays the element only when the expression provided to it evaluates to a truthy value, and hides the element otherwise. The element’s CSS display property is set to none when the expression is false.

• ng-hide, on the other hand, hides the element only when the expression provided to it evaluates to a truthy value, and displays the element otherwise. The element’s CSS display property is set to none when the expression is true.

So, the main difference between these two directives is that ng-show hides the element when the expression is false, while ng-hide hides the element when the expression is true.

Example

Here’s an example usage of ng-show:

  This element is visible when showElement is true.

Here, the div element is displayed only when the expression showElement is truthy.

And here’s an example usage of ng-hide:

  This element is visible when hideElement is false.

Here, the div element is displayed only when the expression hideElement is falsy.

While going to any organization for job, you must ensure to have answers to this type of interview questions on AngularJS for experienced professionals. 

16. What is a module in AngularJS? Why is it important?

A module is a container for different parts of an application, such as controllers, services, directives, filters, etc. It is defined using angular.module() method and can depend on other modules.

Here’s an example of defining a module in AngularJS:

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

Here, the angular.module() method is used to create a new module named ‘myApp’. The second argument, an empty array, specifies that this module has no dependencies on other modules.

Modules are important in AngularJS because they provide a way to organize an application into discrete, reusable components. By separating the different parts of an application into modules, developers can more easily manage and maintain their code.

For example, one module may contain the controllers and templates for a particular feature of the application, while another module may contain the services and filters used throughout the application. These modules can be loaded and used independently of each other, which makes it easier to write modular and testable code.

Modules also provide a way to manage dependencies between different parts of an application. By declaring dependencies on other modules, an AngularJS module can use the components defined in those modules.

17. Explain the concept of scope in AngularJS.

A scope is an object that acts as the binding between the view and the controller in the application. The scope is responsible for storing the model data and functions used in the view, and for notifying the view of changes in the model data.

Every Angular application has a root scope, which is created when the application is initialized. Each controller in the application has its own scope, which is created when the controller is instantiated. The child scope inherits properties and methods from its parent scope, and can also define its own properties and methods.

Here’s an example of using scope in AngularJS:

angular.module('myApp', [])

  .controller('myController', function($scope) {

    $scope.greeting = 'Hello, World!';

  });

In this example, a new module called ‘myApp’ is created with a controller called ‘myController’. The $scope object is injected into the controller function, which allows us to define properties on the scope. In this case, we define a property called greeting with the value ‘Hello, World!’.

In the view, we can use the ng-controller directive to attach the ‘myController’ controller to an element, and then use the {{}} syntax to bind the greeting property to the view:

  
{{greeting}}

When the view is rendered, AngularJS will replace the {{greeting}} expression with the value of the greeting property on the scope, which is ‘Hello, World!’.

18. How to use ng-model in Angular?

ng-model is a directive used to bind the data in an input, select, or textarea element to a property on the scope. This allows the data to be synchronized between the view and the model.

Example of using ng-model in a text input:

Here, the ng-model directive is attached to the input element, and the value of the input will be bound to the $scope.name property in the controller.

Example of using ng-model in a select element:

  Red

  Green

  Blue

In this example, the ng-model directive is attached to the select element, and the selected option will be bound to the $scope.color property in the controller.

Example of using ng-model in a textarea element:

In this example, the ng-model directive is attached to the textarea element, and the content of the textarea will be bound to the $scope.message property in the controller.

19. What are the differences between $watch and $observe in AngularJS?

$watch and $observe are two methods that are used to monitor changes to model data and attributes in the DOM, respectively.

Here are the main differences between $watch and $observe:

Use case: 

$watch is typically used to monitor changes to model data on the scope, while $observe is used to monitor changes to attributes on a DOM element.

Syntax: 

$watch is a method that is called on a scope object, while $observe is a method that is called on an attribute directive.

Execution time: 

$watch is executed during the digest cycle, which is triggered whenever the AngularJS framework detects a change to the model data. $observe, on the other hand, is executed when the attribute value changes, which can be triggered by a change in the scope or by a change to the attribute itself.

Callback function: 

Both $watch and $observe take a callback function as an argument that is executed when the value being monitored changes. The difference is that the $watch callback function is passed the new and old values of the model data being monitored, while the $observe callback function is only passed the new value of the attribute being monitored.

20. What is transclusion in AngularJS? How do you use it?

Transclusion is a technique for including content from a directive’s template into the parent element’s template while preserving the original scope context of the directive.

It is used to create reusable components that can be used in different parts of an application with different content. It allows developers to define a template for a directive and insert it into different locations in the parent template.

To use transclusion in AngularJS, you need to define a directive with a transclude option set to true. This tells AngularJS to include any content between the opening and closing tags of the directive element in the directive’s template.

This is one of the top Angular interview questions. So, prepare well for it.

21. What is the difference between $http and $resource in AngularJS?

Here’s a tabular comparison showing the difference between $http and $resource in Angular:

22. What is the difference between $emit and $broadcast in AngularJS?

Here’s a tabular comparison showing the difference between $emit and $broadcast in Angular:

23. What are promises in Angular?

Promises are used for asynchronous operations that take some time to complete, such as fetching data from a server or reading a file. These provide a way to handle such operations without blocking the execution of other code in the application.

A promise represents the eventual result of an asynchronous operation and can have three states:

• Pending: The initial state, the operation has not yet been completed.
• Fulfilled: The operation was completed successfully, and the promise has a result value.
• Rejected: The operation failed, and the promise has a reason for the failure.

A promise object has two methods: 

• then(): It is called when the promise is fulfilled and takes two callback functions as arguments. The first callback is called when the operation succeeds, and the second is called when the operation fails.
• catch(): It is called when the promise is rejected and takes a callback function as an argument.

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Angular Interview Questions for 5 Years Experience

Here, we are going to know the top Angular interview questions and answers for 5 years experienced professionals. 

24. Explain the AngularJS component-based architecture.

The component-based architecture in Angular is a way of building web applications by breaking them down into smaller, reusable parts called components. A component is a self-contained, modular unit of code that encapsulates a specific functionality or feature of the application.

A component is defined using a combination of a template, a controller, and a set of bindings. The template is an HTML file that defines the component’s view, while the controller is a JavaScript file that defines the component’s behavior. The bindings allow data to be passed between the view and the controller.

Example

Here’s an example of defining a simple component in AngularJS:

angular.module('myApp')

  .component('myComponent', {

    templateUrl: 'my-component.html',

    controller: function() {

      var vm = this;

      vm.message = 'Hello, world!';

    }

  });

Here, the component() method is used to define a new component called myComponent. The templateUrl property specifies the HTML template file that defines the component’s view, while the controller property defines the JavaScript code that implements the component’s behavior. The vm variable is used to store the component’s data and functions, which are made available to the view via the bindings.

Related Reading: JavaScript Interview Questions and Answers

25. What are benefits of component-based architecture of Angular?

The advantages of using a component-based architecture in AngularJS include:

Reusability: 

Components can be easily reused in different parts of the application, reducing duplication of code and increasing development efficiency.

Separation of Concerns: 

Components separate the concerns of the view and the logic, making the code more organized and easier to maintain.

Modularity: 

Components allow the application to be broken down into smaller, manageable pieces, making it easier to develop, test, and deploy.

Encapsulation: 

Components encapsulate their own state and behavior, making them more predictable and less prone to side effects or conflicts with other parts of the application.

This is one of the top Angular interview questions in 2023.

26. How to implement server-side rendering in Angular?

Server-side rendering (SSR) is the process of rendering web pages on the server instead of the client. Implementing SSR can improve the performance and SEO of the application, as well as provide a better user experience.

Here are the steps to implement Angular server-side rendering:

a) Create a new AngularJS application using the Angular CLI:

ng new my-app --skip-install

b) Install the @nguniversal/express-engine and @nguniversal/module-map-ngfactory-loader packages:

npm install @nguniversal/express-engine @nguniversal/module-map-ngfactory-loader

c) Create a new file called server.ts in the root of the application with the following code:

import 'zone.js/dist/zone-node';

import * as express from 'express';

import { ngExpressEngine } from '@nguniversal/express-engine';

import { provideModuleMap } from '@nguniversal/module-map-ngfactory-loader';

import { enableProdMode } from '@angular/core';

const app = express();

const { AppServerModuleNgFactory, LAZY_MODULE_MAP } = require('./dist/server/main');

enableProdMode();

app.engine('html', ngExpressEngine({

  bootstrap: AppServerModuleNgFactory,

  providers: [

    provideModuleMap(LAZY_MODULE_MAP)

  ]

}));

app.set('view engine', 'html');

app.set('views', 'dist/browser');

app.use(express.static('dist/browser'));

app.get('*', (req, res) => {

  res.render('index', { req });

});

app.listen(3000, () => {

  console.log('Listening on port 3000');

});

In the code above, we’re using the ngExpressEngine function from @nguniversal/express-engine to render AngularJS templates on the server. 

We’re also using the provideModuleMap function from @nguniversal/module-map-ngfactory-loader to provide a map of lazy-loaded modules.

d) Build the application for production:

ng build --prod

This will generate a dist folder with the compiled application.

e) Build the server-side bundle:

ng run my-app:server

This will generate a dist/server folder with the server-side bundle.

f) Start the server:

node dist/server.js

This will start the server on port 3000.

With server-side rendering implemented, when a user requests a page, the server will render the page and send the HTML to the client, along with the necessary JavaScript and CSS files. 

The client will then hydrate the page and add any necessary interactivity. This can improve the performance of the application, as the user doesn’t have to wait for the JavaScript to download and execute before seeing the content.

27. What is lazy loading in AngularJS? 

Lazy loading is a technique used to load modules and components on demand, instead of loading everything upfront when the application starts. This can improve the performance of the application, as it reduces the initial load time and only loads the modules and components that are actually needed.

In lazy loading, modules are split into smaller, more manageable chunks called “feature modules”, and components are grouped into these feature modules based on their functionality. 

When a user navigates to a specific feature, the associated feature module is loaded on demand. This can be done using the loadChildren property in the routing configuration.

28. What is change detection in Angular?

Change detection is a core feature that is responsible for detecting changes to the application’s data and updating the view accordingly. It is the mechanism by which AngularJS tracks changes to the application state and updates the view to reflect those changes.

The change detection works by comparing the current view state to the previous view state and updating the view only where necessary. 

The process of change detection involves the following steps:

• AngularJS creates a component tree to represent the application’s view hierarchy.
• The framework sets up a change detection mechanism for each component, which includes a watchlist of properties to monitor for changes.
• Whenever an event occurs that could potentially trigger a change in the view, AngularJS triggers a change detection cycle.
• During the change detection cycle, the framework checks each component’s watchlist for changes.
• If a change is detected, AngularJS updates the component’s view and any child components that depend on the changed data.

There are two modes of change detection in AngularJS: default change detection and on-push change detection. 

In default change detection, AngularJS checks all components in the tree for changes during each change detection cycle. 

In on-push change detection, AngularJS only checks components for changes if their inputs have changed or if an event has occurred that could potentially trigger a change.

29. How to use internationalization (i18n) in an Angular application?

To implement i18n in an Angular application, you can use the built-in AngularJS i18n support, which allows you to define translation files for different languages and use them in your application.

Here are the steps to follow:

a) Install the AngularJS i18n module:

npm install angular-i18n

b) Define the translation files:

Create a separate JSON file for each language you want to support. For example, for English, you might create a file called en.json, and for French, you might create a file called fr.json. The files should contain key-value pairs for each string that needs to be translated. 

For example, for English, you might have:

{

    "greeting": "Hello",

    "message": "Welcome to my application"

}

And for French, you might have:

{

    "greeting": "Bonjour",

    "message": "Bienvenue sur mon application"

}

c) Load the translation files:

In your AngularJS application, load the translation files using the $translateProvider service. 

For example:

angular.module('myApp', ['pascalprecht.translate'])

    .config(['$translateProvider', function ($translateProvider) {

        $translateProvider.useStaticFilesLoader({

            prefix: 'i18n/',

            suffix: '.json'

        });

        $translateProvider.preferredLanguage('en');

        $translateProvider.useSanitizeValueStrategy('escaped');

    }]);

This code tells AngularJS to load the translation files from the i18n/ directory and use the .json extension. It also sets the default language to English (‘en’) and specifies that the translation strings should be escaped for security (‘escaped’).

Here’s a tabular comparison showing the main differences between NgZone and ChangeDetectorRef:

To use the translation strings in your code, you can use the $translate service. 

For example:

angular.module('myApp').controller('MyController', ['$translate', function ($translate) {

    var greeting = $translate.instant('greeting');

    var message = $translate.instant('message');

    console.log(greeting + ' ' + message);

}]);

The $translate.instant method takes a translation key as a parameter and returns the translated string.

By following these steps, you should be able to implement i18n in your AngularJS application and support multiple languages.

30. How to implement unit testing in an AngularJS application using Jasmine and Karma?

To use unit testing in an AngularJS application using Jasmine and Karma, follow these steps:

a) Set up your development environment:

Install Node.js and NPM (Node Package Manager) on your machine. 

Once you have Node.js and NPM installed, you can use NPM to install Karma and Jasmine globally by running the following command in your terminal:

npm install -g karma jasmine

b) Create a Karma configuration file:

module.exports = function(config) {

    config.set({

        basePath: '',

        frameworks: ['jasmine'],

        files: [

            'path/to/angular.js',

            'path/to/angular-mocks.js',

            'path/to/your/tests/**/*.js'

        ],

        exclude: [],

        preprocessors: {},

        reporters: ['progress'],

        port: 9876,

        colors: true,

        logLevel: config.LOG_INFO,

        autoWatch: true,

        browsers: ['Chrome'],

        singleRun: false,

        concurrency: Infinity

    })

}

This file sets up Karma with the Jasmine testing framework, specifies the location of the AngularJS and Angular Mocks libraries, and specifies the location of your test files.

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c) Write your tests:

In your Angular project directory, create a folder named tests (or any other name you prefer) to store your test files. 

Create test files for each component or service you want to test, using the Jasmine syntax. 

For example:

describe('MyService', function() {

    var myService;

    beforeEach(module('myApp'));

    beforeEach(inject(function(_MyService_) {

        myService = _MyService_;

    }));

    it('should return the correct message', function() {

        expect(myService.getMessage()).toEqual('Hello, world!');

    });

});

This code creates a Jasmine test suite for a service named MyService and tests that the getMessage method returns the correct message.

d) Run your tests:

In your terminal, navigate to your Angular project directory and run the following command:

karma start

This will start Karma and run your tests in the Chrome browser (as specified in the karma.conf.js file). You should see the results of your tests in the terminal.

By following these steps, you should be able to implement unit testing in your AngularJS application using Jasmine and Karma.

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31. What is the difference between ngFor and ngIf in AngularJS?

Here is the tabular presentation of all the primary differences between ngFor vs nglf in Angular:

32. How to implement form validation in AngularJS?

You can implement form validation using the built-in form validation directives and the ngModel directive. 

Here are the steps to do so:

1. Add the ng-app directive to the HTML element to initialize the AngularJS application.
2. Add the ng-controller directive to the HTML element to define the controller for the view.
3. Use the ng-form directive to define the form element.
4. Add the name attribute to the form element to identify the form in the controller.
5. Use the ng-model directive to bind the form elements to the scope variables.
6. Use the built-in validation directives such as ng-required, ng-pattern, ng-minlength, ng-maxlength, etc. to validate the form input.
7. Use the ng-show or ng-hide directives to show or hide error messages based on the validation results.
8. Add the ng-submit directive to the form element to call the controller function when the form is submitted.
9. In the controller, define a function that handles the form submission.
10. Use the $valid property of the form object to check if the form is valid.
11. If the form is valid, submit the form data to the server. If the form is invalid, display error messages.

33. What is the difference between reactive forms and template-driven forms in AngularJS?

Here are some tips to optimize the performance of an Angular app handling large datasets:

34. What is the difference between NgZone and ChangeDetectorRef in AngularJS?

Both NgZone and ChangeDetectorRef are important tools in Angular for managing performance and detecting changes. While NgZone is focused on running tasks outside of Angular’s zone to avoid blocking the UI, ChangeDetectorRef is used to manually trigger change detection and update a component’s view.

Here’s a tabular comparison showing the main differences between NgZone and ChangeDetectorRef:

35. What is the difference between @Input and @Output in AngularJS?

Both @Input and @Output are decorators in Angular that enable communication between components in a hierarchical manner. 

@Input is used to pass data from a parent component to a child component, while @Output is used to emit data from a child component to a parent component.

Let’s understand the differences between @Input and @Output:

Angular Interview Questions for 8 Years Experience

Now, let’s discuss some advanced Angular interview questions and answers which are highly relevant for professionals having around 8 years of experience in web development. 

36. Explain the AngularJS Ivy Renderer and its benefits.

It is a new rendering engine introduced in Angular 9 that replaces the previous View Engine. Its primary purpose is to make Angular applications smaller, faster, and more efficient.

Here are some of the benefits of the Ivy Renderer in Angular:

Improved Performance: 

It offers a number of performance improvements over the previous rendering engine. For instance, it offers faster and more efficient rendering of components, which means that applications load faster and respond more quickly to user