29 Most Commonly Asked AngularJS Interview Questions and Answers [For Beginners & Experienced]

AngularJS is one of the most popular web frameworks in the modern tech scene. Although initially, AngularJS was a Google project, later, it became an open-source framework. AngularJS is a client-side JavaScript Model-View-Controller framework that is primarily used to build and dynamic web applications, particularly single-page applications. 

Since AngularJS is wholly based on HTML and JavaScript, it allows you to use HTML as the template language. It not only changes static HTML to dynamic HTML but also helps extend HTML’s abilities by adding built-in attributes. Nit just that, AngularJS also extends HTML’s ability to create custom attributes using JavaScript. What’s best about AngularJS’s is that its data binding and dependency injection features help eliminate the need to write redundant code. 

The popularity of AngularJS has become so widespread that the demand for AngularJS skills in the industry is soaring. However, if you wish to land a job that demands AngularJS skills, you must first crack the AngularJS interview. To help you ace the AngularJS interview, we’ve created a comprehensive list of AngularJS interview questions and answers. 

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Top AngularJS Interview Questions & Answers

1. What is AngularJS? What are the key features of AngularJS?

AngularJS is a JavaScript framework that was developed by Google. It is used for creating dynamic and extensible web applications. It is based on the MVC (Model View Controller) pattern with HTML as the template language. As we mentioned in the introduction, AngularJS runs on plain JavaScript and HTML, which means you need not rely on other external dependencies for using it. AngularJS helps bind JavaScript objects with HTML UI elements.

The core features of AngularJS are:

• Template
• Scope
• Controller
• Services 
• Model
• View 
• Data binding
• Filters

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2. Define Scope in AngularJS.

In AngularJS, Scope is an application model that functions as a link between glue between the application controller and the view. The Scope is designed to monitor expressions and propagate events. Usually, scopes are organized in a hierarchical structure replicating the DOM (Document Object Model) structure of an application. It can watch expressions and propagate events.

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3. Define Data Binding in AngularJS.

In AngularJS, data binding refers to the process in which the data between the model and view components are automatically synchronized. Data binding helps simplify the process of defining interactive applications without worry about pushing or pulling data between view/template and component. There are four data binding forms:

• Event binding
• Property binding
• String interpolation
• Two-way data binding

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4. Define Angular Expression. What is the difference between Angular expressions and JavaScript expressions?

Angular expressions are code snippets that are placed in binding (much like JavaScript’s style), like so:

{{ angular }}

Angular expressions help bind application data to HTML.

The core difference between JavaScript expressions and Angular expressions are:

• While JavaScript expressions are evaluated against a global window, Angular expressions are evaluated against a scope object.
• The evaluation of Angular expressions forgives null and undefined, but in JavaScript, undefined properties usually produce TypeError or ReferenceError.
• Unlike JavaScript, Angular expressions do not permit the use of loops, conditionals, or exceptions.
• While AngularJS supports filters, JavaScript does not.

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5. Name the common IDEs used for the development of AngularJS applications.

Here are the most commonly used IDEs (Integrated Development Environment) for AngularJS:

• Eclipse – This is one of the favourite IDEs of Java/JavaScript Developers. It supports AngularJS plugins.
• Visual Studio – This is a Microsoft IDE that is designed for developing web apps easily and quickly.
• WebStorm – This is undoubtedly one of the most powerful IDEs for modern JavaScript development. It allows for easy integration of dependencies using Angular CLI.
• Aptana – This is an open-source, customized version of Eclipse. It comes loaded with the latest tools and web standards required for web development.
• Sublime Text – This is a highly recommended IDE for HTML, CSS, and JavaScript. Naturally, it is compatible with AngularJS.

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6. What are Directives in AngularJS?

Directives in AngularJS are nothing but extended HTML attributes having “ng” prefix. There are three core directives of AngularJS:

• ng-app – The purpose of this directive is to flag the HTML element that should be considered as the root element of an Angular application. While Angular applies the spinal-case for custom attributes, it uses the camelCase filter for the corresponding directives that implement them.
• ng-model – This directive helps bind the values of HTML controls (input, select, textarea) to the application data. In an ng-model, not only does the Scope reflected in the view change, but even the changes in the view are reflected in the Scope.
• ng-bind – This directive is used to bind modal application data to the HTML view.

7. What is the purpose of AngularJS routes?

Using AngularJS routes allow you to create different URLs for different content in an Angular application. By doing so, you can bookmark URLs to their specific content, and each such URL that is bookmarked is called a route in AngularJS.

8. Define String Interpolation in AngularJS.

In AngularJS, string interpolation refers to a unique syntax that uses template expressions within {{ }} braces for displaying the component data. String interpolation is often referred to as “Moustache Syntax.” When using this syntax, first you need to include the JavaScript expressions (that need to be executed) within the double curly braces and then it embeds the relative output into an HTML code.

9. Define AngularJS “Digest Cycle.”

The digest cycle essentially refers to the process of data binding in AngularJS. In this process, the old and new versions of the scope model values are pitted against each other and compared. Although the digest cycle is triggered automatically, you can also use “$apply()” to manually start the process.

10. What is the difference between One-way Binding and Two-way Binding?

One-way binding is used to bind the data from the model to view without automatically updating the HTML template or view. So, in this approach, you must write a custom code to update the HTML template, which will further update the view each time the data is bound from model to view.

Contrary to this, two-way binding binds the data from the model to view and vice versa by automatically updating the HTML template without requiring you to write any custom code.

11. Define Linking Function. Name the types of Linking Functions.

A link combines the directives with a scope to produce a live view. The link function is used for registering DOM listeners and for updating the DOM. This function is executed immediately after the template is cloned. 

There are two types of linking function:

• Pre-linking function – This function is executed before the child elements are linked and is usually not a safe approach for DOM transformation.
• Post linking function – This function is executed after the child elements are linked.

12. What is an Injector in AngularJS?

An injector is a service locator in AngularJS. The primary purpose of the injector is to receive object instances that are defined by the providers, invoke methods, load modules, and instantiate types. Every Angular application includes an injector that helps to look up object instances by their name.

13. Name the different styling forms that ng-model adds to CSS classes.

An ng-model adds the following styling forms to CSS classes:

• ng- valid
• ng- invalid
• ng-pristine
• ng-dirty

14. Define Dependency Injection. How can an object or function access its dependencies?

Dependency injection (DI) is a software design pattern that determines how code can retrieve its dependencies. It allows components to access their dependencies instead of hardcoding them within a component. To retrieve the elements that are required to be configured when a module is loaded in an application, the “config” operation uses DI.

An object or function can access its dependencies in the following ways:

• A dependency can be created using a new operator.
• A dependency can be looked up by referring to a global variable.

15. Name the components that can be injected as a dependency in AngularJS.

In AngularJS, you can inject the following components into each other as dependencies:

• Value 
• Service
• Factory 
• Constant 
• Provider

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16. What are the steps involved in the compilation process of HTML?

The compilation process of HTML involves the following steps:

• First, the HTML is parsed into DOM using the standard browser API.
• In the next step, the call to the $compile() method is used to perform the compilation of the DOM. The method traverses the DOM to match the directives.
• The final step involves linking the template with a scope by calling the linking function returned from the earlier step.

17. What is a Service in AngularJS?

Services are JavaScript functions that are designed to perform specific tasks. For instance, $https: function is used to make AJAX call to obtain the server data while the $route function is used to define the routing information. There are many more such services that can perform specific tasks.

18. Define Directive in AngularJS. Name the different types of Directives.

In AngularJS, a directive is a behaviour or function that is triggered during the compilation process when specific HTML constructs are encountered. Directives are markers on DOM elements (such as elements, attributes, CSS, etc.). You can also use them to create custom HTML tags that act as new, custom widgets.  

The four core types of directives are:

• Element directives
• Attribute directives
• Comment directives
• CSS class directives

19. Differentiate between an Annotation and a Decorator in AngularJS.

In Angular, annotations are the only metadata set of the class that uses the Reflect Metadata library to create an “annotation” array. Decorators, on the other hand, are design patterns that are used for separating decoration or modification of a class without altering the original source code of an application.

20. Define Controllers.

Controllers are JavaScript functions that are bound to a particular scope. Their primary aim is to provide data and logic to HTML UI. They are the prime actors in the AngularJS framework that control how the data flows from the server to HTML UI. Furthermore, controllers also carry functions to operate on the data and determine which view needs to be updated to display the updated model-based data.

21. How are logs maintained in AngularJS?

To maintain logs, the $log service is used in AngularJS. The primary purpose of the $log service is to help in debugging and troubleshooting through the methods mentioned below:

• log() – It is used to write a log message in the console.
• info()- It is used to write an information message.
• warn()- It is used to write a warning message.
• error()- It is used to write an error message.
• debug()- It is used to write a debug message.

22. Define $rootscope in AngularJS. How does it differ from Scope?

In AngularJS, both $rootscope and $scope are objects that are generally used for sharing data from the controller to view. However, the two are quite different. The main point of difference between $rootscope and $scope is that while the former is globally available across all the controllers, $scope is available only in controllers that have created it along with their children controllers.

23. Name some browsers that AngularJS supports.

Here are some of the browsers that are supported by AngularJS:

• Mozilla Firefox
• Google Chrome
• Microsft Edge
• IE Mobile
• Safari (iOS)
• IE 10,11

24. How can you enable HTML5 mode in Angular 1.x?

To enable the HTML5 mode in Angular 1.x, you must run the code given below:

angular.module(‘myApp’, [ ])

    .config(function($routeProvider, $locationProvider) {

        $routeProvider

            .when(‘/’, {

                templateUrl : ‘partials/home.html’,

                controller : mainController

            })

        // use the HTML5 History API

        $locationProvider.html5Mode(true);

    });

25. Name the built-in validators in AngularJS.

AngularJS supports all standard HTML5 attributes for validating inputs. Here are some of the built-in validators in AngularJS:

• Min 
• Max
• Required 
• Type=” number” OR type=” email”

26. How to make an AJAX call using AngularJS?

You can use the $https: service in AngularJS to make an AJAX call to read data from the server. AngularJS requires data to be in JSON format. The server creates a database call to retrieve the desired records. Once the data is ready, the $https: service can be used to retrieve the data from the server, like so:

function studentController($scope,$https:) {  

   var url = “data.txt”;  

   $https:.get(url).success( function(response) {  

      $scope.students = response;   

   });  

}  

27. What is Internalization in AngularJS?

In AngularJS, internationalization refers to the method used for showing locale-specific information on a website. For instance, a website displaying content in the English language in the United States and Danish in France must be internalized according to the location.

AngularJS offers inbuilt internationalization support for three kinds of filters:

• Date
• Numbers
• Currency

28. Describe the steps of the AngularJS boot process. 

When you load a page in a browser, the AngularJS boot process kicks in. The steps involved are as follows:

• The HTML document file is loaded and evaluated by the browser. Then the AngularJS JavaScript file is loaded, and a global object is created. 
• In the next step, the JavaScript file responsible for registering the controller functions is executed.
• AngularJS scans the HTML to find AngularJS apps and views. When it is successful in finding a view, it connects that particular view to the corresponding controller function.
• Lastly, AngularJS executes the controller functions and renders the views with data from the model populated by the controller, and the page is ready to be viewed by the user.

29. What purpose do filters serve in AngularJS?

Filters are used for formatting the value of an expression and display the same to the user. In AngularJS, filters are added to templates, directives, controllers, and services. You can also create custom filters. By using filters, you can organize data in such a way that the data value will be displayed only when it fulfills a particular criterion. Filters are added to Angular expressions by using the “|” character followed by a filter

Conclusion

So, here are the 29 most commonly asked AngularJS interview questions and answers that will help you break the ice with AngularJS.

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