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50+ AngularJS Interview Questions & Answers To Get You Hired

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AngularJS is a front-end web development framework made popular by one of the music streaming services first into the market, Rdio. While that product was eventually beaten by Spotify, its web application worked in real-time. And that was primarily because of their use of the front-end web framework Angular. Angular is still competing with other web development frameworks such as React or Backbone. But in general, is quite robust. This front-end web framework can be used to send information to a database as well, so in that vein, it's being used to make fully functional front-end only applications. Below are some helpful AngularJS interview questions with answers to help you study for your next job interview. What I always recommend is that you take these answers with a grain of salt. Use them as a study guide and not as an answer guide. Come up with your own set of answers to prepare for the technical interview process. You should expect to answer questions like this, in person, behind a whiteboard or chalkboard. Printing this page and having a friend ask you the questions can also be quite helpful.



1. What is AngularJS?

This is a JavaScript framework that creates single web page applications. AngularJS allows you HTML as your primary template language. In addition, AngularJS enables the user to extend HTML syntax in order to express their application’s components more clearly.

2. What are the key features of AngularJS?

• Data binding: Data binding handles data synchronization across different models, controllers and view.
• Scope: The scope feature in AngularJS acts as the glue layer between controller and view.
• Controllers: Controllers are functions of JS that are bound to the scope object.
• Services: Services in AngularJS are substitutable objects that are bound together using dependency injection.
• Filters: The role of filters in AngularJS is to format the value of expressions for display to the users i.e. uppercase and lowercase
• Directives: Directives are extended HTML that are used to initialize an angular app.
• Templates: These are HTML codes that include AngularJS specific elements and attributes.
• Routing: This is an approach to switch views.
• MVC pattern: This is a design pattern in AngularJS made of three parts;
• Model: this is a data representation either in a static form from a JSON file or in a dynamic form mainly from a database.
• View: renders data to the user.
• Controller: gives control over the model for collating information to the user.
• Deep linking: Enables encoding in the application and vice versa.
• Dependency injection: This is a design pattern meant to let the components injected into each other as dependencies.

3. What are some of the major reasons why AngularJS is perfect for web development?

• AngularJS uses the MVC design pattern that allows for segregation of an application into various components such as Model, View and Controllers. This makes the process of maintaining it easy.
• AngularJS allows HTML to be extended by adding directives to the HTML markup. This feature is what helps define dynamic templates that can include new attributes, expressions and tags.
• AngularJS as a design framework allows for the creation of user-defined directives and reusable components.
• AngularJS supports two-way data binding.
• The AngularJS development framework encapsulates the behavior of your applications with the assistance of dependency injection.
• AngularJS supports built-in services in order to routine tasks for web applications.
• AngularJS has a JavaScript code that is easy to develop and test.
• AngularJS has a broad support over the internet to help developers address and troubleshoot common challenges experienced when using the AngularJS framework.

4. List the IDE Plugins and Extensions that improve the way you code AngularJS

• Sublime Text
• WebStorm
• Eclipse
• Netbeans
• Visual Studio 2012/2013 Express or higher
• TextMate
• Brackets
• ATOM

5. What browsers are supported by the AngularJS framework?

AngularJS works perfectly with browsers such as Chrome, Firefox, Opera 15+ and the IE9+ version of Internet Explorer. AngularJS also supports several mobile-based browsers such as Android, Chrome Mobile, Safari and Opera Mobile.

Note: Internet Explorer was dropped from the list of browsers that are supported by AngularJS. However, the browser is still supported by versions of AngularJS that preceded the 1.3 version of AngularJS.

. What are expressions in AngularJS?

Expressions in AngularJS are features that bind data to HTML. An expression can either be written inside a directive as ng-bind=”expression” or inside double braces: {{expression}}

AngularJS expressions are very much similar to JavaScript expressions. They include operators, literals and variables.

7. What are some of the differences between AngularJS expressions and JavaScript expressions?

• AngularJS expressions are very much like JavaScript expressions. These are code snippets usually placed in bindings such as {{expression}}. Below are the major differences between Angular expressions and JavaScript expressions.
• Context: In JavaScript, the expressions are evaluated against the global window while in Angular expressions; the evaluation is done against a scope object.
• Forgiving: Evaluation in Angular expressions is forgiving to null and undefined while in JavaScript expressions, undefined properties generate TypeError or ReferenceError.
• Control Flow Statements: features such as loops, exceptions and conditionals are not used in Angular expressions.
• Filters: Filters can be used in Angular expressions to format data before displaying it.

8. What are directives in AngularJS applications?

A directive introduces a new syntax. Directives operate in a similar manner as markers on DOM element that attach a special behavior to it. In AngularJS applications, directives are the most vital components.

9. List the tools used in testing AngularJS applications.

When testing AngularJS application, the tools below make the process much easier to set-up and run.

• Karma: This is a JavaScript command that spawns a web server which then loads the source of your application code and executes the test. Karma can be configured and run against several browsers.
• Jasmine: Jasmine is a popular choice for Angular developers for Angular testing. Jasmine helps in structuring your test and making assertions. As your AngularJS tests increase, the need to structure and document them is vital and this is what Jasmine is designed to do.
• Angular-mocks: Angular-mocks is an inbuilt systems provided by AngularJS for testing.

10. What is internationalization in AngularJS?

Internalization in Angular is a way of showing locale-specific information on a website. This method is used to create multi-lingual websites.

11. What is meant by the AngularJS cycle?

The AngularJS cycle is the process that runs data binding in AngularJS. During each digest cycle, the Angular framework makes a comparison between the old and new version of the scope module values. AngularJS digest cycle is triggered automatically but $apply () can also be used to trigger the cycle manually.

12. How do you set up an Angular app?

• Create an angular.module • Assign a controller to the module
• Link your module to HTML with ng-app
• Link the controller to HTML with ng-controller directive

13. What are the main security features provided by AngularJS?

AngularJS has an inbuilt security system that;

• Prevent cross-site scripting attacks- Cross-site scripting is whereby a user can send a request from the clients side and still be able to access confidential information easily. AngularJS therefore makes it harder for a user from the client’s side to access confidential information. • Prevents HTML injection attacks
• Prevents XSRF protection for server-side communication

14. Explain the boot process in AngularJS

Whenever the user loads a page in the browser, the following steps are executed in the background.

• When a webpage is loading, the HTML file that contains the code gets loaded into the browser. The JavaScript file mentioned in the HTML code is then loaded whereby it creates a global object for Angular. It is at this point where the JavaScript that displays the controller functions gets executed. • AngularJS browses the entire HTML code in order to locate the views. If the views are available, Angular links them to the corresponding controller function.
• The last step has AngularJS initiating the execution of the required controller functions. After this, Angular populates the views with data and the page is finally ready.

15. Name some of the characteristics of Scope in AngularJS

Scope in AngularJS can be defined as the object that refers to the application model. In other words, it is the execution context for expressions. Below are some of the main characteristics of Scope.

• Scopes provide APIs ($watch) in order to observe model mutations.
• Scopes provide APIs ($apply) that are used initiate model changes outside the Angular realm.
• Scopes can be used to limit access to applications components and properties while at the same time providing access to shared model properties.
• Scopes provide context for expressions to be evaluated.

16. What are the major advantages of using the Angular.js framework?

• Supports two way data-binding
• Supports MVC pattern
• Support static template and angular template
• Can add custom directive
• Supports REST full services
• Supports form validations
• Support both client and server communication
• Support dependency injection
• Applying Animations
• Event Handlers

17. Explain the factory model in AngularJS.

The factory method is used to create a directive. This method is often invoked when the compiler is able to match the directive for the first time. The factory method can be invoked using $injector.invoke.

Syntax module.factory (‘factoryName’, function);

18. Explain the difference between AngularJS and backbone.js

AngularJS supports individual functionalities and combines other functionalities-mostly from third-party websites, required in the development of HTML5 Apps. On the other hand, backbone.js does these functions individually.

19. What is referred to as Injector in AngularJS?

An Injector can be described as the service locator. An injector is used in the retrieval of object instance as defined by the provider, invoke methods and load modules.

20. On which type of components can a custom directive be created?

AngularJS provides the following support in the creation of a custom directive;

• Element directives: Activates a custom directive when a matching element is encountered.
• Attribute Activates a custom directive when a matching attribute is encountered.
• CSS: Activates a custom directive when the CSS style is encountered.
• Comment: Activates a custom directive when a matching comment is encountered.

21. In AngularJS, what is meant by bootstrapping?

Simply put, bootstrapping in AngularJS is starting or initializing the Angular app. AngularJS supports both manual and automatic bootstrapping.

• Manual bootstrapping: This method gives you more control on when and how to initialize your Angular app. Manual bootstrapping is most useful when you want to perform an action before the Angular wakes up. • Automatic bootstrapping: Automatic bootstrapping takes place when ng-app directive is added to the root of the application. AngularJS loads the module associated with the ng-app directive and then compiles the DOM.

22. How is routing implemented in AngularJS?

Step 1: – Add the “Angular-route.js” file to your view.
Step 2: – Inject “ngroute” functionality while creating Angular app object.
Step 3: – Configure the route provider.
Step 4: – Define hyperlinks.
Step 5: – Define sections where to load the view.

23. What are the most common directives in AngularJS applications?

One of the roles of AngularJS is to extend the behavior of HTML and DOM elements with new attributes known as Directives. Below is a list of the most common AngularJS directives.

• ng-bind –The role of this directive is to tell AngularJS to replace the content of an HTML content with the value of a given expression or variable. The ng-bind directive supports one-way binding and in the event that there is a change in the value of a given value or expression, the content in the HTML element will be updated accordingly.
• ng-model –This directive is responsible for linking the view into the model. Ideally, it operates by binding the value of the HTML element to the application data.
• ng-class –This directive is responsible for binding one or several CSS classes dynamically to an HTML element.
• ng-app –The ng-app works in almost a similar manner as the “Main()” function of Java language. Ng-app marks the beginning of the application to AngularJS HTML compiler and if this directive is not used, an error is generated.
• ng-init –This directive is used to initialize the application data. This process is meant to ensure that the application data is used in the block where it is declared. For example, an application requiring local data such as a single value or an array of values can be achieved by using ng-init directive.
• ng-repeat –The function of the ng-repeat directive is to repeat a set of HTML statement for a specified number of times.

24. List the filters that are provided by AngularJS to transform data.

The role of Angular filters is to transform data before it is passed to the view. Angular filters work hand-in-hand with AngularJS expressions and directives. Below are some of the filters found in AngularJS.

• Currency: The currency filter in AngularJS is used to format a number into a currency format. • Date: The date filter allows users to format the date into a different specified format.
• Filter: Chooses a subject of items form an array.
• Json: formats an object into a JSON string.
• LimitTo: Creates an array of string combination that contains a specific number of elements or characters either at the beginning or at the end.
• Lowercase: converts a string to lower case.
• Number: formats numbers into text.
• OrderBY: enables sorting of an array. Ideally, strings are sorted alphabetically while numbers are sorted alphabetically.
• Uppercase: converts a string to uppercase.

25. What is a Singleton pattern in AngularJS?

This is a design approach that limits the instantiation of a class into a single object. In AngularJS, the dependency injection is used in order to enable the singleton pattern. After a singleton pattern is enabled, the class then creates the object.

26. Name the built-in services in Angular and their functions.

$anchorScroll Scrolls the browser window to a specified anchor
$animate Animates the content transitions.
$compile Processes an HTML fragment to create a function that can be used to generate content.
$controller A wrapper around the $injector service that instantiates controllers
$document Provides a jqLite objects that contains the DOM window.documentobject.
$exceptionHandler Handles exceptions that arise in the application.
$filter Provides access to filters
$http Creates and manages Ajax requests
$injector Creates instances of AngularJS components
$interpolate Processes a string that contains binding expressions to create a function that can be used to generate content.
$interval Provides an enhanced wrapper around the window.setInterval function.
$location Provides a wrapper around the browser location object.
$log Provides a wrapper around the global console object.
$parse Processes an expression to create a function that can be used to generate content.
$provide Implements many of the methods that are exposed by Module.
$q Provides deferred objects/promises.
$resource Provides support for working with RESTful APIs.
$rootElement Provides access to the root element in the DOM.
$rootScope Provides access to the top of the scope hierarchy.
$route Provides support for changing view content based on the browser’sURL path.
$routeParams Provides information about URL routes.
$sanitize Replaces dangerous HTML characters with their display-safecounterparts.
$swipe Recognizes swipe gestures.
$timeout Provides an enhanced wrapper around the window.setITimeout function.
$window Provides a reference to the DOM window object.

27. List down the event listener directives that attach an event listener to an HTML element

• ng-click
• ng-dbl-click
• ng-mousedown
• ng-mouseup
• ng-mouseenter
• ng-mouseleave
• ng-mousemove
• ng-mouseover
• ng-keydown
• ng-keyup
• ng-keypress
• ng-change

28. Explain the top reasons why developers prefer using AngularJS

AngularJS, being an Open-Source web application is designed to create a highly robust and scalable SPA( Single Page Application). Single Page Applications are web applications or websites that encompass a single page thereby offering a more streamlined user experience. AngularJS is written in JavaScript and HTML is used as the templating language. One of the best features why AngularJS is a popular choice among developers is that it provides developers with the option of creating client-based applications. Web developers often take into consideration the following factors when using AngularJS;

• Performance: AngularJS is preferred by developers because of its ease of use and maintenance. This is because AngularJS has intuitive features, offers efficiency when building new features and is robust. It is obvious that most developers will not wish to spend hours debugging when a problem arises. • Effective handling: Dependency injection is very effective in AngularJS. For Single Page Applications for example, AngularJS is very effective when it comes to organizing things such as dependencies and dynamic loading. This means that you can carry out your activities without having to worry about whether you just spun an instance or what namespace it lives.

29. What attributes can be used in the creation of a new AngularJS directive.

• Restrict: This attribute defines how AngularJS triggers the directive within a template. The restrict attribute uses the default value A. This value is what causes the directive to be triggered. The restrict attribute can also have a combination of all the values mentioned above.
• TemplateURL: This attribute sends communication to the AngularHTML compiler that the custom directive should be replaced with HTML content located inside a different file.
• Template: This attribute specifies an inline template as a string. However, it cannot be used if you are specifying a template as a URL.
• Replace: This attribute replaces the current element.
• Transclude: The transclude attributes lets you move the directives to a new location inside a template.
• Scope: The scope attribute creates a new scope for this directive as opposed to inheriting the parent scope.
• Controller: This attribute creates the controller which then publishes an API for communicating across different directives.
• Require: This attribute requires that a different directive be present for this attribute to function correctly.
• Link: This attribute programmatically modifies the results of the DOM element instances as well as adding event listeners and setting up data binders.
• Compile: This attribute programmatically modifies the DOM template where the compile function can also return link functions to modify the resulting element instances.

30. What is One-Way Data Binding in AngularJS?

Simply put, One-Way binding implies that when model values change, the HTML will reflect this change. In other words, a change in the models will be reflected in the view but the view will not change the model. This means that an AngularJS developer must write an extra code to initiate automatic synchronization of data between the model and the view components. One-Way binding is also referred to as one-direction binding.

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

In JavaScript frameworks such as the Backbone and jQuery, the HTML template is parsed as a stream and returns the result as a string. The resulting string is them stored in the DOM where it can be retrieved using the innerHTML() method.

On the other hand, AngularJS process the template differently. AngularJS works directly on HTML DOM instead of using strings and manipulates the HTML DOM as required. AngularJS therefore uses two-way data binding between the view and the model to sync data.

32. Explain the AngularJS Application Lifecycle

The Angular App’s lifecycle consists of the following main phases;

• Bootstrap,
• Compilation, and
• Run-time
• These phases are initiated every time a webpage of an AngularJS app is loaded into the browser.
• The Bootstrap Phase: In the bootstrap phase, the browser downloads the Angular JavaScript library. After the download, AngularJS initialize the necessary modules and components to which the ng-app directive points. After the module is loaded, the necessary dependencies are injected into the module and they become available to that specific code within the module.

33. Mention the steps that take place during the compilation process in HTML?

• The HTML is parsed into DOM using the standard browser API.
• Compilation of the DOM is performed using the call to the $compile () method. This method traverses the DOM and matches the directives.
• The template is linked to the scope by calling the linking function returned from the previous step.

34. What is the linking function in AngularJS?

In AngularJS, link function is responsible for combining directives with a scope thereby producing a live view. The link function is also responsible for registering DOM listeners as well as updating the DOM.

35. What are the different types of link function?

• Pre-linking function: The execution of this function is done before the child elements are linked together. However, pre-linking is nit considered as a safe way of DOM transformation.
• Post-linking function: The execution of this function is done after the linking of the child elements. Post linking is considered as a safe way for DOM transformation.

36. What is the main difference between a compile function and a link function in AngularJS?

The compile function is used for manipulating the DOM template and collecting all the directives while the link function is used to register DOM listeners and DOM manipulation.

37. What are the styling form that ngModel adds to CSS classes?

ngModel adds these CSS classes to allow styling of form as well as control
• ng- valid
• ng- invalid
• ng-pristine
• ng-dirty

38. Who developed AngularJS?

AngularJS was developed by Misko Hevery and Adam Abrons before currently being developed by Google.

39. How many scopes can an AngularJS application have at any given time?

Every AngularJS application has a single root scope but can have several additional child scopes. As child controllers and directives continue to create new child scopes, an AngularJS application can end up having multiple scopes. Once the new scopes are created, they are added to their parent scope as children. Similar to what DOM does, they can also create a hierarchical structure.

40. Name a few built-in validators in AngularJS.

• required
• min
• max
• type=”number” OR type=”email

41. What are the main differences between AngularJS and Angular2?

• AngularJS is based on MVC architecture while Angular 2 is based on service/components.
• AngularJS uses JavaScript to write applications while Angular 2 uses Typescript ( a superset of JavaScript) to write applications.
• AngularJS uses controllers to write logics and interact with Model and view while in Angular 2, Controllers are totally eliminated and components take their place.
• AngularJS is designed to develop single-page web applications while Angular2 is designed to develop native applications for mobile platforms.
• AngularJS is easy to set up provided that you have an AngularJS library while Angular2 is dependent on other modules and packages. It takes a little brainstorming to install and run Angular2.

42. How do you validate an URL in AngularJS?

L validation in AngularJS is done by adding the regex directly to the ng pattern.

43. Name the three types of directives found in AngularJS

• Parent scope: This is the default scope.
• Child scope: This scope is created when the properties and functions set on the default scope are not relevant to other directives.
• Isolated scope: This scope is used when the directive being built is self-contained and reusable.

44. Is AngularJS a framework, a library, a plugin or a browser extension?

• AngularJS can best be described as a framework. However, AngularJS is more lightweight in nature compared to a typical framework which is the reason why it is often confused as being a library.
• AngularJS supports JavaScript and is compatible with both mobile and desktop browsers so it is definitely not a plugin or a browser extension.

45. What is deep linking in AngularJS?

Deep linking lets you encode applications in the URL so that they can be bookmarked. The applications can then be restored from the URL into their original state.

46. Explain the process of AngularJS boot process using a code

The Angular boot process is initialized automatically after the angular.js script is downloaded to the browser and the document.readyState is set to complete. After this, AngularJS looks for the root of angular app compilation which is the ng-app directive. After the ng-app is found, Angular;

• Loads the module associated with the directive.
• Creates the application injector.
• Compiles the DOM starting from the ng-app root element.
• This process is referred to as automatic bootstrapping.

Example:
var app = angular.module('myApp', []);
app.controller('Ctrl', function ($scope) {
$scope.msg = 'World';
});

47. What is jqLite in AngularJS?

jqLite is a jQuery subset that is directly built into the AngularJS framework. The purpose of jqLite is to provide useful basic features of jQuery to the AngularJS framework.

48. How is data shared between controllers in AngularJS?

Using services is the best and most efficient ways of sharing data between controllers in AngularJS. However, there are several other ways of sharing data between controllers as outlined below.

• Using Events
• $parent, nextSibling, controllerAs
• Using the $rootScope

49. What are the five main ways of creating a service in AngularJS?

The following ways can be used to create a service in AngularJS

• Service
• Factory method
• Provider method
• Value method
• Constant method

50. How do you add routing in AngularJS?

var app = angular.module("AngularApp", ['ngRoute']);
app.config(['$routeProvider',
function($routeProvider)
{
$routeProvider.
when('/page1',
{
templateUrl: 'Modules/Page1/page1.html',
controller: 'Page1Controller'
})
.
when('/page2',
{
templateUrl: 'Modules/Page2/page2.html',
controller: 'Page2Controller'
})
.
otherwise
({
redirectTo: '/page1'
});
}
]);

51. What are some of the ways that the object uses to hold dependencies?

• Dependencies can be created using the new operator.
• Dependencies can be looked up by referring a global variable.
• Dependency can be passed to where they are required.

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