Top 90+ AngularJS Interview Questions and Answers for 2024

AngularJS is a widely-used JavaScript framework that has revolutionized web development by providing a structured approach to building dynamic web applications. As the demand for AngularJS developers continues to rise, aspiring candidates must be well-prepared for job interviews. To help you excel in your AngularJS interview, this article presents a comprehensive list of the top 100 Angular JS interview questions. Whether you are a beginner looking to kickstart your career or an experienced developer aiming to enhance your expertise, this compilation of questions will serve as a valuable resource to prepare you for the challenges of an AngularJS interview. From the fundamentals to advanced concepts, we have covered a broad range of topics to ensure you are equipped with the knowledge necessary to showcase your skills and stand out from the competition. So, let's dive into the world of AngularJS and discover the essential AngularJS interview questions and answers that will help you succeed in your career journey.

Most Asked Angular.js Interview Questions and Answers

1. What is AngularJS?

Answer. AngularJS is a JavaScript-based open-source front-end web application framework developed by Google. It allows developers to build dynamic, single-page applications (SPAs) by extending HTML's syntax and providing a modular approach to application development.

2. What are the core technologies used in AngularJS?

Answer. AngularJS primarily uses the following core technologies:

• HTML: AngularJS extends HTML with additional attributes and directives to define dynamic behavior.
• CSS: Styling the AngularJS application is done using CSS, just like in any other web application.
• JavaScript: AngularJS is built on top of JavaScript and uses it extensively to provide the framework's functionality.

3. How does an AngularJS application work?

Answer:  An AngularJS application follows the MVC (Model-View-Controller) pattern, where:

• Model represents the data and business logic.
• View is the user interface that displays the data to the user.
• Controller acts as an intermediary between the Model and View, handling user interactions and updating the Model or View accordingly.
• AngularJS uses declarative HTML templates with additional directives that bind data and behavior to the HTML elements. The application's components, such as controllers, services, and directives, work together to handle data flow, user input, and manipulation of the DOM (Document Object Model).

4. What is TypeScript?

Answer. TypeScript is a superset of JavaScript developed by Microsoft. It introduces optional static typing and other features to JavaScript, making it more robust and scalable for large-scale applications. AngularJS is often written in TypeScript, which allows for better tooling, improved developer experience, and enhanced code maintainability.

5. What is metadata in AngularJS?

Answer. Metadata in AngularJS refers to the annotations or decorators that are used to provide additional information about a class, such as components, directives, or services. It is used by the AngularJS compiler to understand and process the class accordingly. Metadata includes information like selectors, templates, styleUrls, providers, and more.

6. What is the difference between constructor and ngOnInit in AngularJS?

Answer. In AngularJS, the constructor is a standard JavaScript constructor function that is executed when an instance of a component or service is created. It is used for initializing variables, injecting dependencies, and setting up the component.

On the other hand, ngOnInit is a lifecycle hook provided by AngularJS that is called once after the component has been initialized and all its input properties have been bound. It is commonly used to perform initialization tasks that depend on input values being available. ngOnInit is particularly useful when working with asynchronous operations or when you need to interact with the DOM.

7. How is the Dependency Hierarchy formed in AngularJS?

Answer: The Dependency Hierarchy in AngularJS is formed through dependency injection. AngularJS uses a hierarchical injection system to manage the dependencies of components and services. When a component or service requires another component or service, it specifies its dependencies through constructor parameters or through metadata annotations.

The AngularJS injector then resolves these dependencies by traversing up the hierarchical tree of injectors until it finds a provider that can satisfy the dependency. This hierarchical nature allows for easy management and separation of concerns, making the application more modular and maintainable.

8. What is the purpose of the async pipe in AngularJS?

Answer. The async pipe in AngularJS is a built-in pipe that simplifies the handling of asynchronous operations, particularly with Observables. It subscribes to an Observable or Promise and automatically manages the subscription and unsubscription, as well as the handling of emitted values or resolved data.

By using the async pipe, you can directly bind the result of an asynchronous operation in your template, without having to manually subscribe and handle the data in your component. This helps to streamline the code and ensure proper handling of asynchronous data flow within AngularJS applications.

Basic Level: AngularJS Interview Questions for Freshers

Let's dive into some of the top AngularJS basic interview questions.

1. What are the technologies used in Angular?

Answer:  Angular is a modern front-end JavaScript framework developed by Google. Angular itself makes use of several technologies for several reasons to accomplish certain tasks easily as well as to allow developers to have a better experience while developing applications with it. Angular uses TypeScript, which is a superscript of JavaScript. So, any valid JavaScript is a valid TypeScript. However, TypeScript allows us to write JavaScript as a strongly typed language, and we can define our own types as well, which makes catching bugs much easier. It also uses RxJS, which allows developers to better deal with asynchronous operations.

2. How does an Angular application work?

Answer: The working of Angular is based on its components. So the working of the Angular application starts with the configuration file ANGULAR.JSON. The builder refers to this file to find the paths, configurations and the main file. Now the process finally starts. Next comes the MAIN.TS file that acts as the entry point for the configuration file. It basically helps in creating the browser environment that enables it to run the application.

An Angular application operates according to the principles of a client-side web framework. Upon loading the application in a web browser, the following sequence of steps takes place:

• Initialization: The Angular framework initiates the application by bootstrapping the root component, which serves as the entry point.
• Component Rendering: Angular renders components based on their predefined templates. Each component contains a template that describes the structure and layout of the user interface (UI).
• Data Binding: Angular enables data binding, which facilitates the synchronization of data between the component’s model and the view. This synchronization allows for dynamic updates in real time, ensuring that the view consistently and accurately represents the current state of the data.
• Component Interaction: Components communicate with one another through input and output properties, as well as services, facilitating the exchange of data and functionality across different parts of the application.
• Event Handling: Angular manages user interactions, such as button clicks or form submissions, by capturing and responding to events. These events trigger specific actions or updates within the application.
• Dependency Injection: Angular utilizes dependency injection to handle the application’s dependencies and promote modularity. This simplifies the integration of services and reusable code modules that provide specific functionality to components.
• Routing: Angular incorporates a router module that enables navigation within the application. Routes are defined, determining which components are displayed based on the current URL or user actions.
• Compilation and Bundling: An Angular application is typically compiled and bundled before deployment. This process optimizes performance by reducing file sizes and merging multiple files into a single bundle.
• Deployment: Following bundling, the application can be deployed to a web server or hosting service, making it accessible to users.

3. What is TypeScript?

Answer: The TypeScript feature offered by Angular is preferred by a majority of Front-End Developers. TypeScript helps in efficiently detecting bugs and helps in easy compilation by its automatic populating functionality. Also, it offers rich interfaces, access modifiers, hybrid types etc. All these combined lead to reduction in the developing time.

4. Write a pictorial diagram of Angular architecture.

Answer: The architecture of Angular comprises the following elements. The pictorial representation of the same is given below:

• Components and Templates
• Ng Modules
• Metadata
• Data Binding
• Directives
• Services
• Dependency Injection

Angular architecture

5. What is metadata?

Answer: Using metadata is how we tell Angular how to process a class. When we use a component, it acts as a class unless we tell that it’s a component, and we do this with the help of metadata. Metadata is attached in TypeScript using a decorator. Decorators are functions that know the configuration of classes and how they are supposed to work.

6. What is the difference between constructor and ngOnInit?

Answer: The difference between constructor and ngOnInit is given below:

7. How is Dependency Hierarchy formed?

Answer: In Angular, the formation of a Dependency Hierarchy is established through the Angular Dependency Injection (DI) system. The DI system manages the dependencies between different components within an Angular application.

The process of forming a Dependency Hierarchy in Angular involves the following steps:

• Dependency Definition: Components, services, or other Angular constructs declare their dependencies in their respective constructor parameters. These dependencies are specified using TypeScript types or Angular-specific decorators.
• Provider Registration: In Angular, providers assume the responsibility of generating and overseeing instances of dependencies. These providers are enlisted within the dependency injection container of the Angular application, which serves as a repository for available providers.
• Dependency Resolution: When a component or service is requested, Angular’s DI system resolves its dependencies by examining the constructor parameters. It then looks up the corresponding providers from the dependency injection container.

Hierarchical Dependency Injection: Angular’s DI system follows a hierarchical approach for resolving dependencies. Each component or service has its own injector, which contains providers specific to that component or service. If a requested dependency is not found in the current injector, Angular recursively searches the parent injectors until it finds a matching provider or reaches the top-level injector.

8. What is the purpose of the async pipe?

Answer: The async pipe’s purpose is to mark the components that need to be checked for changes. It subscribes to an Observable or Promise and returns the latest value it has emitted. Once this new value is emitted, the components are marked by the async pipe. When any component is destroyed, the async pipe detaches or unsubscribes automatically. Similarly, if the expression reference of the component changes, the async pipe detaches or unsubscribes from the old Observable or Promise and subscribes to a new one.

9. What are the features of Bazel?

Answer: The following are the main features of Bazel:

• It is an internal build tool, through which the application can be customized.
• It also tests the action and performance of multiple machines.
• It constructs a graph through which you can identify useful information.
• It also supports customization.runGuardsAndResolvers

10.What are the main advantages of AngularJS?

Answer: Some of the main advantages of AngularJS are given below:

• Allows us to create a single page application.
• Follows MVC design pattern.
• Predefined form validations.
• Supports animations.
• Open-source.
• Cross-browser compliant.
• Supports two-way data binding.
• Its code is unit testable.

11. What are the disadvantages of AngularJS?

Answer: There are some drawbacks of AngularJS which are given below:

• JavaScript Dependent
  If end-user disables JavaScript, AngularJS will not work.
• Not Secured
  It is a JavaScript-based framework, so it is not safe to authenticate the user through AngularJS only.
• Time Consumption in Old Devices
  The browsers on old computers and mobiles are not capable or take a little more time to render pages of application and websites designed using the framework. It happens because the browser performs some supplementary tasks like DOM (Document Object Model) manipulation.
• Difficult to Learn
  If you are new in AngularJS, then it will not be easy for you to deal with complex entities such as Quite layered, hierarchically and scopes. Debugging the scope is believed a tough task for many programmers.

12. Describe MVC in reference to angular.

Answer: AngularJS is based on MVC framework, where MVC stands for Model-View-Controller. MVCperforms the following operations:

• A model is the lowest level of the pattern responsible for maintaining data.
• A controller is responsible for a view that contains the logic to manipulate that data. It is basically a software code which is used for taking control of the interactions between the Model and View.
• A view is the HTML which is responsible for displaying the data.

For example, a $scope can be defined as a model, whereas the functions written in angular controller modifies the $scope and HTML displays the value of scope variable

13. What is $scope?

Answer: A $scope is an object that represents the application model for an Angular application.

Each AngularJS application can have only one root scope but can have multiple child scopes. For example:

var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
$scope.carname = "Volvo";
});

Some of the key characteristics of the $scope object are given below:

• It provides observers to check for all the model changes.
• It provides the ability to propagate model changes through the application as well as outside the system to other associated components.
• Scopes can be nested in a way that they can isolate functionality and model properties.
• It provides an execution environment in which expressions are evaluated.

14. Is AngularJS dependent on JQuery?

Answer:  AngularJS is a JavaScript framework with key features like models, two-way binding, directives, routing, dependency injections, unit tests, etc. On the other hand, JQuery is a JavaScript library used for DOM manipulation with no two-way binding features.

15. What are the features of AngularJS?

Answer: Some important features of AngularJS are given below:

• MVC- In AngularJS, you just have to split your application code into MVC components, i.e., Model, View, and the Controller.
• Validation- It performs client-side form validation.
• Module- It defines an application.
• Directive- It specifies behavior on the DOM element.
• Template- It renders the dynamic view.
• Scope- It joins the controller with the views.
• Expression- It binds application data to HTML.
• Data Binding- It creates a two-way data-binding between the selected element and the $ctrl.orderProp model.
• Filter- It provides the filter to format data.
• Service- It stores and shares data across the application.
• Routing- It is used to build a single page application.
• Dependency Injection- It specifies a design pattern in which components are given their dependencies instead of hard-coding them within the component.
• Testing- It is easy to test any of the AngularJS components through unit testing and end-to-end testing.

16. What are the directives in AngularJS?

Answer: Directives are the markers on DOM element which are used to specify behavior on that DOM element. All AngularJS directives start with the word "ng". There are many in-built directives in AngularJS such as "ng-app", "ng-init", "ng-model", "ng-bind", "ng-repeat" etc.

• ng-app
  The ng-app directive is the most important directive for Angular applications. It is used to locate the beginning of an Angular application for AngularJS HTML compiler. It marks the HTML elements that Angular intends to make the root element of the application. The custom attributes use spinal-cases, whereas the corresponding directives follow the camelCase. If we do not use this directive and try to process other directives, it gives an error.
• ng-init
  The ng-init directive is useful for initializing the data variable's inline statement of an AngularJS application. Therefore, those statements can be used in the specified blocks where we can declare them. A directive ng-init is like a local member of the ng-app directive, and it may be a single value or a group of the values. It directly supports JSON data.
• ng-model
  The ng-model directive binds the values of HTML elements such as input, select, textarea to the application data. It provides two-way binding behavior with the model value. Sometimes, it is also used for databinding.
• ng-bind
  The ng-bind directive is used to bind the model/variable's value to HTML controls of an AngularJS application. It can also be used with HTML tags attributes like: <p/>, <span/> and more but it does not support two-way binding. We can only check the output of the model values.
• ng-repeat
  The ng-repeat directive is used to repeat HTML statements. It works the same as for each loop in C#, Java or PHP on a specific collection item like an array.

Let's see a simple example of AngularJS directive:

<div** ng-app = "" ng-init = "countries = [{locale:'en-IND',name:'India'}, {locale:'en-PAK',name:'Pakistan'}, {locale:'en-AUS',name:'Australia'}]"**>
**<p>**Enter your Name: <input** type = "text" ng-model = "name"**></p>
**<p>**Hello <span** ng-bind = "name"**></span>!</p>
**<p>**List of Countries with locale:</p>
<ol>
<li** ng-repeat = "country in countries"**>
{{ 'Country: ' + country.name + ', Locale: ' + country.locale }}
</li>
</ol>
</div>

17. What are the uses of controllers in AngularJS?

Answer: AngularJS controllers are used for:

• Setting the initial state of the $scope object
• Adding behavior to the $scope object

18. What are the services in AngularJS?

Answer: Services are objects that can be used to store and share data across the application. AngularJS offers many built-in services, and each of them is responsible for a specific task. They are always used with the prefix $ symbol.

Some of the important services used in any AngularJS application are as follows:

• $http- It is used to make an Ajax call to get the server data.
• $window- It provides a reference to a DOM object.
• $Location- It provides a reference to the browser location.
• $timeout- It provides a reference to the window.set timeout function.
• $Log- It is used for logging.
• $sanitize- It is used to avoid script injections and display raw HTML in the page.
• $Rootscope- It is used for scope hierarchy manipulation.
• $Route- It is used to display browser-based path in browser's URL.
• $Filter- It is used for providing filter access.
• $resource- It is used to work with Restful API.
• $document- It is used to access the window.Document object.
• $exceptionHandler- It is used for handling exceptions.
• $q- It provides a promise object.
• $cookies- It is used for reading, writing, and deleting the browser's cookies.
• $parse- It is used to convert an AngularJS expression into a function.
• $cacheFactory- It is used to evaluate the specified expression when the user changes the input.

19. What is routing in AngularJS?

Answer: Routing is one of the main features of the AngularJS framework, which is useful for creating a single-page application (also referred to as SPA) with multiple views. It routes the application to different pages without reloading the application. In Angular, the ngRoute module is used to implement Routing. The ngView, $routeProvider, $route, and $routeParams are the different components of the ngRoute module, which help for configuring and mapping URL to view

20. What is a template in AngularJS?

Answer: A template consists of HTML, CSS, and AngularJS directives, which are used to render the dynamic view. It is more like a static version of a web page with some additional properties to inject and render that data at runtime. The templates are combined with information coming from model and controller.

21. What are the key differences between Angular expressions and JavaScript expressions?

Answer: The key differences between the Angular expressions and JavaScript expressions are given below:

22. What is the use of filter in AngularJS?

Answer: A filter is used to format the value of the expression to display the formatted output. AngularJS allows us to write our own filter. Filters can be added to expressions by using the pipe character |, followed by a filter. For example:

<div ng-app="myApp" ng-controller="personCtrl">
<p>The name is {{ firstName | uppercase }}</p>
</div>
<script>
angular.module('myApp', []).controller('personCtrl', function($scope) {
$scope.firstName = "Sonoo",
$scope.lastName = "Jaiswal"
});
</script>

Filters can be applied in view templates, controllers, services and directives. It is important to know that filters are case-sensitive. There are some built-in filters provided by AngularJS such as Currency, Date, Filter, JSON, Limit, Lowercase, Number, Orderby, and Uppercase.

23. Explain custom filters with an example.

Answer: We can create our own filters in AngularJS. It can be performed by associating the filter to our module. These types of filters are known as custom filters.

An example given below can be used to count the number of elements in the string by using the filter:

angular.module('myCountFilterApp', [])
.filter('count',function()
{
return(function(input)
{
var out=[];
out=input.split(',');
return out.length;
})
});

As per above example, if the string is "21, 34, 45" then output after applying filter will be 3.

24. What do you understand by Dependency Injection in AngularJS?

Answer: Dependency Injection (also called DI) is one of the best features of AngularJS. It is a software design pattern where objects are passed as dependencies rather than hard coding them within the component. It is useful for removing hard-coded dependencies and making dependencies configurable. To retrieve the required elements of the application that need to be configured when the module is loaded, the "config" operation uses Dependency Injection. It allows separating the concerns of different components in an application and provides a way to inject the dependent component into the client component. By using Dependency Injection, we can make components maintainable, reusable, and testable.

A simple case of dependency injection in AngularJS is shown below:

myApp.controller('myController', function ($scope, $http, $location)
{
//logic
});

Here, a controller is declared with its dependencies.

AngularJS provides the following core components which can be injected into each other as dependencies:

• Value
• Factory
• Service
• Provider
• Constant

25. What do you know about injector?

Answer: An injector is referred to as a service locator. It is used to receive object instances as defined by the providers, invoke methods, instantiate types, and load modules. Each Angular application consists of a single injector which helps to look upon an instance by its name.

26. What is the factory method in AngularJS?

Answer: Factory method is used for creating a directive. Whenever the compiler matches the directive for the first time, the factory method is invoked. Factory method is invoked using $injector.invoke.

Syntax

module.factory('factoryName', function);

27. What do you understand by strict conceptual escaping?

Answer: AngularJS treats all the values as untrusted/ unsecured in HTML or sensitive URL bindings. AngularJS automatically runs security checks while binding untrusted values. It throws an error if it cannot guarantee the security of the result. This type of behavior depends on contexts: HTML can be sanitized, but template URLs cannot.

To illustrate this, consider the following directive

Ng-bind-html

It renders its value directly as HTML. When there is an untrusted input, AngularJS will try to sanitize it before rendering if a sanitizer is available. We will need to mark it as trusted to bypass sanitization and render the input.

28. How can someone make an ajax call using AngularJS?

Answer: AngularJS contains $https: control, which works as a service to make ajax call to read data from the server. The server creates a database call to retrieve the desired records. AngularJS requires data in JSON format. Once the data gets ready, $https: can be used to retrieve the data from the server in the following manner.

function studentController($scope,$https:) {
var url = "data.txt";
$https:.get(url).success( function(response) {
$scope.students = response;
});
}

29. How will you explain deep linking in AngularJS?

Answer: Deep linking is the method which allows us to encode the state of the application in the URL in such a way that it can be bookmarked. Then the application can further be restored from the URL to the same state.

30. Is it possible to have two ng-app directives for a single Angular application?

Answer: No, there can't be more than one ng-app directive for a single AngularJS application.

The ng-app directive helps AngularJS application to make sure that it is the root element. In our HTML document, we can have only one ng-app directive. If there is more than one ng-app directive, then whichever appears first will be used.

31: Explain $rootScope in AngularJS.

Answer: Every AngularJS application contains a $rootScope, which is the top-most scope created on the DOM element. An application can contain only one $rootScope, which will be shared among all its components. Every other scope is considered as its child scope. It can watch expressions and propagate events. By using the root scope, one can set the value in one controller and read it from the other controller.

32. What is the main purpose of $routeProvider in AngularJS?

Answer: $routeProvider is one of the important services which set the configuration of URLs. It further maps them with the corresponding HTML pages or ng-templates and attaches a controller with the same.

33. How will you explain Manual Bootstrap Process in AngularJS?

Answer: Sometimes, we may need to manually initialize the Angular application to have more control over the initialization process. We can perform such task using angular.bootstrap() function within angular.element(document).ready() function. AngularJS uses this function when the DOM is ready for manipulation.

The angular.bootstrap() function uses two parameters, the document, and the module name injector.

34. What are the different types of directives available in AngularJS?

Answer: AngularJS provides support for creating custom directives for the following type of elements:

• Element Directive
  Element directives are activated when a matching element is encountered.
• Attribute
  Attribute directives are activated when a matching attribute is encountered.
• CSS
  CSS directives are activated when a matching CSS style is encountered.
• Comment
  Comment directives are activated when a matching comment is encountered.

35. Explain the compilation process of AngularJS?

Answer: Angular's HTML compiler allows us to teach the browser, new HTML syntax. It also allows the developer to attach new behavior or attributes to any HTML element known as directives. AngularJS compilation process automatically takes place in the web browser. It does not contain any server-side or pre-compilation procedure.

AngularJS uses <$compiler> service for the compilation process of an Angular HTML page. Its compilation process starts after the HTML page (static DOM) is completely loaded.

It occurs in two phases:

• Compile
  It checks into the entire DOM and collects all of the directives.
• Link
  It connects the directives with a scope and produces a live view.

The concept of compile and link has been added from C language. The code is compiled and then linked.

36. What is two-way data binding in AngularJS?

Answer: Two-way data binding in AngularJS allows automatic synchronization of data between the model and the view. Any changes made to the model are immediately reflected in the view, and vice versa.

37. Explain the concept of dependency injection in AngularJS.

Answer: Dependency injection is a design pattern in which objects are given their dependencies rather than creating them within the object. In AngularJS, it helps manage the dependencies between different components and allows easier testing and reusability of code.

38. What are directives in AngularJS?

Answer: Directives are markers on DOM elements that tell AngularJS to attach specific behavior to them or manipulate their appearance. They are used to extend HTML with new attributes and elements and can be used to create reusable components.

39. How do you define routes in AngularJS?

Answer: Routes in AngularJS are defined using the $routeProvider service. You can configure the routes using the .when() method to specify the URL, template or controller to be used for each route.

40. What is the purpose of services in AngularJS?

Answer: Services in AngularJS are singleton objects that are used to organize and share code across different parts of an application. They provide a way to separate business logic from the view and controllers and promote reusability.

41. Explain the AngularJS digest cycle.

Answer: The digest cycle in AngularJS is the process by which AngularJS updates the bindings and synchronizes the data between the model and the view. It starts when an event occurs, such as a user input, and continues until all model changes are propagated to the view.

42. How do you handle form validation in AngularJS?

A: AngularJS provides built-in form validation using the $valid, $invalid, $dirty, and $pristine properties. It also supports custom validation using directives and provides various input types and attributes for validation.

43. What is the difference between $scope and controllerAs syntax?

Answer: $scope is a JavaScript object that acts as a glue between the controller and the view. It is used to expose data and functions to the view. The controllerAs syntax allows you to bind properties and functions directly to the controller using the this keyword.

44. How can you make AJAX calls in AngularJS?

Answer: AngularJS provides the $http service for making AJAX requests. You can use methods like $http.get(), $http.post(), etc., to send HTTP requests and handle the responses using promises or callbacks.

45. Explain function scope in AngularJS

Answer: Scope refers to the application model. It acts like a glue between the application controller and the view. Scopes are arranged in a hierarchical structure and impersonate the DOM (Document Object Model) structure of the application. It can watch expressions and propagate events.

46. What is Angular Expression? Explain the key difference between angular expressions and JavaScript expressions

Answer: Like JavaScript, Angular expressions are code snippets that are usually placed in binding such as {{ expression }}

The key difference between the JavaScript expressions and Angular expressions is:

• Context: In Angular, the expressions are evaluated against a scope object, while the JavaScript expressions are evaluated against the global window
• Forgiving: In Angular expression, evaluation is forgiving to null and undefined, while in JavaScript undefined properties generate TypeError or ReferenceError
• No Control Flow Statements: Loops, conditionals or exceptions cannot be used in an angular expression
• Filters: You can use filters to format data before displaying it.

47. How Angular JS routes work?

Answer: AngularJS routes enable you to create different URLs for different content in your application. Different URLs for different content enable the user to bookmark URLs to specific content. Each such bookmarkable URL in AngularJS is called a route

A value in Angular JS is a simple object. It can be a number, string, or JavaScript object. Values are typically used as configuration injected into factories, services, or controllers. A value should belong to an AngularJS module.

Injecting a value into an AngularJS controller function is done by adding a parameter with the same name as the value

48. What are the benefits of AngularJS?

Answer: Benefits of AngularJS are:

• Registering Callbacks: There is no need to register callbacks. This makes your code simple and easy to debug.
• Control HTML DOM programmatically: Applications which are created using Angular are not required to manipulate the DOM.
• Transfer data to and from the UI: AngularJS helps to eliminate almost all of the boilerplate. It can validate the form, display errors, return to an internal model, and so on.
• No initialization code: With AngularJS, you can bootstrap your app easily. You can use auto injected services into your application in Guice.

49. What is string interpolation in Angular.JS ?

Answer: In Angular.js, the compiler during the compilation process matches text and attributes. It uses interpolate service to see if they contain embedded expressions. As part of the normal digest cycle, these expressions are updated and registered as watches.

50. Explain the linking function and its types

Answer: Link combines the directives with a scope and produces a live view. For registering DOM listeners as well as for updating the DOM, link function is responsible. After the template is cloned, it is executed.

• Pre-linking function: Pre-linking function is executed before the child elements are linked. It is not considered as a safe way for DOM transformation.
• Post linking function: Post linking function is executed after the child elements are linked. It is safe to do DOM transformation by post-linking function

51. Explain injector in AngularJS

Answer: An injector is a service locator. It is used to retrieve object instances as defined by provider, instantiate types, invoke methods, and load modules. There is a single injector per Angular application, it helps to lookup an object instance by its name.

52. What is DI (Dependency Injection) and how an object or function can get a hold of its dependencies?

Answer: DI or Dependency Injection is a software design pattern that deals with how code gets hold of its dependencies. In order to retrieve elements of the application which is required to be configured when the module gets loaded, the operation “config” uses dependency injection.

These are the ways that object uses to hold of its dependencies

• Typically using the new operator, dependency can be created
• By referring to a global variable, dependency can be looked up
• Dependency can be passed into where it is required

53. Explain the concept of scope hierarchy

Answer: Each angular application consists of one root scope but may have several child scopes. As child controllers and some directives create new child scopes, an application can have multiple scopes. When new scopes are formed or created, they are added as a children of their parent scope. They also create a hierarchical structure similar to DOM.

54. How can you integrate AngularJS with HTML?

Answer: Developers can follow the following steps to integrate AngularJS with HTML:

Step 1: including AngularJS JavaScript in html page.

<head>
<script src = "https://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js"></script>
</head>

Step 2: Point out AngularJS application.

You have to add ng-app attribute inside HTML body tag to tell what part of HTML AngularJS app has as shown in the following example:

<body ng-app = "testapp">
</body>

55. How can you integrate AngularJS with HTML?

Answer: Developers can follow the following steps to integrate AngularJS with HTML:

Step 1: including AngularJS JavaScript in html page.

<head>
<script src = "https://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js"></script>
</head>

Step 2: Point out AngularJS application.

You have to add ng-app attribute inside HTML body tag to tell what part of HTML AngularJS app has as shown in the following example:

<body ng-app = "testapp">
</body>

56. Explain ng-click directives in AngularJS with example

Answer: Ng-click directives can be used in a scenario when you have to click on the button or want to perform any operation.

Example:

<button ng-click="count = count ++">Click</button>

57. Explain the use of $routeProvider

Answer: In Angular JS $routeProvider sets the URL configuration. It maps with the related ng-template or HTML page and attaches a controller with the same.

58. What are the common Angular Global API functions

Answer: Some commonly used Angular Global API functions are:

• Angular.isString: It will return true only if the given reference is of type string.
• Angular.lowercase: It converts any string to lowercase
• Angular.uppercase: It converts any string to uppercase.
• Angular.isNumber: It returns true only if the reference is a numeric value or number.

59. What is the syntax of factory method in AngularJS?

Answer: The syntax of Factory is as follows:

app.factory(‘serviceName’,function(){ return serviceObj;})

60. What are template statements?

Answer: The methods or properties in Angular that are used in HTML in response to user events are called template statements. These template statements allow your application to engage users through actions like dynamic content display or form submissions etc.

61. How do you categorize data binding types?

Answer: To categorize data binding in Angular, it is divided into various types. Data Binding in Angular is categorized into following types:

• One Way Data Binding
• Two-Way Data Binding

In One way data binding, the changes in the state affect the view from component to view template. On the contrary it is also possible that the change in the view affects the state by changing it from view template to component.

Now, coming to Two-way Data Binding, the changes in the view can lead to change in the model. Similarly, any changes in the model can change the view from component to view template.

The various types of Two-Way Data Binding are:

• Interpolation
• Property binding
• Class binding
• Style binding
• Attribute binding
• Event binding
• Two-way binding

62. Do you need to bootstrap custom elements?

Answer: No, we do not need to bootstrap custom elements as they are bootstrapped automatically when added to the DOM. Also, the custom elements in Angular get automatically destroyed when removed from the DOM.

63. How to transfer components to custom elements?

Answer: There are two important steps to be followed in order to transfer components to custom elements:

• Creating a custom element class: As a first step, build a custom element class using the createCustomElement() function provided by Angular. The function converts an Angular component (including its dependencies) to a custom element. The NgElementConstructor interface is implemented through this conversion which, in turn, creates a constructor class that is used for producing a self-bootstrapping instance.
• Registering element class with browser: The customElements.define() function is used to register the configured constructor, and its associated custom-element tag with the browser’s CustomElementRegistry.

64. What is a custom pipe?

Answer: A custom pipe is a feature of angular, that enables you to create and use your own reusable data transformation functions in templates. Pipes are used to transform data before displaying it in the user interface.

A custom pipe is specifically created by the developer to perform a specific data transformation or manipulation task. It encapsulates a function that takes an input value, applies a transformation, and returns the transformed output value. Custom pipes are defined as classes in Angular and decorated with the @Pipe decorator.

To use a custom pipe, you can include it in your Angular application’s module and then utilize it in templates by piping the data through the pipe in the template expression. The output of the pipe can be directly used for display or further processing in the template.

Custom pipes offer a way to encapsulate and reuse common data transformations across different components and templates. They promote code modularity, reusability, and readability by separating the data transformation logic from the component code.

Commonly, custom pipes are defined as follows:

import { Pipe, PipeTransform } from '@angular/core';
@Pipe({name: 'Pipename'})
export class Pipeclass implements PipeTransform {
transform(parameters): returntype { }
}

here,

‘Pipename’ is the name of the pipe.

‘Pipeclass’ is the name of the class assigned to the custom pipe.

‘Transform’ is the function to work with the pipe.

‘Parameters’ are the parameters which are passed to the pipe.

‘Returntype’ refers to the type of value that the pipe returns.

65. What is a bootstrapping module?

Answer: In Angular, the root module used for bootstrapping or launching the application is known as the ‘Bootstrapping Module’. A Bootstrapping Module is present in every Angular app and it is stored in the AppModule class. Infact, the Bootstrapping module is also called the AppModule.

66. How can you read the full response?

Answer: In order to read the full response in Angular, the following code should be used:

getUserResponse(): Observable<HttpResponse> {
return this.http.get(
this.userUrl, { observe: 'response' });
}

67. How do you perform Error handling?

Answer: In Angular, error handling can be done by writing a function using HttpClient along with catchError from RxJS.To handle errors, Angular’s HttpClient parses JSON responses and returns a JavaScript object in the OBSERVABLES.

68. What is the digest cycle in AngularJS?

Answer: Digest cycle is important part of the data binding in AngularJS, which compares the old and new version of the scope model. Digest cycle triggered automatically or manually by using $apply() function.

69. What is ngzone?

Answer: The ngzone is a JavaScrip wrapper class which is denoted by Zone.js. It enables developers to explicitly run certain code outside Angular’s zone, which inhibits angular to run any change detection.

70. Define ECMAScript

Answer: ECMAScript (European Computer Manufacturer’s Association) is a standard for scripting languages. JavaScript uses ECMAScript as a core language. Developers can take help of it for writing client-side scripting on the world wide web and or server applications and services. ECMAScript has numerous features like functional, prototype, dynamic, and structured features.

71. What is transclusion in AngularJS?

Answer: The transclusion in AngulaJS enables developers to reallocate the original directive children into a specific location within a template. The directive ng shows the insertion point for a transcluded DOM of the nearest parent directive, which is using transclusion. Ng-transclude-slot or ng-transclude directives are mainly used for transclusion.

72. What are the differences between Angular decorator and annotation?

Answer: In Angular, decorators are design patterns that help in the modification or decoration of the respective classes without making changes in the actual source code.

Annotations, on the other hand, are used in Angular to build an annotation array. They use the Reflective Metadata library and are a metadata set of the given class.

73. What are services in Angular?

Answer: A service in Angular is a term that covers broad categories of functionalities. A service is any value, function, or feature that an app needs. A service is typically used to accomplish a very narrow purpose such as HTTP communication, sending data to a cloud service, decoding some text, validating data, etc. A service does one thing and does it well. It is different from a component as it is not concerned with HTML or any other kind of presentation logic. Normally, a component uses multiple services to accomplish multiple tasks.

74. What is two-way data binding?

Answer: Two-way data binding is done in Angular to ensure that the data model is automatically synchronized in the view. For example, when a user updates some data in a model and that model is being displayed in multiple places in a component, that update should be reflected in all the places.

Two-way data binding has been supported in Angular for a long time. Although, it is something that should be used with careful consideration as it could lead to poor application performance or performance degradation as time goes on. It is called two-way data binding because we can change some data that is in the component model from the view that is HTML, and that change can also propagate to all other places in the view where it is displayed.

Intermediate Level: AngularJS Interview Questions and Answers

75. What is bootstrapping?

Answer: Angular bootstrapping, in simple words, allows professionals to initialize or start the Angular application. Angular supports both manual and automatic bootstrapping. Let’s briefly understand the two.

• Manual bootstrapping: It gives more control to professionals with regards to how and when they need to initialize the Angular app. It is extremely useful in places where professionals wish to perform other tasks and operations before the Angular compiles the page.
• Automatic bootstrapping: Automatic bootstrapping can be used to add the ng-app directive to the application’s root, often on the tag if professionals need Angular to automatically bootstrap the application. Angular loads the associated module once it finds the ng-app directive and, further, compiles the DOM.

76. What are Angular building blocks?

Answer: The following building blocks play a crucial role in Angular:

• Components: A component can control numerous views wherein each of the views is a particular part on the screen. All Angular applications have a minimum of one component called the root component. This component is bootstrapped in the root module, the main module. All the components include the logic of the application that is defined in a class, while the main role of the class is to interact with the view using an API of functions and properties.
• Data binding: Data binding is the process in which the various sections of a template interact with the component. The binding markup needs to be added to the HTML template so that Angular can understand how it can connect with the component and template.
• Dependency injection: It uses DI so that it can offer the necessary dependencies: mainly services, to the new components. The constructor parameters of a component inform Angular regarding the numerous services needed by the component, and DI provides a solution that gives the necessary dependencies to the new class instances.
• Directives: Angular templates are of a dynamic nature, and directives help Angular understand how it can transform the DOM while manifesting the template.
• Metadata: Classes have metadata attached to them with the help of decorators so that Angular will have an idea of processing the class.
• Modules: Module or NgModule is a block of code organized using the necessary capabilities set, having one specific workflow. All Angular applications have at least one module, the root module, and most of the applications have numerous modules.
• Routing: The Angular router helps interpret the URL of a browser to get a client-generated experience and view. This router is bound to page links so that Angular can go to the application view as soon as the user clicks on it.
• Services: Service is a vast category that ranges from functions and values to features that play a significant role in Angular applications.
• Template: The view of each component is linked with a template, and an Angular template is a type of HTML tag that allows Angular to get an idea of how it needs to render the component.

77. How can one create a service in Angular?

Answer: A service in Angular is an object that can be substituted. It is wired and combined with the help of dependency injection. Services are developed by getting registered in a module that they need to be executed in. The three methods of creating a service in Angular are as follows:

• Service
• Factory
• Provider

Advanced Level: Angular JS Interview Questions and Answers

Here are some angularjs interview questions for experienced professionals

78. How do you create directives using CLI?

Answer: To create a directive using Angular CLI, the following steps are used:

Start a new project using Angular CLI through the following command:

‘ng new [application-name]’

Now change the directory into a new directory through the command:

‘cd [application-name]’

Once done with changing the directory, use the following command to generate a new directive:

‘ng generate directive [path-to-directives/my-directive]’

79. What is multicasting in Angular?

Answer: In Angular, when we use the HttpClient module to communicate with a backend service and fetch some data, after fetching the data, we can broadcast it to multiple subscribers in one execution. This task of responding with data to multiple subscribers is called multicasting. It is specifically useful when we have multiple parts of our applications waiting for some data. To use multicasting, we need to use an RxJS subject. As observables are unicast, they do not allow multiple subscribers. However, subjects do allow multiple subscribers and are multicast.

80. Explain the different kinds of Angular directives.

Answer: There are three kinds of directives in Angular. Let’s discuss them:

• Components: A component is simply a directive with a template. It is used to define a single piece of the user interface using TypeScript code, CSS styles, and the HTML template. When we define a component, we use the component decorated with the @ symbol and pass in an object with a selector attribute. The selector attribute gives the Angular compiler the HTML tag that the component is associated with so that now when it encounters this tag in HTML, it knows to replace it with the component template.
• Structural: Structural directives are used to change the structure of a view. For example, if we wish to show or hide some data based on some property, we can do so by using the ngIf directive, or if we wish to add a list of data in the markup, we can use *ngFor, and so on. These directives are called structural directives because they change the structure of the template.
• Attribute: Attribute directives change the appearance or behavior of an element, component, or another directive. They are used as the attributes of elements. Directives such as ngClass and ngStyle are attribute directives.

81. What is the purpose of the common module in Angular?

Answer: In Angular, the common module that is available in the package @angualr/common is a module that encapsulates all the commonly needed features of Angular, such as services, pipes, directives, etc. It contains some sub-modules as well such as the HttpClientModule, which is available in the @angular/common/http package. Because of the modular nature of Angular, its functionalities are stored in small self-contained modules, which can be imported and included in our projects if we need these functionalities

82. What are the differences between Angular expressions and JavaScript expressions?

Answer: Angular expressions and JavaScript expressions are quite different from each other as, in Angular, we are allowed to write JavaScript in HTML, which we cannot do in plain JavaScript. Also, all expressions in Angular are scoped locally. But, in JavaScript, these expressions are scoped against the global window object. However, these differences are reconciled when the Angular compiler takes the Angular code we have written and converts it into plain JavaScript, which can then be understood and used by a web browser.

83. What is the difference between AngularJS and Angular?

Answer: AngularJS refers to version 1.x of the framework, whereas Angular refers to version 2.x and above. Angular is a complete rewrite of AngularJS and introduces many architectural and syntax changes.

84. How does AngularJS handle routing?

Answer: AngularJS provides the $routeProvider service for routing. By defining routes using the .when() method, you can specify the URL, template, and controller for each route, enabling navigation within the application.

85. What is the purpose of filters in AngularJS?

Answer: Filters are used in AngularJS to format and manipulate data displayed in the view. They can be used to filter arrays, format dates, convert text to uppercase or lowercase, and perform various other transformations.

86. Explain the concept of directives' link function in AngularJS.

Answer: The link function in AngularJS directives is used to manipulate the DOM element to which the directive is attached. It allows you to add event listeners, modify the element's behavior, or interact with other directives associated with it.

87. How do you handle exceptions in AngularJS?

Answer: AngularJS provides the $exceptionHandler service to handle exceptions globally. You can override this service to define custom error handling logic and display meaningful error messages to users.

88. What is the purpose of ng-repeat directive in AngularJS?

Answer: The ng-repeat directive is used to iterate over a collection and generate HTML elements based on each item in the collection. It allows you to create dynamic lists or tables in the view.

89. What are AngularJS directives? Provide some examples.

Answer: Directives in AngularJS are markers on DOM elements that instruct AngularJS to perform specific actions or apply behavior to the element. Examples include ng-model, ng-show, ng-click, ng-class, and ng-if.

90. How do you perform unit testing in AngularJS?

Answer: AngularJS provides a built-in testing framework called "Jasmine" and a testing utility called "Karma." With Jasmine, you can write unit tests to test individual components, and Karma allows you to run these tests in different browsers.

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

Answer: The $rootScope is the parent scope of all AngularJS scopes. It is accessible throughout the application and can be used to define variables and functions that need to be available globally.

92. How can you optimize the performance of an AngularJS application?

Answer: To optimize the performance of an AngularJS application, you can:

• Minify and compress JavaScript and CSS files.
• Use one-time bindings (::) where possible.
• Implement pagination and lazy loading for large data sets.
• Use ng-cloak to prevent the display of uncompiled AngularJS markup.
• Avoid unnecessary watchers and bindings.
• Use the "track by" syntax in ng-repeat for better performance.

93. What is the difference between interpolated content and the content assigned to the innerHTML property of a DOM element?

Answer: The angular interpolation happens when in our template, we type some JavaScript expression inside double curly braces ‘{{ someExpression() }}’. This is used to add dynamic content to a web page. However, we can do the same by assigning some dynamic content to the innerHTML property of a DOM element. The difference between the two is that, in Angular, the compiler always escapes the interpolated content, i.e., HTML is not interpreted, and the browser displays the code as it is with brackets and symbols, rather than displaying the output of the interpreted HTML. However, in innerHTML, if the content is HTML, then it is interpreted as the HTML code.

94. What are HttpInterceptors in Angular?

Answer: HttpInterceptors are part of the @angular/common/HTTP module and are used to inspect and transform HTTP requests and HTTP responses as well. These interceptors are created to perform checks on a request, manipulate the response, and perform cross-cutting concerns, such as logging requests, authenticating a user using a request, using gzip to compress the response, etc.

95. How does one share data between components in Angular?

Answer: There is not one but various methods to share data between components in Angular. They are mentioned as below:

• Parent to Child: via Input
• Child to Parent: via Output() and EventEmitter
• Child to Parent: via ViewChild
• Unrelated Components: via a Service

96. What are macros?

Answer: A macro is a portion of a  programming code that helps automate routine tasks. It usually runs in an Excel environment. In Angular, Macros is supported in functions, static methods, etc. Consider the below example of a Macros code in Angular :

export function wrapInArray<T>(value: T): T[] {
return [value];
}

97. What is the state function?

Answer: The state function in Angular declares an animation state within a trigger attached to an element. The following is the syntax for the state function:

state(name: string, styles: AnimationStyleMetadata, options?: { params: { [name: string]: any; }; }): AnimationStateMetadata

Conclusion

Mastering AngularJS is crucial for developers seeking to excel in the ever-evolving field of web development. By going through this collection of the top 100 AngularJS interview questions, you have gained a solid understanding of the framework's concepts, features, and best practices. From understanding two-way data binding to exploring the nuances of dependency injection and testing, you have acquired the essential knowledge needed to tackle challenging interview questions and answers on AngularJS. Remember, success in an interview goes beyond just memorizing answers. It's important to comprehend the underlying principles and demonstrate your ability to apply them effectively in real-world scenarios. So, continue to explore and experiment with AngularJS, build projects, and refine your skills. With dedication and practice, you will be well-prepared to impress interviewers, secure job opportunities, and embark on a successful career as an AngularJS developer.