We will list some of the most important Angular Interview Questions and Answers in this article to help you stand out during the interview process. Angular is a powerful front-end JavaScript framework widely used in app development. Angular developers are in high demand as the technology grows in popularity. Angular is known as the Swiss army knife of front-end developers, with over 7.2 Million repositories on GitHub! This is why Angular Certification is the most desirable certification in the scripting arena.



Let’s start with some of the most frequently asked Angular interview questions.




1. Explain string interpolation and property binding in Angular.


Angular data binding includes string interpolation and property binding.
Data-binding is an Angular feature that enables the communication between your component (Model) and its view (HTML template).

There are two types of data binding: one-way binding and two-way binding.
In Angular, data from the component can be injected into the HTML template. In one-way binding, any changes to the component are reflected directly inside the HTML template, but vice versa is not possible. This is not possible in two-way binding.

String interpolation and property binding only support one-way data binding. In string interpolation, the double curly brackets are used to display data from the component. Angular automatically evaluates the expression typed inside the curly brackets; for example, 2 + 2 will be evaluated by Angular, and the result 4, will be displayed within the HTML template. Property binding allows us to connect the DOM properties of an HTML element to the properties of a component. For property binding, the square brackets [] syntax is used.



2. What are Single Page Applications (SPA)


Single-page applications are web applications that only load once and add functionality through user interface enhancements. It generates dynamically rather than loading new HTML pages to display the new page’s content. This is made possible by JavaScript’s ability to manipulate the DOM elements on the existing page. A SPA method is faster, which leads to a more consistent user experience.





3. By default, Angular applications use client-side rendering. Is it possible to build an Angular app that renders on the server?


Yes, Angular Universal is a technology that can be used to render server-side applications.

Some of the advantages of using Angular Universal are as follows: First-time users can immediately see a view of the application. This contributes to a better user
Because many search engines require sites to be written in plain HTML, Universal can ensure that your content is found by all search engines, resulting in better SEO.
Any server-side rendered application loads faster because rendered pages are available to the browser sooner.




 4. What exactly is data binding? Angular uses which type of data binding?


It is a phenomenon in which anyone with a Web browser can change the elements of a Web page. It makes use of dynamic HTML and does not require any scripting or programming. Data binding is used in interactive elements such as forms, calculators, tutorials, and games on websites. When pages contain a large amount of data, incremental display of a webpage facilitates data binding.

Angular employs the two-way binding. Any changes to the user interface are reflected in the corresponding model state. Model state changes, on the other hand, are reflected in the UI state. This allows the framework to connect the DOM to the Model data via the controller. This strategy, however, has an impact on performance because every change in the DOM must be processed.




5. What are the perks of AOT?

Some of the advantages of AOT compilation are as follows:


Fast rendering: Because the browser will receive a pre-compiled version of our programme after compilation, it will be able to render it without having to compile it.

Requests that are less asynchronous: It incorporates external HTML templates and CSS style sheets into the JavaScript application, reducing the number of Ajax queries.

Download size: The compiler will minify the code for us, which will result in smaller download size.

During the compilation step, the compiler will detect and report any errors in the templates, allowing them to be corrected before production.




6. What exactly is the scope?

A scope in Angular is an object that refers to the application model. It’s a location where you can test expressions. These scopes are organised hierarchically, similar to the application’s DOM structure. A scope facilitates the propagation of various events and the monitoring of expressions.




7. What does it mean to subscribe to RxJS?

When using observables in RxJS, we must subscribe to an observable in order to use the This information is generated by a publisher and consumed by a subscriber. When we subscribe to an observable, we pass in a function for the data and another for errors, so that if there is an error, we can display a message or process the message in some way.




8. What exactly is bootstrapping?

Angular bootstrapping, in its most basic form, allows professionals to start or initialise an Angular application. Angular supports both manual and automatic bootstrapping. Let’s take a quick look at both of them.

 manual bootstrapping, professionals have more control over how and when they need to initialise the Angular app. It is useful when experts need to complete other tasks and processes before Angular generates the page.

Automatic bootstrapping (also known as bootstrapping): If professionals need Angular to automatically bootstrap the application, automatic bootstrapping can be used to add the ng-app directive to the application’s root, which is usually on the tag. When Angular finds the ng-app directive, it imports the relevant module and constructs the DOM.





9. What exactly is Angular multicasting?

When we use the HttpClient module in Angular to communicate with a backend service and fetch some data, we can broadcast it to multiple subscribers all in one execution. Multicasting is the process of responding with data to multiple subscribers. It is especially useful when multiple parts of our applications are waiting for data. An RxJS subject is required to use multicasting. Because observables are unicast, multiple subscribers are not permitted. Subjects, on the other hand, support multiple subscribers and are multicast.




10. What are the various compilers used in Angular?

In Angular, we use two types of compilers:
JIT (just-in-time) compiler
AOT (ahead-of-time) compiler

Both of these compilers are useful, but for very different reasons. Because our browsers do not understand TypeScript, we use the JIT compiler to convert it to JavaScript. This compilation step is performed in a development environment, which means that less time is spent on compilation and more time is spent on development in order to quickly iterate over features. When we use the ng serve or ng build commands to serve the app locally or create an uncompressed build of the entire codebase, we use the JIT compiler.

The AOT compiler, on the other hand, is used to generate a minified production build of the entire codebase that can be used in production. To use the AOT compiler, we must use the ng build command with the –prod blog parameter: ng build –prod This tells the Angular CLI to build an optimised production build of the codebase. This takes a little longer because optimizations like minification take time, but for production builds, this time can be saved.




11. In Angular, what is the difference between $scope and scope?

In Angular, $scope is used to implement the concept of dependency injection (D.I), whereas a scope is used for directive linking.

A scope can be anything, such as a function parameter name, and is provided by $scopeProvider, which can be injected into controllers, directives, or other services.




12. What is Angular Transpiling?

In Angular, transpiring refers to the process of converting source code from one programming language to another. This conversion is typically performed in Angular from TypeScript to JavaScript. It is an unspoken process that occurs internally.




13. How does animation work in Angular?

To perform animation in an Angular application, include the Animate Library and then refer to the ngAnimate module in your application or add the ngAnimate as a dependency inside your application module.



14. What are the new Angular 9 ‘providedIn’ options?

The @Injectable decorator is used to add Angular services to the injector. Angular 9 adds two more options for injecting existing additional options into services, as shown below.
platform – If all applications on that page share a singleton platform injector and you want a service to be available in that, specify providedIn:’platform’.
any – You can specify providedIn:’any’ whenever you want a unique instance in every module (including lazy modules) that injects the token.




15. Differentiate between DOM and BOM.





1. Stands for Document Object Model

1. Stands for Browser Object Model

2. Represents the contents of a web page

2. Works a level above web page and includes browser attributes

3. All the Objects are arranged in a tree structure and the document can be manipulated & accessed via provided APIs only

3. All global JavaScript objects, variables & functions become members of the window object implicitly

4. Manipulates HTML documents

4. Access and manipulate the browser window

5. W3C Recommended standard specifications

5. Each browser has its own implementation





16. What exactly is Angular Universal?

Angular Universal is a package that allows Angular applications to use server-side rendering. Using the Angular CLI, we can easily prepare our application for server-side rendering. To accomplish this, enter the following command:

@nguniversal/express-engine ng add

This enables our Angular application to function properly with an ExpressJS web server, which compiles HTML pages with Angular Universal based on client requests. In addition, the server-side app module, app.server.module.ts, is created in our application directory.





17. What is the distinction between interpolated content and content assigned to a DOM element’s inner HTML property?


Angular interpolation occurs when we type a JavaScript expression inside double curly braces’someExpression()’in our template. This is used to include dynamic content on a website. However, we can achieve the same result by assigning some dynamic content to a DOM element’s innerHTML property. 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 with brackets and symbols rather than the output of the interpreted HTML. However, if the content is HTML, it is interpreted as HTML code in innerHTML.





18. What are Angular HttpInterceptors?

HttpInterceptors are a component of the @angular/common/HTTP module that inspects and transforms HTTP requests and responses. These interceptors are designed to perform checks on a request, manipulate the response, and handle cross-cutting concerns such as logging requests, authenticating a user using a request, compressing the response with gzip, and so on.



19. What are Angular building blocks?

The following building blocks are essential in Angular:

Components: A component can control multiple views, each of which is a different part of the screen. All Angular applications have at least one component known as the root component. The root module, the main module, bootstraps this component. The logic of the application is defined in a class, and the main role of the class is to interact with the view via an API of functions and properties.


Data binding is the process by which the different sections of a template interact with the component. The binding markup must be added to the HTML template so that Angular understands how to communicate with the component and template.

Dependency injection: It employs DI to provide the necessary dependencies, primarily services, to the new components. The function Object() { [native code] } parameters of a component inform Angular about the various services required by the component, and DI provides a solution that assigns the required dependencies to the new class instances.


Directives: Because Angular templates are dynamic, directives assist Angular in understanding how it can transform the DOM while manifesting the template.


Metadata: Classes have metadata attached to them using decorators so that Angular knows how to process the class.

Module: A module, also known as a NgModule, is a block of code that is organised using the required capabilities set and has a single workflow. Every Angular application has at least one module, the root module, and the majority of applications have multiple modules.

Routing: The Angular router aids in the interpretation of a browser’s URL in order to obtain a client-generated experience and view. This router is bound to page links so that when the user clicks on it, Angular will go to the application view.

Services: Services are a broad category that includes everything from functions and values to features that are important in Angular applications.


 Template: Each component’s view is associated with a template, and an Angular template is a type of HTML tag that allows Angular to determine how to render the component.




20. What exactly is dependency injection?

Dependency injection (DI) in Angular is a programme design technique in which objects are provided as dependencies rather than being hard-coded in the components. This concept is extremely useful for decoupling the development of object logic from its use.

The function config makes use of DI, which must be enabled before the module and application elements can be retrieved. Furthermore, this capability allows professionals to tailor dependencies to their specific requirements.







This is the end of our topic. We hope we helped you in some way. The topics covered in this Core  Angular  Interview Questions blog are among the most sought-after skillsets for an Angular professional, according to recruiters. These Angular  Interview Questions will undoubtedly assist you in acing your job interview.


Best wishes for your interview!


If you still have any queries, please let us know in the comment section.