Most Important Angular 8 Interview Questions with Answers

Following is the list of frequently asked Angular 8 Interview Questions. These interview questions and answers are prepared by Angular 8 Professionals working in top MNC Companies. We hope this interview questions' list will be very useful and helpful to get the best possible job in this IT industry.

1) What is Angular 8?

Angular 8 is a client-side TypeScript based framework used to create dynamic web applications. It is very similar to its previous versions except having some extensive features. It was developed by the same team that develops AngularJS and is a complete rewrite of its first version. Now, this is led and maintained by the Angular Team at Google and also by a community of individuals and corporations.

Read more information here: https://www.javatpoint.com/angular-8

2) When was Angular 8 released, and how was it different from Angular 7?

Angular 8 was released on May 28, 2019, worldwide. It has a lot of similarity to its previous versions, such as Angular 7, except having some extensive features.

The most distinguish features of Angular 8 are:

Angular 8 provides differential loading for all application code.
Dynamic imports for lazy routes
Web workers
It provides support for TypeScript 3.4
It provides Angular Ivy as an opt-in preview which has some other advantages:
1. Generated code that is easier to read and debug at runtime
2. Faster re-build time
3. Improved payload size
4. Improved template type checking
5. Backward compatibility

3) Can we upgrade the older version of Angular that we have installed on our system to the Angular 8 version? If yes, then how?

Yes. If you want to upgrade your Angular CLI or any older version of Angular to Angular version 8, you can easily do it. Follow the steps given below:

First, check the older version of Angular that you are using. Run the ng --version command on the Node.js command prompt.
Now, you have to uninstall the older version of Angular by using the following command.

npm uninstall -g angular-cli // For Windows Open Powershell on Administrator Mode  
sudo npm uninstall -g angular-cli // For Mac 

Now, verify and clear the cache by using the following commands.

npm cache verify 
npm cache clean  

Now, install the latest Angular CLI (Angular 8) by using the following command.

You can now verify that you are using the correct version by using the following command.

4) Why is Angular so popular in Modern Application Development?

Nowadays, Angular is a very popular framework and platform which had made robust web applications development very easy. There are many reasons behind its popularity: it unites the declarative templates, dependency injection, the end to end tooling, and integrates the top perform to resolve developers' development challenges. Angular 8 facilitates developers to develop applications that could be live on the web and mobile, respectively.

5) What are the most prominent features of Angular 8?

Angular 8 is a very popular Typescript development framework used to develop Web Applications. Following is the list of most prominent features of Angular 8 that makes this framework powerful.

Angular 8 support Cross-Platform Features

The Angular 8 platform can be used to develop Progressive Web Apps. By using Angular 8, you can develop an extremely fast website that can provide app-like experiences with zero-step installation and high-quality performance.
With Angular 8, you can create native mobile apps by using strategies like Ionic, Cordova, or NativeScript.
With Angular 8, by using native OS APIs, the developers can create Desktop-Installed apps for Windows, Mac, and Linux.

Better Speed & Performance

Angular 8 supports code generation facility that covert the templates into highly optimized code for JavaScript virtual machines. That's why Angular 8 is super fast.
Angular 8 apps and websites are SEO friendly.
Angular 8 uses a new Component Router to provide a code-splitting facility that makes apps load faster.

High Productivity

Angular 8 provides easy and powerful template syntax to create UI views.
It provides Angular CLI, which is a command-line tool. This tool is used to start building fast, add components and tests, and then instantly deploy it.
Angular's IDEs make development easy and help you to find errors instantly. You can also see the other feedback in editors and IDEs.

Provide Full Development Support

Angular 8 supports animation. The developers can create high-performance animations with intuitive API and a very little code of Angular.
The angular framework helps to create accessible applications with ARIA-enabled mechanism and developer guides.

6) What is the latest released version of Angular?

Angular 10 is the latest released version of Angular, released on June 24, 2020.

7) What are the most significant differences between Angular 7 and Angular 8?

Following is the list of most important differences between Angular 7 and Angular 8:

Angular 7	Angular 8
Angular 7 is slightly difficult to use because it was expanded to the entire platform, including Core framework, Angular Material, CLI, etc.	Angular 8 is comparatively smaller, faster, and easier to use. It has made Angular developer's life easier by providing a lot of advanced features.
Angular 7 has some features such as Angular Material, CLI prompts, Drag, and Virtual and Drop & Component Dev Kit (CDK), Virtual scrolling, Application performance, Bundle budget, Angular compiler, Angular elements, NativeScript, Better error handling, etc.	Angular 8 has some advanced level unique features such as Ivy rendering Engine, Bazel support, Differential Loading, API builders, Support for $location, Router backward compatibility, Opt-In Usage sharing, web- workers, etc. along with updated angular core framework, Angular Material, and the Command Line Interface of Angular 7.
The most significant changes in Angular 7 were Component Dev Kit (CKD), Material design library, and virtual scrolling.	The most significant changes in Angular 8 were the Core framework, Angular, material library, and CLI.
Till the Angular 7 version, Angular was supported by all types of Node.js version.	Angular 8 supports the Node.js version 12 or later.
Angular 7 supports a lower version of the typescript language.	Angular 8 supports the updated Typescript t version 3.4.x
The Angular 7 command-line interface (CLI) prompts supported the older version of CLI v7.0.2.	Angular 8 provided the stable CLI Builder API to developers who want to customize the Angular CLI by adding or modifying commands.

8) What do you know by Bazel in Angular 8?

Bazel is a new feature of Angular 8. It is a new build system available for a short period and provides a platform to make your back-end and front-end with a similar tool.

Following is the list of main features of Bazel:

Bazel is an internal build tool that is used to customize the application.
Bazel is used to test the action and performance of multiple machines.
Bazel facilitates you to construct a graph through which you can identify the useful information.
Bazel also supports customization.

9) What is the use of the Wildcard route in Angular 8?

In Angular 8, the Wildcard route is used to define the route of pages. You can make specific changes/updates while defining the route using Wildcard.

10) What are the differences between promises and observables in Angular 8?

Following is the list of differences between promises and observables in Angular 8:

Promises	Observables
Promises can deal with a single asynchronous event at a time.	The observables can handle a sequence of asynchronous events over a period of time.
Promises are always asynchronous.	Observables are both synchronous as well as asynchronous.
Promises generally provide only a single value.	Observables can emit multiple values.
Promises are not lazy. They can execute immediately after creation.	Observables are very lazy. They can't be executed until you subscribe to them using the subscribe() method.
Promises are not cancellable.	Observables have subscriptions that can be canceled using the unsubscribe() method. After that, they stop the listener from receiving further values.
Promises don't provide any operations.	Observables provide the map for forEach, filter, reduce, retry, and retryWhen operators.
Promises push errors to the child promises.	Observables deliver errors to subscribers.

11) What is the usage of Codelyzer?

Codelyzer is an open-source tool in Angular 8 that sits on top of TSLint. It is used to check whether Angular TypeScript projects follow a set of rules or not. It also checks the errors in codes, not following pre-defined rules. It contains more than 50 rules for checking if an Angular application follows best practices. It runs on the tslint.json file and checks only the static code in Angular 8.

Codelyzer is by default inbuilt with the projects set up with the Angular command-line interface (CLI).

12) How Angular 8 has enhanced the performance over its previous versions?

Angular 8 consists of advanced level features such as differential loading, CLI workflow improvements, Dynamic imports for lazy routes, Ivy rendering engine, Bazel, etc. which ensure systematic workflow and performance improvements.

13) What do you mean by Ivy in Angular 8?

Ivy is the code name for next-generation compilation and Rendering pipeline or Rendering Engine. It was released in Angular 8 as Opt-in. At the release of Angular 9, Ivy was intended to be the by default rendering engine instead of the older compiler and runtime, known as View Engine.

14) What is the usage of Wildcard Route in Angular 8?

In Angular 8, the Wildcard Router is used to set a route when the requested URL doesn't match any router paths. After using the Wildcard Router, the set route matches to every URL as an instruction to get a clear client-generated view. This Wildcard route always comes last as it needs to perform its task at the end only. So, the Wildcard Router is mainly used to define the route of the pages in Angular 8.

15) How do you check what version of Angular CLI you are using?

Use the ng -version command to check your current version of Angular CLI.

16) Which command do you use to run and load the Angular App?

Use the ng serve command to run and load the Angular App.

17) Which command is used to install the latest version of Angular CLI?

The following command is used to install the latest version of Angular CLI:

18) What do you mean by typeofchecks in Angular 8?

In Angular 8, the typeofchecks is used to check the type of value assigned to the variable. It is used same we used in JavaScript. In Angular version 8, you can also check the value assigned to the object by using typeofchecks.

19) What are the most important parts of the Angular 8 Architecture?

The architecture of an Angular 8 application follows some fundamental concepts. The basic building blocks are NgModules that are used to provide compilation context for components and collect related code into functional sets. A set of NgModules are used to define an Angular app.

Following is the list of most important parts of the Angular 8 architecture:

Modules
Components
Templates
MetaData
Data-Binding
Directives
Services
Dependency Injection

Read more information about Angular 8 Architecture https://www.javatpoint.com/angular-8-architecture

20) What is the requirement and usage of Angular 8 components?

The Angular 8 components are the list of classes with decorators that mainly mark their own types and provide metadata that guide Angular to do things.

Every Angular application always has at least one component known as a root component that connects a page hierarchy with page DOM. Each component defines a class that contains application data and logic and is associated with an HTML template that defines a view to be displayed in a target environment.

21) What is the usage of NgUpgrade in Angular 8?

The NgModules in Angular 8 is used for the following things:

The NgModule is a class marked by the @NgModule decorator where the @NgModule decorator is used to take a metadata object that describes how to compile a component's template and how to create an injector at runtime.
The NgModules is used to configure the injector and the compiler and also help to organize the related things together.
The NgModule is used to identify the module's own components, directives, and pipes. It can also make some of them public, through the exports property, to facilitate external components to use them.

22) What is the usage of NgUpgrade in Angular 8?

The NgUpgrade is an Angular 8 library mainly used to integrate both AngularJS and Angular components in the application. The NgUpgrade library is also used to bridge the gap between the Dependency Injection Systems in both AngularJS and Angular.

23) What is the usage of Angular 8 ngFor Directive?

The Angular 8 ngFor directive is used to repeat a portion of the HTML template once per each item from an iterable list (Collection). The ngFor is an Angular structural directive and is similar to ngRepeat in AngularJS. Some local variables like Index, First, Last, odd, and even are exported by ngFor directive.

Syntax for ngFor Directive

Read more information about ngFor directive: https://www.javatpoint.com/angular-8-ngfor-directive

24) What is the usage of Angular 8 ngIf Directive?

The Angular 8 ngIf directive is a structural directive that is used to add or remove HTML elements according to the expression. The expression must return a Boolean value true or false. You can see the functioning of nglf directive clearly. If the expression is false, then the element is removed. Otherwise, the element is inserted. It is similar to the ng-if directive of AngularJS.

Syntax for ngIf Directive

<p *ngIf="condition">  
    condition is true and ngIf is true.  
</p>  
<p *ngIf="!condition">  
    condition is false and ngIf is false.  
</p>  

Read more information about ngIf directive: https://www.javatpoint.com/angular-8-ngif-directive

25) What is data binding in Angular 8?

Data Binding is one of the key concepts of Angular 8. It is the most eminent technique which is used to link your data to the view layer. It is used to make a communication between the DOM and the TypeScript code of your component. In simple words, you can say that data binding is a communication between the typescript code of your component and your template, which the user sees. It makes it easy to define interactive applications without worrying about pushing and pulling data.

There are two types of data binding i.e., one-way data binding, two-way data binding.

26) What is String Interpolation in Angular 8, and why is it used?

String Interpolation is a one-way data-binding technique in Angular 8. It is used to extract the output data from a TypeScript code to the HTML template view layer. It shows the data from the component to view layer in the form of curly braces. This interpolation technique adds the value of property to the component.

String Interpolation Example:

Read more information about Angular 8 String Interpolation: https://www.javatpoint.com/string-interpolation-in-angular-8

27) What is the Purpose of Event Binding in Angular 8?

Event binding is a technique in Angular 8 used to handle the events raised from the DOM like button click, mouse move etc. When the DOM event happens (eg. click, change, keyup, keydown), it calls the specified method in the component.

See an example of event binding. In this example, the playMusic() method from the component will be called when you will click the button:

For example:

Read more information about Angular 8 Event Binding: https://www.javatpoint.com/event-binding-in-angular-8

28) How can you create an app in Angular 8?

You can easily create an Angular 8 web app using Angular CLI. Type the following command to create the Angular 8 web app.

Syntax:

Example:

The above command will create an Angular 8 app with the name "myapp." Then, the Angular CLI will automatically install the required NPM modules. Before this, you must ensure that you have Node.js, Angular 8, and installed Angular CLI using the following command:

You can also manually create an app folder and install ng dependencies.

29) What is the main purpose of Angular 8 forms?

The main purpose of Angular 8 forms is to handle the user's input. You can also use these Angular forms in your application to enable users to log in, update profiles, enter information, or perform many other data-entry tasks.

There are two approaches to handle the user's input through forms in Angular 8:

Reactive forms
Template-driven forms

Both approaches are used to collect user input events from the view, validate the user input, create a form model and data model to update, and provide a way to track changes.

30) What is the use of reactive forms in Angular 8?

Reactive forms use a model-driven approach to handle form inputs where values constantly change over time. It uses an explicit and immutable approach to manage the state of a form at a specific time. Every time the changes occur to the form state, it returns a new state. The reactive forms are used mainly for the following features:

Reactive forms are more robust than template-driven forms.
Reactive forms are more scalable, reusable, and testable.
Reactive forms are preferred to use when the forms are a key part of the application, or the application is already built using reactive patterns. In both cases, reactive forms are best to use.

31) What are the benefits of using Template-driven forms in Angular 8?

Following are the benefits of using Template-driven forms:

You should use Template-driven forms if you want to add a simple form to your application because template-driven forms use two-way data binding to update the data model in the component. By using this, you can see the changes instantly as you make changes in the template and vice versa.
Template-driven forms are easy to use in the application, but they are not as scalable as Reactive forms, so they are preferred to use in test applications for learning purposes.
Template-driven forms are mainly used if your application requires a very basic form and logic. It can easily be managed in a template.

32) What is the difference between reactive forms and Template-driven forms in Angular 8?

Both Reactive forms and Template-driven forms are used to manage and process data differently. Each form offers different advantages. Here, we have compared both forms to see the differences:

Reactive Forms	Template-driven forms
Reactive forms are more robust, so they are best to use.	Template-driven forms are best if you want to add a simple form to your application. For example email list signup form.
Reactive forms are more scalable, reusable, and testable, so they are preferred to use in professional websites for the industry.	Template-driven forms are easy to use in the application, but they are not as scalable as Reactive forms, so they are preferred to use in test applications for learning purposes.
Reactive forms are most preferred to use if forms are a key part of your application, or your application is already built using reactive patterns. In both cases, reactive forms are best to use.	Template-driven forms are mainly used if your application requires a very basic form and logic. It can easily be managed in a template.

33) What do you mean by Angular Universal?

Angular Universal is a technology that is used to render Angular applications on the server. This process is called SSR (server-side rendering). A simple Angular application is executed on the browser as all the Angular applications are single-page applications, so the rendering always occurs on the browser. This process of rendering single-page applications is called the client-side rendering process (CSR). On the other hand, the Angular Universal is executed on the server, generating static application pages that later get bootstrapped on the client. That's why Angular Universal application generally renders more quickly, giving users a chance to view the application layout before it becomes fully interactive.

34) What is AOT in Angular 8?

In Angular 8, AOT stands for Ahead-of-Time compiler. It pre-compiles the application components and their templates during the build process.

There are several reasons why apps compiled with AOT launch faster:

The application components that are compiled with AOT execute immediately, without client-side compilation.
Here, templates are embedded as code within their components, so there is no client-side request for template files. That's why it is fast.
The compiler doesn't entertain the unused Angular directives. It's also a reason for its fast response.

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