Angular 8 Interview Questions | Eklavya Online

Angular 8 Interview Questions

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

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:

{{data}}

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.

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.

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.

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.

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:

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

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.

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.

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.

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.

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

Syntax:

ng new angular_app_name
Example:

ng new myapp
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:

npm install -g @angular/cli
You can also manually create an app folder and install ng dependencies.

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

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:

  • Generated code that is easier to read and debug at runtime
  • Faster re-build time
  • Improved payload size
  • Improved template type checking
  • Backward compatibility

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.

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).

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.

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

npm install -g @angular/cli@latest

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.
    npm install -g @angular/cli@latest
  • You can now verify that you are using the correct version by using the following command.
    ng –version

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.

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.

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.

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.

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.

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.

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.

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.

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.

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