Angular Interview Questions and Answers

Angular developers are in great demand because of the features the framework offers across a variety of sectors. With the framework, you can design beautiful, scalable user interfaces that hold up well over time. Better performance, an improved user experience, cross-platform compatibility, integrated testing tools, and numerous other advantages are all provided by Google, which also develops and maintains Angular.

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Angular Coding Interview Questions for Beginners

What is Angular?

Google is the creator and maintainer of Angular, one of the most popular JavaScript frameworks. It is a TypeScript-based front-end web framework that is available for free. Its code is reusable and maintainable, making it ideal for creating enterprise web applications.

Which strong features are included in Angular?

Descriptive templates, end-to-end tooling, dependency injection, and other strong technologies that streamline the development process are all included in Angular. Know the difference between Angular and jQuery to gain expertise in web development.

What is Angular’s primary goal?

The primary goal of Angular is to build scalable, dynamic, and quick web apps. With Angular, we can simply develop these applications by utilizing directives and components.

Angular began off as a single-page application (SPA) framework, but thanks to dependency injection, it can now provide dynamic content depending on various users. It gives front-end developers the ability to curate cross-platform applications and offers a framework for the simple construction of web-based applications.

What are the main benefits of utilizing Angular?

Below is a list of the main advantages of using the Angular framework:

Angular facilitates bidirectional data coupling.
Its architecture adheres to the MVC pattern.
Both Angular and static templates are supported.
It makes adding a custom directive easier.
RESTful services are also supported.
Angular provides functionality for validation.
Angular enables client and server communication.
Support for dependency injection is offered.

What is TypeScript? Why is it used in Angular?

TypeScript is a Microsoft-developed and maintained statically typed superset of JavaScript. Its main objective is to make JavaScript applications more reliable, scalable, and maintainable by including optional types, classes, interfaces, and modules. This helps identify any problems early in the development process rather than after they arise. Static typing, classes and interfaces, decorators, the TypeScript compiler, namespaces and modules, and decorators are among the essential components of TypeScript.

Because TypeScript offers enhanced type checking, greater tooling support, and other features like decorators and interfaces, it is incorporated into Angular.

Which type of data binding does Angular employ?

Angular binds in two ways. Modifications made to the user interface are mirrored in the matching model state. On the other hand, the UI state reflects any modifications made to the model state. This makes it possible for the framework to use the controller to link the DOM to the model data. However, because each DOM change needs to be recorded, this method has an impact on performance.

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Which technologies make up Angular?

Angular leverages several internal technologies to deliver a productive development environment. These crucial technologies include, among others:

TypeScript: TypeScript is the main programming language of Angular

RxJS: Reactive Extensions for JavaScript, or RxJS, is a library that uses observables to manage event handling and asynchronous data flow.

Zone.js: Zone.js is a JavaScript framework that creates “zones”—execution contexts—that enable Angular to monitor and identify changes in the state of the application.

Dependency Injection: To provide instances of classes, services, or values to components, directives, or other services, Angular uses a hierarchical dependency injection (DI) architecture.

Angular CLI: An effective tool for creating, constructing, testing, and deploying Angular apps is the Angular Command Line Interface (CLI).

Angular Material: This library of UI components offers a selection of excellent, easily obtainable, and modular UI components that adhere to Material Design principles.

How do you create a dependency hierarchy?

Angular utilizes hierarchical dependency injection. It is made up of an injector tree that runs parallel to the component tree of the application. In configuration, a hierarchy of dependencies is created. Any level of the component tree can be used to reconfigure injectors. In the injector hierarchy, providers for various injectors can also be set.

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How similar are Angular 2 and Angular JS?

Yes, they are comparable because Google maintains both front-end frameworks. They vary, though; Angular 2 is more than just an improved iteration of Angular JS. A brand-new framework that was created entirely from scratch is called Angular 2. It will thus be necessary to rewrite the code if someone wants to go from Angular JS to Angular 2.

How do you refresh your display when changes are made to your data model outside of Zone?

The view can be updated using the following techniques:

The ApplicationRef.prototype.run method will help update the view by doing change detection on the entire component tree.

The NgZone.prototype.run method can achieve the same result by carrying out change detection on the entire tree in a comparable way. The function that has to be performed is handled through the parameter that comes before the tick and is invoked internally with the run method. The current component and its offspring are subjected to change detection by the ChangeDetectorRef.prototype.detectChanges method.

How can we select between external and inline templates?

External templates are typically used for views that are relatively larger than inline templates, which are typically used for smaller codes. However, organizational policy, circumstances, etc., can occasionally influence the decision between using inline or external templates.

Single-page applications (SPAs): What are they?

Single-page web apps only load once when new features or UI elements are added. The fresh content is generated dynamically rather than by loading new HTML pages. JavaScript’s ability to work with the DOM elements on the current page makes it feasible. Because an SPA method is quicker, users will have a smoother experience.

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In Angular, what are decorators?

Angular decorators are a type of design pattern that allows you to add meta-data annotations to classes, properties, methods, and parameters without altering their functionality. In essence, decorators use declarative syntax to let developers change or add to a class’s or its members’ functionality. They can be thought of as protective coverings for individual students or classrooms.

For angular uses, there are four primary decorators:

Class decorators: They can be used to define metadata or change a class’s behavior.

Property decorators: Class properties employ property decorators. They offer metadata for property bindings and assist in configuring properties.

Method decorators: They are frequently used to respond to lifecycle events and apply to class methods.

Decorators for parameters: Decorators for parameters are applied to method or constructor parameters, offering extra information about the parameter.

When is it necessary to load modules lazily?

If the code is to be divided up into smaller chunks, then the modules must load slowly. The whole application code does not load when an app is downloaded to a browser. The lazy loading module loads the code into the browser during the lazy loading transition to the route.

In Angular, what are template-driven forms?

One of the two methods available to manage forms in Angular is template-driven forms. They rely on Angular’s auto-generated forms and directives in the form template. Simple forms with little validation should be used with template-driven forms.

What is the purpose of the shared and core modules?

There is a generic module called the Shared module that is used for all modules, components, etc. that need not be included in a single copy for the application and must instead be imported into separate modules. A core module is used to store services that need to appear in a single copy throughout the application. For instance, user authentication shows as a core module when it is required for data storage.

Distinguish between one-to-one testing and unit testing. Mention a few Angular application testing tools.

Unit testing is used to evaluate isolated pieces to see whether they are performing properly. On the other hand, one-to-one testing can be used to make sure that complete sets of components are operating as intended and that the application is functioning as intended. To make sure apps are working properly, one-to-one tests frequently use simulations of user interaction. The testing tools Jasmine and Karma are both useful.

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What in Angular are templates?

HTML, which has elements and attributes unique to Angular, is used to write Angular templates. These templates are further generated in conjunction with the controller’s and model’s data to give the user a dynamic view.

What do Angular annotations mean?

To give the Angular compiler more information, annotations are used in Angular to add metadata to a class, function, or property. Decorator functions, which are appended to the class, method, or property before its definition, are used to define annotations.

In Angular, what are directives?

Angular’s special capabilities, called directives, let you modify or expand the behavior of DOM elements, components, and properties within your application. In essence, they are directives to the Angular renderer about how to manage elements and their attributes within the DOM. There are three categories of directives:

Component Directives
Structural Directives
Attribute Directives

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Angular Advanced Interview Questions

What are the lifecycle hooks available in Angular? Give a brief explanation of them.

The angular components have a lifecycle that begins at creation and ends when they are destroyed. Throughout the entire process, angular lifecycle hooks are used to monitor the phases and initiate modifications at particular points.

ngOnChanges(): This function is invoked whenever one or more of the component’s input properties change. A SimpleChanges object with the property’s previous and current values is sent to the hook.

ngOnInit(): The second lifecycle hook is ngOnInit(). It comes after the ngOnChanges hook and is called once. It is used to set the component’s input properties and initialize the component.

ngDoCheck(): This hook is used to identify and handle changes that Angular is unable to detect. It is called after ngOnChanges and ngOnInit. We can use this hook to put our change detection technique into practice.

The ngAfterContentInit() hook is called after the initial ngDoCheck hook. After the content is projected inside the component, this hook reacts.

ngAfterContentChecked(): This hook is called each time a ngDoCheck is performed after ngAfterContentInit. Once the projected content has been verified, it reacts.

ngAfterViewInit(): This hook is used to initialize the view of a child component or to be called after a component’s view.

The hook ngAfterViewChecked() is invoked after ngAfterViewInit. It reacts when the view of the child component is checked or after the view of the component.

ngOnDestroy(): This hook is invoked immediately before the component is destroyed by Angular. This is how event handlers are detached and the code is cleaned away.

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What is the primary difference in Angular between JIT and AOT?

The primary distinctions between Angular’s JIT and AOT compilers are as follows:

Ahead-of-Time (AOT) compilers are used to compile your app at build time on the server, while Just-in-Time (JIT) compilers compile our software in the browser at run-time.

When you use the CLI commands ng build (build alone) or ng serve (build and serve locally), the JIT compilation is executed automatically. Development uses this. However, to enable AOT compilation, we must use the –aot option when using the ng build or ng serve commands.

In an Angular project, code can be compiled using one of two methods: JIT or AOT. AOT is used in production mode, whereas the JIT compiler is used in development mode.

JIT is simple to apply. We have a map file here, which AOT does not, so we can simply implement features and debug in JIT mode. However, the main benefit of adopting AOT in production is that it speeds up rendering by reducing the size of the bundle.

What does Angular’s scope hierarchy mean?

Angular provides the $scope objects in a hierarchy that is typically used in views. This is known as the scope hierarchy in Angular. There could be one or more “child scopes” included within its root scope.

Every view in a scope hierarchy has a unique ‘$scope’. Therefore, other view controllers won’t be able to access the variables set by a view’s view controller.

The standard example of a scope hierarchy is as follows:

Root $scope

$scope for Controller 1

$scope for Controller 2

…

$scope for Controller n

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What prompted the introduction of client-side frameworks such as Angular?

Before Angular was released, web developers created dynamic websites with VanillaJS and jQuery. The fundamental disadvantage of these technologies is that as a website’s logic increased, the code became more difficult to maintain. Developers have to work extra hard to maintain the separation of concerns for apps and websites that use complicated logic. Furthermore, jQuery lacked features for handling data across views.

The aforementioned issues were addressed with the introduction of client-side frameworks like Angular. By offering a new feature called components for managing the separation of concerns and breaking code into smaller informational chunks, it offers developers numerous advantages over VanilaJS and jQuery.

Developers can use client-side frameworks like Angular to create complex online apps, including single-page applications. Thus, the primary motivations behind Angular’s introduction were to facilitate the rapid, dynamic, and scalable development of online applications.

What does RouterState mean to you?

A tree of active routes makes up the RouterState. Each node within this tree is aware of the extracted parameters, resolved data, and “consumed” URL segments. Using the router service and the routerState property, we can get the current ‘RouterState’ from anywhere in the application.

@Component({templateUrl:’template.html’})

class MyComponent {

constructor(router: Router) {

const state: RouterState = router.routerState;

const root: ActivatedRoute = state.root;

const child = root.firstChild;

const id: Observable<string> = child.params.map(p => p.id);

//…

}

Angular renders its apps client-side by default. Is it feasible to create server-side rendering for an Angular application?

Certainly, it is feasible to create a server-side Angular application. For server-side application rendering, Angular offers a technique called Angular Universal.

The following are the main benefits of utilizing Angular Universal:

Rendering an Angular application server-side can result in a better user experience. This allows new users to obtain an overview of the application right away. Thus, it might be applied to improve the user interface.
It might improve your application’s SEO. The rationale is that a lot of search engines anticipate basic HTML pages. Therefore, Angular Universal is beneficial for improved SEO and may guarantee that your content is found on all search engines.
Applications that are rendered server-side load more quickly than standard web pages. The reason for this is that the browser can access the produced pages faster.

An open-source TypeScript-written JavaScript framework is called Angular. Angular is a framework that offers developers a common structure to work with and has several obvious advantages. To succeed in web developer job interviews, we think that these angular interview questions and answers will be useful. Gain expertise with our Angular JS training in Chennai for a successful career in web development.