Last updated: January 5, 2023

Are you preparing for an interview for a job that requires knowledge of Angular? If so, you’ve come to the right place. To prepare for an angular interview, it is important to have a good understanding of the core concepts of the framework. This includes topics such as components, services, directives, modules, and routing. Additionally, candidates should have a good understanding of the latest version of the framework and its features. You are also supposed to be familiar with the tools and libraries used in the framework, such as TypeScript, RxJS, and Angular CLI. Finally, it is key to be able to answer questions about the development process, such as debugging, testing, and deployment.

This blog post will provide you with a comprehensive overview of the most common Angular interview questions and how to answer them. We’ll cover topics such as the basics of Angular, components, services, directives, and more. We’ll also provide tips on how to answer each question in a way that will make you stand out from the competition. With this blog post, you’ll be well-prepared to ace your Angular interview and land the job of your dreams. So, let’s get started.

Angular interview questions: Explanation and examples

Angular Basics

What is Angular?
Angular is an open-source, front-end web application framework. It is maintained by Google and is used to build single-page applications and dynamic web pages. It is written in TypeScript and uses HTML, CSS and JavaScript to create dynamic, interactive web pages and applications. The purpose of Angular is to increase the speed, performance and scalability of web applications.

What is the difference between AngularJS, Angular 2 and Angular 4?
AngularJS is the first version of the Angular framework and is based on JavaScript. It was released in 2010. Angular 2 is a complete re-write of the AngularJS framework and is based on TypeScript. It was released in 2016 and is not compatible with AngularJS. Angular 4 is the latest version of the Angular framework and was released in 2017. It is backwards compatible with Angular 2 and is focused on improving performance and reducing the size of the generated code.

What are the benefits of using Angular?
The benefits of using Angular include: enhanced scalability, enhanced speed, improved performance, increased code re-usability, faster development and improved code readability. Angular also provides a number of features to make developing web applications easier, such as two-way data binding, templating and dependency injection.

What is DOM and why is it important in Angular?
The Document Object Model (DOM) is a tree-like structure that stores and organizes HTML documents. It is important in Angular as it is used to render the application in a browser. Angular uses the DOM to access and manipulate HTML, as well as update the browser when changes are made in the application.

What is a component in Angular?
A component in Angular is a reusable, self-contained unit of code that is used to create web applications. Components are the basic building blocks of an Angular application and are composed of three elements: a template, a component class and metadata.

What is the difference between components and directives?
The main difference between components and directives is that components are self-contained elements that are used to create custom HTML elements, while directives are used to extend and manipulate the existing HTML elements. Components have their own HTML templates, while directives have their own logic and do not require a template.

What is scope in Angular?
Scope in Angular is the context in which a component or directive is executing. It is a JavaScript object that is a part of the component or directive and contains the data and methods that can be used by the component or directive.

What is the difference between scope and controller in Angular?
The main difference between the scope and the controller in Angular is that the scope is the context in which the component or directive is executing and contains the data and methods that can be used by the component or directive, while the controller is the logic that handles the data and methods that can be used by the component or directive.

What is an Angular module?
An Angular module is a container for different parts of an application, such as components, services, directives and pipes. Modules are used to organize the various parts of an application into cohesive blocks that can be easily maintained and updated.

What is the role of services in Angular?
Services in Angular are used to encapsulate code that is used across different components or directives. They can be used to store and manipulate data, access remote resources or perform server-side operations.

What is ng-model and how is it used?
Ng-model is a directive in Angular that is used to bind an HTML element’s value to a property in the component or directive. It is used to create two-way data binding between the HTML element and the component or directive, allowing changes in the HTML element to be reflected in the component or directive and vice-versa.

What is the purpose of ng-repeat directive?
The ng-repeat directive is used to repeat a set of HTML elements or components based on an expression. It is used to create dynamic lists of elements or components based on an array of data.

Angular Components

How to create a component in Angular?
To create a component in Angular, you need to use the Angular CLI command “ng generate component ”. This command will create a new component in the src/app directory. The newly created component will include three files: an HTML template file, a TypeScript file, and a CSS file. In the TypeScript file, you will find your component class with an associated decorator. You can then modify the HTML template file and the CSS file to customize the appearance and behavior of the component.

How do components communicate with each other?
Components in Angular can communicate with each other using the @Input and @Output decorators. Components can pass data to each other using the @Input decorator, while the @Output decorator is used to emit custom events from one component to another. Components can also communicate using a shared service, which is a singleton object that can be injected into multiple components.

How to use pipes and directives in components?
Pipes and directives can be used in components in Angular to transform or modify the data before displaying it to the user. Pipes are used to format data according to a specific format, for example a date or a currency. Directives are used to add custom behavior to a component, such as responding to user events or manipulating the DOM.

What is the life cycle of a component in Angular?
The life cycle of a component in Angular consists of 8 different phases, from creation to destruction. These phases are: creation, setting of the input properties, creation of the child components, checking of the bindings, rendering, checking of the bindings again, destruction of the child components, and finally destruction. During these phases, the component will go through different lifecycle hooks that can be used to perform certain actions.

How can you create custom components and directives?
You can create custom components and directives in Angular by using the Angular CLI command “ng generate component ” or “ng generate directive ”. These commands will generate a new component or directive in the src/app directory, with the necessary files needed to create your custom component or directive.

What is the purpose of the ngOnInit() method?
The ngOnInit() method is a lifecycle hook in Angular that is called after the constructor has been called, and the input properties have been set. This method is used to initialize the component and to perform any necessary setup, such as retrieving data from a service or setting up subscriptions.

What is dependency injection and how is it used in Angular?
Dependency injection is a software design pattern used in software development to provide an external source of dependencies for a software component, rather than the component having to manage its own dependencies. In Angular, dependency injection is used to inject services and other objects into components and other services. Dependency injection allows components and services to be decoupled and makes them easier to test and maintain.

How to unit test components in Angular?
Components in Angular can be unit tested using the Jasmine testing framework, in combination with the Karma test runner and Angular testing utilities. Tests should be written for each component to ensure that the component is working as expected, and that any potential bugs can be identified and fixed. Unit tests should cover the component’s functionality, validations, use of inputs and outputs, and any other important logic.

Angular Services

How to create a service in Angular?
A service in Angular can be created by using the Angular CLI command ‘ng generate service’ with the name of the service being specified. This will generate a new TypeScript file in the src/app folder, which contains the code for the service. Angular services are typically classes with a one-to-one mapping with the service name. The service classes can have any number of methods and properties which can help in implementing the required functionality.

What is the purpose of a service in Angular?
The purpose of a service in Angular is to provide a centralized place to store and share application data and business logic across multiple components. Services are a great way to maintain a single source of truth for application data and help promote reusability, maintainability, and scalability.

What are the different types of services in Angular?
There are two types of services in Angular: Singleton services and Factories. Singleton services are services that are instances of a single object, whereas Factories are services that can create multiple instances of the same object.

How to handle asynchronous requests in services?
Asynchronous requests can be handled in an Angular service by using the RxJS library. This library provides a set of operators that can be used to perform asynchronous operations such as HTTP requests. The RxJS library also provides a set of functions like the ‘of’ operator which can be used to convert data into a stream of events that can be handled by the service.

What is the difference between a service and a factory?
The main difference between a service and a factory is that a service is a single instance of an object, while a factory can create multiple instances of the same object. This means that a service can only have one set of data and logic associated with it, whereas a factory can create multiple versions of the same object with different data and logic associated with it.

How to handle errors in services?
Errors can be handled in an Angular service by using the error handling operators from the RxJS library. These operators provide a set of functions that can be used to catch any errors that occur during asynchronous requests and handle them accordingly. This ensures that the application does not crash due to an unexpected error.

How to use dependency injection in services?
Dependency injection can be used in an Angular service by using the @Inject decorator. This decorator can be used to inject the dependencies of the service into the constructor of the service class. This allows the service to access the dependencies that it needs and makes the service more modular and easier to maintain.

What are the best practices for using services?
The best practices for using services in Angular include keeping the services small and focused on a particular task, making the services reusable and testable, using dependency injection to inject the necessary dependencies into the service, and using the error handling operators from the RxJS library to handle any errors that may occur during asynchronous requests.

Angular Routing

What is routing in Angular?
Routing in Angular is the process of linking different components together to enable navigation between views or different parts of an application. It provides the user with the ability to switch between the different views or components of an application without having to reload the entire application. This helps to create a seamless experience for the user and reduces loading times.

Data binding and Events

What is data binding in Angular?
Data binding in Angular is the mechanism by which a view and its underlying data is connected, allowing user input and other events in the view to be reflected in the data and vice versa. This is done by using a combination of HTML templates, components, expressions, and events. By using data binding, Angular can keep the view and the data synchronized, making sure that the changes in the view are reflected in the data, and vice versa.

Angular Forms

What is the difference between template-driven forms and reactive forms?
Template-driven forms are a way of creating forms in Angular that rely on directives to create and manage the form, its fields, and validation. This is based on the traditional approach of Angular forms. They are straight-forward to use, however the logic and the form controls are defined in the template, making it hard to unit test. On the other hand, Reactive forms use a model-driven approach to handle form inputs. This approach allows the developer to define the form logic in the component class, making it easier to tweak the form validation and test the form. Reactive forms also offer more flexibility in terms of customizing the validation rules and providing a better user experience.

How to create a form in Angular?
To create a form in Angular, you can use either template-driven or reactive forms approach. With template-driven forms, you need to create the form in the template using directives such as ngModel, ngForm and formGroup. For reactive forms, you need to define the form model in the component class using the FormGroup, FormArray and FormControl classes. Then, you can use the form model in the template using the formGroup and formControlName directives.

How to validate forms in Angular?
Forms can be validated in Angular using both the template-driven and reactive forms approaches. With template-driven forms, you need to use the built-in validators in directives such as ngModel and formGroup. With reactive forms, you need to define the validation rules in the component class using the FormGroup and FormControl classes. You can also use custom validators to create more complex rules.

What are the different types of form controls?
In Angular, there are two types of form controls: template-driven and reactive. Template-driven forms use directives such as ngModel and formGroup to create and manage the form and its fields. Reactive forms use the FormGroup, FormArray and FormControl classes to define the form model in the component class.

How to handle form submission in Angular?
To handle form submission in Angular, you can use either template-driven, reactive forms or a custom approach. With template-driven forms, you need to use the ngSubmit directive along with ngModel to create the form and its fields. With reactive forms, you need to use the FormGroup and FormControl classes in the component class to define the form model. Then, you can use the formGroup directive in the template to bind the form to the form model. You can also use a custom approach and handle the form submission as desired.

What is the purpose of ngModelGroup?
The ngModelGroup directive is used to group form controls in template-driven forms. It can be used to create a nested structure for the form fields, making it easier to work with complex forms. It can also be used to add validation to specific groups of fields.

What is the updateOn property?
The updateOn property is used in reactive forms to specify when the form control should be updated with the new value. It can be set to either ‘change’ or ‘blur’ which indicates that the form control will be updated on the change or blur events.

What is the purpose of formControlName?
The formControlName directive is used in both template-driven and reactive forms to bind a form control to a form model. In template-driven forms, the form control is bound to the ngModel directive. In reactive forms, it is used to bind the form control to the FormControl instance.

Angular Security

What are the security measures required for Angular applications?
Security measures for Angular applications involve the use of authentication and authorization to protect user data. Authentication ensures that users are who they say they are by verifying their identity through a login process, while authorization ensures that users are granted access to only the resources and data that they are allowed to see. Other security measures, such as implementing secure sockets layer (SSL) encryption and using HTTPS for secure communication, can also act as additional layers of protection for user data.

Angular Testing

What are the different types of tests in Angular?
Angular offers a variety of different types of tests. Unit tests are written using Jasmine, a behavior-driven development testing framework, and can be run using the Karma test runner. End-to-end (E2E) tests can be written using Protractor, which is an extension of Jasmine. Angular also provides snapshot testing, which compares a rendered component to a stored version of the same component to detect differences between the two. Finally, there are integration tests, which test the combined functionality of components and services.

Angular interview questions: FAQs concisely answered

What is Angular?

Is a TypeScript-based open-source web application framework developed and maintained by Google. It is used to create dynamic web applications and is widely known for its speed, scalability, and ease of use. Angular makes it easier to create single-page applications (SPAs) by providing a comprehensive framework for creating and managing web applications.

What are the advantages of using Angular?

Angular offers a wide range of advantages, including: increased speed and performance, improved code quality, increased development productivity, and easier testing and maintenance. Angular also promotes the use of reusable components, making it easier to create and manage complex applications. Additionally, Angular has a wide range of tools that can be used to create and manage web applications.

What is the difference between Angular and React?

The main difference between them is that Angular is a full-fledged framework, while React is a library. Angular provides a comprehensive set of features for creating and managing web applications, while React is more focused on the view layer of the application.

What is the Angular CLI?

The Angular CLI (Command Line Interface) is a powerful tool used for creating and managing Angular applications. It provides a set of commands that can be used to create, build, and test Angular applications. The CLI uses a configuration file, known as angular.json, to store all settings related to the project.

What is two-way data binding in Angular?

Two-way data binding in Angular is a mechanism that allows data to be automatically synchronized between the model and the view. It enables developers to keep the model and view in sync at all times, making it easier to develop and maintain applications. Two-way data binding is achieved by using the ngModel directive, which is used to bind the view and model together.

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