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30+ Angular Interview Questions And Answers

Angular is a widely-used, open-source web application framework led by the Angular Team at Google and a community of individuals and corporations. It enables developers to create dynamic, single-page applications efficiently. Angular integrates a range of features such as declarative templates, dependency injection, end-to-end tooling, and much more that facilitate web development. This framework is a part of the JavaScript ecosystem and predominantly used for building frontend parts of applications. The following questions cater to a range of Angular-related topics, from basic to advanced levels, aimed at assessing the knowledge and skills of individuals in job interviews for Angular-focused roles.


Most asked Angular interview questions



What is the purpose of Angular and what kind of applications is it used for?

Angular is a platform and framework for building client-side applications using HTML, CSS, and TypeScript. It is used for developing single-page applications where the page does not need to reload during use. It is particularly good for data-binding, building reusable components, and handling form submissions.


Can you explain what a component is in Angular?

In Angular, a component is a main building block. It is a class that interacts with the HTML template and acts as a controller for the view. Components have a decorator @Component() that provides metadata, including the template, styles, and selector.


What is a directive in Angular?

Directives are instructions in the DOM. There are three types: Components, Structural directives that change the DOM layout by adding and removing DOM elements, and Attribute directives that change the appearance or behavior of an element.


What is data binding and what are the types in Angular?

Data binding is a feature that allows communication between a template (view) and its component (class). The four types of data binding in Angular are: Interpolation, Property binding, Event binding, and Two-way binding.


What are Angular pipes? Give an example.

Pipes are simple functions used in Angular templates that transform input values to a desired output. For example, date pipe can format a date object into a readable string.

{{ currentDate | date:'medium' }}


What is a service and why would you use it?

A service in Angular is a broad category that encompasses any value, function, or feature needed by an app. A component can delegate certain tasks to services to achieve separation of concerns.


How do you create a service in Angular?

You create a service by defining a service class with the @Injectable() decorator. This ensures that the Angular dependency injection system can provide an instance of the service.


Explain the concept of Dependency Injection in Angular.

Dependency Injection (DI) is a design pattern in which a class requests dependencies from external sources rather than creating them itself. Angular's DI system provides dependencies to a class.


What is a module in Angular and why is it used?

A module is a way to group components, services, directives, and pipes. It is used to organize code or features that belong together, making the app easier to develop and test.


How can you pass data between components?

Data can be passed between components using Input and Output decorators. Input allows data to be passed from parent to child, while Output allows data to be emitted from child to parent.


Can you name the lifecycle hooks in Angular?

Common lifecycle hooks include ngOnInit(), ngDoCheck(), ngAfterContentInit(), ngAfterContentChecked(), ngAfterViewInit(), ngAfterViewChecked(), and ngOnDestroy().


What is TypeScript and why does Angular use it?

TypeScript is a superset of JavaScript that adds static typing. Angular uses TypeScript because it provides more robust tools for large-scale applications, including strong typing, classes, and interfaces.


What are Observables in Angular?

Observables provide support for passing messages between parts of your application. They are used heavily in Angular and are an essential part of working with the HTTP client and event handling.


Can you explain how routing works in Angular?

Routing in Angular allows navigation from one view to another. Developers define paths and map them to components. The RouterOutlet directive is used to display the component for the active route.


What is the difference between a Promise and an Observable?

A Promise handles a single event when an async operation completes or fails, while an Observable is like a stream and allows passing zero or more events where callback is called for each event.

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Explain the concept of lazy loading modules in Angular.

Lazy loading is a design pattern that defers the initialization of an object until it's needed. In Angular, modules can be lazy loaded to help keep the initial download small, making the app load faster.


Discuss the use of 'trackBy' function in ngFor directives.

The 'trackBy' function is used to improve the performance of ngFor when dealing with a large list of items. It prevents the recreation of DOM elements by tracking the identity of each element.


How would you manage state in an Angular application?

State management can be achieved using services with BehaviorSubject, using a state management library like NgRx or Akita, or through component state and inputs.


How do you handle forms in Angular?

Forms can be managed through template-driven forms or reactive forms. Reactive forms offer more flexibility and control as they are more scalable, reusable, and testable.


Can you explain the Angular Change Detection mechanism?

Change detection is the process by which Angular checks to see if data has changed and updates the DOM to reflect those changes. It uses a strategy called 'zone.js' to detect when to run a detection cycle.


What are 'pure' and 'impure' pipes in Angular?

A 'pure' pipe is called only when Angular detects a change in the input value. An 'impure' pipe is called for every change detection cycle, regardless of changes in inputs.


Explain the concept of decorators in Angular.

Decorators are design patterns used to separate decoration/modification of a class without modifying the original source code. In Angular, decorators like @Component, @Directive, @Pipe, and @Injectable are used.


What are dynamic components and how are they used in Angular?

Dynamic components are components that are created and added to the DOM at runtime. They are used in Angular to build complex UIs and for placeholders where various components can be loaded dynamically.


Discuss AOT compilation and its advantages.

Ahead-of-Time (AOT) compilation converts Angular HTML and TypeScript code into efficient JavaScript code during the build phase, before the browser downloads and runs the code. This results in faster rendering, reduced download size, and improved security.


How does Angular support internationalization (i18n)?

Angular supports internationalization by providing a way to localize an application by translating text into multiple languages and by providing locale-specific formats for dates, currencies, etc.


Explain template reference variables and how they are used in Angular templates.

<input #refVar type="text">

A template reference variable is a way to access a DOM element directly within a template. It is denoted with a hash (#) and the variable name. It allows direct access to the element from within the template or component class.


What is the difference between constructor and ngOnInit in Angular?

The constructor is a default class constructor used for injecting dependencies. ngOnInit is a lifecycle hook that is called after the constructor and is used for further component initializations.


Discuss the concept of content projection in Angular and how to implement it.

Content projection is a way to insert HTML content from a parent component into the view of a child component. It is done using the tag within the child component's template.


How do you handle HTTP requests and responses in Angular?

HTTP requests are handled using the HttpClient service, which returns observables and enables easy construction of request URLs and handling of responses.


Give an example of a custom structural directive in Angular.

  selector: '[myCustomDirective]'
export class MyCustomDirective {
  constructor(private templateRef: TemplateRef<any>, private viewContainer: ViewContainerRef) {}

A custom structural directive controls whether an element or its children are rendered. It is created with the @Directive decorator and by implementing the necessary logic in the class.


Angular Interview Tips

Understand the Basics

  • Start by ensuring that you have a solid understanding of Angular's core concepts. The basics can include knowledge about the framework's architecture, components, directives, services, and modules. Make sure to review how Angular implements two-way data-binding, dependency injection, and services before the interview. This foundational understanding will help you easily grasp and answer more complex questions during the discussion.

Stay Current

  • Always keep up-to-date with the latest Angular versions and their features. This demonstrates to the interviewer that you have an interest in the field and that you are passionate about staying informed on the latest trends and best practices. Additionally, being familiar with recent updates might give you an edge when answering questions about new functionalities and how they improve the platform.

Practice Hands-On Coding

  • Theory is essential, but the ability to apply your knowledge by coding is what sets candidates apart. Try to build small applications or components in Angular, which will not only improve your understanding but also give you confidence when discussing technical details about the framework. During the interview, if asked to provide coding samples or live coding, this practice can be invaluable.

Understand Common Scenarios

  • Anticipate questions that may involve common scenarios that developers encounter when using Angular, such as dealing with forms, HTTP requests, or state management. Reflect on your experiences and go through the best practices for tackling such scenarios. Having ready examples will help you answer these questions with ease.

Explain Your Answers

  • When giving your answers, do not just provide a solution but explain the rationale behind your choices. Discuss the 'why' as much as the 'how'. This showcases your in-depth understanding and helps the interviewer gauge your problem-solving approach. If there's an opportunity, also talk about the performance implications and scalability of your solutions.


How much does it cost to hire Angular developers?

The cost varies by region and experience level, starting from $45/hour with FireHire's scalable solutions. Read more: How much does it cost to hire Angular developers?

How do I hire an Angular developer?

Simply contact FireHire, detail your requirements, and we'll swiftly match you with pre-vetted Angular experts in just 5 days. Read more: How do I hire an Angular developer?

How much do Angular developers make?

Angular developer salaries differ globally, reflecting experience and locale, but with FireHire, you gain access to top talent within your budget. Read more: How much do Angular developers make?

Why using FireHire for hiring Angular developers is the best choice?

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