Top Angular Interview Questions and Answers

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If you are looking to interview candidates for a developer role using Angular, you may want to use some of these questions to test their knowledge and skills in Angular. In this article, we will discuss some of the top Angular interview questions and provide answers to help you better prepare for to interview candidates.

Introduction to Angular Interview Questions

Before we dive into the specific Angular interview questions, let’s introduce Angular and its key features.

What is Angular?

Angular is a popular JavaScript framework used to build dynamic web applications. It was created by Google in 2010 as AngularJS and later rewritten as Angular. Angular allows developers to write clean, maintainable, and scalable code using TypeScript.

Why is Angular popular?

Angular is widely used in the industry because it offers several benefits:

  • It uses the Model-View-Controller (MVC) architecture to separate application logic from the User Interface (UI) logic.
  • The code is testable, thanks to the built-in testing tools and the Angular CLI.
  • It offers two-way data binding, which saves developers time and effort in managing the state of the application.
  • It has a large community that provides support and resources for developers.

One of the main advantages of Angular is that it allows for the creation of Single Page Applications (SPAs). This means that the application loads only once and subsequent interactions with the user are handled through dynamic updates to the page, rather than requiring a full page reload. This results in a faster and more seamless user experience. Additionally, Angular provides a wide range of tools and libraries that make it easy to build complex web applications with sophisticated functionality.

Another key feature of Angular is its use of directives, which allow developers to extend HTML with custom attributes and tags. This makes it easier to create reusable components and simplify the overall structure of the application.

Furthermore, Angular is known for its strong focus on code quality and maintainability. The framework provides a number of tools and best practices that help developers write clean, modular code that is easy to understand and maintain over time. This makes it an ideal choice for large-scale projects where code complexity can quickly become overwhelming.

Finally, Angular has a large and active community of developers who contribute to the ongoing development and improvement of the framework. This means that there are always new features and improvements being added, and that developers can rely on a wealth of resources and support when working with Angular.

Basic Angular Interview Questions

Beginners in Angular should be capable of answering the following basic Angular interview questions.

What are Angular components?

Angular components are the basic building blocks of an Angular application. They consist of three parts: template, class, and metadata. The template defines the user interface, while the class handles the component logic, and the metadata provides information about the component, such as its selector and dependencies.

Components are reusable and can be nested within other components to create complex user interfaces. They are also modular, meaning that they can be easily swapped in and out of an application without affecting other parts of the application.

Explain data binding in Angular

Data binding is a mechanism in Angular that synchronizes the data between the component and the view. Angular supports four types of data binding:

  • Interpolation binding: {{ expression }}
  • Property binding: [property]="expression"
  • Event binding: (event)="expression"
  • Two-way binding: [(ngModel)]="expression"

Interpolation binding is used to display the value of an expression within the HTML template. Property binding is used to set the value of a property of an HTML element. Event binding is used to respond to user events, such as clicks and keystrokes. Two-way binding is used to bind the value of an input field to a property of a component and update both the component and the view when the value changes.

What are directives in Angular?

A directive is a UI element in Angular that adds behavior to the HTML elements. It can be used to create custom attributes, elements, or structural directives. There are three types of directives in Angular:

  • Component directives
  • Attribute directives
  • Structural directives

Component directives are used to create reusable components that can be used throughout an application. Attribute directives are used to change the behavior or appearance of an HTML element, such as changing the color or font size. Structural directives are used to change the structure of the HTML, such as adding or removing elements based on a condition.

Directives are a powerful feature of Angular that allow developers to create custom UI elements and extend the functionality of existing elements.

Intermediate Angular Interview Questions

Now, let’s move on to the intermediate Angular interview questions that require a deeper understanding of the framework.

What is the difference between AngularJS and Angular?

AngularJS is the first version of Angular and was released in 2010. It uses JavaScript and follows the MVC architecture. AngularJS is code-intensive and can be difficult to maintain. Angular, on the other hand, uses TypeScript and is based on a component-based architecture. Angular also has better performance and a simpler learning curve than AngularJS.

Angular has a more modern approach to web development and is optimized for building complex applications. It offers a more streamlined development experience and provides a powerful set of tools for building dynamic web applications.

The biggest difference between AngularJS and Angular is that Angular is a complete rewrite of AngularJS. Angular is a more powerful and flexible framework that is designed to meet the needs of modern web development.

Explain the role of dependency injection in Angular

Dependency injection is a design pattern in which the objects are passed their dependencies instead of creating them. In Angular, dependency injection is used to provide the dependencies to the components, services, and other objects. This allows for better code organization, easier testing, and increased flexibility.

Dependency injection makes it easier to manage complex applications by decoupling the components and services from each other. This makes it easier to replace or modify individual components without affecting the rest of the application.

Dependency injection also makes it easier to test individual components by allowing you to mock or replace dependencies. This makes it easier to isolate and test individual components, which can help you catch bugs and improve the overall quality of your code.

How does change detection work in Angular?

Change detection is a mechanism in Angular that detects changes in the application state and updates the UI accordingly. Angular uses a hierarchical change detection mechanism that starts from the root component and propagates down the component tree. Angular performs change detection after every user interaction, such as clicking a button or entering data in a form.

When a change is detected, Angular updates the view with the new data. This is done by re-rendering the affected components and updating the DOM. Angular uses a zone-based change detection mechanism that automatically detects changes and updates the view.

Change detection is an important part of Angular because it ensures that the UI is always up-to-date with the application state. By keeping the UI in sync with the application state, Angular provides a seamless and responsive user experience.

Advanced Angular Interview Questions

Finally, here are some advanced Angular interview questions that require an expert level of knowledge in the framework.

What are the different types of decorators in Angular?

Decorators are used in Angular to modify or define the behavior of a class, property, method, or parameter. There are several types of decorators in Angular, such as:

  • Class decorators, such as @Component and @NgModule
  • Property decorators, such as @Input and @Output
  • Method decorators, such as @ViewChild and @ContentChild
  • Parameter decorators, such as @Inject and @Optional

Class decorators are used to modify the behavior of a class. They can be used to define a component, directive, pipe, or module. Property decorators are used to modify the behavior of a class property. They can be used to define an input or output property. Method decorators are used to modify the behavior of a class method. They can be used to define a view child or content child. Parameter decorators are used to modify the behavior of a class parameter. They can be used to inject a dependency or define an optional parameter.

Explain lazy loading in Angular

Lazy loading is a technique in Angular in which the large parts of the application are loaded only when needed. This can significantly reduce the initial loading time of the application, improve performance, and reduce the size of the application bundle. Lazy loading is implemented using the Angular Router and allows for better code organization and scalability.

When lazy loading is used, the application is split into smaller modules that are loaded on demand. This means that the user only downloads the code that they need, rather than downloading the entire application upfront. This can lead to faster loading times and a better user experience. Additionally, lazy loading can improve the maintainability of the application by reducing the complexity of the code.

How to optimize Angular application performance?

Performance is a critical aspect of any Angular application. To optimize Angular application performance, developers should follow these best practices:

  • Use the OnPush change detection strategy. This strategy can significantly improve the performance of the application by reducing the number of times that the change detection mechanism is triggered.
  • Avoid heavy computations in the templates. This can slow down the rendering of the application and lead to a poor user experience.
  • Minimize the application bundle size using lazy loading and tree shaking. This can reduce the amount of code that the user needs to download and improve the initial loading time of the application.
  • Use Ahead-of-Time (AOT) compilation to reduce the application load time. AOT compilation can significantly reduce the size of the application bundle and improve the application's initial rendering time.
  • Use server-side rendering (SSR) to improve the application‚Äôs initial rendering time. SSR can significantly improve the application's initial rendering time and improve the user experience.

By following these best practices, developers can ensure that their Angular applications are optimized for performance and provide a great user experience.


In conclusion, these are some of the top Angular interview questions that candidates should be familiar with to excel in an Angular job interview.