Chapters Premium | Chapter-1: Angular Fundamentals Part-1
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Chapter-1: Angular Fundamentals Part 1.

Welcome to the ultimate resource for mastering Angular, the dynamic and powerful JavaScript framework that has revolutionized web development. This comprehensive ReadioBook which is also available as in Android app will guide you through a meticulously curated collection of 300 interview questions and answers, ensuring you gain a deep understanding of Angular concepts and emerge as a confident Angular developer.
Whether you're a beginner eager to break into the Angular realm or an experienced developer seeking to refine your skills, this ReadioBook cater to your learning needs. The meticulously crafted questions and detailed answers provide a thorough exploration of Angular's core concepts, including components, directives, services, dependency injection, data binding, routing, and more. Why Choose This ReadioBook?
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Upon completing the audiobook and app, you'll possess the knowledge and skills to confidently tackle any Angular challenge.

Embrace the Future of Web Development:
Angular has become the cornerstone of modern web development, empowering developers to create dynamic, interactive, and scalable web applications.
By mastering Angular, you'll open doors to a wealth of opportunities in the ever-evolving tech landscape.This ReadioBook on our Android app is your gateway to Angular proficiency. Embark on this learning journey and transform yourself into an in-demand Angular developer, ready to take on the challenges and rewards of the digital world. So, lets start from this first chapter with top-22 questions, which you will always encounter and later we will cover more concepts in depth which are advanced, when you clear your first round of interview then later for advanced round it would be very helpful. has covered almost all the required concepts of Angular framework and if genuinely go through each question and answer and understand the given program example, you will certainly crack your technical round of interview in any organization and also these all concepts make you master when you start working after getting selected. Hence, lets start and move ahead in this fast moving technology world.

What is Angular?

Answer: Angular is a platform and framework for building single-page client applications using HTML and TypeScript. It's developed and maintained by Google. Angular implements core and optional functionality as a set of TypeScript libraries that you import into your applications. The architecture of an Angular application relies on certain fundamental concepts.The basic building blocks are NgModules, which provide a compilation context for components. Components define views, which are sets of screen elements that Angular can choose and modify according to your program logic and data. Services provide specific functionality not directly related to views, and service providers can be injected into components as dependencies, making your code modular, reusable, and efficient.

For example, if you want to create a simple component to display a user's information, you would define a TypeScript class with properties for the user data and annotate it with ‘@Component’ to tell Angular it's a component. Here's a brief code snippet: Angular Interview Questions And Answer 001
In this code, ‘@Component’ defines the metadata, including the selector used in the HTML to instantiate the component and the template that defines the view.
The class ‘UserComponent’ then handles the data and behavior of the view.

What is declarative template?

In Angular, a declarative template refers to the HTML view where you describe what should be rendered, not how it should be done. Angular takes care of the "how" by using its template syntax and data-binding features to render the UI based on your application's state.
For example, consider a simple component that displays a list of items.

The declarative template would look something like this: Angular Interview Questions And Answer 002
In this code snippet, ‘*ngFor’ is a structural directive that tells Angular to repeat the element for each item in the ‘items’ array. The double curly braces ‘{{ item }}’ are used for interpolation to bind the data from the component to the view.
This is a declarative way to transform your model data into a user interface.

What is the reason you choose Angular?

Angular provides a robust framework that offers a comprehensive solution for developing scalable web applications. It embraces TypeScript, which ensures higher security with strong typing and enhances developer productivity with better tooling. Angular's component-based architecture allows for reusable code and easier maintenance, while its built-in features like dependency injection, services, and directives streamline development.

For example, to create a simple component in Angular, you would use the following TypeScript code: Angular Interview Questions And Answer 003
This snippet defines a new component with a selector ‘app-example’, which can be used as an HTML element, and a simple template that displays a welcome message.

What is RESTFul API?

A RESTful API is an architectural style for an application program interface (API) that uses HTTP requests to access and use data. That data can be used to GET, PUT, POST, and DELETE data types, which refers to the reading, updating, creating, and deleting of operations concerning resources.
In Angular, you often interact with a RESTful API by using the HttpClient service provided by the framework.

Here's a brief example of how you might use it to get data from an API: Angular Interview Questions And Answer 005
In this snippet, ‘HttpClient’ is injected into a service called ‘DataService’, and we're defining a method ‘getData’ that will make a GET request to a fictional API endpoint. The ‘Observable’ returned by ‘getData’ can then be subscribed to in a component to handle the asynchronous data once it's retrieved.

Please explain why RESTFul is called architectural style?

RESTful is referred to as an architectural style because it outlines a set of constraints and principles for designing distributed systems, specifically for web services. It’s not a standard or a protocol, but rather an approach or a set of guidelines that when followed, enables systems to be scalable, simple, and modular.
In the context of web services, REST stands for Representational State Transfer. It’s called “representational” because it deals with the transfer of representations of resources. A resource can be any meaningful concept that an application can address, and a representation is a format that captures the current state of a resource, typically in JSON or XML format.
For example, in a RESTful web service, you might have a URL like ‘’ which represents a user with the ID of 1. When you want to get information about this user, you would make a GET request to that URL, and the server would respond with a representation of that user's state in a format like JSON: Angular Interview Questions And Answer 006
This approach to building web services enables interactions that are stateless between requests, and it allows for the potential to cache responses to improve performance.
Each operation you perform on the web service, such as retrieving a user, updating a user, or deleting a user, is a stateless operation, meaning that each request from client to server must contain all the information necessary to understand and complete the request. By following REST principles, developers can create web services that are more maintainable and extensible over time.

What is the template in Angular?

In Angular, a template is a part of the component that defines the HTML markup to render the component's view. It's where you put the HTML that dictates how that part of your application will be displayed in the browser. You can bind data to the template, respond to events, and structure your application's display logic using Angular's template syntax.

Let me give you a simple example. Suppose you have a component that needs to display a user's name and age. The component's class might look like this: Angular Interview Questions And Answer 007
Here, the ‘template’ property within the ‘@Component’ decorator contains the HTML that will be displayed. The curly braces ‘{{ }}’ are used to bind the ‘user’ object's properties to the view.
Whenever the ‘user’ object changes, Angular updates the DOM to reflect the new values.

What is the difference between an Annotation and a Decorator in Angular?

In Angular, the terms 'annotation' and 'decorator' are often used interchangeably, but they refer to concepts that are part of the language and framework respectively. An annotation is a TypeScript concept used for adding metadata to classes, whereas a decorator is an Angular-specific feature built on top of the TypeScript decorator.
Decorators are design patterns that are used to separate modification or decoration of a class without modifying the original source code. In Angular, decorators are functions that add metadata to a class, its members, or its method arguments.Angular provides built-in decorators like ‘@Component’, ‘@NgModule’, ‘@Directive’, ‘@Input’, and ‘@Output’.
These decorators are used to define components, modules, directives, and to create input and output properties. Here's a simple example using the ‘@Component’ decorator: Angular Interview Questions And Answer 008
In this code, ‘@Component’ is a decorator that tells Angular that ‘ExampleComponent’ is a component and provides essential metadata about the component, such as its selector and template.
Annotations, as a concept in TypeScript, are used in Angular internally when it transpiles decorators into JavaScript code, but as an Angular developer, you will primarily deal with decorators.

Why was Angular introduced as a client-side framework?

Angular was introduced to address various challenges encountered in developing single-page applications (SPAs). It provides a structured framework that makes it easier to develop rich internet applications by enabling developers to use HTML as their template language and extending HTML's syntax to express the application's components clearly and succinctly.
One of the main reasons Angular gained popularities was its ability to make HTML more expressive and less static. It introduced data-binding, which allows for an automatic synchronization of data between the model (the business logic) and the view (what the user sees in the app). This meant that developers no longer needed to write significant amounts of boilerplate code to handle dynamic updates to the UI.
For example, Angular’s two-way data binding can be illustrated with a simple input field in HTML: Angular Interview Questions And Answer 009
In this code snippet, ‘[(ngModel)]’ is a directive that enables two-way data binding. As a user types into the input field, ‘’ is updated in the component's model, and the greeting in the ‘

‘ tag is updated in real-time to reflect the change. This seamless synchronization between the model and the view is one of the core features that made Angular stand out as a client-side framework.

In simple term and steps, can you explain how Angular application work?

An Angular application works by following a series of well-defined steps:

The application starts by bootstrapping the main module. This is where Angular initializes and starts to execute the code. Angular Interview Questions And Answer 011

Components and Templates:
At the core of Angular are components that control views (templates).
Each component manages a section of the screen and logic behind it. Angular Interview Questions And Answer 012

Dependency Injection:
Angular uses dependency injection to provide new components with services or other things they need. Services are typically singletons that carry out common tasks. Angular Interview Questions And Answer 013

Directives and Data Binding:
Angular extends HTML with directives to add functionality to the HTML elements.
Data binding is a mechanism to bind parts of a template to parts of a component. Angular Interview Questions And Answer 014

Angular provides a way to manage navigation between views with a routing module. It interprets browser URLs as instructions to navigate to a client-generated view. Angular Interview Questions And Answer 015

Services and Data Management:
For data management, services are used to connect to external APIs and provide data to components. Angular Interview Questions And Answer 016

Change Detection:
Whenever data changes, Angular's change detection mechanism updates the DOM to reflect those changes, ensuring the user interface is up to date.
Angular's architecture is designed to support development practices like modularity, maintainability, and testability. It's a powerful framework that handles a lot of the heavy lifting for you, making it easier to build complex applications.

What are the differences between Angular.js and Angular? When is it better than React?

AngularJS, often referred to simply as Angular.js, is the very first version of the Angular framework. It was a standalone framework that introduced many concepts in web development, such as two-way data binding, MVC (Model-View-Controller) architecture, and dependency injection. However, it was primarily based on JavaScript and didn't align well with the emerging web components standard or mobile development.
Angular, on the other hand, usually refers to versions 2 and above. It's a complete rewrite of AngularJS, utilizing TypeScript, which is a superset of JavaScript providing static typing, classes, and interfaces. It's more component-based, aligning with the web components standard, and offers better performance, especially for single-page applications (SPAs).
It also supports mobile development. Here's a quick code comparison:

In AngularJS, you might define a component and its template like this: Angular Interview Questions And Answer 017

In Angular, you'd use decorators and TypeScript, like this: Angular Interview Questions And Answer 018

Regarding when Angular might be better than React:

- TypeScript:
Angular is built with TypeScript, which can lead to more maintainable and error-free code due to its static typing.

- Consistency:
Angular provides a standardized and structured framework with a set of tools and components. This can be particularly beneficial for large teams and projects.

- RxJS:
Angular heavily relies on RxJS, which is a library for reactive programming. It can be more powerful for managing asynchronous data streams than React's built-in capabilities.

- Full Framework:
Angular is a full-fledged framework, meaning it provides a lot out of the box, like routing, form validation, and HTTP client. React is more of a library and requires additional libraries for different aspects.

- Material Design:
Angular Material provides a wide range of well-integrated UI components following Material Design principles, which can speed up the development process.
Each tool has its own strengths, and the choice often comes down to the specific needs of the project and the familiarity of the development team with the toolset. React might be preferred for its simplicity and flexibility, while Angular could be the choice for its comprehensive feature set and design consistency.

Name key Angular advantages?

Angular's key advantages include:

Two-Way Data Binding:
This feature ensures that the model and the view are updated simultaneously, simplifying the development process. For example: Angular Interview Questions And Answer 019

Angular organizes code into modules, making it more manageable and reusable.

Dependency Injection:
Angular's DI framework provides dependencies to components and services, enhancing modularity and code reuse.

Example: Angular Interview Questions And Answer 020

Angular directives allow you to attach behavior to elements in the DOM.

Example: Angular Interview Questions And Answer 021

Angular is built with TypeScript, offering more consistent code, tooling, and debugging.

Ahead-of-Time Compilation:
Compiling HTML and TypeScript into JavaScript during the build process improves performance and security.

Angular CLI:
The command-line interface is powerful for scaffolding the application and managing Angular projects.

Angular uses RxJS, a library for reactive programming, to handle asynchronous operations and events.
These features make Angular a robust framework for developing scalable and maintainable single-page applications.

Give examples of lifecycle hooks in Angular and what it is?

In Angular, lifecycle hooks are functions that allow us to tap into specific moments in the life of a component or directive. They give us visibility into key events in the rendering process and the life of a component, from its creation to its eventual destruction. Here are some of the main lifecycle hooks:

This is called once the component has been initialized.
This is a good place to put initialization logic. Angular Interview Questions And Answer 022

It's called before ‘ngOnInit’ and whenever one or more data-bound input properties change. It receives a SimpleChanges object of current and previous property values. Angular Interview Questions And Answer 023

Triggered after every change detection run.
It allows you to implement your own change detection algorithm for the component. Angular Interview Questions And Answer 024

Called once Angular has performed any content projection into the component's view. Angular Interview Questions And Answer 026

Called after the ‘ngAfterContentInit’ and every subsequent ‘ngDoCheck’. Angular Interview Questions And Answer 028

Called once the component's view and child views have been initialized. Angular Interview Questions And Answer 030

Called after the ‘ngAfterViewInit’ and every subsequent ‘ngAfterContentChecked’. Angular Interview Questions And Answer 032

This is the cleanup phase just before Angular destroys the component.
We can use this hook to perform any necessary cleanup like unsubscribing from observables or detaching event handlers. Angular Interview Questions And Answer 033
These hooks provide a powerful way to interact with the component lifecycle, letting you perform operations at the right stage in the life of a component.

How do you add the Angular router to your application?

To add the Angular router to an application, you would start by installing the router package if it's not already present by running ‘npm install @angular/router’. Then, you would import the ‘RouterModule’ and ‘Routes’ in your app module, set up your routes, and then add them to the imports array of your ‘@NgModule’ decorator.

Here's a simple code example that demonstrates this: Angular Interview Questions And Answer 034
In this example, ‘RouterModule.forRoot(routes)’ initializes the router with the routes we've defined, and we export the ‘RouterModule’ so that it's available throughout the app. Additionally, you'd need to add the Angular Interview Questions And Answer 035
directive in your template where you want the router to display the components for the active route.

What is single page application and how it relates to Angular?

A single-page application (SPA) is a web application or website that interacts with the user by dynamically rewriting the current page rather than loading entire new pages from the server. This approach avoids interruption of the user experience between successive pages, making the application behave more like a desktop application.
In the context of Angular, it is a framework that's well-suited for building SPAs. Angular provides a robust structure that allows developers to create large-scale applications composed of components and services that work together seamlessly. It also has powerful features like two-way data binding, modular development, and dependency injection, which facilitate the development of complex applications within a single page framework.
For example, here’s a simple Angular component that could be part of a SPA: Angular Interview Questions And Answer 036
This component could be part of a larger SPA where different components are loaded dynamically based on the user's interaction, without the need for full page reloads.

What are the disadvantages of the single page application?

Single-page applications (SPAs) have several disadvantages which are important to consider:

- SEO Challenges:
Traditional SPAs often struggle with search engine optimization because search engines may not effectively index dynamic content that is loaded asynchronously.

- Performance Issues:
SPAs can suffer from slow initial load times because the browser may need to load large frameworks and libraries before the user sees anything.

- JavaScript Must be Enabled:
If a user’s browser doesn’t support JavaScript or has it disabled, the SPA won’t work because it relies heavily on JavaScript to render pages.

- Memory Leaks:
Because SPAs are typically running on the same page, they can be prone to memory leaks if not managed properly, which can lead to performance degradation over time.

- Browser History Management:
SPAs can complicate the management of browser history and the back button may not work as users expect, leading to a poor user experience.

- Security Risks:
SPAs have more exposure to cross-site scripting (XSS) attacks because much of the content is loaded dynamically.

Here's an Angular code snippet illustrating how you might load a component dynamically, which can be both a powerful feature and a source of performance issues if not managed correctly: Angular Interview Questions And Answer 038
In the code above, ‘MyDynamicComponent’ is loaded dynamically into ‘myContainer’. This is convenient but requires careful management to ensure the application remains performant and secure.

What is cross-site-scripting (XSS)?

Cross-site scripting, commonly known as XSS, is a security vulnerability typically found in web applications. It's a type of injection where an attacker can inject malicious scripts into content from otherwise trusted websites. This malicious content is then delivered to an unsuspecting user's browser, where it can execute with the privileges of the trusted context, potentially stealing data or performing actions on behalf of the user without their consent.

In Angular, we mitigate XSS risks by treating all values as untrusted by default. Angular's templating engine automatically escapes values to make them safe to embed in the DOM. Here's a simple example:

Suppose we have a component that binds a user input to the page: Angular Interview Questions And Answer 039
If ‘userInput’ contains a script tag, Angular will sanitize it when rendering it to the DOM.

However, if we trust the content and we want to bypass Angular's sanitization, we can use the ‘DomSanitizer’ service: Angular Interview Questions And Answer 041
In this case, ‘updateInput’ would be called with user input, and the sanitizer's ‘bypassSecurityTrustHtml’ method would allow for potentially unsafe HTML to be bound directly to the innerHTML.
It's essential to use this method judiciously as it opens up the potential for XSS if the content isn't adequately controlled or sanitized before this point.

What is Angular Sanitizer?

Angular Sanitizer is a security feature that's part of the Angular platform, which is used to prevent Cross Site Scripting (XSS) attacks. It works by sanitizing values to be safe to use in the different DOM contexts. For instance, when binding HTML content to the document in a way that is potentially unsafe, Angular will automatically sanitize the values to prevent malicious code injection.

For example, if you are using the ‘innerHtml’ binding to dynamically add HTML content to your component's template, Angular will sanitize the content to ensure that any potentially dangerous scripts or styles are disabled. Here's a simple code example: Angular Interview Questions And Answer 043
In this example, the ‘DomSanitizer’ service is injected into the component and used to sanitize the ‘unsafeHtmlContent’.
The method ‘bypassSecurityTrustHtml’ is one of the sanitizer methods that tells Angular to trust the given HTML and bypass the sanitization. This should only be done with content that has been verified to be safe, as it could open up security vulnerabilities if misused.

When are uppercase and lowercase used in Angular?

In Angular, uppercase and lowercase are used primarily in the context of pipes to transform the case of text content. Pipes in Angular are a way to write display-value transformations that you can declare in your HTML.
The ‘uppercase’ pipe transforms text to all upper letters, and the ‘lowercase’ pipe transforms text to all lower letters.
These are commonly used for formatting the text content directly within the template of an Angular component.
For example, if you have a component property called ‘greeting’ which contains the string "Hello World", you can use the pipes in the template like this: Angular Interview Questions And Answer 044
It's a simple and declarative way to format text without needing to modify the underlying data.
These pipes are part of the ‘CommonModule’, which is included by default when you create a new application with the Angular CLI.

What’s the difference between Angular and JavaScript expressions?

In a face-to-face interview setting, I would explain that the fundamental difference between Angular and JavaScript expressions lies in their execution context and capabilities. Angular expressions are evaluated within the scope of an Angular application, meaning they are tied to the Angular framework's context.

They are primarily used for data binding within templates. Angular expressions can be written inside double curly braces:
‘{{ expression }}’. They support filters and can be used directly in the HTML. However, Angular expressions are more limited than JavaScript expressions. For instance, they don't allow for loops, conditionals, or exceptions, and you can't directly call a function with side effects from an Angular expression.
JavaScript expressions, on the other hand, are evaluated in the pure JavaScript context. They are more powerful and less restricted than Angular expressions. They can contain loops, conditionals, and you can invoke functions that have side effects. JavaScript expressions are generally used in the script part of the application where business logic resides.
For example, in Angular, you might bind a property to an element like this: Angular Interview Questions And Answer 045

In JavaScript, you could achieve a similar result by manipulating the DOM directly: Angular Interview Questions And Answer 046
This illustrates how Angular abstracts away the direct DOM manipulation in favor of a more declarative approach to updating the UI.

What is client-side application?

Client-side applications are programs that run within a user's browser, handling everything from user interaction to data manipulation without the need for constant server communication. In the context of Angular, it's a powerful framework for building such client-side applications. Angular provides a structured environment to develop single-page applications (SPAs), which load once and then dynamically update content as the user interacts with the app.

For example, consider a simple Angular component that displays a list of items: Angular Interview Questions And Answer 048
In this snippet, ‘ItemListComponent’ uses Angular's ‘*ngFor’ directive to iterate over an array of items, dynamically creating an ‘li’ element for each item and displaying its name. The entire process occurs on the client side, providing a responsive user experience without needing to request a new page from the server each time.

What is the reason you prefer Angular framework above others available?

Angular is a comprehensive framework that offers a robust set of tools for building scalable, maintainable, and efficient web applications. One of its core strengths is the opinionated architecture, which provides a standardized way to build applications. This can significantly speed up the development process because it reduces the need for making decisions about the structure of the project and the tools to use.
Another reason I prefer Angular is its powerful two-way data binding. This feature allows the application's state to be synchronized in real-time between the model and the view. It simplifies the development process by eliminating the need to write boilerplate code to constantly sync the UI with the underlying data model. TypeScript is another major advantage. It's a superset of JavaScript that adds static types, which can lead to more robust code and can catch errors early during the development phase. This can be a huge productivity boost and improve the quality of the code.Dependency injection is a design pattern that Angular uses extensively, making it easier to manage and test the application. Services, which are singleton objects, can be injected into components and modules, providing a modular and reusable way to add functionality.

What is an opinionated architecture mean?

When we talk about an opinionated architecture in the context of a software framework like Angular, we're referring to a set of guidelines and best practices that the framework enforces or recommends for building applications. It means that the framework has specific opinions about how things should be done, which can include file structure, naming conventions, module system, etc.
For instance, Angular is considered opinionated because it encourages the use of TypeScript, has a defined structure for projects, and promotes certain patterns like the use of services for business logic, components for views, and modules for organization. It also comes with its own CLI which further enforces these patterns by generating boilerplate code in a consistent manner.
For example, when you want to create a new component in Angular, you typically use the Angular CLI and run a command like: Angular Interview Questions And Answer 049
This command will not only create the necessary files for the component but also place them in a specific directory structure and even wire up a basic test file for you.
The CLI's actions reflect Angular's opinions on how the app should be structured.This opinionated nature can be a double-edged sword; on one hand, it provides a standardized way of doing things which can be great for team collaboration and maintaining code quality. On the other hand, it might be limiting if you want to do something outside of what the framework considers the 'norm'. However, most of the time, these opinions are based on best practices that have evolved over time within the community.