45 Angular Interview Questions in 2025: Prepare Like a Pro

Angular Overview

Angular is a free, open-source, TypeScript-based framework for front-end development maintained by Google. It is popular for single-page applications but is also used to build enterprise-level web applications, progressive web applications (PWAs), and mobile apps.

Client-side frameworks like Angular were introduced to provide a more responsive user experience. It provides various tools, APIs, and libraries to streamline development. Angular’s features, such as lazy loading, AoT, and change detection, improve performance and speed up loading times.

Data from BuiltWith shows that over 690,000 websites have historically used Angular, and 246,000+ websites currently use it.

Angular Interview Questions and Answers for Beginners

Learn the most frequent Angular interview questions and answers that freshers are expected to know.

1. What is Angular? Why was it introduced?

Angular is an open-source web application framework for building dynamic, single-page applications (SPAs) with highly intuitive user interfaces. It encompasses 2-way data binding, component-based architecture, and dependency injection.

Angular was introduced to create SPAs, bring structure and consistency to web applications, and provide excellent scalability and maintainability.

2. What is TypeScript?

TypeScript is a programming language that builds on JavaScript by adding extra features to make it powerful and easy to use. Its potential is implemented especially in large projects.

TypeScript allows developers to define the data type that the variables should hold. Furthermore, it helps identify errors during development, making debugging easier.

3. What is Data Binding in Angular? Which type of Data Binding does Angular deploy?

Data binding allows any internet user to manipulate web page elements using a web browser. It uses dynamic HTML and does not require complex scripting or programming.

Data binding in Angular is commonly used in web pages that contain interactive components such as forms, calculators, tutorials, and games. Incremental display of a webpage makes data binding convenient when pages have enormous amounts of data.

The four types of data binding include Interpolation, Property Binding, Event Binding, and Two-Way Binding.

4. What are Single Page Applications (SPAs)?

A SPA or single-page application loads a single web page and dynamically updates it as the user interacts with it.

Unlike traditional websites, an SPA only loads the main page once. After that, it updated parts of the page without needing to refresh the whole page. SPAs are faster, more responsive, and provide a seamless experience to users.

5. Differentiate between Angular and AngularJS

Google developed Angular and AngularJS frameworks for building web applications, but they differ significantly. AngularJS is the original version, built with JavaScript, whereas Angular (often called Angular 2+) is a complete rewrite, built with TypeScript, offering better performance, enhanced features, and more flexibility.

Angular uses a component-based architecture, while AngularJS uses a directive-based approach. Angular also provides more advanced tools for handling forms, routing, and HTTP requests, making it more suited for modern, large-scale applications.

Recommended Read: AngularJS vs. Angular 2 Vs. Angular 4

6. What are Decorators in Angular?

Decorators are special markers (aka functions) that add metadata to classes, methods, properties, and parameters. They provide Angular with information about how to treat or use those elements in the code.

Common Angular decorators include @Component, @Injectable, and @NgModule.

7. What are the popular advantages of Angular?

Some of the common advantages of Angular are,

• MVC Architecture: Angular is a full-fledged MVC framework that provides a firm opinion on how the application should be structured. It also offers bidirectional data flow and updates the real DOM.
• Modules: Angular consists of different design patterns, such as components, directives, pipes, and services, which help create applications smoothly.
• Dependency Injection: Components dependent on other components can be easily worked around using this feature.

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8. What are Templates in Angular?

Templates in Angular are the HTML views that define the structure and layout of what users see in the web browser.

Though they are like HTML files, templates can also include special Angular code to make web pages dynamic and interactive. Within the Templates, developers can use Angular features such as data binding, loops, and conditionals based on user interaction and data patterns.

For example, in a template, a list of items is shown like this:

<ul>
<li *ngFor="let item of items">{{ item.name }}</li>
</ul>

Here, the *ngFor directive tells Angular to loop over a list of items and display each item's name property.

9. What are Annotations in Angular?

Annotations in Angular are similar to decorators. They are attached to classes, methods, or properties to provide metadata. This metadata informs Angular about how to treat those classes.

@Component({
selector: 'app-header',
templateUrl: './header.component.html',
styleUrls: ['./header.component.css']
})
export class HeaderComponent {
// Component logic here
}

Here, @Component is an annotation that marks the HeaderComponent class as an Angular component and provides additional information, such as the template and associated styles.

10. What are Directives in Angular?

Directives in Angular are special markers in HTML that tell Angular how to modify the appearance, behavior, and layout of the page elements. There are 3 major types of Directives:

• Structural Directives
• Attribute Directives
• Component Directives

import { Directive, ElementRef, Renderer2 } from '@angular/core';
@Directive({
selector: '[appHighlight]'
})
export class HighlightDirective {
constructor(private el: ElementRef, private renderer: Renderer2) {
this.renderer.setStyle(this.el.nativeElement, 'background-color', 'yellow');
}
}

11. What is an AOT Compiler?

The Ahead-Of-Time (AOT) compiler converts the Angular HTML and TypeScript code into JavaScript during the build phase, i.e., before the browser downloads and runs the code.

Instead of compiling code in the browser, as is the case with JIT (Just-in-Time) compilation, AOT compiles the code at the time of building the project.

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12. What are the Components in Angular?

Components in Angular are the basic building blocks of an application. Each component controls a part of the user interface (UI) and is made up of 3 crucial factors:

• Template (HTML/structure)
• Class (CSS/appearance)
• Styles (JavaScript/behavior)

13. What are Pipes in Angular?

Pipes in Angular help transform data into templates. They also allow for modifying how data is displayed to the user without changing the actual data.

A developer can use pipes to format dates, transform text to uppercase/lowercase, and format numbers as currency.

<p>{{ userName | uppercase }}</p>

This will display the userName in uppercase.

Common Built-In Pipes:

• uppercase: Converts text to uppercase.
• Example: {{ 'hello' | uppercase }} → HELLO

• date: Formats a date.
• Example: {{ currentDate | date:'longDate' }}

• currency: Formats a number as currency.
• Example: {{ amount | currency:'USD' }}

• json: Converts an object into a JSON string.
• Example: {{ user | json }}

• slice: Returns a slice (a portion) of an array or string.
• Example: {{ 'Angular' | slice:0:3 }} → Ang

14. What is the PipeTransform Interface?

The PipeTransform interface in Angular is a contract that allows you to create custom pipes. It defines how the pipe should transform the input data before displaying it on the screen.

When a developer creates a custom pipe, Angular needs to know how the pipe will change the data. The PipeTransform interface provides the necessary structure by defining the transform() method that must be implemented. This method takes the input data, processes it, and returns the transformed data.

import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
name: 'greet'
})
export class GreetPipe implements PipeTransform {
transform(value: string): string {
return `Hello, ${value}`;
}
}

15. What is an ngModule? 

ngModules are containers that reserve a code block for an application domain or a workflow. @ngModule takes a metadata object that generally describes compiling a component's template and generating an injector at runtime.

In addition, it identifies the module's components, directives, and pipes, making some of them public through the export property so that external components can use them.

16. What is Change Detection?

Change detection in Angular is a mechanism that determines when and how to update the user interface based on changes in the application's data model. Angular uses a tree of change detectors to track changes in component properties and update the DOM accordingly.

When a change occurs, Angular performs a change detection process. This process involves checking each component's properties for changes and updating the DOM if necessary. The change detection mechanism keeps the UI in sync with the application's data.

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17. What is a Parameterized Pipe?

A parameterized pipe in Angular accepts one or more arguments, also known as parameters. Pipes transform data in Angular templates, and parameterized pipes allow developers to customize the transformation based on specific requirements.

By passing parameters to a pipe, you can modify its behavior and apply different transformations to the data.

18. What are Class decorators?

Class decorators in Angular are a type of decorator that can be applied to a class declaration. They modify the class's behavior or add additional functionality. Class decorators are defined using the @ symbol followed by the decorator name and placed immediately before the class declaration.

They can be used for various purposes, such as adding metadata, applying mixins, or extending the functionality of a class.

19. What are Method decorators?

Method decorators in Angular can be applied to methods within a class. They modify the method's behavior or add additional functionality. Method decorators are defined using the @ symbol followed by the decorator name and placed immediately before the method declaration.

They can be used for tasks like logging, caching, or modifying the method's behavior based on specific conditions.

20. What are Property decorators?

Property decorators in Angular are decorators that can be applied to class properties. They modify the behavior of the property or add additional functionality. Property decorators are defined using the @ symbol followed by the decorator name and placed immediately before the property declaration.

They can be used for tasks like validation, memoization, or accessing metadata associated with the property.

Angular Interview Questions and Answers For Experienced

Explore the list of Angular interview questions and answers for 5 years of experience, designed to help developers prepare for advanced roles and showcase their expertise in Angular's core concepts, frameworks, and best practices.

21. What is RxJS in Angular?

RxJS is a library that provides reactive programming support for Angular applications. It allows you to work with asynchronous data streams and handle events over time.

RxJS is based on Observables, data streams that can be subscribed to and processed using operators. It provides a powerful and flexible way to handle complex asynchronous operations in Angular.

22. What are Router Links?

Router links in Angular are used for navigation within an application. They are defined using the routerLink directive and provide a way to navigate to different routes or components.

Router links can be used in HTML templates and are typically placed on anchor (<a>) tags or other clickable elements. By specifying the destination route or component, router links allow users to navigate between different parts of an Angular application.

23. What is the Router State?

The Angular router state represents the current state of the Angular router. It contains information about the current route, including the URL, route parameters, query parameters, and other related data.

The Angular router service allows access to and manipulation of the router state. It provides a way to navigate programmatically, retrieve information about the current route, and handle route changes in Angular applications.

24. What does Angular Material mean?

Angular Material is a UI component library for Angular applications. It provides a set of pre-built and customizable UI components that follow the Material Design guidelines, such as buttons, forms, navigation menus, and dialog boxes.

Angular Material simplifies building consistent and visually appealing user interfaces in Angular. It offers a range of features and styles that can be easily integrated into Angular projects.

25. What is Transpiling in Angular?

Transpiling in Angular refers to converting TypeScript code into JavaScript code that web browsers can execute. Angular applications are built using TypeScript, a superset of JavaScript that adds static typing and additional features to the language.

Since browsers can only run JavaScript, the TypeScript code needs to be transpiled into JavaScript before it can be executed. This is typically done using the TypeScript compiler (tsc) or build tools like Angular CLI.

26. What are HTTP interceptors?

HTTP interceptors in Angular are a feature that allows you to intercept HTTP requests and responses globally. Interceptors provide a way to modify or handle HTTP requests and responses at a centralized location before they reach the server or client. This can be useful for logging requests, adding authentication headers, handling errors, or modifying request/response data.

Interceptors can be registered in the Angular module and are executed in a specific order based on the request/response pipeline.

27. What is a Bootstrapping Module? 

A bootstrapping module in Angular is the main entry point of an Angular application. It is responsible for starting the application and initializing the root component. The bootstrapping module is typically defined in the main.ts file and is configured in the Angular AppModule.

It sets up the necessary environment, loads the required modules, and invokes the Angular platform to start the application. The bootstrapping module plays a crucial role in the Angular application's lifecycle.

28. What is the MVVM Architecture? 

MVVM architecture is an architectural pattern used mainly in software engineering. It stands for Model-View-ViewModel. MVVM is a variation of the traditional MVC (Model-View-Controller) software design pattern.

The main difference between the two is that MVVM separates the user interface logic from the business logic, while MVC separates the data access logic from the business logic. This separation of concerns makes developing, testing, and maintaining software applications easier.

29. What is Dependency Injection?

Dependency injection is a technique for creating loosely coupled code. It allows pieces of code to be reused without hard-coded dependencies, making the code more maintainable and easier to test.

Dependency injection is often used in frameworks like AngularJS, ReactJS, and VueJS. It is also possible to use dependency injection in vanilla JavaScript.

30. What type of DOM does Angular implement? 

Angular implements a Real DOM (Document Object Model) through Change Detection with its own optimized approach, which can be called View DOM.

For performance optimization, Angular uses a Real DOM (the View DOM) with Change Detection. This means Angular checks the parts of the UI that need updating based on changes in the data rather than re-rendering the entire page. 

Shadow DOM can be encapsulated, but Angular's default approach focuses on efficient change detection within the Real DOM.

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31. What is the difference between AOT and JIT

The Ahead-Of-Time (AOT) compilation converts your code during the build time before the browser downloads and runs that code. This ensures faster rendering to the browser. To specify AOT compilation, include the “--aot” option with the ng build or ng serve command.

The Just-In-Time (JIT) compilation process is a way of compiling computer code to machine code during execution or run time. It is also known as dynamic compilation. JIT compilation is the default when you run the ng build, or ng serve CLI commands.

32. What is the @Component Decorator? 

The @Component decorator in Angular defines and configures a component. It tells Angular that a class is a component and provides the necessary metadata for the component to function properly. The @Component decorator does the following:

• It marks a class as a component.
• It connects the class to an HTML template that defines the UI structure.
• It can attach styles (CSS) that apply to the component’s template.
• The class contains the logic for how the component behaves.

@Component({
selector: 'app-example',          // The component’s HTML tag to use in templates
templateUrl: './example.component.html', // Path to the HTML template
styleUrls: ['./example.component.css']   // Path to the component’s CSS file
})
export class ExampleComponent {
// Component's logic (properties, methods, etc.)
}

33. What are Services in Angular?

Angular Services perform tasks used by multiple components. These tasks could include data and image fetching, network connections, and database management. 

They perform all the components' operational tasks and avoid rewriting code. A service can be written once and injected into all the components that use that service.

34. What are the Promises and Observables in Angular?

A Promise is a built-in JavaScript object representing a value that will be available in the future. It handles one-time asynchronous operations, such as fetching data from a server or reading a file, and resolves with a single value or an error.

let promise = new Promise((resolve, reject) => {
// Simulating async task (e.g., HTTP request)
setTimeout(() => {
resolve('Data fetched successfully');
}, 2000);
});
promise.then((data) => {
console.log(data);  // Logs "Data fetched successfully"
}).catch((error) => {
console.log(error);
});

An Observable is part of the RxJS library and is used extensively in Angular. It represents a stream of values that can emit multiple items over time. Observables are much more powerful and flexible than promises and are ideal for dealing with multiple asynchronous events (e.g., user clicks, real-time data, etc.).

import { Observable } from 'rxjs';
// Creating an observable
let observable = new Observable(observer => {
observer.next('First value');
observer.next('Second value');
observer.complete(); // No more values
});
// Subscribing to the observable
observable.subscribe(
(data) => console.log(data), // On data
(error) => console.log(error), // On error
() => console.log('Complete!') // On completion
);

35. What is ngOnInit?

ngOnInit is a lifecycle hook and a callback method that Angular runs to indicate that a component has been created. It takes no parameters and returns a void type.

export class MyComponent implements OnInit {
constructor() { }
ngOnInit(): void {
//....
}
}

36. How to use ngFor in a tag?

The ngFor directive builds lists and tables in HTML templates. In simple terms, it iterates over an array or object and creates a template for each element.

<ul>
<li *ngFor = "let items in itemlist"> {{ item }} </li>
</ul>

“Let item” creates a local variable that will be available in the template

“Of items” indicates that we are iterating over the iterable items. 

The * before ngFor creates a parent template.

37. What are Template-driven and Reactive-form approaches?

Template-driven forms are easy to set up and rely heavily on Angular's template (HTML) to handle the form’s structure and validation. In this approach, most logic is written directly in the template, and Angular takes care of much of the form functionality behind the scenes.

<form #form="ngForm" (ngSubmit)="onSubmit(form)">
<label for="name">Name</label>
<input type="text" id="name" name="name" [(ngModel)]="user.name" required>  
<button type="submit" [disabled]="!form.valid">Submit</button>
</form>

Reactive forms are more structured and programmatic. In this approach, form controls are defined and managed in the component's TypeScript code using Angular's FormGroup, FormControl, and FormBuilder classes. This approach provides greater flexibility and control over form creation, validation, and data handling.

import { Component } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
@Component({
selector: 'app-reactive-form',
templateUrl: './reactive-form.component.html'
})
export class ReactiveFormComponent {
form: FormGroup;
constructor(private fb: FormBuilder) {
this.form = this.fb.group({
name: ['', Validators.required]
});
}
onSubmit() {
if (this.form.valid) {
console.log(this.form.value);
}
}
}

Recommended Read: What are Angular Forms?

38. What is Eager and Lazy Loading? 

Eager loading is the default module-loading strategy. Under this strategy, feature modules are loaded before the application starts. This is typically used for small applications.

Lazy loading dynamically loads the feature modules when there's a demand, making the application faster. It is used for bigger applications where not all the modules are required at the start of the application.

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39. What type of DOM does Angular implement? 

DOM (Document Object Model) treats an XML or HTML document as a tree structure in which each node is an object representing a part of the document. 

Angular uses the regular DOM, which updates the entire tree structure of HTML tags until it reaches the data to be updated. However, to ensure that speed and performance are not affected, Angular implements Change Detection.

40. How are Angular expressions different from JavaScript expressions?

Here’s a table summarizing the differences between Angular and JavaScript:

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41. How would you create a dynamic component in Angular?

To create a dynamic component in Angular, the key steps are:

• Create the component you want to load dynamically.

import { Component, Input } from '@angular/core';
@Component({
selector: 'app-dynamic',
template: '<h3>{{ title }}</h3><p>{{ content }}</p>',
})
export class DynamicComponent {
@Input() title: string;
@Input() content: string;
}

• Create a host component. This will have <ng-template>. The dynamic component will be inserted in this. You will also require a ViewContainerRef to access this <ng-template>. The ComponentFactoryResolver will be used to create instances of the dynamic component.

import { Component, ComponentFactoryResolver, ViewChild, ViewContainerRef } from '@angular/core';
import { DynamicComponent } from './dynamic.component';
@Component({
  selector: 'app-host',
  template: '<ng-template #dynamicComponentContainer></ng-template>',
})
export class HostComponent {
@ViewChild('dynamicComponentContainer', { read: ViewContainerRef }) 
dynamicComponentContainer: ViewContainerRef;
constructor(private componentFactoryResolver: ComponentFactoryResolver) {}
loadDynamicComponent(title: string, content: string) 
{
const componentFactory = 
this.componentFactoryResolver.resolveComponentFactory(DynamicComponent);
const componentRef = 
this.dynamicComponentContainer.createComponent(componentFactory);
// Set input properties of the dynamic component
componentRef.instance.title = title;
componentRef.instance.content = content;
}
}

• Update the host component template to include a button that calls loadDynamicComponent().

<button (click)="loadDynamicComponent('Dynamic Title', 'This is a dynamically loaded component!')">
Load Dynamic Component
</button>

• Ensure DynamicComponent is declared in AppModule.

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { HostComponent } from './host.component';
import { DynamicComponent } from './dynamic.component';
@NgModule({
declarations: [
AppComponent,
HostComponent,
DynamicComponent // Declare Dynamic Component
],
imports: [BrowserModule],
bootstrap: [AppComponent]
})
export class AppModule {}

• Modify app.component.html to use the HostComponent (which loads the dynamic component).

<app-host></app-host>

42. How would you debug an Angular application?

There are several ways for debugging an Angular application, which can be explained as follows:

• Using Angular DevTools:
• This is a browser extension for Chrome and Firefox. It displays a tree of components and directives to quickly view your application's layout. You can inspect every part and its details and update property values directly from the properties view.
• Using Browser Developer Tools:
  • Console Logs (console.log) – Helps in printing variables and debugging outputs.
  • Breakpoints in Sources Tab – Allows stopping code execution and inspecting variables.
  • Network Tab – Monitors API requests and responses.
• Browsers have built-in developer tools that aid in debugging Angular applications. For instance:

43. How would you handle a slow-loading Angular application?

The two commonly used tips to improve a slow-loading Angular application are:

• Lazy Loading Modules and Images
• The design approach is to delay initializing an item until it is truly required. This reduces the resources and time employed to load and initialize objects that may not be used. It involves modularizing the application and planning the routes to achieve lazy loading.
• Setting the loading attribute to lazy helps with images. It ensures the browser won’t load the resource until it is in the viewport. Thus, lazy loading aims to load only what the user needs to see first, thereby reducing the Angular app's initial load time.
• Checking your bundle size
• Use Angular’s built-in source-map-explorer (npm install -g source-map-explorer). It helps analyze and optimize the size of your JavaScript bundles.
• When using external libraries, we should avoid adding them directly to the index.html file unless necessary. Instead, we can load them lazily by utilizing a shared service.

44. How do you manage version control in Angular projects?

Here are the best practices to manage version control in Angular projects:

• Git: The distributed version control system that ensures everyone has a copy of the full change log for the code base. Using commands like git add, git commit, and git push helps manage changes in an Angular project.
• Keeping Commits Atomic and Descriptive: This commit practice ensures each commit represents a single logical change. It makes the history easier to read and debug.
• Creating a .gitignore File: This project structure and organizing practice exempts files and folders that are not meant to be tracked in your repository. These could be node_modules, DS_Store, and build artifacts.

45. How do you create a custom attribute directive in Angular?

The steps to create a custom attribute directive in Angular are:

• Import the Directive and ElementRef modules from @angular/core.

import { Directive, ElementRef, Input, OnInit } from '@angular/core';

• Define the directive using the @Directive decorator and provide a selector for the directive.

@Directive({
selector: '[appHighlight]'
})

@ngModule({
declarations: [
AppComponent,
HighlightDirective
],
...
})
export class AppModule { }

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Tips to Prepare for an Angular Interview

In addition to being thorough with Angular interview questions and answers, follow the tried-and-tested tips shared below:

• Develop a solid grasp of Angular's fundamental concepts, including components, modules, and services, and how they interact. Learn about data binding and its types.
• Understand structural and attribute directives and how they modify the DOM. Know how services are injected and used. Be familiar with routing, template-driven and reactive forms, observables, and RxJS.
• Opt for courses that reinforce Angular knowledge and provide hands-on experience. These courses offer a triple benefit: the knowledge, interview prep modules, and a certificate that further validates your skills before a potential employer.
• Practice coding problems and Angular system design concepts. To build confidence, it is best to simulate an interview environment.
• When answering behavioral questions, utilize the STAR method (Situation, Task, Action, Result). Practice explaining your thought process and solutions clearly.

Conclusion

You can ace your interview prep with these Angular interview questions and answers for different experience levels. The framework’s demand is on the rise. You should understand its core concepts, features, and best practices.

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