Sure, here are the top 30 Angular interview questions and answers for 2024, categorized into basic, intermediate, and advanced levels:
Basic:
1. What is Angular?
2. What is Angular CLI? How do you install it?
3. What are Angular components?
4. Explain the Angular template syntax.
5. What is data binding in Angular?
6. What are directives in Angular? Provide examples.
7. What is Angular module? How do you create one?
8. What is the purpose of NgModule in Angular?
9. What is dependency injection in Angular?
10. How do you handle user input in Angular forms?
Intermediate
11. What are Angular services? How do you create and inject them?
12. Explain the difference between ngOnInit and constructor in Angular.
13. What is Angular routing? How do you set up routing in Angular?
14. What is lazy loading in Angular? Why is it used?
15. How do you make HTTP requests in Angular?
16. Explain the difference between Observables and Promises in Angular.
17. What are pipes in Angular? Provide examples.
18. What is Angular CLI schematics? How do you use it?
19. How do you handle errors in Angular applications?
20. What is Angular material? How do you integrate it into an Angular project?
Advanced:
21. What are Angular guards? Explain the different types.
22. What is Angular Ivy? How does it improve Angular applications?
23. How do you implement server-side rendering (SSR) in Angular?
24. What is AOT compilation in Angular? How does it differ from JIT compilation?
25. Explain the concept of zone.js in Angular.
26. What are ngModules in Angular? How do they facilitate lazy loading?
27. How do you optimize performance in Angular applications?
28. Explain the concept of change detection in Angular.
29. What is Angular Universal? How do you use it for server-side rendering?
30. How do you deploy an Angular application to production?
These questions should help gauge a candidate’s understanding of Angular across different skill levels.
Certainly! Here are some additional important Angular interview questions for 2024:
Important: Angular Interview Questions :
31. What is Angular Ivy and how does it differ from View Engine?
32. Explain Angular’s concept of Zones and its significance in change detection.
33. What is Angular Material and how does it enhance Angular applications?
34. Describe the difference between ngOnChanges and ngOnInit lifecycle hooks.
35. How do you handle authentication and authorization in Angular applications?
36. What are Angular Forms? Explain Template-driven and Reactive forms.
37. What is Angular Universal and when would you use it?
38. Describe the concept of Change Detection Strategy in Angular and its types.
39. How do you implement internationalization (i18n) in Angular?
40. What are Angular Schematics and how do they streamline project development?
41. Explain the concept of ViewChild and ContentChild in Angular.
42. How do you implement lazy loading of modules in Angular?
43. What is the purpose of the Angular Router Outlet?
44. How do you handle state management in large Angular applications?
45. Describe the difference between Angular testing methodologies: TestBed vs. ComponentFixture.
46. How do you handle asynchronous tasks in Angular?
47. Explain the concept of Interceptors in Angular HTTPClient.
48. What are Angular decorators? Provide examples of built-in decorators.
49. Describe the role of TypeScript in Angular development.
50. How do you handle cross-origin resource sharing (CORS) in Angular applications?
Angular Interview Questions These questions delve deeper into Angular concepts and practices, providing a more comprehensive understanding of the framework.
1. What is Angular?
– Angular is a TypeScript-based open-source front-end web application framework maintained by Google. It’s used for building single-page web applications (SPAs) and dynamic web pages. Angular provides a robust framework for client-side development, offering features like data binding, dependency injection, routing, and more.
2. What is Angular CLI? How do you install it?
– Angular CLI (Command Line Interface) is a powerful tool for initializing, developing, scaffolding, and maintaining Angular applications. It allows developers to quickly set up projects, generate components, services, modules, and more, as well as run development servers and build production-ready bundles.
– To install Angular CLI, you need to have Node.js and npm (Node Package Manager) installed on your system. Then, you can install Angular CLI globally using npm with the following command:
npm install -g @angular/cli3. What are Angular components?
– Angular components are the building blocks of Angular applications. They are TypeScript classes that are decorated with the `@Component` decorator and define views, behavior, and data for a specific part of the UI. Components encapsulate HTML templates, styles, and logic, making the application modular and easier to maintain.
– Example of a simple Angular component:
import { Component } from '@angular/core';
@Component({
selector: 'app-example',
templateUrl: './example.component.html',
styleUrls: ['./example.component.css']
})
export class ExampleComponent {
// Component logic goes here
}<h1>{{ title }}</h1>
<button (click)="handleClick()">Click me</button>
<ul>
<li *ngFor="let item of items">{{ item }}</li>
</ul>4. Explain the Angular template syntax.
– Angular template syntax is a combination of HTML and Angular-specific syntax used to define views and render data dynamically. It allows for data binding, interpolation, event handling, and structural directives.
– Example of Angular template syntax:
5. What is data binding in Angular?
– Data binding in Angular is the automatic synchronization of data between the model (component) and the view (template). It allows you to manipulate and display data dynamically, ensuring that changes in one area are reflected in another. Angular supports several types of data binding, including:
– Interpolation (`{{ }}`)
– Property binding (`[ ]`)
– Event binding (`( )`)
– Two-way binding (`[(ngModel)]`)
– Example of data binding:
<input type="text" [value]="name">
<p>Hello, {{ name }}!</p>
<button (click)="changeName()">Change Name</button>
Also Read: Top 30 JavaScript Interview Questions And Answers For 2024 Angular Interview Questions Angular Interview Questions
6. Directives in Angular:
Directives in Angular are markers on a DOM element that tell Angular to attach a specific behavior to that element or transform the DOM element and its children. There are three types of directives in Angular: component directives, attribute directives, and structural directives.
-Component Directives:
These are directives with a template. They are the most common type of directive and are used to create reusable UI components.
@Component({
selector: 'app-example',
template: '<p>This is an example component directive.</p>'
})
export class ExampleComponent {}
– Attribute Directives:
These are directives that change the appearance or behavior of an element, component, or another directive.
@Directive({
selector: '[appExampleDirective]'
})
export class ExampleDirective {
constructor(private el: ElementRef) {
this.el.nativeElement.style.backgroundColor = 'yellow';
}
}– Structural Directives:
These are directives that change the DOM layout by adding or removing DOM elements.
7. Angular Module:
<div *ngIf="isVisible">Content is visible</div>
An Angular module is a container for different parts of your application like components, directives, services, etc. It helps to organize the application into cohesive blocks of functionality.
To create a module, you use the `@NgModule` decorator. Here’s an example of creating a module:
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
@NgModule({
declarations: [
AppComponent
],
imports: [
BrowserModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }8. Purpose of NgModule in Angular:
NgModule is used to consolidate components, directives, and pipes into cohesive blocks of functionality, known as modules. It helps in organizing an application into smaller, manageable pieces, making it easier to develop, understand, and maintain , Angular Interview Questions .
9. Dependency Injection in Angular:
Dependency Injection (DI) is a design pattern in which components are given their dependencies instead of creating them internally. In Angular, DI is used to provide instances of services to components.
Here’s an example of how dependency injection works in Angular:
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root',
})
export class DataService {
getData() {
return 'Data from DataService';
}
}
import { Component } from '@angular/core';
import { DataService } from './data.service';
@Component({
selector: 'app-root',
template: '<p>{{ data }}</p>',
})
export class AppComponent {
data: string;
constructor(private dataService: DataService) {
this.data = this.dataService.getData();
}
}
Also Read: Top 30 JavaScript Interview Questions And Answers For 2024 Angular Interview Questions Angular Interview Questions
10. Handling User Input in Angular Forms:
Angular provides two-way data binding and event binding for handling user input in forms. You can use template-driven forms or reactive forms to achieve this.
Template-driven form example:
<input [(ngModel)]="name" name="name" placeholder="Enter your name">
<p>Your name is: {{ name }}</p>Reactive form example:
import { Component, OnInit } from '@angular/core';
import { FormGroup, FormControl } from '@angular/forms';
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
myForm: FormGroup;
ngOnInit() {
this.myForm = new FormGroup({
name: new FormControl('')
});
}
onSubmit() {
console.log(this.myForm.value);
}
}<form [formGroup]="myForm" (ngSubmit)="onSubmit()">
<input formControlName="name" placeholder="Enter your name">
<button type="submit">Submit</button>
</form>
11. What are Angular services? How do you create and inject them?
Definition:
Angular services are singleton objects that are instantiated only once during the lifetime of an application. They are used to organize and share code across the application, such as data sharing, communication with servers, logging, etc.
Creation and Injection:
To create a service in Angular, you can use the Angular CLI command:
ng generate service <service-name>
This will create a service file (`.service.ts`) with a corresponding class in Angular.
To inject a service into a component or another service, you can add it as a parameter in the constructor of the consuming component or service. Angular's dependency injection system will then provide an instance of the service when the component or service is created.
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root', // or 'any' or specific module
})
export class MyService {
constructor() { }
// Methods and properties of the service
}
12. Explain the difference between ngOnInit and constructor in Angular.
constructor:
- The `constructor` method is a standard TypeScript constructor that is called when the class is instantiated.
- It is used for basic initialization such as initializing class properties, but Angular-specific initialization should be avoided here.
- Angular constructs like input properties and injected services are not available in the constructor.
ngOnInit:
- `ngOnInit` is an Angular lifecycle hook that is called after Angular has initialized all data-bound properties of a directive.
- It is specifically designed for Angular initialization tasks, such as fetching data from a backend service.
- Angular constructs like input properties and injected services are fully initialized and available in `ngOnInit`.
import { Component, OnInit } from '@angular/core';
@Component({
selector: 'app-my-component',
template: '...',
})
export class MyComponent implements OnInit {
constructor() {
// Constructor logic
}
ngOnInit(): void {
// Initialization logic
}
}
13. What is Angular routing? How do you set up routing in Angular? Angular Interview Questions
Angular Routing:
Angular routing allows you to build single-page applications by managing the navigation between different views or components of the application.
Setup:
1. Import `RouterModule` and `Routes` from `@angular/router`.
2. Define an array of routes with path-component mappings.
3. Configure the routes using `RouterModule.forRoot()` in the root module's `imports` array.
4. Use the `<router-outlet></router-outlet>` directive in the main component's template to display routed components.
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import { HomeComponent } from './home/home.component';
import { AboutComponent } from './about/about.component';
const routes: Routes = [
{ path: 'home', component: HomeComponent },
{ path: 'about', component: AboutComponent },
];
@NgModule({
imports: [RouterModule.forRoot(routes)],
exports: [RouterModule]
})
export class AppRoutingModule { }
14. What is lazy loading in Angular? Why is it used?
Lazy Loading:
Lazy loading is a technique in Angular where modules or components are loaded asynchronously when needed, rather than loading them all when the application starts. This can significantly improve the initial loading time of the application.
Usage:
1. Identify the feature modules or components that are not needed during the initial application load.
2. Separate them into their own Angular modules.
3. Configure lazy loading by using the `loadChildren` property in the route definition, pointing to the module's file path.
const routes: Routes = [
{ path: 'admin', loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule) },
];
15. How do you make HTTP requests in Angular?
HTTP Requests:
1. Import `HttpClientModule` in the root or feature module.
2. Inject `HttpClient` service into the component or service where you want to make HTTP requests.
3. Use methods like `get`, `post`, `put`, `delete`, etc., from `HttpClient` to make HTTP requests.import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root',
})
export class DataService {
constructor(private http: HttpClient) { }
fetchData() {
return this.http.get('https://api.example.com/data');
}
}
Also Read: Top 30 JavaScript Interview Questions And Answers For 2024 Angular Interview Questions Angular Interview Questions
16. Observables vs. Promises in Angular:
Observables:
– Observables are part of the RxJS library and represent a stream of data that can be observed over time.
– They are used extensively in Angular for handling asynchronous operations such as HTTP requests, event handling, and more.
– Observables provide operators like `map`, `filter`, `reduce`, etc., for transforming and manipulating data streams ( Angular Interview Questions )
Promises:–
Promises are a built-in JavaScript feature for handling asynchronous operations.
– They represent a single future value that may be available now, or in the future, or never.
– Promises can only handle a single value, while observables can handle multiple values over time.
– Promises are less flexible compared to observables but are simpler to use in some scenarios.
Example:
// Observables
import { Observable } from 'rxjs';
const observable = new Observable(observer => {
setTimeout(() => {
observer.next('Hello from Observable!');
observer.complete();
}, 1000);
});
observable.subscribe({
next: value => console.log(value),
complete: () => console.log('Observable complete')
});
// Promises
const promise = new Promise((resolve, reject) => {
setTimeout(() => {
resolve('Hello from Promise!');
}, 1000);
});
promise.then(value => console.log(value));17. Pipes in Angular:
Pipes:
– Pipes are a feature in Angular for transforming data in templates.
– They take in data as input and transform it into the desired output.
– Angular provides several built-in pipes like `DatePipe`, `UpperCasePipe`, `LowerCasePipe`, etc.
– You can also create custom pipes for specific transformations , Angular Interview Questions.
Example:
<!-- Built-in pipes -->
<p>{{ today | date }}</p>
<p>{{ 'hello' | uppercase }}</p>
<p>{{ 'WORLD' | lowercase }}</p>
<!-- Custom pipe -->
<p>{{ message | customPipe }}</p>18. Angular CLI Schematics:
Angular CLI Schematics:
– Angular CLI Schematics are a powerful tool for generating and modifying code in Angular projects.
– They allow you to create custom blueprints for generating components, modules, services, etc.
– Schematics can automate repetitive tasks and enforce project conventions ( Angular Interview Questions ).
– You can create your own schematics or use existing ones provided by the community or Angular itself.
Example:
# Generate a new component using Angular CLI
ng generate component my-component
# Generate a new service using Angular CLI
ng generate service my-service
# Create a custom schematic
ng generate @schematics/angular:module my-module19. Error Handling in Angular:
Error Handling:
– In Angular, errors can be handled using try-catch blocks or by subscribing to the error property of observables.
– Global error handling can be implemented using Angular’s ErrorHandler service.
– You can also use the catchError operator from RxJS to handle errors in observables.
Example:
import { catchError } from 'rxjs/operators';
someObservable.pipe(
catchError(error => {
console.error('Error occurred:', error);
// Handle error or rethrow it
throw error;
})
).subscribe();20. Angular Material Integration:
Angular Material:
– Angular Material is a UI component library for Angular applications.
– It provides a set of reusable and accessible UI components following Material Design principles.
– Components include buttons, cards, forms, dialogs, tables, etc.
– Integration involves installing Angular Material, importing required modules, and using components in your project ( Angular Interview Questions ).
Example:
# Install Angular Material
ng add @angular/material
# Import required modules in your Angular module
import { MatInputModule } from '@angular/material/input';
import { MatButtonModule } from '@angular/material/button';
@NgModule({
imports: [
MatInputModule,
MatButtonModule
]
})Also Read: Top 30 JavaScript Interview Questions And Answers For 2024 Angular Interview Questions Angular Interview Questions
31. Angular Ivy vs. View Engine
Angular Ivy is the next-generation compilation and rendering pipeline for Angular applications. It’s a complete overhaul of the Angular compiler and runtime code generation process. It brings various benefits like improved build times, smaller bundle sizes, enhanced type checking, better debugging, and better template type checking. Ivy is designed to replace View Engine gradually. It’s more powerful, efficient, and easier to maintain.
Code Example:
// app.module.ts
import { NgModule } from ‘@angular/core’;
import { BrowserModule } from ‘@angular/platform-browser’;
import { AppComponent } from ‘./app.component’;
@NgModule({
declarations: [AppComponent],
imports: [BrowserModule],
bootstrap: [AppComponent]
})
export class AppModule {}
32. Zones in Angular and Change Detection
Zones in Angular are execution contexts that allow you to intercept and execute asynchronous operations. Angular’s change detection mechanism relies on zones to track asynchronous tasks and trigger change detection when those tasks are complete. Zones help Angular know when to update the view based on changes in the application state.
**Code Example:**
// app.component.ts
import { Component } from ‘@angular/core’;
@Component({
selector: ‘app-root’,
template: `<button (click)=”onClick()”>Click me</button>`
})
export class AppComponent {
onClick() {
setTimeout(() => {
// This code is executed outside Angular’s zone
console.log(‘Timeout completed’);
}, 1000);
}
}
33. Angular Material for Enhanced UI
Angular Material is a UI component library for Angular applications that implements Google’s Material Design. It provides a set of reusable and customizable UI components such as buttons, forms, navigation, layout, and data tables. Angular Material enhances Angular applications by providing consistent and modern UI elements, reducing development time, and improving user experience.
Code Example:
# Install Angular Material
ng add @angular/material
34. ngOnChanges vs. ngOnInit Lifecycle Hooks
– `ngOnChanges`: This lifecycle hook is called whenever one or more input properties of a component change. It receives a SimpleChanges object containing the previous and current values of the input properties.
– `ngOnInit`: This hook is called after Angular has initialized all data-bound properties of a directive/component. It’s a good place to perform initialization logic like fetching data from a server.
Code Example:
import { Component, Input, OnChanges, SimpleChanges } from ‘@angular/core’;
@Component({
selector: ‘app-example’,
template: `{{ message }}`
})
export class ExampleComponent implements OnChanges {
@Input() inputMessage: string;
message: string;
ngOnChanges(changes: SimpleChanges) {
if (changes.inputMessage) {
this.message = changes.inputMessage.currentValue;
}
}
ngOnInit() {
console.log(‘Component initialized’);
}
}
35. Authentication and Authorization in Angular
Authentication in Angular typically involves techniques like token-based authentication using JWT (JSON Web Tokens) or session-based authentication. Authorization involves controlling access to certain parts of an application based on user roles or permissions. This can be achieved using route guards, role-based access control (RBAC), or custom authorization logic.
Code Example:
// auth.guard.ts
import { Injectable } from ‘@angular/core’;
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot, Router } from ‘@angular/router’;
import { AuthService } from ‘./auth.service’;
@Injectable({
providedIn: ‘root’
})
export class AuthGuard implements CanActivate {
constructor(private authService: AuthService, private router: Router) {}
canActivate(
next: ActivatedRouteSnapshot,
state: RouterStateSnapshot): boolean {
if (this.authService.isAuthenticated()) {
return true;
} else {
this.router.navigate([‘/login’]);
return false;
}
}
}