Angular Fundamentals

A Complete Guide with Expected Interview Questions and Answers

Angular is one of the most popular frameworks for building dynamic web applications. Mastering its fundamentals is critical for any developer aiming to excel in an Angular interview. This blog covers the core concepts of Angular, along with frequently asked interview questions and their answers, tailored to help you succeed.

Key Angular Fundamentals

1. Components: The building blocks of any Angular application, responsible for handling the UI and logic.
2. Modules: Containers that group related components, directives, services, and pipes.
3. Services and Dependency Injection (DI): Enable data sharing and business logic implementation across components.
4. Data Binding: Mechanisms to synchronize data between the view and the component.
5. Directives: Special markers in the DOM that attach behaviors to elements or manipulate DOM elements.
6. Pipes: Transform data in the template for display.
7. Component Lifecycle: A series of events from creation to destruction of a component.

Expected Interview Questions and Answers

1. What is Angular? Why is it popular?

Answer: Angular is a TypeScript-based front-end framework developed by Google for building single-page web applications. It is popular due to its component-based architecture, rich ecosystem, built-in tools like RxJS for reactive programming, and features such as two-way data binding and dependency injection.

2. What is the role of components in Angular?

Answer: Components control the view and logic of a part of the application. They consist of:

• HTML Template: Defines the structure.
• CSS/SCSS: Styles the view.
• TypeScript Class: Implements business logic and data.
• Metadata (@Component): Configures the component with a selector, template, and styles.

3. What are Angular modules? Why are they used?

Answer: Modules group related components, directives, services, and pipes into a functional unit. The root module is AppModule, and additional feature modules can be created to organize code better and enable lazy loading.

4. What is Dependency Injection in Angular?

Answer: Dependency Injection (DI) is a design pattern in Angular where the framework provides instances of a class to other classes (like services). This reduces tight coupling and enhances testability and maintainability.

5. What are the types of data binding in Angular?

Answer:

• Interpolation: Binding data from the component to the template (e.g., {{value}}).
• Property Binding: Binding an attribute of an element to a property in the component (e.g., [src]="imageUrl").
• Event Binding: Binding an event (e.g., (click)="onClick()").
• Two-way Binding: Combines property and event binding using [(ngModel)].

6. What are directives in Angular?

Answer: Directives add behavior to elements. Types include:

• Structural Directives: Alter DOM layout (e.g., *ngIf, *ngFor).
• Attribute Directives: Modify the appearance or behavior of elements (e.g., ngClass, ngStyle).
• Custom Directives: Defined by developers for specific behaviors.

7. What is the purpose of pipes in Angular?

Answer: Pipes transform data for display in templates. Example:

<p>{{ today | date:'longDate' }}</p>

Common pipes include date, uppercase, lowercase, currency, and json.

8. Explain the Angular Component Lifecycle Hooks.

Answer: Lifecycle hooks are special methods that Angular calls during the lifecycle of a component. Examples:

• ngOnInit(): Called after the component is initialized.
• ngOnChanges(): Responds to changes in input properties.
• ngOnDestroy(): Cleanup before the component is destroyed.
• ngDoCheck(): Detects custom changes.

Example Angular Code Demonstrating Fundamentals

Here’s an example illustrating components, modules, services, and data binding:

app.module.ts:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { UserComponent } from './user/user.component';

@NgModule({
  declarations: [
    AppComponent,
    UserComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

app.component.ts:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `<h1>{{ title }}</h1><app-user></app-user>`,
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'Angular Fundamentals Example';
}

user.component.ts:

import { Component } from '@angular/core';

@Component({
  selector: 'app-user',
  template: `<p>Hello, {{ name }}!</p>`,
  styleUrls: ['./user.component.css']
})
export class UserComponent {
  name = 'John Doe';
}

Conclusion

Understanding Angular fundamentals is crucial for acing interviews and building scalable web applications. Practice these concepts thoroughly, and use this guide as a reference for your preparation.

Let us know your thoughts or questions in the comments below. Stay tuned for the next blog in this Angular interview series!