Top 100 Angular Interview Questions And Answers

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1. What is Angular?

Answer

Angular is a TypeScript-based open-source framework for building client-side web applications.

Code Snippet

// main.ts
import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';

platformBrowserDynamic().bootstrapModule(AppModule);

Explanation

In this code snippet, weโ€™re bootstrapping the Angular application using the AppModule.

Reference

Angular Overview


2. What is a Component in Angular?

Answer

A component controls a patch of the screen called a view in Angular.

Code Snippet

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

@Component({
  selector: 'app-root',
  template: `<h1>Hello, {{title}}</h1>`,
})
export class AppComponent {
  title = 'Angular App';
}

Explanation

Here, we define a component with a selector and a template. The selector is the custom HTML tag that will be replaced by this componentโ€™s template.

Reference

Angular Components


3. What is Angular CLI?

Answer

Angular CLI is a command-line tool for scaffolding and building Angular applications.

Code Snippet

ng new my-app

Explanation

The command ng new my-app generates a new Angular application in a directory called my-app.

Reference

Angular CLI


4. Explain Angular Modules

Answer

Angular modules help in organizing an application into cohesive blocks of functionality.

Code Snippet

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 { }

Explanation

The AppModule is the root module that tells Angular how to assemble the application.

Reference

Angular Modules


5. How to Implement Two-Way Data Binding?

Answer

Two-way data binding can be achieved using the ngModel directive.

Code Snippet

<input [(ngModel)]="name" />

Explanation

The ngModel directive binds the input element to the name property, making it reflect any changes in both the UI and the component.

Reference

Two-Way Data Binding


6. What is Dependency Injection in Angular?

Answer

Dependency Injection (DI) is a design pattern used in Angular to provide dependencies to components and services.

Code Snippet

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

@Injectable({
  providedIn: 'root'
})
export class DataService {
  // Implementation here
}

Explanation

The @Injectable decorator marks DataService as available for DI.

Reference

Dependency Injection


7. Explain Directives

Answer

Directives add behavior to elements in the DOM. There are three types: Components, Structural Directives, and Attribute Directives.

Code Snippet

<p *ngIf="showParagraph">Hello</p>

Explanation

*ngIf is a structural directive that conditionally includes a template based on the value of showParagraph.

Reference

Angular Directives


8. What is RxJS?

Answer

RxJS (Reactive Extensions for JavaScript) is a library for reactive programming using Observables.

Code Snippet

import { Observable } from 'rxjs';

const observable = new Observable(subscriber => {
  subscriber.next('Hello, RxJS!');
});

Explanation

Here we create a new Observable. Observables help in handling asynchronous operations in Angular.

Reference

RxJS in Angular


9. Explain Pipes in Angular

Answer

Pipes transform displayed values within a template.

Code Snippet

{{ name | uppercase }}

Explanation

The uppercase pipe transforms name to uppercase before rendering.

Reference

Pipes


10. How to Handle Events in Angular?

Answer

Event binding in Angular allows you to listen for and respond to user actions.

Code Snippet

<button (click)="doSomething()">Click Me</button>

Explanation

The (click) event calls the doSomething method when

the button is clicked.

Reference

Event Binding


11. What are Angular Lifecycle Hooks?

Answer

Lifecycle hooks are methods that Angular calls at specific points in the componentโ€™s lifecycle.

Code Snippet

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

@Component({
  // ...
})
export class MyComponent implements OnInit {
  ngOnInit() {
    // Initialization logic here
  }
}

Explanation

Here, the ngOnInit lifecycle hook is implemented. It runs after the componentโ€™s initialization.

Reference

Lifecycle Hooks


12. How to Make HTTP Requests in Angular?

Answer

The HttpClient module is used to make HTTP requests.

Code Snippet

import { HttpClient } from '@angular/common/http';

constructor(private http: HttpClient) {}

fetchData() {
  this.http.get('https://api.example.com/data').subscribe(data => {
    console.log(data);
  });
}

Explanation

Here, an HTTP GET request is made using HttpClient. The .subscribe() method handles the asynchronous response.

Reference

HttpClient


13. What is Lazy Loading?

Answer

Lazy loading is a technique to load Angular modules only when they are needed, reducing the initial load time.

Code Snippet

// app-routing.module.ts
const routes: Routes = [
  { path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) }
];

Explanation

The FeatureModule is lazily loaded when navigating to the feature path.

Reference

Lazy Loading


14. How to Pass Data to Components?

Answer

Use @Input and @Output decorators to pass data between parent and child components.

Code Snippet

// child.component.ts
import { Component, Input } from '@angular/core';

@Component({
  // ...
})
export class ChildComponent {
  @Input() data: string;
}

Explanation

Here, the data property is marked with @Input(), allowing data to be passed from a parent component.

Reference

Component Interaction


15. What is Angular Forms?

Answer

Angular provides two ways to work with forms: Reactive Forms and Template-Driven Forms.

Code Snippet

<!-- Template-Driven -->
<input [(ngModel)]="name" />

<!-- Reactive Forms -->
<form [formGroup]="form">
  <input formControlName="name" />
</form>

Explanation

In Template-Driven Forms, you use directives like ngModel for two-way data binding. In Reactive Forms, you use formGroup and formControlName to bind controls to form groups.

Reference

Angular Forms


16. What is the use of Services in Angular?

Answer

Services are singletons that carry out specific functionalities and can be injected into components or other services.

Code Snippet

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

@Injectable()
export class MyService {
  // service logic here
}

Explanation

Using the @Injectable() decorator, MyService can be injected into components or other services.

Reference

Services in Angular


17. Explain HostBinding and HostListener

Answer

HostBinding and HostListener are decorators used to bind properties and listen for events on the host element of the directive.

Code Snippet

import { Directive, HostBinding, HostListener } from '@angular/core';

@Directive({
  selector: '[appHighlight]'
})
export class HighlightDirective {
  @HostBinding('class.active') isActive = false;

  @HostListener('click') toggleActive() {
    this.isActive = !this.isActive;
  }
}

Explanation

The @HostBinding decorator binds a host element property to a directive property. @HostListener listens for events on the host element.

Reference

Attribute Directives


18. What are Query Parameters?

Answer

Query parameters are a set of key-value pairs that appear after the question mark in a URL.

Code Snippet

import { ActivatedRoute } from '@angular/router';

constructor(private route: ActivatedRoute) {
  this.route.queryParams.subscribe(params => {
    console.log(params);
  });
}

Explanation

Using ActivatedRoute, you can subscribe to queryParams to react to changes in query parameters.

Reference

Angular Routing


19. What are Resolvers in Angular?

Answer

Resolvers are interfaces that pre-fetch data before a route is activated.

Code Snippet

import { Resolve } from '@angular/router';
export class DataResolver implements Resolve<Data> {
  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Data {
    return fetchData();
  }
}

Explanation

The resolve() method fetches data before the route is activated, enhancing UX by reducing loading times.

Reference

Route Resolvers


20. How do you create a custom pipe?

Answer

Custom pipes can be created using the @Pipe decorator.

Code Snippet

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({ name: 'myCustomPipe' })
export class MyCustomPipe implements PipeTransform {
  transform(value: any): any {
    return value + ' transformed';
  }
}

Explanation

The transform method is where the custom logic for the pipe is defined.

Reference

Creating Custom Pipes


21. Explain AOT Compilation.

Answer

Ahead-of-Time (AOT) compilation converts Angular HTML and TypeScript into JavaScript during the build process.

Code Snippet

ng build --aot

Explanation

Using the --aot flag while building the application triggers AOT compilation, which optimizes the appโ€™s performance.

Reference

AOT Compilation


22. What is Angular Universal?

Answer

Angular Universal allows Angular applications to be rendered on the server.

Code Snippet

ng add @nguniversal/express-engine

Explanation

By running the above command, you can add server-side rendering capabilities to your Angular application.

Reference

Angular Universal


23. Explain Data Binding in Angular.

Answer

Data Binding in Angular is the synchronization between the model and the view. Types of data binding include Interpolation, Property Binding, Event Binding, and Two-Way Binding.

Code Snippet

@Component({
  selector: 'app-root',
  template: `
    <h1>{{ title }}</h1>
    <button (click)="handleClick()">Click Me!</button>
    <input [(ngModel)]="name">
  `
})
export class AppComponent {
  title = 'Hello World';
  name = 'John Doe';

  handleClick() {
    this.title = 'Clicked';
  }
}

Explanation

  • Interpolation: {{ title }}
  • Event Binding: (click)="handleClick()"
  • Two-Way Binding: [(ngModel)]="name"

Reference

Data Binding in Angular


24. What is Dependency Injection (DI)?

Answer

Dependency Injection (DI) is a design pattern used in Angular to increase modularity and reusability by providing dependencies to components or services.

Code Snippet

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

@Injectable()
export class MyService {
  constructor(private httpClient: HttpClient) { }
}

Explanation

In the above code, HttpClient is injected into MyService, making it easier to manage and test.

Reference

Dependency Injection


25. What is Lazy Loading?

Answer

Lazy loading is a technique to defer the loading of a module until itโ€™s needed, reducing initial load times.

Code Snippet

const routes: Routes = [
  {
    path: 'lazy',
    loadChildren: () => import('./lazy/lazy.module').then(m => m.LazyModule)
  }
];

Explanation

The loadChildren property defers the loading of LazyModule until the โ€˜/lazyโ€™ route is accessed.

Reference

Lazy Loading


26. Explain Component Lifecycle Hooks.

Answer

Lifecycle hooks are methods that get invoked at specific times during a componentโ€™s life in Angular.

Code Snippet

@Component({ /* ... */ })
export class MyComponent implements OnInit, OnDestroy {
  ngOnInit() { /* ... */ }
  ngOnDestroy() { /* ... */ }
}

Explanation

  • ngOnInit: Called after the component is initialized.
  • ngOnDestroy: Called just before Angular destroys the component.

Reference

Lifecycle Hooks


27. How to handle forms in Angular?

Answer

Angular provides two ways to handle forms: Reactive Forms and Template-Driven Forms.

Code Snippet

// Reactive Form
this.myForm = this.fb.group({
  name: ['', Validators.required]
});

// Template-Driven Form
<form #myForm="ngForm">
  <input name="name" ngModel required>
</form>

Explanation

  • Reactive Forms: Use FormBuilder and Validators for more programmatic control.
  • Template-Driven Forms: Directly use directives like ngModel in the HTML template.

Reference

Angular Forms


28. What are Decorators?

Answer

Decorators are functions that modify classes, methods, or properties. They are prefixed with @.

Code Snippet

@Component({
  selector: 'app-my-component',
  template: '<p>Hello</p>'
})
export class MyComponent { }

Explanation

Here, @Component is a decorator that tells Angular to treat MyComponent as a component.

Reference

Decorators


29. How to make HTTP requests?

Answer

HTTP requests can be made using the HttpClient service.

Code Snippet

this.httpClient.get('https://api.example.com/data').subscribe(data => {
  console.log(data);
});

Explanation

The get method fetches data from a URL and returns an Observable.

Reference

HttpClient


30. What is Routing in Angular?

Answer

Routing allows navigation between different components in an Angular application. It enables the switching of views based on the URL.

Code Snippet

const routes: Routes = [
  { path: 'home', component: HomeComponent },
  { path: 'about', component: AboutComponent }
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
})
export class AppRoutingModule { }

Explanation

  • The RouterModule is imported and configured with an array of route objects.
  • The path maps to a specific component.

Reference

Angular Routing


31. What is a Directive?

Answer

Directives are instructions in the DOM that tell Angular to attach specific behavior to elements or even transform them.

Code Snippet

@Directive({
  selector: '[appHighlight]'
})
export class HighlightDirective {
  constructor(private el: ElementRef) { }
}

Explanation

  • @Directive decorator marks it as a directive.
  • ElementRef injects a reference to the host DOM element.

Reference

Angular Directives


32. What is an Angular Module?

Answer

An Angular Module, denoted by @NgModule, is a container for components, directives, and services that are part of an application.

Code Snippet

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

Explanation

  • declarations: List of components in the module.
  • imports: List of imported modules.
  • bootstrap: The root component that Angular creates and inserts into the HTML.

Reference

Angular Modules


33. What is the Angular CLI?

Answer

Angular CLI is a command-line interface tool used for initializing, developing, and maintaining Angular applications.

Code Snippet

ng new my-app
ng serve

Explanation

  • ng new: Creates a new Angular application.
  • ng serve: Starts the development server.

Reference

Angular CLI


34. Explain Event Emitters in Angular.

Answer

Event Emitters are used to emit custom events from child components to parent components in Angular.

Code Snippet

@Output() myEvent = new EventEmitter<string>();

emitEvent() {
  this.myEvent.emit('Hello from child');
}

Explanation

  • @Output() decorator exposes myEvent as an output property.
  • emit() method triggers the custom event.

Reference

EventEmitter


35. What is AOT Compilation?

Answer

Ahead-of-Time (AOT) Compilation compiles Angular components and templates into native JavaScript and HTML during the build phase, rather than at runtime.

Code Snippet

ng build --prod

Explanation

Running ng build --prod performs AOT compilation, reducing the runtime overhead and increasing performance.

Reference

AOT Compilation


36. What is an Angular Service?

Answer

Angular services are singleton objects used for sharing methods and data across components.

Code Snippet

@Injectable({
  providedIn: 'root'
})
export class MyService {
  constructor() { }
}

Explanation

  • @Injectable() marks it as a service.
  • providedIn: 'root' ensures that the service is a singleton.

Reference

Angular Services


37. How to use Observables?

Answer

Observables are constructs from RxJS and are used to handle asynchronous operations in Angular.

Code Snippet

import { Observable } from 'rxjs';

const myObservable = new Observable(observer => {
  observer.next('Data 1');
});

Explanation

  • new Observable() creates an Observable.
  • observer.next() pushes data through the Observable.

Reference

Observables in Angular


38. What is Dependency Injection in Angular?

Answer

Dependency Injection (DI) is a design pattern used in Angular to increase modularity and flexibility, allowing components to request services they require.

Code Snippet

constructor(private myService: MyService) { }

Explanation

  • constructor injects MyService.
  • private myService creates a private variable to be accessible within the class.

Reference

Dependency Injection


39. How to use Interceptors?

Answer

Interceptors allow you to intercept HTTP requests and responses to modify them or handle errors.

Code Snippet

@Injectable()
export class MyInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req);
  }
}

Explanation

  • Implements HttpInterceptor interface.
  • intercept() method is where the interception occurs.

Reference

HTTP Interceptors


40. What is Angular Universal?

Answer

Angular Universal is a technology for server-side rendering (SSR) of Angular applications, improving performance and SEO.

Code Snippet

ng add @nguniversal/express-engine

Explanation

  • ng add @nguniversal/express-engine adds Universal capabilities to your Angular application.

Reference

Angular Universal


41. What is Lazy Loading?

Answer

Lazy Loading is a technique to load Angular modules only when they are needed, improving application start-up performance.

Code Snippet

const routes: Routes = [
  { path: 'lazy', loadChildren: () => import('./lazy/lazy.module').then(m => m.LazyModule) }
];

Explanation

  • loadChildren specifies the path to the lazy-loaded module.

Reference

Lazy Loading


42. How to implement Form Validation?

Answer

Angular provides Reactive Forms and Template-driven Forms for validating user input.

Code Snippet

this.myForm = this.fb.group({
  email: ['', [Validators.required, Validators.email]]
});

Explanation

  • Validators.required and Validators.email are used for validation.

Reference

Form Validation


43. What are Angular Elements?

Answer

Angular Elements are Angular components packaged as custom HTML elements, enabling them to be used in any HTML page.

Code Snippet

createCustomElement(MyComponent, { injector: this.injector })

Explanation

  • createCustomElement() converts Angular components into custom elements.

Reference

Angular Elements


44. What is Zone.js?

Answer

Zone.js is a library for Angular that helps manage asynchronous operations, ensuring change detection works seamlessly.

Code Snippet

Zone.current.fork({ name: 'myZone' }).run(() => {
  console.log('In myZone');
});

Explanation

  • Zone.current.fork() creates a new Zone.
  • run() executes code within the Zone.

Reference

Zone.js


45. What are Lifecycle Hooks?

Answer

Lifecycle hooks are functions that Angular calls at specific milestones in a componentโ€™s lifecycle, like initialization and destruction.

Code Snippet

ngOnInit() {
  console.log('Component initialized');
}

Explanation

  • ngOnInit() is called after the componentโ€™s data-bound properties are initialized.

Reference

Lifecycle Hooks


46. What is an Angular Module?

Answer

Angular Module, denoted by @NgModule, is a container for a cohesive block of code dedicated to an application domain, a workflow, or a closely related set of capabilities.

Code Snippet

@NgModule({
  declarations: [MyComponent],
  imports: [BrowserModule],
})
export class MyModule {}

Explanation

  • declarations: Components, directives, and pipes that belong to this module.
  • imports: Other modules whose exported classes are needed by component templates.

Reference

Angular Modules


47. How to Handle Events in Angular?

Answer

Angular uses event binding to handle DOM events like clicks, mouse movements, keypresses.

Code Snippet

<button (click)="handleClick()">Click Me!</button>

Explanation

  • (click) is an event binding that listens for a click event.
  • handleClick() is the method to execute when the button is clicked.

Reference

Event Binding


48. What is AOT Compilation?

Answer

Ahead-of-Time (AOT) Compilation converts Angular TypeScript code into efficient JavaScript code during the build phase before the browser downloads and runs that code.

Code Snippet

ng build --aot

Explanation

  • ng build --aot command will compile the Angular application using AOT.

Reference

AOT Compilation


49. How Do You Use Two-Way Data Binding?

Answer

Two-way data binding uses the ngModel directive to bind a form element value to a component property.

Code Snippet

<input [(ngModel)]="username">

Explanation

  • [(ngModel)]: Two-way data binding directive.
  • username: Property in the component tied to the input field.

Reference

Two-way Data Binding


50. What is Angular CLI?

Answer

Angular CLI is a command-line interface for scaffolding and managing Angular applications.

Code Snippet

ng new my-app

Explanation

  • ng new my-app will create a new Angular application called my-app.

Reference

Angular CLI


51. How Do You Create a Custom Pipe?

Answer

Custom pipes are created by implementing the PipeTransform interface and using the @Pipe decorator.

Code Snippet

@Pipe({ name: 'myCustomPipe' })
export class MyCustomPipe implements PipeTransform {
  transform(value: any): any {
    return value.toUpperCase();
  }
}

Explanation

  • @Pipe defines the name for this pipe.
  • transform method defines the logic.

Reference

Custom Pipes


52. What are Angular Services?

Answer

Angular Services are singleton objects that encapsulate reusable logic, providing methods to perform functionalities that can be injected into components, directives, and other services.

Code Snippet

@Injectable()
export class MyService {
  getData() {
    return 'Some Data';
  }
}

Explanation

  • @Injectable: Decorator that marks the class as injectable.
  • getData: Method that provides some functionality.

Reference

Angular Services


53. How Do You Implement Lazy Loading?

Answer

Lazy loading in Angular allows you to load specific modules only when needed, improving performance. This is done using Angular Routing.

Code Snippet

const routes: Routes = [
  {
    path: 'feature',
    loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule)
  }
];

Explanation

  • loadChildren: Specifies the module to be lazily loaded when the โ€˜featureโ€™ path is navigated.

Reference

Lazy Loading


54. What are Observables?

Answer

Observables are part of the RxJS library and provide a way to handle asynchronous operations and events in Angular applications.

Code Snippet

import { Observable } from 'rxjs';

const myObservable = new Observable(observer => {
  observer.next('Hello');
  observer.complete();
});

Explanation

  • Observable: Constructs a new observable.
  • observer.next: Pushes new data.

Reference

Observables


55. How to Use Async Pipe?

Answer

The async pipe subscribes to an Observable or Promise and returns the latest emitted value, automatically unsubscribing when the component is destroyed.

Code Snippet

<div>{{ myObservable$ | async }}</div>

Explanation

  • myObservable$: Observable variable.
  • async: Angular pipe for handling observables or promises.

Reference

Async Pipe


56. What is Angular Universal?

Answer

Angular Universal is a technology for server-side rendering (SSR) of Angular applications, improving load time and SEO.

Code Snippet

ng add @nguniversal/express-engine

Explanation

  • @nguniversal/express-engine: Package for adding Angular Universal to your project.

Reference

Angular Universal


57. How Do You Create a Component?

Answer

Components are the building blocks of an Angular application. Use the ng generate component or ng g c command to create a new component.

Code Snippet

ng generate component my-component

Explanation

  • ng generate component: CLI command to generate a new component.

Reference

Angular Component


58. How Do You Share Data Between Components?

Answer

Data can be shared between Angular components using @Input, @Output decorators, services, or a shared parent component.

Code Snippet

// Child component
@Input() dataFromParent: string;

Explanation

  • @Input(): Decorator to mark an input property that accepts data from the parent component.

Reference

Component Interaction


59. What is Angular CLI?

Answer

Angular CLI (Command-Line Interface) is a powerful tool to initialize, develop, scaffold, and maintain Angular applications directly from a command shell.

Code Snippet

ng new my-app

Explanation

  • ng new: CLI command to generate a new Angular application.

Reference

Angular CLI


60. What are Angular Forms?

Answer

Angular provides two approaches for handling forms: Reactive Forms and Template-Driven Forms. Both methods provide a way to create forms and validate user input.

Code Snippet

<!-- Template-Driven Forms -->
<input [(ngModel)]="username">

Explanation

  • [(ngModel)]: Two-way binding for form control in Template-Driven Forms.

Reference

Angular Forms


61. What is Dependency Injection?

Answer

Dependency Injection (DI) is a design pattern used in Angular to increase the efficiency and modularity of an application by providing a way to supply dependencies to components.

Code Snippet

constructor(private myService: MyService) {}

Explanation

  • constructor: The place where dependency injection happens.
  • MyService: A service that is injected as a dependency.

Reference

Dependency Injection


62. Explain the Angular Lifecycle Hooks.

Answer

Angular provides lifecycle hooks that allow you to tap into different phases of a componentโ€™s lifecycle, such as initialization, rendering, and destruction.

Code Snippet

ngOnInit() {
  // Initialization code here
}

Explanation

  • ngOnInit: A lifecycle hook called after Angular initializes the componentโ€™s data-bound properties.

Reference

Lifecycle Hooks


63. How Do You Use Pipes?

Answer

Pipes are used to transform data in Angular templates. They can be chained, parameterized, and even be created custom.

Code Snippet

{{ 'hello world' | uppercase }}

Explanation

  • uppercase: A built-in Angular pipe to transform text to uppercase.

Reference

Pipes


64. What is AOT Compilation?

Answer

Ahead-of-Time (AOT) compilation converts Angular HTML and TypeScript into efficient JavaScript code during the build phase, improving runtime performance.

Code Snippet

ng build --prod

Explanation

  • --prod: Flag to enable AOT compilation during production build.

Reference

AOT Compilation


65. How to Handle HTTP Requests?

Answer

Angular provides the HttpClient module to perform HTTP requests, which return Observables.

Code Snippet

this.httpClient.get('https://api.example.com/data');

Explanation

  • httpClient.get: Method to perform an HTTP GET request.

Reference

HttpClient


66. What is Angular Material?

Answer

Angular Material is a UI component library that implements Material Design guidelines, providing a wide variety of UI components.

Code Snippet

ng add @angular/material

Explanation

  • @angular/material: Angular Material package.

Reference

Angular Material


67. What is Interpolation?

Answer

Interpolation is a way to bind expressions to text between HTML tags or attributes.

Code Snippet

<p>{{ name }}</p>

Explanation

  • {{ name }}: Interpolation syntax to bind the name variableโ€™s value.

Reference

Interpolation


68. How Do You Create a Custom Directive?

Answer

You can create a custom directive using the @Directive decorator and specifying a selector.

Code Snippet

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

Explanation

  • @Directive: Decorator to define a custom directive.
  • selector: The attribute that will trigger the directive.

Reference

Directive


69. How to Generate a New Component?

Answer

You can generate a new component using Angular CLIโ€™s ng generate component command.

Code Snippet

ng generate component my-component

Explanation

  • ng generate component: CLI command to generate a new component.

Reference

Angular CLI


70. How to Debug Angular Apps?

Answer

You can debug Angular applications using browser developer tools, Angular DevTools, or third-party packages like Augury.

Code Snippet

console.log("Debugging message");

Explanation

  • console.log: Basic JavaScript method useful for debugging.

Reference

Angular DevTools


71. What is Lazy Loading?

Answer

Lazy loading is a technique in Angular to load Angular modules as needed rather than loading all modules at initial bootstrap.

Code Snippet

{ path: 'lazy', loadChildren: () => import('./lazy.module').then(m => m.LazyModule) }

Explanation

  • loadChildren: Property in Angular route configuration for lazy loading.

Reference

Lazy Loading


72. How Do You Use Observables?

Answer

Observables are used with RxJS to handle asynchronous operations and can be subscribed to in components.

Code Snippet

observable.subscribe(data => console.log(data));

Explanation

  • .subscribe(): Method to handle data, error, and completion callbacks.

Reference

Observables


73. How to Handle Forms Validation?

Answer

Angular provides built-in validators and custom validators for form controls. The Validators class has methods like required, minLength for validation.

Code Snippet

this.form = this.fb.group({
  name: ['', Validators.required]
});

Explanation

  • Validators.required: Built-in validator to make a form control mandatory.

Reference

Form Validation


74. How Do You Create a Service?

Answer

Services in Angular are singleton objects where you can store data and methods to share between components. Use the @Injectable decorator.

Code Snippet

@Injectable({
  providedIn: 'root'
})
export class MyService {}

Explanation

  • @Injectable: Decorator to mark a class as injectable service.

Reference

Services


75. What Are Event Emitters?

Answer

EventEmitter is used with @Output() to emit custom events from child to parent components.

Code Snippet

@Output() myEvent = new EventEmitter<string>();

Explanation

  • @Output(): Decorator for properties that will output data.

Reference

EventEmitter


76. What Are Angular Lifecycle Hooks?

Answer

Lifecycle hooks are methods that Angular calls at specific points in a componentโ€™s lifecycle, like initialization, updates, and teardown.

Code Snippet

ngOnInit() {
  console.log('Component Initialized');
}

Explanation

  • ngOnInit(): Lifecycle hook called once the component is initialized.

Reference

Angular Lifecycle


77. How to Pass Data to a Child Component?

Answer

You can pass data to a child component using @Input() decorator.

Code Snippet

@Input() data: string;

Explanation

  • @Input(): Decorator that marks a class field as an input property.

Reference

@Input()


78. What is Dependency Injection?

Answer

Dependency Injection (DI) is a design pattern used in Angular to inject dependencies into a class.

Code Snippet

constructor(private service: MyService) {}

Explanation

  • constructor: Angularโ€™s injector determines which instance of MyService to pass in.

Reference

Dependency Injection


79. How Do You Use ngIf Directive?

Answer

ngIf is used for conditional rendering of HTML elements.

Code Snippet

<div *ngIf="showElement">Content</div>

Explanation

  • *ngIf="showElement": The div will only render if showElement is true.

Reference

ngIf


80. How Do You Create a Pipe?

Answer

Custom pipes are created by implementing the PipeTransform interface and using the @Pipe decorator.

Code Snippet

@Pipe({
  name: 'myPipe'
})
export class MyPipe implements PipeTransform {
  transform(value: any): any {
    return value.toUpperCase();
  }
}

Explanation

  • @Pipe: Decorator for defining a pipe.
  • PipeTransform: Interface that must be implemented for creating a pipe.

Reference

Custom Pipes


81. What is Route Guard?

Answer

Route guards are interfaces which can tell the Angular router to navigate or not depending on certain conditions.

Code Snippet

canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): boolean {
  return this.authService.isLoggedIn();
}

Explanation

  • canActivate: Guard method to decide if a route can be activated.

Reference

Route Guards


82. How to Use ngSwitch?

Answer

ngSwitch is used for conditional rendering similar to switch-case in programming languages.

Code Snippet

<div [ngSwitch]="value">
  <div *ngSwitchCase="'one'">One</div>
  <div *ngSwitchDefault>Default</div>
</div>

Explanation

  • [ngSwitch]: Binds an expression to evaluate.
  • *ngSwitchCase: Case statement.

Reference

ngSwitch


83. What is Angularโ€™s AOT Compilation?

Answer

Ahead-of-Time (AOT) compilation compiles Angular HTML and TypeScript code into efficient JavaScript code during the build phase before the browser downloads and runs it.

Code Snippet

ng build --prod --aot

Explanation

  • --aot: The flag enables AOT compilation, making the application faster and more secure.

Reference

AOT Compilation


84. What is Angular Universal?

Answer

Angular Universal is a technology for server-side rendering (SSR) of Angular applications.

Code Snippet

ng add @nguniversal/express-engine

Explanation

  • @nguniversal/express-engine: Adds Universal support to the project.

Reference

Angular Universal


85. Explain Angularโ€™s Change Detection Strategy

Answer

Angularโ€™s default change detection strategy is Default, which checks for changes in all components. You can also use OnPush to optimize performance by only checking when the input properties change.

Code Snippet

@Component({
  changeDetection: ChangeDetectionStrategy.OnPush
})

Explanation

  • ChangeDetectionStrategy.OnPush: Only checks the component when its input properties change.

Reference

Change Detection Strategy


86. How to Use ngClass Directive?

Answer

ngClass directive is used to add, remove, or update classes on an HTML element dynamically.

Code Snippet

<div [ngClass]="{'active': isActive}"></div>

Explanation

  • [ngClass]: Applies the class active when isActive is true.

Reference

ngClass


87. How to Make HTTP Requests?

Answer

Angularโ€™s HttpClient module is used to make HTTP requests.

Code Snippet

this.httpClient.get('https://api.example.com/data');

Explanation

  • httpClient.get(): Makes a GET request to the specified URL.

Reference

HttpClient


88. How to Lazy Load Modules?

Answer

Lazy loading is the technique of loading modules only when they are needed, to improve performance.

Code Snippet

{ path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) }

Explanation

  • loadChildren: The function import fetches the module asynchronously.

Reference

Lazy Loading


89. How to Use Observables?

Answer

Observables are used for handling asynchronous operations and events in Angular, often used with RxJS.

Code Snippet

observable.subscribe(value => console.log(value));

Explanation

  • subscribe(): Method to listen for updates from an observable.

Reference

RxJS Observables


90. What is Angular CLI?

Answer

Angular CLI (Command Line Interface) is a toolchain for managing Angular applications, from initialization to deployment.

Code Snippet

ng new my-app

Explanation

  • ng new my-app: Creates a new Angular application named โ€˜my-appโ€™.

Reference

Angular CLI


91. What is Dependency Injection in Angular?

Answer

Dependency Injection (DI) is a design pattern used to handle dependencies. Angular has its DI framework to manage service instances.

Code Snippet

constructor(private service: MyService) { }

Explanation

  • constructor(private service: MyService): DI happens at the constructor level, where MyService is injected.

Reference

Dependency Injection


92. How to Use ngIf Directive?

Answer

The ngIf directive conditionally includes a template based on a condition.

Code Snippet

<div *ngIf="showDiv">Content</div>

Explanation

  • *ngIf="showDiv": If showDiv is true, the div is rendered.

Reference

ngIf


93. What is ngOnInit Lifecycle Hook?

Answer

ngOnInit is a lifecycle hook that gets invoked after Angular initializes the componentโ€™s data-bound properties.

Code Snippet

ngOnInit() {
  // Initialization code
}

Explanation

  • ngOnInit(): Called during the component initialization phase.

Reference

ngOnInit


94. How to Use Two-Way Data Binding?

Answer

Two-way data binding uses the [(ngModel)] directive to bind data from the component to the template and vice-versa.

Code Snippet

<input [(ngModel)]="username">

Explanation

  • [(ngModel)]="username": Changes to the input field update the username variable and changes to username update the input field.

Reference

Two-way data binding


95. How to Build a Reactive Form?

Answer

Reactive forms are more scalable, reusable, and testable. They are defined in the component class using FormControl and FormGroup.

Code Snippet

this.myForm = this.fb.group({
  name: [''],
  age: ['']
});

Explanation

  • this.fb.group(): Creates a form group with the controls โ€˜nameโ€™ and โ€˜ageโ€™.

Reference

Reactive Forms


96. How do you use ngFor directive?

Answer

The ngFor directive is used to iterate over an array or list and populate the template for each item.

Code Snippet

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

Explanation

  • *ngFor="let item of items": Iterates over each item in the โ€˜itemsโ€™ array.

Reference

ngFor


97. What is OnDestroy Lifecycle Hook?

Answer

The OnDestroy lifecycle hook is called when the component is destroyed. It is used to perform cleanup operations.

Code Snippet

ngOnDestroy() {
  // Cleanup code here
}

Explanation

  • ngOnDestroy(): Executes when the component instance is destroyed, enabling resource cleanup.

Reference

OnDestroy


98. What is Angular Router?

Answer

Angular Router enables navigation between different views of an application based on URL paths.

Code Snippet

const routes: Routes = [
  { path: '', component: HomeComponent },
  { path: 'about', component: AboutComponent }
];

Explanation

  • const routes: Routes: Defines routes for the Angular application.

Reference

Angular Router


99. What is an Angular Module?

Answer

Angular Module, denoted by @NgModule, is a container for a cohesive block of code dedicated to an application domain, a workflow, or a closely related set of capabilities.

Code Snippet

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule],
  bootstrap: [AppComponent]
})

Explanation

  • @NgModule(): Defines a module that contains components, directives, pipes, and services.

Reference

Angular Module


100. What is Interpolation?

Answer

Interpolation is a one-way data binding technique used to output a componentโ€™s data into an HTML template.

Code Snippet

<p>{{ message }}</p>

Explanation

  • {{ message }}: The value of the โ€˜messageโ€™ property from the component is rendered within the paragraph.

Reference

Interpolation