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, weโre bootstrapping the Angular application using the AppModule
.
Reference
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 componentโs template.
Reference
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
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
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
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
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
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
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
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
11. What are Angular Lifecycle Hooks?
Answer
Lifecycle hooks are methods that Angular calls at specific points in the componentโs 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 componentโs initialization.
Reference
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
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
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
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
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
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
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
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
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
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 appโs performance.
Reference
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
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
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
25. What is Lazy Loading?
Answer
Lazy loading is a technique to defer the loading of a module until itโs 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
26. Explain Component Lifecycle Hooks.
Answer
Lifecycle hooks are methods that get invoked at specific times during a componentโs 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
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
andValidators
for more programmatic control. - Template-Driven Forms: Directly use directives like
ngModel
in the HTML template.
Reference
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
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
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
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
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
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
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 exposesmyEvent
as an output property.emit()
method triggers the custom event.
Reference
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
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
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
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
injectsMyService
.private myService
creates a private variable to be accessible within the class.
Reference
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
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
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
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
andValidators.email
are used for validation.
Reference
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
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
45. What are Lifecycle Hooks?
Answer
Lifecycle hooks are functions that Angular calls at specific milestones in a componentโs lifecycle, like initialization and destruction.
Code Snippet
ngOnInit() {
console.log('Component initialized');
}
Explanation
ngOnInit()
is called after the componentโs data-bound properties are initialized.
Reference
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
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
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
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
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 calledmy-app
.
Reference
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
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
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 โfeatureโ path is navigated.
Reference
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
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
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
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
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
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
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
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
62. Explain the Angular Lifecycle Hooks.
Answer
Angular provides lifecycle hooks that allow you to tap into different phases of a componentโs lifecycle, such as initialization, rendering, and destruction.
Code Snippet
ngOnInit() {
// Initialization code here
}
Explanation
ngOnInit
: A lifecycle hook called after Angular initializes the componentโs data-bound properties.
Reference
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
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
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
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
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 thename
variableโs value.
Reference
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
69. How to Generate a New Component?
Answer
You can generate a new component using Angular CLIโs ng generate component
command.
Code Snippet
ng generate component my-component
Explanation
ng generate component
: CLI command to generate a new component.
Reference
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
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
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
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
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
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
76. What Are Angular Lifecycle Hooks?
Answer
Lifecycle hooks are methods that Angular calls at specific points in a componentโs lifecycle, like initialization, updates, and teardown.
Code Snippet
ngOnInit() {
console.log('Component Initialized');
}
Explanation
ngOnInit()
: Lifecycle hook called once the component is initialized.
Reference
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
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
: Angularโs injector determines which instance ofMyService
to pass in.
Reference
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"
: Thediv
will only render ifshowElement
istrue
.
Reference
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
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
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
83. What is Angularโs 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
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
85. Explain Angularโs Change Detection Strategy
Answer
Angularโs 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
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 classactive
whenisActive
is true.
Reference
87. How to Make HTTP Requests?
Answer
Angularโs 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
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
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
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 โmy-appโ.
Reference
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, whereMyService
is injected.
Reference
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"
: IfshowDiv
is true, the div is rendered.
Reference
93. What is ngOnInit
Lifecycle Hook?
Answer
ngOnInit
is a lifecycle hook that gets invoked after Angular initializes the componentโs data-bound properties.
Code Snippet
ngOnInit() {
// Initialization code
}
Explanation
ngOnInit()
: Called during the component initialization phase.
Reference
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 theusername
variable and changes tousername
update the input field.
Reference
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 โnameโ and โageโ.
Reference
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 โitemsโ array.
Reference
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
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
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
100. What is Interpolation?
Answer
Interpolation is a one-way data binding technique used to output a componentโs data into an HTML template.
Code Snippet
<p>{{ message }}</p>
Explanation
{{ message }}
: The value of the โmessageโ property from the component is rendered within the paragraph.