Top 55+ Angular interview questions for senior developer 2023
Are you ready to take your career as an Angular developer to the next level? If so, we must probably be preparing for a job interview.
Introduction:
Practicing advanced angular interview questions for senior developers can help you nail your upcoming technical interview. You must give proper answers to the interview questions with angular interview questions care and translate into creating user experiences and interfaces using Angular through them.
Top IT companies hiring UI, FullStack,FrontEnd, and Angular software developers Soper Angular interview questions who know various in-demand Angular frameworks. You ensure that master the programming and develop skills related to Angular frameworks. Strategic preparation can build knowledge to searching for a job. Continue reading to get in Angular interview questions and answers for the experience.
- Latest Angular Interview Questions for Experienced Professionals :
What’s new in angular 16?
Ans - The Angular 16 release date on May 3, 2023.
Signals are the latest feature that enables you to manage state changes within Angular applications. Inspired by Solid.js, Signals are functions that return a value using the get() method and can be updated by calling them with a new value using the set() method.
Angular signal are creation reactive value graph that automatically updates dependencies as they change and can be combined with RxJS observables, still supported in the Angular latest version, to create powerful and declarative data.
This feature in the current Angular version 16 enables you to enhance your documentation and schematics and assists you in producing standalone components for your Angular applications. The standalone components are not depend on any specific module and can be used in any part of your application. these components are advantageous in developing reusable UI elements.
ng generate @angular/core: standalone
Standalone ng new collection
ng new -- standalone
By doing this, you will obtain a simple project structure without any NgModules. the generators in the project will produce standalone directives, components, and pipes!
Angular Interview Questions for Experienced Professionals :
1)What are the Filters used in Angular?
Ans - Angular mostly used predefined in-build pipes for filtration of data,
1)Uppercase - Used for converting your string data to Capital-Uppercase Letters,
Ex. Var_Name:string = "Angualr Think"
<h2>{{ var_name | uppercase}}</h2>
2)Lowercase - Used for converting your srting data Small-lowercase Letters,
Ex. var_name:string="ANGUALR_THINK"
<h2>{{var_name | Lowercase}}</h2>
3)TitleCase - Used for convert your string in Title or title case, Ex.var_name:string="ANGUALR_THINK"
<h2>{{var_name | Titlecase}}</h2>
4)Currency - Used for adding your number adding country currncy symboll ,
Ex. var_one:number=1000;
<h2>{{var_one | currncy:"INR"}}</h2> etc.EUR ,USD $,INR र
5)slice - use for slice your string as requird it posible using slice filter,
Ex.var_name:string="ANGUALR_THINK"
<h2>{{var_one | slice:"1","5"}}</h2>
6)Date - used for adding current date & time to your application with different format,
Ex. var_one = new date()
<h2>{{var_one | date:"Fulldate"}}</h2>
<h2>{{var_one | date:"Shortdate"}}</h2>
<h2>{{var_one | date:"Middiumdate"}}</h2>
<h2>{{var_one | date:"DD-MM-YY"}}</h2>
<h2>{{var_one | date:"HH-MM--SS"}}</h2>
2)What are Decorators? Which types of decorators are used in Angular
Ans - Decorators are one of the important features of Typescript, which is used for passing Metadata
Decorators mostly return the function, this decorator is invoked at run time and its allows invoked function, Decorators mostly start with @ symbol. different types of decorators used in angular,
Class Decorators - @ngModule,@Component
Property Decorators - @input,@Output
Method Decoretors - @Hostlistner
Parameters Decorators - @Inject
3)What is Subscribing in Angular?
Ans - The angular Subscribe() method on observable type, The Observable that Syncronus or Asyncronus stream data to a component or service that has subscribed to Observable.
Three methods of Subscribing in angular :
Next(): Each item emitted by observable used function.
Error(): If somewhere in the stream & an error is found.
Complete(): At the time all items are complete from the stream.
4)What is REST in Angular?
Ans - REST means Representational State Transfer, REST is mostly used for API is an Application programming interface,
they are used styles that work with in HTTP requests.
5)What is Eager Loading?
Ans -This means to load a module Egarly, We need to import into an application module using import metadata of @ngModule decorators.
In Eager loading mostly module will be loaded before the application start.
That the regions subsequence requests to the application will be faster.
6)What is lazy Loading?
Ans - Lazy loading means On demand Loading, With lazy loading does not need to load everything at once,
It only needs to load on demand, what we expect to see application first load.
the module are lazily loaded will only be loaded when user navigate to routes, modules are loaded on demand its called lazy Loading, By using LoadChildren Property in routes configuration, In lay loading Modules are loaded Asynchronously
Ex. Count routes: Roures=[
{ path:'country', loadchildren:'app/country/country.module#CountryModule}
]
7)What is used in Angular Content Projection?
Ans - Content Projection allows us to insert shadow DOM in your component,
If you want to insert an HTML element or component reused to your component and then used to concept content projection,
<ng-content></ng-content> tags are used for content projection. you can reusable components and scalable applications by using this property.
8)What is Intercepter in angular?
Ans- HttpClintModule provide Intercepter to Authenticate user request, Intercepter executes before each request, we will implement an interceptor by using a custom service.
9)What is HttpclintModule?
Ans -HttpClintModule is a pridefine module of angular 4 and above version. They are present in @angualr/common/http package,
HttpClintModule flows causes- 1) HttpClint 2) HttpErrorResponse
HttpClintModule important features are
1)AJAX call 2)Observable 3)Promise 4)Intercepter 5)ErrorHandling
10)What are the Error Handling service calls?
Ans- 1)HttpClient -
It is a predefined class used to handle service calls with error events and response events,
HttpClient class present in @angualr/common/http package,
HttpClient class present in 'HttpClinentModule'
2)HttpErrorResponse-
This Predefined class it handle both Client side and Server side errors.
* What are the main building blocks of Angular?
Ans - Main building blocks of angular application are as follows:
•Modules •Components •Templates •Metadata •Data binding •Directives •Services •Dependency injection
11)How many types of directives?
There are three types of directives in angular and these are as follows:
Ans- 1)Components: It is a directive with a template.
2)Structural directives: These directives change of DOM layout element by adding and removing DOM elements.
For example, *NgFor,*NgIf etc.
3)Attribute directives: These directives change the behavior or appearance of an element, component, or another directive. For example, ngStyle, ngClass, ngClick, ngModel, etc.
12)What are the components?
Ans- Components are the building block of a UI in an Angular application. Angular apps are tree of Angular components.
Components are the smallest building blocks to distribute your code as required to a developer,
syntax:
import { Component } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
name = 'Angular';
}
13)What are the differences between Component and Directive?
14)What are lifecycle hooks available?
There are 8 angular page lifecycles, and these are as follows:
ngOnChanges: This method is called When the value of a data bound property changes
ngOnInit: This is called whenever the initialization of the directive/component after Angular first displays the data-bound properties happens.
ngDoCheck: This lifecycles hook is for the change detection and to act on changes that Angular cannot or won't detect on its own.
ngAfterContentInit: This lifecycles hook is called in response after Angular projects external content into the component's view.
ngAfterContentChecked: This lifecycles hook is called in response after Angular checks the content projected into the component.
ngAfterViewInit: This lifecycles hook is lifecycles hook called in response after Angular initializes the component's views and child views.
ngAfterViewChecked: This lifecycles hook is called in response after Angular checks the component's views and child views.
ngOnDestroy: This lifecycles hook is the clean-up phase just before Angular destroys the directive/component.
15) Whats a data binding?
Ans - Data binding is a core concept of Angular application which allows to define communication between a component and the DOM element, it makes very easy to define interactive applications without worrying about pushing and pulling data.
There are four types of data binding in angular and these are as follows:
A) Interpolation : {{ value }} adds the value of a property from the component
app.component.ts file
import { Component } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
firstName='John';
lastName='Doe'
}
app.component.html file
<h3> Angular Interview Question </h3>
<p> First Name : {{firstName}} </p>
<p> Last Name : {{lastName}} </p>
B) Property binding : Value is passed from the component to the specified property, which can be a simple html attribute:
Syntax : [property]=”value”
Example
app.component.ts file
import { Component } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
firstName='John';
lastName='Doe'
}
app.component.html file
C) Event binding : When a specific DOM event happens like click, change etc., then call the specified method of the component.
Syntax : (event)=”functionName()”
Example :
app.component.ts file
import { Component } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
onDoneClicked(){
console.log( ' On Done Button Clicked ' )
}
}
app.component.html file
<h3> Angular Interview Question </h3>
<button (click)=" onDoneClicked() "> Done</button>
D) Two-way Binding : Two-way data binding allows in both ways components to template and voice-versa.
Syntax : [(ngModel)]=”value”
Example : app.component.ts file
import { Component } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
firstName=' John ';
lastName=' Doe ' ;
}
16) What is metadata?
Ans -Metadata is used to decorate the class so that it can configure the expected behavior of a class. Metadata can be attached to the TypeScript using the decorator.
A) Class decorators : e.g. @NgModule and @Component
import { Component } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
firstName='John';
lastName='Doe';
}
@NgModule({
imports: [ ],
declarations: [ ],
bootstrap: [ ]
})
export class AppModule { }
B) Property decorators Used for properties inside component. for example, @Input and @Output
import { Component ,Input} from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
@Input() title: string;
firstName = ' John ';
lastName = ' Doe ';
}
C) Method decorators: Used for methods inside component class, e.g. @HostListener
@HostListener( ' click ', ['$event'] )
onHostClicked ( event: Event ) {
console.log( ' HostListener event ' )
}
}
D) Parameter decorators Used for parameters inside component class constructors, e.g. @Inject
export class AppComponent {
constructor(@Inject(Service1) Service1) {
console.log(Service1);
}
}
17)What is the difference between constructor and ngOnInit?
Constructor -
It is a by default method of the class to that component.
Used for Injecting dependencies
Called by JavaScript engine
ngOnInit -
It is a component life cycle hook called by Angular
to indicate that the Angular is done creating the component.
business logic performed
Called by angular
In order to use import it in the component class like this:
import {Component, OnInit} from '@angular/core';
18)What is a service?
Ans -A service is used when a common business logic functionality needs to be provided to many modules. The main objective of a service is to organize and share business logic, data, models and functions with different components of an Angular application.
import { Injectable } from '@angular/core';
@Injectable()
export class GreetingService {
constructor() { }
public sayHello(){
console.log('Hello John Doe')
}
}
19)What is @Injectable() services?
Ans -Angular Injectable symbol and annotates the class with the @Injectable() decorator. This marks the class as one that participates in the dependency injection system.
20)How to inject service in root level?
Ans - Use providedIn: 'root' in the @Injectable() to register the service in the root level and this service will be available in all the components.
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root',
})
export class GreetingService {
constructor() { }
public sayHello(){
console.log('Hello John Doe')
}
}
21)What is dependency injection in Angular?
Ans -Dependency Injection (DI) is software design pattern and it is a core concept of Angular which allows a class receive dependencies from another class. In Angular Application, DI is done by injecting a service class into a component class or module.
Service :
@Injectable()
export class GreetingService {
constructor() { }
public sayHello(){
console.log('Hello John Doe')
}
}
component
import { Component ,HostListener } from '@angular/core';
import {GreetingService} from './greeting.service'
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ],
providers:[GreetingService]
})
export class AppComponent {
constructor(
private greetingService:GreetingService
) {
greetingService.sayHello()
}
}
22) What is the purpose of an async pipe?
The async pipe subscribes to an Observable or Promise and returns the latest value it has emitted. the a new value can be emitted to async pipe marks the component to be checked for changes.
import { Component , HostListener } from '@angular/core';
import { Observable } from 'rxjs';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
currentNumber : Observable <number>
constructor( ) {
}
ngOnInit() {
this.currentNumber = Observable.create(observer => {
let value = 0
const interval = setInterval ( () => {
observer.next(value)
value++
}, 1000 )
return () => clearInterval (interval)
})
}
}
<h3> Angular Interview Question </h3>
<p>
Current Numbe is {{currentNumber | async}}
</p>
23). What is the purpose of ngFor directive?
ngFor is a built-in template directive which makes it easy to iterate over an array and display each item of array.
Component
import { Component ,HostListener } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
numbers= [1,2,3,4,5,6,7,8,8,9];
constructor( ) {
}
}
Html Template
<ul>
<li *ngFor = " let number of numbers " > {{ number }} </li>
</ul>
24) What is the purpose of ngIf directive?
NgIf is a built-in directive which adds or removes DOM element depending on if the expression passed to it is true or false.
Component
import { Component ,HostListener } from '@angular/core';
@Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
showElement=true
constructor( ) {
}
}
HTML template
<p *ngIf=" showElement ">
Show it when showElement is true
</p>
25) What is the purpose of NgSwitch directive?
ngSwitch is a structural directive which adds or removes templates when the next match expression matches the switch expression.
Component
import { Component ,HostListener } from '@angular/core';
@Component({
selector: ' my-app ',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
gender=' Male '
constructor( ) {
}
}
<div [ngSwitch]=" gender ">
<p *ngSwitchCase= " ’ 'Male ' ">Male</p>
<p *ngSwitchCase=" ' Female ' ">Female</p>
<p *ngSwitchDefault> Not Provided </p>
</div>
26) What is interpolation?
Ans-Interpolation is used display a component property in the template with double curly braces{{}} syntax.
Ex.
<h2>Greetings {{ name }}! </h2>
27)What is a parameterized pipe?
Ans- parameter is separated with a colon symbol (:) after the pipe
Syntax : {{value | Pipe1: parameter1: parameter2 }}
Ex. <p> BirthDate is {{ birthDate | date: 'dd/mm/yyyy' }} </p>` op// 02/02/2020
28)How do you chain pipes?
Ans- You can chain multiple pipes together which helps in scenarios where we need to associate more than one pipe that needs to be applied.
`<p> BirthDate is {{ birthDate | date:'fullDate' | uppercase}} </p>`
// SUNDAY, FEBRUARY 2, 2020
29)What is module?
Ans - Modules are mostly used for provide business logic,Modules are piece of code and its break of break your application into small-small group of tasks.
* Why use NgModule in Angular?
Ans - NgModules provides below benefits.
•It makes your business logic organized. You can create feature wise module so it easy to manage/ organize
•the option to make your module lazy loading via the router.
30)What is the difference between pure and impure pipe?
Ans - impure-pipe: works for every change in the component
pure-pipe : works only when the component is loaded.
31)How to make pipe or impure pure?
Ans-
@Pipe({
name: 'sort',
pure: false //true makes it pure and false makes it impure
})
export class myPipe implements PipeTransform {
transform(value: any, args?: any): any {
//your logic here and return the result
}
}
31)How to create custom pipe?
import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
name: 'sum',
})
export class Sum implements PipeTransform {
transform(value:[number]): number {
return value.reduce((first, second) => first + second);
}
}
numbers = [1, 2, 3, 4,5, 6];
<h2>Sum :{{ numbers | sum }} </h2>
33)How to create custom pipe?
Ans -
import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
name: 'sum',
})
export class Sum implements PipeTransform {
transform(value:[number]): number {
return value.reduce((first, second) => first + second);
}
}
numbers = [1, 2, 3, 4,5, 6];
<h2>Sum :{{ numbers | sum }} </h2>
34)What is RxJS?
Ans - RxJS (Reactive Extensions for JavaScript) is a library for reactive programming using observables that makes it easier to compose asynchronous or callback-based code.
RxJS can implementation of the Observable type, which is mostly needed until the type becomes part of the language and until browsers support it.
These utility functions can be used for:
Converting existing code for async operations into observables
Iterating through the values in a stream
Mapping values to different types
Filtering streams
Composing multiple streams
import { from } from 'rxjs';
35)What is an Operator?
Ans - RxJS provides numerous operators like map(), filter(), concat(), of(), pipe(), etc.
the operators to perform complex manipulation of the collection on the source observables. These Operators are like functions, the operators takes configuration options, and return a function that takes a source observable.
Some RxJS operators are as follows:
•of() •map() •filter() •from() •concat() •share() •switchMap()
36)What is router outlet?
Ans - The RouterOutlet is used to Hold Target Template, it is a directive from the router library and this can be acts as a placeholder that marks the spot in the template where the router should display the components for that outlet.
Router outlet is used like a component, The RouterOutlet is a directive which is available in the router library and it is used like a component. that acts as placeholder that marks spot in the template where the router should display the components for that outlet.
<router-outlet></router-outlet>
37)What are router links?
Ans -The RouterLink is used so we can move from one page to another page without refreshing we nevigate one to another,
The RouterLink is a directive on the anchor tags gives the router control over those elements. The navigation paths are fixed, so you can assign a string value to the router link.
<h1>Angular Router Links</h1>
<nav>
<a routerLink="/list">List</a>
<a routerLink="/ detail">Detail</a>
</nav>
<router-outlet></router-outlet>
38)What is the purpose of the Wildcard route?
Ans -If the URL does not match any predefined routes then the router will throw an error and crash the app. You can use the wildcard route to avoid this error. the path of consisting two asterisks to define match every URL and navigate to the configured route.
For example, we can define PageNotFoundComponent page for wildcard route if routes are not configured.
{ path: '**', component: PageNotFoundComponent }
39)What are different types of compilation in Angular?
Ans -Angular offers two ways to compile your application,
• Just-in-Time (JIT)
• Ahead-of-Time (AOT)
40)What is JIT?
Ans -Just-in-Time (JIT) is a type of compilation that compiles your app in the browser at runtime. JIT compilation is the compiles your by default when you run the ng build (build only) or ng serve (build and serve locally) CLI commands. Below commands used for JIT compilation,
> ng build
> ng serve
41)What is AOT?
Ans -Ahead-of-Time (AOT) is a type of compilation that compiles your app at build time. For AOT compilation, include the --aot option with the ng build or ng serve command as below,
ng build --aot
ng serve --aot
42)Can I use arrow functions in AOT?
Ans -
Arrow functions or lambda functions can’t be used to assign values to the decorator properties. For example, the following snippet is invalid:
@Component({
providers: [{
provide: MyService, useFactory: () => getService()
}]
})
To fix this, it has to be changed as following exported function:
function getService(){
return new MyService();
}
@Component({
providers: [{
provide: MyService, useFactory: getService
}]
})
43)What are differences between a Promise and an Observable ?
Observable
1. Emits multiple values over a period of time
2. Is not called until we subscribe to the Observable
3. Can be canceled by using the unsubscribe() method
4. Provides the map, forEach, filter, reduce, retry, and retryWhen operators
5. possibly asynchronous
6. Support socket
Promise
1. Emits only a single value at a time
2. Calls the services without .then and .catch
3. Cannot be canceled
4. Does not provide any operator
5. Always asynchronous
44)What are the differences between Constructors and OnInit?
Constructors:-
1. The constructor is a by default class of component, the method that runs when the component is being constructed.
2. The constructor is a typescript feature and it is used only r a class instantiation and has nothing to do with Angular
3. The constructor call the first time before the ngOnInit().
ngOnInit:-
1. The ngOnInit is fist position execute of Angular life-cycle event method that is called after the first ngOnChanges and the ngOnInit method is use to parameters defined with @Input otherwise the constructor is OK.
2. The ngOnInit is execute call after the constructor and ngOnInit is called after the first ngOnChanges.
3. The ngOnChanges is call the input or output binding value changes.
45)What are some advantages of lazy loading in angular ?
Ans - Some advantages of lazy loading as follows:
•High performance in bootstrap time on initial load.
•Modules are grouped according to their functionality.
46)What is your experience using the Angular framework?
47)Describe a complex project you have worked on that involved Angular development.
48)Do you have any experience with deploying Angular applications to production environments?
49)What is your experience with integrating APIs into Angular applications.
50)Which your version control system used you deploy code? (git)
Conclusion:
We are preparing for a job interview With the help of this information and angular interview questions on Angular.In this article, we ensuring that you master the programming and developing skills related to Angular frameworks.
Angular interview questions we provide some knowledge and strategic preparation can strengthen your chances of bagging a job at many other Tier-1 companies.
We must ensure that angular interview questions for a senior developer the hiring process goes smoothly and successfully – allowing you to hire a great programming team to get your project completed on time and on budget.
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