Top 10 interview questions and answers for angular that every developer must prepare before their interview in 2023

 

As a front end developer, you can't go wrong by preparing for your interview with questions and answers about Angular. 

Angular is a JavaScript framework that is constantly evolving, so it's important to stay up to date on the latest changes. Here are the top top 10 interview questions and answers for angular that every developer must prepare before their interview in 2023

If you're an Angular developer looking for a job in 2023, you'll need to be prepared  to answer some angular coding interview questions. these angular coding questions may help you for your targeted job.

In this article, we'll give you the top 10 interview questions and answers for angular that every developer must know before their interview. With these angular scenario based interview questions and answers for experienced  or freshers in your toolkit, you'll be one step closer to getting the job of your dreams.

Question 1. What are standalone components in angular and what advantages a standalone component can give you ?

Answer: 

A standalone component is a piece of code that can be independently reused. Angular provides a number of benefits to developers who choose to use standalone components. These benefits include a simpler development process, increased flexibility, and improved performance.

Standalone component is a new feature comes with Angular 14 that is not bound to a particular module and can be used in any module. This provides a great deal of flexibility and reusability. 

Advantages: 

• The learning experience benefits from removing the element of complexity at lower entries.
• This is intended to quicken build times.
• Angular standalone component still permits to be lazy load.
• You can even use NgModule-based components and standalone ones with a zoneless technique. Collaborating to decide when to introduce this innovation is not difficult, but there is no rationale to realize this suggestion at present.
• There are no implied dependencies.
• Less boilerplate to write means there are fewer files.

Reference : How  to create Angular standalone components (no ngModule required) in angular.

Question 2. What are lifecycle hooks in angular and how many lifecycle hooks are there in angular ?

Answer: 

Lifecycle hooks are Angular features that give us specific points in a component's life to tap into. Angular comes with eight built-in hooks, which you can find more about here. 

It is very important question to be answered in any interview because anguar framework is component based framework and everything you do in component based on their lifecycles.

Lifecycle hooks are  important for tasks like fetching external data or managing state before and after a component renders. However, lifecycle hooks should only be used when necessary, as they can add complexity to an application.

Lifecycle hooks are simply functions that get executed at certain points during a component's life in an Angular application. 

There are 8 different lifecycle hooks, and they are: 

• ngOnChanges()
• ngOnInit()
• ngDoCheck()
• ngAfterContentInit()
• ngAfterContentChecked()
• ngAfterViewInit()
• ngAfterViewChecked()
• ngOnDestroy()

Question 3. Explain what is transpiling in angular ? 

Answer:

Transpiling is the process of converting code from one language to another. In the case of Angular, transpiling is used to convert TypeScript code into JavaScript code. This is important because TypeScript is a superset of JavaScript, which means that it contains additional features that are not available in JavaScript. 

By transpiling TypeScript code into JavaScript, Angular allows developers to use these additional features while still being able to run their code in browsers that only support JavaScript.

This is important because TypeScript is not yet supported by all browsers. By transpiling the code, Angular can ensure that it will run correctly in any browser.

Question 4. What are the difference between ActivatedRouteSnapshot and ActivatedstateSnapshot in angular ?

Answer:

When working with the Angular Router, there are two types of route snapshots that can be used: the ActivatedRouteSnapshot and the ActivatedStateSnapshot. 

Both of these snapshots give information about a route at a particular moment in time, but they differ in what kind of information they provide. 

The ActivatedRouteSnapshot gives information about a route when it is first activated. This snapshot includes information about the URL, the params, and the queryParams.

ActivatedStateSnapshot. An ActivatedRouteSnapshot is a snapshot of the state of the router at a given point in time. 

It can be used to traverse the router state tree and extract information about the current route. An ActivatedStateSnapshot is a snapshot of the state of the router at a given point in time.

Reference: How to use ActivatedRouteSnapshot and ActivatedstateSnapshot in Angular applications?

Question 5. What are guard in angular , Explain each of guards type in angular ?

Answer:

Guards are essential to ensuring the security of your Angular application.

Guards are functions that can prevent a user from accessing certain pages on a website. They can also be used to restrict access to certain features of an app.

By properly configuring guards, you can help protect your application from unauthorized access and ensure that only authorized users are able to access your data.

Types of angular guards

-CanActivate guard: CanActivate guard is used to decide if a route can be activated or not.

-CanDeactivate guard: CanDeactivate guard is used to decide if a route can be deactivated or not.

-CanActivateChild guard: CanActivateChild guard is used to prevent unauthorized access to child routes.

-CanLoad guard: Canload guard is used to decide if a module can be loaded or not.

-Resolve guard: Resolve resolve guard is a feature of the router that allows you to pre-fetch data before displaying a route.

Reference: How Guards Can Help You in Angular 2023.

Question 6. Explain What is ngTemplateOutlet in angular and how to use it ?

Answer:

There is a special directive called ngTemplateOutlet that allows you to render a template dynamically. This is particularly useful when you want to reuse a component with different templates.

This directive allows you to specify a template to be used for insertion, and provides a context object that can be used within the template.

For example, you could use ngTemplateOutlet to render a different login form for different user types. Another use case for this directive is when you want to reuse a component without having to duplicate code.

Example:

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

@Component({
  selector: 'my-app',
  template: `      
<ng-template #estimateTemplate let-lessonsCounter="estimate">
    <div> Approximately {{lessonsCounter}} lessons ...</div>
</ng-template>
<ng-container 
   *ngTemplateOutlet="estimateTemplate;context:ctx">
</ng-container>
`})
export class AppComponent {

    totalEstimate = 10;
    ctx = {estimate: this.totalEstimate};
  
}

You can use *ngTemplateOutlet in many other place like:

• Pass template to a Child Component
• Use ViewChild to Access the template

Reference: How to use queryParamsHandling In Angular.

Question 7. Explain the difference an observable and promise?

When it comes to asynchronous programming in JavaScript, An observable is an object that can be used to pass data between parts of a program. A promise is an object that represents the result of an asynchronous operation. 

The difference between an observable and a promise is that an observable can be used to pass data between parts of a program, while a promise represents the result of an asynchronous operation.

In other words, 

Observable:

• Can emit multiple value at a time.
• It delivers errors to subscribers
• Can make use of multiple available operators to map there values
• Can be unsubscribes to stop the execution.
• Observables are lazy.

Promise:

• Emit a single value at a time.
• It delivers errors to catch function.
• Can not make use of any operator to map the value.
• Can not be unsubscribes or stopped.
• Promises are not lazy, can be executed just after the creation.

Reference:  Angular Promises Versus Observables.

Question 8. Define Dependency injection in angular?

Answer:

Dependency Injection (DI) is a software design pattern in which components are given their dependencies instead of hardcoding them within the component. 

Angular 2+ has a built-in dependency injection framework that can be used to provide dependencies to components. The DI framework provides APIs for requesting dependencies from providers. 

Providers can be registered at different levels, such as the component level, the module level, or the application level.

Question 9. Difference between ng-template, ng-container and ng-content ?

Answer:

ng-template: 

An ng-template is a type of Angular element used to hold HTML that is not yet rendered. It can be used to dynamically generate portions of the page based on conditions at runtime, as well as to cache and reuse DOM trees. 

Because ng-templates are not rendered until they are called, they can significantly improve performance in large applications.

ng-container:

Ng-container is a directive that is used to group a set of HTML elements together. This directive is used as a container for Angular structural directives, and can be used to wrap other Angular directives.

The purpose of using this directive is to improve the performance of Angular applications by making it easier for the Angular compiler to optimize the application.

<ng-template #templateRef let-cellvalues="cellvalue" let-rowvalue="rowvalue">
  {{ cellvalues}}
</ng-template>

<ng-container>
   <ng-template *ngTemplateOutlet="templateRef;context:{cellvalue :2}">
   </ng-template>
</ng-container>


@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent implements AfterViewChecked {

  @ViewChild('templateRef')
  public templateref: TemplateRef;

  getTraslateValue(cellvalue){
    return 'some value'
  }
  ngAfterViewChecked() {
    console.log(this.templateref.elementRef)
}

ng-content:

Ng-content is a directive in Angular that is used to insert external content into the main content of a component. This is useful if you want to reuse a component, but have the flexibility to change the content that is inserted into it. 

For example, you could use ng-content to insert a different header or footer into a component depending on the context it is used in.

// app.component.html

 <app-lottery>
   <app-random-number> </app-random-number>
 </app-lottery> 

// lottery.component.html

 <button (click)="toggle = !toggle">ON / OFF </button>
 <br />
 <ng-container *ngIf="toggle">
  The winner number is: 
   <ng-content> </ng-content>
 </ng-container>



// NumberComponent

@Component({
  selector: 'app-random-number',
  template: `{{winnerNumber}}`,
  styleUrls: ['./number.component.css']
})
export class NumberComponent implements OnInit {

  public winnerNumber: number;

  constructor() { }

  public ngOnInit() {
    this.winnerNumber = Math.floor(Math.random() * 90 + 10);
  }
}

Output: The winner number is: 76 🎉

Question 10. What is AOT Compilation and it is different from JIT  ?

Answer:

AOT compilation is a ahead-of-time compilation. This means that the code is compiled before it is executed. JIT compilation is a just-in-time compilation. 

It is a process of converting computer code into machine code that can be read by a computer's processor. This is in contrast to JIT compilation, which converts code into machine code at the time that it is needed. 

AOT complilation can offer better performance than JIT compilation, as the code is already in a form that can be read by the processor. 

However, AOT compilation can also be more time-consuming and difficult to implement.

AOT is faster but JIT uses less memory. AOT is better for server response time while JIT is more flexible.

Stay tuned and follow for more angular updates in future.

Conclusion

In conclusion, these are the top 10 interview questions and answers for angular that every developer should prepare before their interview in 2023. Be familiar with these topics as these are the topics that i had experenced giving the interviews in my journey in order to become a frontend developer, you'll be more confident and better prepared to impress your potential employer. 

By understanding and memorizing these concepts, you will be well on your way to becoming an Angular expert.

Knowing these will help you better understand the framework and be able to use it more effectively.

Be sure to study up on these topics and familiarize yourself with the angular framework before your next interview. Thanks for reading Good luck!