Angular

10 Interview Questions Every Angular Developer Should Know

Angular is one of the most popular open-source Javascript Frontend Framework made and maintained by google. Due to it vast popularity, there is also a significant increase in cracking Angular Developer Interviews. And that is why we have corrugated this artilce to show 10 Interview Questions that every angular developer should know.

Every interview is different from the past one and the scope of a job is different too. Keeping this in mind we all need a different strategy for each interview we are going to face and prepare properly for the same.

Keeping these things in mind, we have designed the most common Angular Developer Interview Questions and answers to help you get success in your next Angular Developer Interview.

Angular Developer Interview Questions

What are the key components of Angular?

Angular has the below key components.

  1. Component: These are the basic building blocks of angular application to control HTML views.
  2. Modules: An angular module is set of angular basic building blocks like component, directives, services etc.
    An application is divided into logical pieces and each piece of code is called as “module” which perform a single task.
  3. Templates: This represent the views of an Angular application.
  4. Services: It is used to create components which can be shared across the entire application.
  5. Metadata: This can be used to add more data to an Angular class.

What are components in Angular?

Components are one of the most important and useful part of the angular app. It helps in building the UI block of an Angular App. Components are subset of directives. Unlike directives, components always have a template and only one component can be instantiated per an element in a template.

Here is an example of Component in Angular

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

@Component ({
   selector: 'my-app',
   template: ` <div>
      <h1>{{title}}</h1>
      <div>Learn Angular6 with examples</div>
   </div> `,
})

export class AppComponent {
   title: string = 'Welcome to Angular world';
}

What do you mean by Dependency Injection in Angular?

Dependency injection (DI), is an important application design pattern in which a class asks for dependencies from external sources rather than creating them itself. It is a pattern that deals with how components get hold of their dependencies.

Fortunately, Angular comes with its own dependency injection framework for resolving dependencies( services or objects that a class needs to perform its function).So you can have your services depend on other services throughout your application.

What is HttpClient and its benefits in Angular?

It’s a need of most of the frontend web applications to communicate with some sort of backend services over HTTP protocol using either XMLHttpRequest interface or the fetch() API.

Angular provides a inbuilt support for that by a simplified client HTTP API known as HttpClient which is based on top of XMLHttpRequest interface. This client is avaialble from @angular/common/http package. For using the module you can simply import it in you angular application as shown below

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

Some of the most common benefits of HttpClient are as follows

  1. It contains testablity feature
  2. It provides request and response objects
  3. We can intercept request and response of the API.
  4. Support Observables APIs.
  5. Support streamlined error Handling.

How to deal with error handling in observables?

In Angular Observables, you can handle errors by specifying an error callback on the observer instead of relying on try/catch which are ineffective in asynchronous environment. Let’s understand this with an example

myObservable.subscribe({
  next(num) { console.log('Next num: ' + num)},
  error(err) { console.log('Received an errror: ' + err)}
});

Also Read: What are Observables and Subscribers in Angular

What is the difference between a service and a factory in Angular ?

In Angular, Service refers to a function that is used for the business layer of the appication. Services allow for greater separation of concerns for your application and better modularity by allowing you to extract common functionality out of components.

Here is the example of a Service in Angular Application

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

@Injectable({ // The Injectable decorator is required for dependency injection to work
  // providedIn option registers the service with a specific NgModule
  providedIn: 'root',  // This declares the service with the root app (AppModule)
})
export class RepoService{
  constructor(private http: Http){
  }

  fetchAll(){
    return this.http.get('https://api.github.com/repositories');
  }
}

Whereas factory() is a function which works similar to the service() but is much more powerful and flexible. factory() are design patterns which help in creating Objects.

What is AOT in Angular?

AOT refers to Ahead-of-Time (AOT) is a type of compilation that compiles your app at build time. AOT is used for pre-compiling the application components and along with their templates during the build process.

The Angular Application which are compiled using the AIT method usually have a smaller launching time then the general ones. Also, components of these applications can execute immediately, without needing any client-side compilation.

For AOT compilation, include the –aot option with the ng build or ng serve command as shown below

ng build --aot
ng serve --aot

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