Explain on how to use HttpClient with an example?

Below are the steps need to be followed for the usage of HttpClient.

Import HttpClient into root module:

import { HttpClientModule } from '@angular/common/http';
@NgModule({
  imports: [
    BrowserModule,
    // import HttpClientModule after BrowserModule.
    HttpClientModule,
  ],
  ......
  })
  export class AppModule {}

Inject the HttpClient into the application: Let's create a userProfileService(userprofile.service.ts) as an example. It also defines get method of HttpClient

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

const userProfileUrl: string = 'assets/data/profile.json';

@Injectable()
export class UserProfileService {
  constructor(private http: HttpClient) { }

  getUserProfile() {
    return this.http.get(this.userProfileUrl);
  }
}

Create a component for subscribing service: Let's create a component called UserProfileComponent(userprofile.component.ts) which inject UserProfileService and invokes the service method,

fetchUserProfile() {
  this.userProfileService.getUserProfile()
    .subscribe((data: User) => this.user = {
        id: data['userId'],
        name: data['firstName'],
        city:  data['city']
    });
}

Since the above service method returns an Observable which needs to be subscribed in the component.

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