In Angular 5, you can extend the HttpClient to create your custom service that extends its functionality. Extending HttpClient allows you to add additional methods or behavior specific to your application's needs.

Here's how you can extend HttpClient in Angular 5:

  1. Create a Custom Service: Create a new TypeScript class that extends HttpClient. This new class will be your custom service.

    typescript
    // custom-http-client.service.ts import { Injectable } from '@angular/core'; import { HttpClient, HttpHeaders } from '@angular/common/http'; import { Observable } from 'rxjs'; @Injectable() export class CustomHttpClientService extends HttpClient { constructor() { super(); } // Add custom methods or override existing ones here customGet(url: string, options?: any): Observable<any> { // Perform additional logic or modification here if needed return super.get(url, options); } customPost(url: string, body: any, options?: any): Observable<any> { // Perform additional logic or modification here if needed return super.post(url, body, options); } // Add more custom methods as required }
  2. Provide the Custom Service: In your app module or any other module where you want to use the custom service, provide the CustomHttpClientService instead of the default HttpClient.

    typescript
    // app.module.ts import { NgModule } from '@angular/core'; import { HttpClientModule, HttpClient } from '@angular/common/http'; import { CustomHttpClientService } from './custom-http-client.service'; @NgModule({ imports: [HttpClientModule], providers: [{ provide: HttpClient, useClass: CustomHttpClientService }], }) export class AppModule {}

    By providing CustomHttpClientService with the token { provide: HttpClient, useClass: CustomHttpClientService }, Angular will use CustomHttpClientService wherever HttpClient is injected.

  3. Use the Custom Service: Now, you can inject and use the CustomHttpClientService in your components or services just like you would with the regular HttpClient.

    typescript
    import { Component } from '@angular/core'; import { CustomHttpClientService } from './custom-http-client.service'; @Component({ selector: 'app-my-component', template: '<div>{{ data | json }}</div>', }) export class MyComponent { data: any; constructor(private customHttpClient: CustomHttpClientService) { this.customHttpClient.customGet('https://api.example.com/data').subscribe((response) => { this.data = response; }); } }

With this setup, you have extended the functionality of HttpClient with custom methods in CustomHttpClientService. You can now use the custom methods to make HTTP requests or add additional logic as needed.

Remember that extending HttpClient is optional, and in many cases, you can achieve your requirements using regular HttpClient with interceptors or other Angular features. Extending HttpClient should be done when you need specific functionalities or methods that are not available in the default implementation.

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