Egghead.io: HttpInterceptor with Angular 4.3.1

<!DOCTYPE html>
<html>

  <head>
    <base href="." />
    <script type="text/javascript" charset="utf-8">
      window.AngularVersionForThisPlunker = 'latest'
    </script>
    <title>angular playground</title>
    <link rel="stylesheet" href="style.css" />
    <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script>
    <script src="https://unpkg.com/zone.js/dist/zone.js"></script>
    <script src="https://unpkg.com/zone.js/dist/long-stack-trace-zone.js"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script>
    <script src="https://unpkg.com/systemjs@0.19.31/dist/system.js"></script>
    <script src="config.js"></script>
    <script>
    System.import('app')
      .catch(console.error.bind(console));
  </script>
  </head>

  <body>
    <my-app>
    loading...
  </my-app>
  </body>

</html>

/* Styles go here */

### Angular Starter Plunker - Typescript

var angularVersion;
if(window.AngularVersionForThisPlunker === 'latest'){
  angularVersion = ''; //picks up latest
}
else {
  angularVersion = '@' + window.AngularVersionForThisPlunker;
}

System.config({
  //use typescript for compilation
  transpiler: 'typescript',
  //typescript compiler options
  typescriptOptions: {
    emitDecoratorMetadata: true
  },
  paths: {
    'npm:': 'https://unpkg.com/'
  },
  //map tells the System loader where to look for things
  map: {
    
    'app': './src',
    '@angular/core': 'npm:@angular/core'+ angularVersion + '/bundles/core.umd.js',
    '@angular/common': 'npm:@angular/common' + angularVersion + '/bundles/common.umd.js',
    '@angular/common/http': 'npm:@angular/common' + angularVersion + '/bundles/common-http.umd.js',
    '@angular/compiler': 'npm:@angular/compiler' + angularVersion  + '/bundles/compiler.umd.js',
    '@angular/platform-browser': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser.umd.js',
    '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic.umd.js',
    '@angular/http': 'npm:@angular/http' + angularVersion + '/bundles/http.umd.js',
    '@angular/router': 'npm:@angular/router' + angularVersion +'/bundles/router.umd.js',
    '@angular/forms': 'npm:@angular/forms' + angularVersion + '/bundles/forms.umd.js',
    '@angular/animations': 'npm:@angular/animations' + angularVersion + '/bundles/animations.umd.js',
    '@angular/platform-browser/animations': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-animations.umd.js',
    '@angular/animations/browser': 'npm:@angular/animations' + angularVersion + '/bundles/animations-browser.umd.js',
    
    '@angular/core/testing': 'npm:@angular/core' + angularVersion + '/bundles/core-testing.umd.js',
    '@angular/common/testing': 'npm:@angular/common' + angularVersion + '/bundles/common-testing.umd.js',
    '@angular/compiler/testing': 'npm:@angular/compiler' + angularVersion + '/bundles/compiler-testing.umd.js',
    '@angular/platform-browser/testing': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-testing.umd.js',
    '@angular/platform-browser-dynamic/testing': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic-testing.umd.js',
    '@angular/http/testing': 'npm:@angular/http' + angularVersion + '/bundles/http-testing.umd.js',
    '@angular/router/testing': 'npm:@angular/router' + angularVersion + '/bundles/router-testing.umd.js',
    'tslib': 'npm:tslib@1.6.1',
    'rxjs': 'npm:rxjs',
    'typescript': 'npm:typescript@2.2.1/lib/typescript.js'
  },
  //packages defines our app package
  packages: {
    app: {
      main: './main.ts',
      defaultExtension: 'ts'
    },
    rxjs: {
      defaultExtension: 'js'
    }
  }
});

//main entry point
import {platformBrowserDynamic} from '@angular/platform-browser-dynamic';
import {AppModule} from './app';

platformBrowserDynamic().bootstrapModule(AppModule)

//our root app component
import {Component, NgModule, VERSION} from '@angular/core'
import {BrowserModule} from '@angular/platform-browser';
import { HttpClientModule, HttpClient, HTTP_INTERCEPTORS } from '@angular/common/http';

import { MyHttpLogInterceptor } from './http.interceptor';

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Testing the new Angular HttpClient</h2>
    </div>
    
    <p>Open the devtools console and inspect the interceptor output there</p>
    
    <button (click)="fetchPeople()">Fetch people</button>
    <button (click)="raiseHttpError()">Raise http error</button>
    
    <hr />
    
    List of people
      
    <ul>
      <li *ngFor="let person of people$ | async">{{ person.name }}</li>
    </ul>
  `,
})
export class App {
  people$;
  
  constructor(private http: HttpClient) {
  }
  
  fetchPeople() {
    this.people$ = this.http
      .get('./data/people.json');
  }
  
  raiseHttpError() {
    this.people$ = this.http
      .get('./data/unavailableendpoint.json');
  }
}

@NgModule({
  imports: [ BrowserModule, HttpClientModule ],
  providers: [
    { provide: HTTP_INTERCEPTORS, useClass: MyHttpLogInterceptor, multi: true }  
  ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}

[
  {
    "name": "Juri"
  },
  {
    "name": "Christoph"
  }
]

import { Injectable } from '@angular/core';
import {
  HttpInterceptor,
  HttpRequest,
  HttpResponse,
  HttpErrorResponse,
  HttpHandler,
  HttpEvent
} from '@angular/common/http';

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';

@Injectable()
export class MyHttpLogInterceptor implements HttpInterceptor {
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    console.log('processing request', request);

    const customReq = request.clone({
      headers: request.headers.set('app-language', 'it')
    });

    return next
      .handle(customReq)
      .do((ev: HttpEvent<any>) => {
        if (ev instanceof HttpResponse) {
          console.log('processing response', ev);
        }
      })
      .catch(response => {
        if (response instanceof HttpErrorResponse) {
          console.log('Processing http error', response);
        }

        return Observable.throw(response);
      });
  }
}