title: How to add multiple headers in Angular 5 HttpInterceptor
body: <p>I'm trying to learn how to use <code>HttpInterceptor</code> to add a couple of headers to each HTTP request the app do to the API. I've got this interceptor:</p>
  <pre class="lang-js prettyprint-override"><code>import { Injectable } from '@angular/core';
  
  import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest } from '@angular/common/http';
  
  import { Observable } from 'rxjs/Observable';
  
  
  @Injectable()
  export class fwcAPIInterceptor implements HttpInterceptor {
    intercept(req: HttpRequest&lt;any&gt;, next: HttpHandler): Observable&lt;HttpEvent&lt;any&gt;&gt; {
  
      const authReq = req.clone({
        headers: req.headers.set('Content-Type', 'application/json')
      });
  
      console.log('Intercepted HTTP call', authReq);
  
      return next.handle(authReq);
    }
  }
  </code></pre>
  <p>Apart of the <code>'Content-Type'</code> header I need to add an <code>'Authorization'</code> but I don't how to do it (the documentation of Angular HttpHeaders is just the list of the methods, without any explanation).</p>
  <p>How can I do it? Thanks!</p>