How to add multiple headers in Angular 5 HttpInterceptor

Question

I\'m trying to learn how to use HttpInterceptor to add a couple of headers to each HTTP request the app do to the API. I\'ve got this interceptor:

Answer 1

Edit: Following suggestions in comments I have unified both answers

Overwriting all headers

@Injectable()
export class fwcAPIInterceptor implements HttpInterceptor {
  intercept (req: HttpRequest, next: HttpHandler): Observable> {

  const authReq = req.clone({
    headers: new HttpHeaders({
      'Content-Type':  'application/json',
      'Authorization': 'my-auth-token'
    })
  });

  console.log('Intercepted HTTP call', authReq);

  return next.handle(authReq);
}

Adding more headers without overwriting (credits to Ketan Patil - see answer in this post)

const authReq = req.clone({
    headers: req.headers.set('Content-Type', 'application/json')
        .set('header2', 'header 2 value')
        .set('header3', 'header 3 value')
});