Interceptor Angular 4.3 - Set multiple headers on the cloned request

Question

I just noticed that the Header Object that was possible to use in the previous HTTP RequestsOption is not anymore supported in the new Interceptor.

It's the new Interceptor logic:

// Get the auth header from the service.
const authHeader = this.auth.getAuthorizationHeader();
// Clone the request to add the new header.
const authReq = req.clone({headers: req.headers.set('Authorization', authHeader)});

I have, now, two ways to add my headers in this request:

Example:

headers?: HttpHeaders;

    headers: req.headers.set('token1', 'asd')

---

setHeaders?: {
   [name: string]: string | string[];
};

    setHeaders: {
             'token1': 'asd',
             'token2': 'lol'
    }

How can I add multiple headers conditionally on this request? Same to what I used to do with the Header Object:

 myLovellyHeaders(headers: Headers) {
    headers.set('token1', 'asd');
    headers.set('token2', 'lol');
     if (localStorage.getItem('token1')) {
     headers.set('token3', 'gosh');
     }
    }
    const headers = new Headers();
    this.myLovellyHeaders(headers);

Answer 1

Angular 4.3+

Set multi headers in Interceptor:

import {
  HttpEvent,
  HttpInterceptor,
  HttpHandler,
  HttpRequest,
  HttpHeaders
} from '@angular/common/http';
import {Observable} from 'rxjs/Observable';

import {environment} from '../../../../environments/environment';

export class SetHeaderInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    const headers = new HttpHeaders({
      'Authorization': 'token 123',
      'WEB-API-key': environment.webApiKey,
      'Content-Type': 'application/json'
    });


    const cloneReq = req.clone({headers});

    return next.handle(cloneReq);
  }
}

Answer 2

My code worked with the following approach to add new headers to replace previous values by new values:

headers: req.headers.set('token1', 'asd')
.set('content_type', 'asd')
.set('accept', 'asd')

Answer 3

The new HTTP client works with immutable headers object. You need to store a reference to the previous headers to mutate the object:

 myLovellyHeaders(headers: Headers) {
     let p = headers.set('token1', 'asd');   
     p = p.set('token2', 'lol');
     if (localStorage.getItem('token1')) {
        p = p.set('token3', 'gosh');
     }

See Why HttpParams doesn't work in multiple line in angular 4.3 to understand why you need to store the reference to the returned value.

It's the same thing for headers:

export class HttpHeaders {
  ...
  set(name: string, value: string|string[]): HttpHeaders {
    return this.clone({name, value, op: 's'});
  }

  private clone(update: Update): HttpHeaders {
    const clone = new HttpHeaders();
    clone.lazyInit =
        (!!this.lazyInit && this.lazyInit instanceof HttpHeaders) ? this.lazyInit : this;
    clone.lazyUpdate = (this.lazyUpdate || []).concat([update]);
    return clone;
  }

To learn more about mechanics behind interceptors read:

• Insider’s guide into interceptors and HttpClient mechanics in Angular