interceptor

to create : 

 ng g interceptor HttpConfigInterceptor

HttpConfigInterceptor.ts

import { Injectable } from '@angular/core';

import {

  HttpRequest,

  HttpHandler,

  HttpEvent,

  HttpInterceptor,

  HttpResponse

} from '@angular/common/http';

import { Observable } from 'rxjs';

import { map } from 'rxjs/operators';

@Injectable()

export class HttpConfigInterceptorInterceptor implements HttpInterceptor {

  constructor() {}

  intercept(request: HttpRequest<unknown>, next: HttpHandler): Observable<HttpEvent<unknown>> {

    const token = localStorage.getItem('token');

    if (token) {

      request = request.clone({ headers: request.headers.set('Authorization', 'Bearer ' + token) });

  }

  if (!request.headers.has('Content-Type')) {

      request = request.clone({ headers: request.headers.set('Content-Type', 'application/json') });

  }

  request = request.clone({ headers: request.headers.set('Accept', 'application/json') });

  return next.handle(request).pipe(

            map((event: HttpEvent<any>) => {

                if (event instanceof HttpResponse) {

                    console.log('event--->>>', event);

                }

                return event;

            }));

  }

}

Appmodule.ts

------------ add below code

providers: [ { provide: HTTP_INTERCEPTORS, useClass: HttpConfigInterceptorInterceptor, multi: true }],