custom.interceptor.ts

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

@Injectable()
export class CustomInterceptor implements HttpInterceptor
    {
        log = (req: HttpRequest<any>) => tap((res: HttpEvent<any>) =>
                                             {
                                                 if ((res instanceof HttpResponse))
                                                 {
                                                     console.log(this.logJson(req, res));
                                                 }
                                             }, res =>
                                             {
                                                 if ((res instanceof HttpErrorResponse))
                                                 {
                                                     console.log(this.logJson(req, res));
                                                 }
                                             });
        
        logJson(req: HttpRequest<any>, res): string
        {
            return `
 Method=${req.method}
Url=${req.urlWithParams}
Url Params=${JSON.stringify(req.params.keys()
                               .reduce((acc, c) => (acc[c] = req.params.get(c), acc), {}))}
Body Params=${JSON.stringify(req.body, null, " ")}
Headers=${JSON.stringify(req.headers.keys()
                            .map(x => ({[x]: req.headers.get(x)})), null, " ")}
----------------------------------------------------------------------------
Response=${JSON.stringify(res, null, " ")}
Headers=${JSON.stringify(res.headers.keys()
                            .map(x => ({[x]: res.headers.get(x)})), null, " ")}`;
        }
        
        intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>>
        {
            return next.handle(req)
                       .pipe(this.log(req));
        }
    }