Angular 4.3 HttpClient：拦截响应

Since Angular 6 release, RxJs 6.0 changed its interface, so you cannot use operators the same way (like .map(), .tap()...).
Because of that, most of the above solutions are outdated.
This is how you correctly modify content of an Observable using RxJs 6.0+ (with pipe):

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

@Injectable()
export class ResponseInterceptor implements HttpInterceptor {

    intercept(req: HttpRequest, next: HttpHandler): Observable<HttpEvent<any>> {

        return next.handle(req).pipe(map((event: HttpEvent<any>) => {
            if (event instanceof HttpResponse) {
                event = event.clone({body: this.modifyBody(event.body)});
            }
            return event;
        }));

    }

    private modifyBody(body: any) {
        /*
        * write your logic to modify the body
        * */
    }
}