Why doesn't map work in Angular 4?

Question

Angular

Good afternoon!
Can't figure out why the content of response.json() is empty in Angular4 (Angular CLI). Tell me, where is the joint?
The code is the following:

import { Injectable } from '@angular/core';
import { Response } from '@angular/http';
import { Observable } from 'rxjs';
import 'rxjs/add/operator/map'
import {HttpClient, HttpHeaders} from "@angular/common/http";


@Injectable()
export class AuthenticationService {
    public token: string;

    constructor(private http: HttpClient) {
        var currentUser = JSON.parse(sessionStorage.getItem('currentUser'));
        this.token = currentUser && currentUser.token;

    }
login(username: string, password: string): Observable<boolean> {
        return this.http.post('http://apiserver.com/api/v1/login', JSON.stringify({ username: username, password: password })
            .map((response: Response) => {
            var token = response.json() && response.json().token;
            if (token) {
                // set token property
                this.token = token;
                localStorage.setItem('currentUser', JSON.stringify({username: username, currentUser: token}));
                return true;
            } else {
                return false;
            }
        }
    }

Answer 1

HttpClient does not need to use json()
var token = response && response.token