export class LoginRequest {
  username : string;
  password : string;
}

export class LoginResponse {
  token : string;
  message : string;
  status : string;
}

export class LoginComponent {
    ...
    loginRes : LoginResponse;
    ...

    login(loginReq : LoginRequest)  {
        // here how can I get return object
        this.loginRes = this.loginService.login(this.loginReq);
    }
}

export class LoginService {
    ...
    loginRes : LoginResponse;
    ...

    login()  {
        // here how can I return  loginRes object
        this.http.post(API_URL + "weblogin", loginReq)
        .subscribe(
            res => {
                this.loginRes =  res.json() as LoginResponse;
            },
            err => {
                this.loginRes = new LoginResponse();
                this.loginRes.message = "Failed to conntect the server";
                this.loginRes.status = "NOT_OK";
                this.loginRes;
            }
        );
    }
}