How to send data in post body in angular 4

Request was sent successfully using below method:

Angular:

login(username: string, password: string) {
      const data = {'username': username, 'password': password};
      const config = { headers: new HttpHeaders().set('Content-Type', 'application/json') };
      return this.http.post<any>(this.authUrl, data, config)
                                .map(res => {
                                  console.log(res);
                                  if (res.user === true) {
                                    localStorage.setItem('currentUser', res.user);
                                    localStorage.setItem('role', res.role);
                                  }
                                  return res;
                                  },
                                  err => {
                                    return err;
                                  }
                                );

    }

Node

var bodyParser = require('body-parser');
router.use(bodyParser.json());

router.post('/api/auth', function(req, res){
  console.log("request received " + req.body);
});