在发送请求时，确保将JWT作为请求头部分发送，并在NodeJS服务器端进行正确的验证。

以下是一个实现JWT鉴权的示例代码：

Angular代码：

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class AuthService {
  private apiUrl = 'http://localhost:3000/auth'; // your auth API endpoint

  constructor(private http: HttpClient) {}

  loginUser(user: any) {
    return this.http.post(`${this.apiUrl}/login`, user);
  }

  registerUser(user: any) {
    return this.http.post(`${this.apiUrl}/register`, user);
  }

  getUserProfile() {
    const token = localStorage.getItem('access_token');
    const headers = new HttpHeaders().set('Authorization', `Bearer ${token}`);
    return this.http.get(`${this.apiUrl}/profile`, { headers });
  }
}

NodeJS代码：

const jwt = require('jsonwebtoken');
const express = require('express');
const app = express();

const secretKey = 'your secret key'; // you secret key for JWT

app.use(express.json()); // body parser middleware

// login endpoint
app.post('/auth/login', (req, res) => {
  const { username, password } = req.body;

  // verify user credentials from DB
  const user = { id: 123, username: 'example' };
  const token = jwt.sign({ sub: user.id }, secretKey, { expiresIn: '7d' });

  res.json({ access_token: token });
});

// register endpoint
app.post('/auth/register', (req, res) => {
  // create new user in DB and return success response
});

// protected endpoint
app.get('/auth/profile', (req, res) => {
  const authHeader = req.headers.authorization;
  if (!authHeader) {
    return res.status(401).json({ message: 'Unauthorized' });
  }

  const token = authHeader.split(' ')[1];

  try {
    const decoded = jwt.verify(token, secretKey);
    req.user = decoded;
    res.json({ user: req.user });
  } catch(err) {
    console.error(err);
    res.status(401).json({ message: 'Unauthorized' });
  }
});

app.listen(3000, () => console.log('Server started on port 3000'));

在这个示例中，JWT被用于对受保护的控制器进行鉴权，如果未提供有效的JWT，则会返回401错误状态码。为了避免JWT未发送的错误状态码问题，需要确保在