如何修复CORS错误：请求没有通过访问控制检查？[副本]

Question

import express from 'express';
import cors from 'cors';
import bodyParser from 'body-parser';
import mongoose from 'mongoose';
import helmet from 'helmet';
import config from './config/config.js';
import authRoutes from './routes/auth.js';
import userRoutes from './routes/user.js';

mongoose.connect(config.mongoUri, { useNewUrlParser: true });
mongoose.connection.on('error', () => {
  throw new Error(`unable to connect to database: ${config.mongoUri}`);
});
const port = 9000;
const app = express();

app.use(helmet());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(cors());
app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Methods', 'POST,GET,LINK');
});
app.use('/', authRoutes);
app.use('/', userRoutes);
app.listen(port, () => console.log(`Example app listening on port ${port}!`));

import express from 'express';

import authCtrl from '../controllers/auth.controller.js';

const router = express.Router();

router.route('/auth/signin').post(authCtrl.signin);
router.route('/auth/signout').get(authCtrl.signout);

export default router;

const signin = user => {
  console.log('user', user);
  return fetch('http://localhost:9000/auth/signin/', {
    method: 'POST',
    headers: {
      'Access-Control-Allow-Origin': '*',
      Accept: 'application/json',
    },
    credentials: 'include',
    body: JSON.stringify(user),
  })
    .then(response => {
      return response.json();
    })
    .catch(err => console.log(err));
};

在网络中，我可以看到可选的请求：access-control-allog-headers：access-control-allog-orgin access-control-allog-methods：GET,HEAD,PUT,PATCH,POST,DELETE

那么如何解决这个问题呢？

Answer 1

当您使用cors npm时：

在您的应用程序js中，只需添加以下内容并删除不必要的代码

import cors from 'cors';

app.use(cors());

在package.json文件中的react项目文件夹中：

"proxy": "http://localhost:9000",

const signin = user => {
  console.log('user', user);
  return fetch('/auth/signin', {
    method: 'POST',
    credentials: 'include',
    body: JSON.stringify(user),
  })
    .then(response => {
      return response.json();
    })
    .catch(err => console.log(err));
};