ExpressJS：请求已被 CORS 策略阻止：请求的资源上不存在“Access-Control-Allow-Origin”标头

Question

在我的浏览器开发人员工具栏中，我收到以下 POST 请求的错误消息：

Access to XMLHttpRequest at 'http://localhost:8000/api/tags/' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

但是，当我查看 server.js 时，我确实允许访问：

app.prepare().then(() => {
    const server = express();

    server.use(function(req, res, next) {
        res.header("Access-Control-Allow-Origin", "*");
        res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
        next();
    });

有谁知道为什么现在被阻止

Answer 1

最好使用“cors”包，如下所示。

const express = require('express');
const path = require('path');
const bodyParser = require('body-parser');
const cors = require('cors');

const app = express();
app.use(cors());

// some route controllers
const customRoute = require('./customRoute.controller');

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));


// Custom routes
app.use('/api/tags', customRoute);

app.use(express.static(path.join(__dirname, 'dist')));


// Catch all other routes & return index file
app.get('*', (req, res) => {
  res.sendFile(path.join(__dirname, 'dist/index.html'));
});

module.exports = app;