javascript - NodeJS 中请求的资源不存在 'Access-Control-Allow-Origin' header

Question

我正在使用运行的 NodeJS 应用程序，

http://localhost:3000

我还有一个 NodeJS API 正在 http://localhost:3002 上运行。

当我在应用程序中调用 API 时，收到以下错误。

Failed to load http://localhost:3002: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access.

我已经在http://localhost:3002的server.js文件中添加了CORS

var cors = require('cors');

app.options('*', cors()); 

app.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();   
});

// define a simple route
app.get('/', (req, res) => {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept"); 
    res.json({"message": "Welcome to Application"});
});

app.listen(3002, () => {
    console.log("Server is listening on port 3002");
});

我仍然收到错误。每当我打开 URL http://localhost:3000 时，我可以在 chrome 开发者控制台中看到错误。

Answer 1

你应该像这样使用cors

app.use(cors()); 

<小时/>

引用

Simple Usage (Enable All CORS Requests)

var express = require('express')
var cors = require('cors')
var app = express()

app.use(cors())

app.get('/products/:id', function (req, res, next) {
  res.json({msg: 'This is CORS-enabled for all origins!'})
})

app.listen(80, function () {
  console.log('CORS-enabled web server listening on port 80')
})