Question

我的Express.js服务器在端口3001上运行，我的React前端在端口3000上运行。我已经使用npm install cors --save设置了cors npm包，并将其配置为：

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

 var app = express();
 var router = express.Router();
 app.use(cors());

服务器正在运行并响应Postman上的请求。但是，在尝试GET我的数据时，客户端会出现此错误：

 XMLHttpRequest cannot load localhost:3001/api/comments. 
 Cross origin requests are only supported for protocol schemes: 
 http, data, chrome, chrome-extension, https, chrome-extension-resource.
 __________________________
 (anonymous) @ VM455:1
 dispatchXhrRequest @ xhr.js:175
 xhrAdapter @ xhr.js:12
 dispatchRequest @ dispatchRequest.js:52
 createError.js:15 Uncaught (in promise) Error: Network Error
 etc.

我设置了cors包只有在我的server.js文件中手动设置我的标题后出现此问题：

app.use(function(req, res, next) {
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Credentials', 'true');
  res.setHeader('Access-Control-Allow-Methods', 'GET, HEAD, OPTIONS, POST, PUT, DELETE');
  res.setHeader('Access-Control-Allow-Headers', 'Access-Control-Allow-Headers, Origin, Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-Headers');
  next();
});

我找不到任何有关正确设置CORS中间件但仍有错误的人的信息。我尝试了各种不同的配置（包括主机名和cors包的其他选项，例如在this answer等），但没有成功。我不确定我可以采取哪些措施来进一步解决这个问题。

编辑：检查我的邮递员响应显示正确返回CORS标头：

Access-Control-Allow-Credentials →true
Access-Control-Allow-Headers →Access-Control-Allow-Headers, Origin, Accept, X-    Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-   Request-Headers
Access-Control-Allow-Methods →GET, HEAD, OPTIONS, POST, PUT, DELETE
Access-Control-Allow-Origin →*

尽管使用了cors npm包，但express.js中的CORS错误

0 个答案: