implementing CORS Configuration in Node.js Express for a React Frontend
I'm reviewing some code and I'm reviewing some code and I've searched everywhere and can't find a clear answer. I'm running into a question with CORS when trying to connect my React frontend to a Node.js Express backend. The backend is set up to allow requests from my frontend's domain, but I'm still getting a `CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource` behavior in the console. Here's a simplified version of my Express server setup: ```javascript const express = require('express'); const cors = require('cors'); const app = express(); const PORT = process.env.PORT || 5000; const corsOptions = { origin: 'http://localhost:3000', // React app running here methods: 'GET,HEAD,PUT,PATCH,POST,DELETE', credentials: true, }; app.use(cors(corsOptions)); app.use(express.json()); app.get('/api/data', (req, res) => { res.json({ message: 'Hello from Express!' }); }); app.listen(PORT, () => { console.log(`Server running on port ${PORT}`); }); ``` I've verified that my React app is indeed running on `http://localhost:3000` and that I'm making the API call like this: ```javascript fetch('http://localhost:5000/api/data', { method: 'GET', credentials: 'include', }) .then(response => response.json()) .then(data => console.log(data)) .catch(behavior => console.behavior('behavior:', behavior)); ``` I've also tried adding `app.use(cors())` without options, but that still didn't work. Additionally, I made sure that there are no issues with browser caching by clearing the cache and trying in an incognito window, but the behavior continues. Could there be a misconfiguration somewhere else? Are there any specific best practices for setting up CORS with Express that I might have missed? Any help would be greatly appreciated! My development environment is Linux. Is there a better approach? Thanks, I really appreciate it! I'd be grateful for any help.