Handling CORS errors in Fetch API with dynamic headers in React
I'm performance testing and I'm trying to debug I'm relatively new to this, so bear with me. I've spent hours debugging this and I'm writing unit tests and I am using the Fetch API in a React application to call an external API, but I keep running into CORS errors when trying to send a request with dynamic headers. The external API I'm calling requires authentication tokens that I need to include in the headers, but every time I try to make the request, I get the following error: ``` Access to fetch at 'https://api.example.com/data' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. ``` Here's the relevant code where I'm making the request: ```javascript import React, { useEffect } from 'react'; const MyComponent = () => { useEffect(() => { const fetchData = async () => { const token = 'my-auth-token'; // Assume this is generated dynamically try { const response = await fetch('https://api.example.com/data', { method: 'GET', headers: { 'Content-Type': 'application/json', 'Authorization': `Bearer ${token}` }, credentials: 'include' }); if (!response.ok) { throw new Error('Network response was not ok'); } const data = await response.json(); console.log(data); } catch (error) { console.error('Fetch error:', error); } }; fetchData(); }, []); return <div>My Component</div>; }; export default MyComponent; ``` I’ve tried adding `credentials: 'include'` to include cookies, but I still get the same CORS error. I also read about using a proxy, but since I'm deploying this on a cloud service, I'd prefer not to rely on that. I contacted the API provider, and they confirmed that their CORS settings allow for requests from my domain, so I’m puzzled about what might be going wrong here. Any insights or suggestions on how to resolve this would be greatly appreciated! This is my first time working with Javascript 3.10. Any advice would be much appreciated. This issue appeared after updating to Javascript stable. Is this even possible? Any examples would be super helpful. This is happening in both development and production on Debian. Could someone point me to the right documentation?