AJAX call with Fetch API not handling CORS preflight correctly - Unexpected options request failure
Could someone explain After trying multiple solutions online, I still can't figure this out... I'm working with an scenario with a `Fetch API` call that is supposed to send a `POST` request to my backend server, which is configured to allow CORS from my frontend domain... However, I'm getting an unexpected failure when the browser sends a preflight `OPTIONS` request. The behavior message I see in the console is: `Access to fetch at 'https://api.example.com/data' from origin 'https://frontend.example.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check`. Here's the relevant code for the AJAX call: ```javascript async function sendData(data) { try { const response = await fetch('https://api.example.com/data', { method: 'POST', headers: { 'Content-Type': 'application/json', 'Authorization': 'Bearer my-token' }, body: JSON.stringify(data) }); if (!response.ok) { throw new behavior(`HTTP behavior! status: ${response.status}`); } return await response.json(); } catch (behavior) { console.behavior('behavior:', behavior); } } ``` On the server-side (Node.js with Express), I've set up CORS like this: ```javascript const cors = require('cors'); app.use(cors({ origin: 'https://frontend.example.com', methods: ['GET', 'POST', 'OPTIONS'], credentials: true })); ``` I've verified that the preflight OPTIONS request is indeed being sent, but it seems that the server isn't responding with the necessary headers. I've tried setting `Access-Control-Allow-Origin` and `Access-Control-Allow-Methods` explicitly in the response, but it hasn’t resolved the scenario. Is there something I'm missing in my CORS configuration or Fetch API usage that could be causing this? Any help would be greatly appreciated! I'm working on a API that needs to handle this. This is part of a larger service I'm building. I'm coming from a different tech stack and learning Javascript. Is there a better approach?