I keep encountering an error in my application (using Node.js as API) and Angular 8 as frontend. The error message says:
Access to XMLHttpRequest at 'http://localhost:3000/socket.io/?EIO=3&transport=polling&t=NQJpoTm' from origin 'http://localhost:4200' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: The value of the 'Access-Control-Allow-Credentials' header in the response is '' which must be 'true' when the request's credentials mode is 'include'. The credentials mode of requests initiated by the XMLHttpRequest is controlled by the withCredentials attribute.Here is the server code:
const io = require('socket.io')(server, {
cors: {
origin: config.ui_host,
methods: ['GET', 'POST'],
},
});
And here is the Angular code :
this.socket = io(socketEndpoint,
{
transportOptions: {
polling: {
extraHeaders: {
'Authorization': JSON.parse(localStorage.getItem('token')),
'Access-Control-Expose-Headers': 'Authorization',
// 'Accept': 'application/json, text/plain',
// 'Accept-Encoding': 'gzip, deflate, br',
}
}
},
}
);