corsConfig.ts

let corsConfig = function (req, res, next) {


    // Website you wish to allow to connect
    //res.setHeader('Access-Control-Allow-Origin', 'http://localhost:3000');
    //res.setHeader('Access-Control-Allow-Origin', 'http://localhost:3001');

    //allow origin.
    if (req.headers.origin) {
        let origin = req.headers.origin;
        if (origin.indexOf('localhost') > 0) {
            res.setHeader('Access-Control-Allow-Origin', origin);
        }
        // Request methods you wish to allow
        res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');

        // Request headers you wish to allow
        res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');

        // Set to true if you need the website to include cookies in the requests sent
        // to the API (e.g. in case you use sessions)
        res.setHeader('Access-Control-Allow-Credentials', true);
    }
    // Pass to next layer of middleware
    next();

};

module.exports = corsConfig;