NodeJS - CORS middleware `origin` undefined

Question

I have an app using the cors npm package as middleware. I have it set up like this:

  if(process.env.NODE_ENV === 'production') {     var whitelist = ['http://mywebsite.com', 'https://mywebsite.com']     var corsOptions = {       origin: (origin, callback) => {           var originIsWhitelisted = whitelist.indexOf(origin) !== -1;           console.log('ORIGIN: ', origin);  // => undefined           callback(originIsWhitelisted ? null : 'Bad Request', originIsWhitelisted)       },       credentials:true     }     app.use(cors(corsOptions));   } 

The origin parameter in my corsOptions is undefined. Why is this and how can I fix it?

Answer 1

If you do not want to block REST tools or server-to-server requests, add a !origin check in the origin function like so:

var corsOptions = {   origin: function (origin, callback) {     if (!origin || whitelist.indexOf(origin) !== -1) {       callback(null, true)     } else {       callback(new Error('Not allowed by CORS'))     }   } }