var express = require('express')
var cors = require('cors')
var app = express()
app.use(cors())
app.get('/products/:id', function (req, res, next) { res.json({msg: 'This is CORS-enabled for all origins!'})
})
app.listen(80, function () { console.log('CORS-enabled web server listening on port 80')
})

// Wide listing a cors to accept a specific domain route
const cors = require('cors');
const corsOption = { origin: ['http://localhost:3000'],
};
app.use(cors(corsOption));

app.use(function(req, res, next) { res.header("Access-Control-Allow-Origin", "*"); res.header("Access-Control-Allow-Headers", "X-Requested-With"); next(); });

Cross-Origin Resource Sharing (CORS) is an HTTP-header based mechanism that
allows a server to indicate any other origins (domain, scheme, or port) than
its own from which a browser should permit loading of resources. CORS also
relies on a mechanism by which browsers make a “preflight” request to the
server hosting the cross-origin resource, in order to check that the server
will permit the actual request. In that preflight, the browser sends headers
that indicate the HTTP method and headers that will be used in the actual
request.