CODE EXAMPLE FOR JAVASCRIPT

npm

var express = require('express')
var cors = require('cors')
var app = express()
 
var whitelist = ['http://example1.com', 'http://example2.com']
var corsOptions = {
  origin: function (origin, callback) {
    if (whitelist.indexOf(origin) !== -1) {
      callback(null, true)
    } else {
      callback(new Error('Not allowed by CORS'))
    }
  }
}
 
app.get('/products/:id', cors(corsOptions), function (req, res, next) {
  res.json({msg: 'This is CORS-enabled for a whitelisted domain.'})
})
 
app.listen(80, function () {
  console.log('CORS-enabled web server listening on port 80')
})