Working around CORS

While building web applications, I sometimes run into the case where my http requests fail because the web server does not support Cross-origin resource sharing or CORS.  One way to workaround this by using a http proxy which adds the missing CORS header to the response.  This can be easily done with Node.js and the http-proxy library.  Here is the script that will create a proxy that listens on port 8000, proxies each HTTP request to localhost:8042 and return the response with the CORS header added:

var http = require('http'),
    httpProxy = require('http-proxy');

var proxy =  httpProxy.createProxyServer({target:'http://localhost:8042'}).listen(8000);

proxy.on('proxyRes', function(proxyReq, req, res, options) {
  // add the CORS header to the response
  res.setHeader('Access-Control-Allow-Origin', '*');
});

proxy.on('error', function(e) {
  // suppress errors
});

You can also workaround this by disabling CORS in your browser.  For example, chrome can be started with the --disable-web-security flag.