CORS Sandbox

Installation (requires node)

git clone https://github.com/jordanpatton/cors-sandbox.git
cd cors-sandbox
npm install
node app.js

Usage

Go to example.com, open your browser console, and enter this:

function requestWithCors(method, url, successCallback, failureCallback) {
  successCallback = successCallback || console.log;
  failureCallback = failureCallback || console.error || console.warn || console.log;
  var xhr = (typeof XDomainRequest !== 'undefined') ?
    (new XDomainRequest()) :
    (new XMLHttpRequest());
  xhr.onreadystatechange = function (event) {
    if (event.target.readyState === 4) {
      /* perform callback according to HTTP status code */
      return (xhr.status > 0 && xhr.status < 400) ?
        successCallback(event.target.response) :
        failureCallback(event.target.response);
    }
  };
  xhr.open(method, url, true);
  xhr.send();
}

In the same console, enter this:

requestWithCors('GET', 'http://localhost:3000?username=john&password=madden');

If you inspect your network traffic, you should see a response with the following headers:

Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: http://www.example.com

As you can see, CORS can be enabled per-origin at the point where the request is parsed.

Questions

Q: What do I do if I get 500 Internal Server Error?

A: Stop your server (Ctrl + C) and restart it (node app.js). In your browser, hard reload.