Exception for CORS

[jrvjrv]

In your page, https://javascript.info/cross-window-communication, an important CORS exception, to me at least, is that the protocol "file:" is always considered to be cross-domain. If you are writing javascript that has to work from a "file:" url, it can't access other local files directly (https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSRequestNotHttp). You have to use cross-window messaging to talk into/out-of an iframe.