[layer8]

It’s more obscure for users if they have to open http://localhost:some_port/. You also have to decide on a hopefully free port.

As an aside, if the application isn’t careful, that approach can potentially open up a security hole, because external javascript on a web page in your browser can perform requests to localhost.

[mozey]

CORS policy usually requires that the port must match. This issue potentially applies to all web apps, not only those hosted on localhost