With the changes with client side and server side security policy regarding the HTTP requests and responses between two domains (origins), new developers who are just getting the feel of the language can experience hell when it comes to sending a request through jQuery to NodeJS application, whether it be the same server your contents are hosted in or in different servers.
It’s a given, once a developer learns how to build an API (Application program interface), he or she will try to integrate their API with their client side application. It is not possible to do so because of the CORS security policy.