In my blog Cross domain request in ABAP and Java with two workaround I introduce the step how to deal with Cross Domain issue using Cross-origin resource sharing ( CORS ) supported by almost all modern browsers.
And there is another alternative for cross domain issue, that is JSONP which can work on legacy browsers which predate CORS support.
In this blog, I will first explain how to use JSONP and then introduce the secret behind it.
JSONP in nodeJS server
Suppose I have two employee ID lookup service hosted by the port 3000 and 3001 in my local server. The service will simply return employee name by ID.
The client web page is hosted in port 3000. According to same origin policy, the web page hosted in port 3000 is allowed to access the service hosted in localhost:3000, but forbidden for localhost:3001.
