How to get the base-url in node-red?

I'm trying to expose a JSON as a POST request, where I'm trying to append the base-url with another value.

How could I get the base url value?

I tried using:

 var root = RED.settings.httpNodeRoot;

but then it returned only /, where as I'm expecting something like http://localhost:1880.

Is it possible to get the base url by using any node-red api? Any help could be appreciated.

via R2-D2