how get server URI from attribute customization javascript

Hello,

is there a way of getting the server URI and context root from a Attribute Customization javascript?

The following lines don't work:

var PublicUri = net.jazz.ajax.BootstrapProperties.FRONTSIDE_URL;
var Contexturl = net.jazz.ajax._contextRoot;

However, these do work in other contexts like provisioning an Attribute Presentation.

Is there a way of achieving the same in this type of customizations?

Thanks!

Regards,

Jorge.