Reference Process Application Provided Classes in Javascript

I am attempting to reference a custom type that has several levels of nesting of complex types in a javascript listener. I notice there is a specific way to do this in groovy ref:

But there is no documentation on the javascript equivalent

The error I get is this:

The process could not be started. :
Cannot instantiate process definition CustomerQuoteProcess:10:2a49b8f5-7cfc-11ec-b590-8e712f552304: Unable to evaluate script while executing activity 'dealershipContactInformation' in the process definition with id 'CustomerQuoteProcess:10:2a49b8f5-7cfc-11ec-b590-8e712f552304':org.graalvm.polyglot.PolyglotException: TypeError: writeMember (dealership) on za.co.flow.model.CustomerApplication.vehicleInformation failed due to: Message not supported.

This is the script:

var scriptApplication = customerApplication;
scriptApplication.vehicleInformation.dealership = dealershipInformation["dealershipName"];

scriptApplication.vehicleInformation.dealerTelephone = dealershipInformation["dealershipTelephone"];

scriptApplication.vehicleInformation.dealerEmail = dealershipInformation["dealershipEmail"];

customerApplication = scriptApplication