Suitescript: copying sublist data from one record to another - suitescript2.0

Question

I have a before load user event function on an invoice record that create a button called 'create vendor bill'.
When this button is pressed, a new vendor bill record is opened. The UE script:
/**
*#NApiVersion 2.x
*#NScriptType UserEventScript
*/
define([
"N/url",
"N/record",
"N/runtime",
"N/ui/serverWidget",
"N/redirect",
], function (url, record, runtime, serverWidget, redirect) {
var exports = {};
/**
* #param {UserEventContext.beforeLoad} context
*/
function beforeLoad(context) {
if (
context.type == context.UserEventType.EDIT ||
context.type == context.UserEventType.VIEW
) {
var record = context.newRecord;
var recordId = record.id;
var recordType = record.type;
var customer = record.getValue({ fieldId: "entity" });
log.debug("entity", customer);
var scriptObj = runtime.getCurrentScript();
var customForm = scriptObj.getParameter({
name: "custscript_custom_form_vb",
});
var recordSublist = record.getSublist({ sublistId: "item" });
log.debug("item", recordSublist);
var form = context.form;
log.debug("form", form);
var userVarStr = record;
log.debug("uservarstr", userVarStr);
var userVarURL = url.resolveRecord({
recordType: "vendorbill",
params: {
entity: parseInt(customer),
supportcase: recordId,
cf: parseInt(customForm),
},
});
form.addButton({
id: "custpage_button_test",
label: "Create Vendor Bill",
functionName: "getDetails('" + userVarURL + "')",
});
}
}
exports.beforeLoad = beforeLoad;
return exports;
});
Once the page redirects to the vendor bill form, a client script (deployed on the form), sets the field values on the body of the vendor bill using the parameters passed in the url
This is working as expected.
Where I am getting stuck is trying to work out how to pass the 'item' sublist values to from the invoice to the vendor bill?
Would I pass this as an array?
From what I understand, there is a limit to the number of characters that can be passed via the url.
I can't find anything online or in the Netsuite documentation that deals with passing sublist values between records

Answer 1

For starters I would want to see the Client Script.
One option would be to only pass the Invoice Record ID and Type. Then you can create a Suitelet to be used as a proxy and get the sublist data by a saved search.
Something to keep in mind is that if the sublist is very very long you may reach a execution timeout so you may want to consider triggering a MapReduce script to populate the sublist again you would pass it the recType and ID of the invoice and vendor bill and then use a saved search to get the data.
There are other approaches but I would need to see the client script.