Code issue, getxml wait no longer supported

[Sunpreetk]

This is script include:

var contractorOnboardingUtils = Class.create();

contractorOnboardingUtils.prototype = Object.extendsObject(global.AbstractAjaxProcessor, {

generateContractorId: function() {

var latestId = '';

var userGr = new GlideRecord('sn_hr_core_profile');

userGr.addQuery('u_contractor_id', 'STARTSWITH', 'CXP');

userGr.orderByDesc('u_contractor_id');

userGr.query();

if (userGr.next()) {

latestId = userGr.getValue('u_contractor_id');

}

return latestId;

},

type: 'contractorOnboardingUtils'

});

This is my onchange catalog client script

function onChange() {

var prefix = 'CXP';

var startingIndex = 100001;

// Fire GlideAjax but DO NOT block form submission

setTimeout(function() {

var ga = new GlideAjax('sn_hr_le.contractorOnboardingUtils');

ga.addParam('sysparm_name', 'generateContractorId');

ga.getXMLAnswer(function(latestId) {

var nextNumber;

if (latestId && latestId.length > 3) {

var numericPart = latestId.substring(3);

var numValue = parseInt(numericPart);

nextNumber = isNaN(numValue) ? prefix + startingIndex : prefix + (numValue + 1);

} else {

nextNumber = prefix + startingIndex;

}

g_form.setValue('u_contractor_id', nextNumber);

});

}, 10); // delay the call slightly

return true; // Allow the form to submit immediately

}

it says getxml wait not supported in portal. Please help me out i want to populate this contracor id field before or on form submission so that it get reflected in the description field of hr case.