Below is user event script to sync Salesforce customers to Netsuite:

/**

• @NApiVersion 2.x

• @NScriptType UserEventScript
  */
  define([‘N/record’, ‘N/https’, ‘N/log’], function(record, https, log) {

  function afterSubmit(context) {
  // Get access token for Salesforce
  var accessToken = ‘jhbfjsegbrfhbehgb’;

   if (context.type === context.UserEventType.CREATE) {
       var rec = context.newRecord;
       var customerId = rec.id;
       var name = rec.getValue({ fieldId: 'companyname' });
  
       try {
           // Create customer in Salesforce
           var createBody = {
               Name: name
           };
           var createSalesforceResponse = createSalesforceCustomer(accessToken, createBody);
           log.debug("createSalesforceResponse", createSalesforceResponse);
  
           if (createSalesforceResponse.success) {
               record.submitFields({
                   type: rec.type,
                   id: customerId,
                   values: {
                       custentity_sf_customer_id: createSalesforceResponse.id
                   }
               });
               log.debug("Customer Created in Salesforce", "Customer ID: " + createSalesforceResponse.id);
           } else {
               throw new Error('Failed to create customer in Salesforce: ' + JSON.stringify(createSalesforceResponse.error));
           }
  
       } catch (e) {
           log.error('Error creating customer in Salesforce', e.message);
       }
   } else if (context.type === context.UserEventType.EDIT) {
       var rec = context.newRecord;
       var salesforceCustomerId = rec.getValue({ fieldId: 'custentity_sf_customer_id' });
       log.debug("salesforceCustomerId", salesforceCustomerId);
       var name = rec.getValue({ fieldId: 'companyname' });
  
       try {
           // Update customer in Salesforce
           var updateBody = {
               City__c: "Kochi"
           };
           log.debug("calling salesforceResponse", "calling salesforceResponse");
           var updateSalesforceResponse = updateSalesforceCustomer(accessToken, updateBody, salesforceCustomerId);
  
       } catch (e) {
           log.error('Error creating customer in Salesforce', e.message);
       }
   }
  

  }

  function createSalesforceCustomer(accessToken, customerData) {
  var response = https.post({
  url: ‘https://abc4-dev-ed.develop.my.salesforce.com/services/data/v61.0/sobjects/Customer/’,
  headers: {
  ‘Authorization’: ‘Bearer ‘ + accessToken,
  ‘Content-Type’: ‘application/json’
  },
  body: JSON.stringify(customerData)
  });

   var responseBody = JSON.parse(response.body);
   if (response.code === 201) {
       return {
           success: true,
           id: responseBody.id
       };
   } else {
       log.error('Error creating customer in Salesforce', responseBody);
       return {
           success: false,
           error: responseBody
       };
   }
  

  }

  function updateSalesforceCustomer(accessToken, updateData, salesforceId) {
  log.debug(‘salesforceId parameter’, salesforceId);

   var response = https.post({
       url: 'https://abc4-dev-ed.develop.my.salesforce.com/services/data/v61.0/sobjects/Customer/' + salesforceId + '?_HttpMethod=PATCH',
       headers: {
           Authorization: 'Bearer ' + accessToken,
           'Content-Type': 'application/json'
       },
       body: JSON.stringify(updateData)
   });
  
   log.debug('response', response);
  

  }

  return {
  afterSubmit: afterSubmit
  };
  });