Use nlapiLookupField() for joined fieldsThe following example returns the customer email, contact email and contact entity id for a customer specified by the customer recordId. In this scenario, using a joined field lookup on the array "cust_fields" eliminates having to perform multiple nlapiLookupField calls (one for customer's email, and another for contact.email and contact.entityid) to obtain the customer and contact information:
var customer_id = 1;// customer's internal id
var cust_fields = ['email','contact.email','contact.entityid'] ;
var contactfname = nlapiLookupField('customer',customer_id,cust_fields);
var custEmail= contactfname.email;
var conEmail= contactfname['contact.email'];
var conEnt = contactfname['contact.entityid'];
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