lookUpObject.id = <guid>; lookUpObject.name = "Joe CRM"; lookUpObject.entityType = 2; Xrm.Page.getAttribute("<LookUpFieldName>").setValue(lookUpObject);
var partlistData = new Array(); partlistData = new Object(); partlistData.id = <guid>; partlistData.name = "Joe CRM"; partlistData.entityType = 2; Xrm.Page.getAttribute("to").setValue(partlistData);
The PartyList field is used in multiple places in addition to the Phone Call. For example, the To field on an Email, or the Required field on the Appointment.
For more resources on this topic, check out our blog on Reporting on Activities in Microsoft Dynamics CRM, which describes the different PartyList fields and how they are used.