Creating multiple related objects from execute jscript list button

Question

I'm trying to create multiple records of an object called Guarantor__c, a child of Opportunity and Contact, on button click. All of the Guarantor records should relate to the Opportunity on the page where the button is. The records are all of the Contacts of the Opportunity's Account with the Guarantor record type. The SOQL below is pretty straightforward. This runs without an error, but doesn't enter any records. Any ideas?

{!REQUIRESCRIPT('/soap/ajax/27.0/connection.js')} 
var url = parent.location.href; 
var updateRecords = []; 
var principalContacts = sforce.connection.query("Select Id From Contact where AccountId ='{!Account.Id}' and RecordTypeId ='012A0000000nr4BIAQ'"); 
var principalContactsArray = principalContacts.getArray("records"); 
if (principalContactsArray.length < 1){ 
    alert("There are no guarantors for this opportunity. Go back to the Account and enter the guarantors.")  
}else{ 
    for (eachPrincipalContact in principalContactsArray){ 
        var newGuarantor = new sforce.SObject("Guarantor__c"); 
        newGuarantor.COntact__ = eachPrincipalContact; 
        newGuarantor.Opportunity__c ="{!Opportunity.Id}"; 
        updateRecords.push(newGuarantor); 
        sforce.connection.update(updateRecords); 
    } 
}

Answer 1

Looks like you are querying Contacts, and creating these Guarantor records, but you are trying to update the new Guarantor records instead of inserting them.

The new records in your updateRecords list are never inserted into SF. You should be using a create call, not an update. You are trying to update objects that don't yet exist.

Change

sforce.connection.update(updateRecords); 

To

sforce.connection.create(updateRecords); 

You also should move the DML statement outside of the loop.