Error when trying to Update using nforce to Product2 object

Question

I am trying to update a custom field on the Product2 object, namely S3_Image__c - it is a URL field, linking to an image on AWS S3.

Now, I've basically lifted the code from the examples given on the nforce github, and I believe I have the syntax right.

When I run it, the error I am getting is:

Error: Provided external ID field does not exist or is not accessible: undefined

I have tried setting an external ID and I've tried entering dummy data in S3_Image__c, in case it shouldn't be blank. I am basically out of ideas. Any help would be appreciated!

I've included a lot of code but I don't want to miss a key detail. Sorry if it's too much.

function uploadS3Path(filetype, s3url){
    var outcome;
    return new Promise ( result => {
        var queryFileUpdate = 'SELECT S3_Image__c FROM Product2 WHERE Id = \'01t2w000006aKY5AAM\'';// + Id__c;                
        querySFDC(queryFileUpdate).then( result => {
        if(result.length > 0) {
      
            var acc = result[0];
            if(filetype == 'PDF'){
              acc.set('S3_PDF__c', s3url);
            }
            else{
                acc.set('S3_Image__c', s3url);
            }

            org.update({ sobject: acc }).then( result => {
                console.log(result);
                return result;
            }).catch(error => {
                console.error(error);
            });                
          }                  
    });
    });            
}

function querySFDC(query) {
    return new Promise( result => {
        var queryresult;
        console.log("Query Running: " + query);
        org.query({ query: query }).then( results => {
            if (results.records.length > 0) {
                queryresult = results.records;
            } else {
                console.log("Returned No records");
            }
        result(queryresult);
    });            
    });
}

Answer 1

Turns out I needed to query the "Id," so it was contained in the sObject. Little bit obvious looking back, but it had me puzzled for a day or so.

For anyone interested in the working code:

function uploadS3Path(filetype, s3url){
            var outcome;
            return new Promise ( result => {
                var queryFileUpdate = 'SELECT Id, S3_Image__c, S3_PDF__c FROM Product2 WHERE Id = \'01t2w000006aKY5AAM\'';// + Id__c;                
                querySFDC(queryFileUpdate).then( result => {
                if(result.length > 0) {
              
                    var acc = result[0];
                    //console.log(acc.getId());
                    if(filetype == 'PDF'){
                      acc.set('S3_PDF__c', s3url);
                    }
                    else{
                        acc.set('S3_Image__c', s3url);
                    }

                    org.update({ sobject: acc }).then( result => {
                        console.log(result);
                        return result;
                    }).catch(error => {
                        console.log('Error: ', error.message);
                    });                
                  }                  
            });
            });            
        }