I am trying to query the contact and another data extension and then upsert a third data extension called customerETL.

Everything works if I hardcode values into the function but when I pass values through a for loop, I get the following error:

{"message":"Length cannot be less than zero.\r\nParameter name: length","description":"System.ArgumentOutOfRangeException: Length cannot be less than zero.\r\nParameter name: length - from Jint\r\n\r\n"}

Here is the code:

<script runat="server" language="JavaScript">
Platform.Load("core", "1.1.1");

    function getPreferences(subkey, email, deName, fieldname){
        var dataExt = DataExtension.Init(deName);
        var dataFilter = {Property:"Subscriberkey",SimpleOperator:"equals",Value:subkey};
        var data = dataExt.Rows.Retrieve(dataFilter);
        data = data[0]
        var dataConcatList = "";
        var dataTrueFields = [];
        for (var key in data){
            if(data[key] === "True"){
        for (var i = 0; i < dataTrueFields.length; i++) {
            dataConcatList += dataTrueFields[i] + "|";
        var result = dataConcatList.slice(0, -1);
        var attribute = Stringify(result);
        attribute = attribute.replace(/"/g, '');

        var deName = "customerETL"; 
        whereColumnArr = ["attribute:sfmcContactKey","attribute:emailAddress"];
        whereColumValueArr = [subkey, email]; 
        upsertColumnArr = [fieldname]; 
        upsertColumnValueArr = [attribute];

        var upsertedRowCount = Platform.Function.UpsertDE(
try {

    var contactDE = DataExtension.Init("Contact");
    var contactData = contactDE.Rows.Retrieve();
    var listOfsubkeys = [];
    var listOfemails = [];
    for (var n = 0; n < contactData.length; n++){
    for (var i = 0; i < contactData.length; i++){
catch (error){
    var err = Stringify(error);



Thanks in advance.

1 Answer 1


Seems like the version of JavaScript running in MC, does not support negative parameters in the slice() method:

var result = dataConcatList.slice(0, -1);

Replace it with something like this:

if(dataConcatList.length > 1){
    var result = dataConcatList.slice(0, dataConcatList.length-1);

Keep in mind that SSJS is an ancient version of JavaScript. As the documentation states:

The Core library currently stands at version 1.1.1 and supports ECMAscript 3.0. This version represents the current, original version of the server-side JavaScript library and contains no revisions.

  • 1
    Also as a note, it is not an exact 1:1 match with ECMAscript 3 as its not only Server-side (so removes window and DOM capabilities) but also its built on a .NET JS processor (an older version of JINT - github.com/sebastienros/jint), So there are certain aspects that do not translate correctly and provide some unexpected behaviors or restrictions from 'regular' vanilla JS. May 13 at 13:07
  • In the end I created a very long series of SQL queries to do the same thing as SSJS is such a pain and is so limited.
    – neo2049
    Jun 26 at 12:49

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