How to Determine the Correct Package Sublist ID in NetSuite Item Fulfillments

The internal ID of the Packages sublist in NetSuite Item Fulfillments is dynamic, varying based on the shipping method chosen. For implementations utilizing legacy integrated shipping methods, the sublist ID may be 'packagefedex' for FedEx, 'packageups' for UPS, or simply 'package' for other methods. To correctly identify and interact with the appropriate sublist, implement the following SuiteScript 2.x logic:

javascript
/**
 * @NApiVersion 2.x
 * @NModuleScope SameAccount
 */
define(['N/record', 'N/error'], function(record, error) {

    function getPackageSublistId(itemFulfillmentRecord) {
        var packageSublistSuffix = null;

        // The "package" sublist ID changes depending on the shipping method
        if (itemFulfillmentRecord.getLineCount({ sublistId: 'package' }) !== -1) {
            packageSublistSuffix = '';
        } else if (itemFulfillmentRecord.getLineCount({ sublistId: 'packagefedex' }) !== -1) {
            packageSublistSuffix = 'fedex';
        } else if (itemFulfillmentRecord.getLineCount({ sublistId: 'packageups' }) !== -1) {
            packageSublistSuffix = 'ups';
        } else {
            throw error.create({
                name: 'ERR_PACKAGE_SUBLIST_NOT_SUPPORTED',
                message: 'Package sublist must be "package", "packagefedex", or "packageups" for this record.'
            });
        }
        return 'package' + packageSublistSuffix;
    }

    function setTrackingNumberOnAllPackages(itemFulfillmentRecord) {
        var packageSublistId = getPackageSublistId(itemFulfillmentRecord);

        // Set the same tracking number on All packages on IF
        var packagesCount = itemFulfillmentRecord.getLineCount({ sublistId: packageSublistId });
        for (var lineIndex = 0; lineIndex < packagesCount - 1; lineIndex++) { // Loop iterates for lines 0 to packagesCount-2, skipping the last package as per original logic

            var trackingNumber = g_currentScdRecord.getFieldValue("custrecord_track_number");
            if (trackingNumber !== null && trackingNumber !== "") {
                itemFulfillmentRecord.setSublistValue({
                    sublistId: packageSublistId,
                    fieldId: "packagetrackingnumber" + (packageSublistId.includes('fedex') || packageSublistId.includes('ups') ? packageSublistId.replace('package', '') : ''),
                    line: lineIndex,
                    value: trackingNumber
                });
            }
        }
    }

    return {
        getPackageSublistId: getPackageSublistId,
        setTrackingNumberOnAllPackages: setTrackingNumberOnAllPackages
    };
});