UPDATE. Never mind, solved it.

Hi everybody,

I'm wondering how can I make the second function generic (e.g. utilize the column name instead of using quantity):

adjustmentLinesLabelsPrintingController.prototype.total = function (column) {

        let result = 0;
        if (this.model && this.model.lineItems) {
            result = _.sumBy(this.model.lineItems, column);
        }
        return result;
    };

    adjustmentLinesLabelsPrintingController.prototype.totalPositive = function (column) {

        let result = 0;
        if (this.model && this.model.lineItems) {
            result = _.sumBy(this.model.lineItems, function (o) {
                return Math.abs(o.quantity); // Here what is the correct syntax to use column?
            });
        }
        return result;
    };

Thanks a lot in advance.