Reference property from parent object in child object

Question

Look at the switch statement in the second JS object below.

How can I reference the first object which should be it's parent?

$parent.Sorttest() doesn't seem to work.

function FListGroup(title, fListCount, fItemGroup) {
    var self = this;
    self.Title = title;
    self.FListCount = fListCount;
    self.FItemGroup = ko.observableArray(fItemGroup);
    self.Sorttest = ko.observable("Score");
}

function FItemGroup(name, fItemSum, fItemCount, fItemAvrg) {
    var self = this;
    self.Name = name;
    self.FItemSum = fItemSum;
    self.FItemCount = fItemCount;
    self.FItemAvrg = fItemAvrg;
    self.DisplayedSort = ko.computed(function () {
        switch($parent.Sorttest()) {
            case "Score":
                return FItemSum
                break;
            case "Count":
                return FItemCount
                break;
            case "Average":
                return FItemAvrg
                break;
        }
    });
}

Answer 1

I hope this is not Knockoutjs specific, but you can pass the instance to the second ? Something like this:

function FListGroup() {
    this.foo = function() {
      console.log('foo() was called!');
    };
}

function FItemGroup(FListGroupInstance) {
  FListGroupInstance.foo();
}

var FListGroupInstance = new FListGroup();

FItemGroup(FListGroupInstance);

In your case, you could check if the instance exists already, something like this:

function FItemGroup(name, fItemSum, fItemCount, fItemAvrg) {
    var self = this;
    self.instance = false;
    self.DisplayedSort = ko.computed(function () {

        if (self.instance === false) {
            self.instance = new FListGroup();
        }

        switch(self.instance.Sorttest()) {
            case "Score":
                return FItemSum
                break;
            case "Count":
                return FItemCount
                break;
            case "Average":
                return FItemAvrg
                break;
        }
    });
}