How to use knockoutjs to filter child viewmodels of a parent viewmodel?

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jQuery

Knockout.js

I have a viewmodel that gets its data from a MVC controller and is converted to JSON in the view. The data is comprised of two lists (PlayList and TeamMembers). I use Knockout Mapping make the data observable.

I would like to create a function called 'getSelected' for each child viewModel (playListItems and teamMemberItems) and be able to call the method from within the view. However, my attempt seems to return the entire parent viewmodel and not the filtered child viewmodel.

Any help would be appreciated.

What I have tried:

var ViewModel = function(data) {
        var self = this;
        self.playListItems = data.PlayList;
        self.teamMemberItems = data.TeamMembers;

        self.playListItems.getSelected = ko.observable(function(id) {
            var currentItem = ko.utils.arrayFirst(self.playListItems(),
                function(item) {
                    return item.RecordingId() === id;
                }).item;

            return currentItem;
        });
    }