var Item = function(name, parent) {   this.name = ko.observable(name);     this.isSelected = ko.computed(function() {       return this === parent.selectedItem();           }, this);};var ViewModel = function() {   this.selectedItem = ko.observable();   this.items = ko.observableArray([       new Item("one", this),       new Item("two", this),       new Item("three", this)       ]);};    ko.applyBindings(new ViewModel());

.selected {
    background-color: #ccc; }

Sample here: 

If all you care about is the selected status, then you can tweak it to pass a reference to theselectedItem observable to the child constructor like: 

If your parent view model is stored in a global variable, then you could consider not passing it to the child and using it directly like: . I prefer to pass the reference to the child though.