Track observable changes

JavaScript

var Person = function() {
    this.name = ko.observable("john doe");
    this.age = ko.observable(45);
};

var ViewModel = function() {
    var self = this;
    self.Owner = ko.observable(new Person());

    self.test = ko.computed(function(){
        ko.toJS(self.Owner);
    });

    self.test.subscribe(function() {
        alert("Someone updated owner");
    });
};

var vm = new ViewModel();
vm.Owner().age(34);