knockoutjs checked binding for a list of objecs

http://stackoverflow.com/questions/8613602/knockoutjs-checked-binding-for-a-list-of-objecs

HTML

<script src="http://github.com/downloads/SteveSanderson/knockout/knockout-2.0.0.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.4.2/underscore-min.js"></script>
<script src="http://cloud.github.com/downloads/kamranayub/UnderscoreKO/underscore-ko-1.1.0.min.js"></script>
<ul data-bind="foreach: people">
    <li>
        <input type="checkbox" data-bind="attr: { value: id }, checked: $root.selectedPeople">
        <span data-bind="text: name"></span>
    </li>
</ul>

<hr/>

<div data-bind="text: ko.toJSON($root)"></div>

JavaScript

function Person(id,name,age) {
    this.id = id;
    this.name = name;
    this.age = age;
}

var listOfPeople = [
    new Person(1, 'Fred', 25),
    new Person(2, 'Joe', 60)
    
];

var viewModel = {
    people: ko.observableArray(listOfPeople),
    selectedPeople: ko.observableArray()
};

viewModel.selectedPeopleViewModels = ko.computed(function() {
    return viewModel.selectedPeople.map(function(id) {
        return viewModel.people.find(function(person) {
            return person.id == id;
        });            
    });
});
    
ko.applyBindings(viewModel);