Sorting in knockout

http://jsfiddle.net/rrahlf/EZUEF/2/

var viewModel = function(){

    var self = this;

    self.people = ko.observableArray([

        {firstName:'James',lastName:'Smith',age:38},

        {firstName:'Susan',lastName:'Smith',age:36},

        {firstName:'Jeremy',lastName:'Smith',age:10},

        {firstName:'Megan',lastName:'Smith',age:7},

        {firstName:'James',lastName:'Jones',age:40},

        {firstName:'Martha',lastName:'Jones',age:36},

        {firstName:'Peggy',lastName:'Jones',age:10}

    ]);

    self.headers = [

        {title:'First Name',sortPropertyName:'firstName', asc: true},

        {title:'Last Name',sortPropertyName:'lastName', asc: true},

        {title:'Age',sortPropertyName:'age', asc: true}

    ];

    self.activeSort = self.headers[0]; //set the default sort

    self.sort = function(header, event){

        //if this header was just clicked a second time

        if(self.activeSort === header) {

            header.asc = !header.asc; //toggle the direction of the sort

        } else {

            self.activeSort = header; //first click, remember it

        }

        var prop = self.activeSort.sortPropertyName;

        var ascSort = function(a,b){ return a[prop] < b[prop] ? -1 : a[prop] > b[prop] ? 1 : a[prop] == b[prop] ? 0 : 0; };

        var descSort = function(a,b){ return a[prop] > b[prop] ? -1 : a[prop] < b[prop] ? 1 : a[prop] == b[prop] ? 0 : 0; };

        var sortFunc = self.activeSort.asc ? ascSort : descSort;

        self.people.sort(sortFunc);

    };

}

ko.applyBindings(new viewModel());

----------------------------------------------------------------------

<table>

<thead>

    <tr data-bind="foreach: headers">

        <th data-bind="click: $parent.sort, text: title"></th>

    </tr>

</thead>

    <tbody data-bind="foreach: people">

        <tr>

            <td data-bind="text: firstName"></td>

            <td data-bind="text: lastName"></td>

            <td data-bind="text: age"></td>

        </tr>

    </tbody>

</table>

--------------------------------------------------------------------

th

{

    cursor:pointer;

}