knockout bind value issue

by pointbypointuk

HTML

<script src="http://knockoutjs.com/downloads/knockout-2.2.1.js"></script>
<input type="button" data-bind="value:$data.order.name, click=$root.changeName"> <span id="log">hi</span>
    <hr>
                <span id="rptName" data-bind="html: 'OrderID:<b>'+$data.order.OrderHeaderID + '</b>'"></span>

JavaScript

$(document).ready(function () {
        
    function rootViewModel() {
            var self = this;
            self.products = ko.observableArray();
            self.countProducts = function () {
                return self.products().length;
            };
            self.selectedCols = ko.observableArray(),
            self.order ={
                    name : 'bob'
            };
            self.changeName = function (data, sender) {


            };
        }

        var testModel = new rootViewModel();
        $("#log").text("log initialised");
     $("#log").append(testModel.order.name);
        ko.applyBindings(testModel);
    
});